Wikipedia:Reference desk/Archives/Science/2009 September 24

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September 24

are alkenes, alkynes, etc. suitable for making Grignard reagents with?

Hi. I'm wondering if it's legal (according to the laws of chemistry) to make a Grignard reagent from say, chloroethylene (vinyl chloride). Would the electron density in the alkene activate the nucleophilicity of the carbon even further (does a Grignard reagent benefit much from further activation anyway?)) ... would magnesium be less likely to react with an alkene carbon because of polar repulsion?

The same goes for alkynes... also what if the halogen is on an aliphatic ring? (Or say you replaced one of the hydrogens in glucose with sugar. Excluding the hydroxyl ones of course.) John Riemann Soong (talk) 02:27, 24 September 2009 (UTC)

Alkenyl and aryl grigards are easy to make. I assume alkynyl would work, but that's a pretty complicated way to do it...easier just to deprotonate the alkyne-H with a base. Having an oxygen attached to the halogenated atom is not a problem either. However, a hydroxyl anywhere in the structure is likely to quench the grigard as soon as you form it. DMacks (talk) 02:40, 24 September 2009 (UTC)

protic solvents and group I/II metals

It sounds kind of funny, but they never discussed the real mechanism of hydroxide formation in high school and secondary school so now in my 2nd year of college I have this knowledge that magnesium, sodium, potassium, lithium, etc. react violently with water but I actually have no idea how the reaction proceeds. With the Group I metals, I'm having an especially hard time coming up with a viable mechanism because they can only donate a radical electron .... so they can't donate an electron pair to H+, which I think sort of undermines its reactivity.

Would group I metals be more explosive in water if not for the fact that they can only donate radical electrons? (Since radicals react best with radicals?)

So what I think happens is that say, Na donates an electron pair to HOH, making HOH(-), an anion radical. The radical electron goes in an antibonding orbital? So okay, now I have a radical anion. What do I do with it? I mean, part of the problem is that I somehow to form some sort of free hydride, which I don't see happening...

I thought of the metal forming some sort of metal hydride, e.g. NaH or something, which would then react with more water to create a hydroxide anion, but I don't see that very likely. The bond for a metal hydride would be so weak -- wouldn't H+ prefer to stay on the oxygen! Na* + HOH --> NaH + *OH? NaH and OH radical, really? That's the thing ... the kinetic barrier would seem so high I don't know why sodium reacts explosively. John Riemann Soong (talk) 03:28, 24 September 2009 (UTC)

I'm pretty sure they donate a single electron to the H+ ion forming an H· radical, which instantly dimerizes and forms H2 gas. This is an approximation, since the H+ ion (and it's surrogate the H3O+ "hydronium" ion) do not really "exist" in solution, but on the balance, if you are "pushing electrons", that is my best guess as a likely mechanism. The "explosive" nature of the reaction is because of the high exothermic nature of it, because heat + H2 gas = big boom. Being an aqueous-state reaction, it occurs at nanosecond speeds like most such reactions, even aqueous reactions that don't blow up in your face occur at similar rates to sodium + water reactions. It isn't the chemical kinetics that makes it explosive in this case, its the thermodynamics. --Jayron32 03:43, 24 September 2009 (UTC)

Well yes, but the radical kinetics seem prohibitive. Alkynes aren't very reactive at room temperature either, and are harder to attack with halogens, even though they are thermodynamically way more unstable than alkenes and alkanes. Why would HOH*- dimerise -- in fact, how does it do it, and what's the chance that HOH radicals would meet each other especially in dilute solution? (Or is it rapid radical transfer, like rapid proton transfer?) And is H* really such a good leaving group? After all, HOH radical would be a radical anion ... and would radical anions react with each other? They'd be both nucleophiles. John Riemann Soong (talk) 03:58, 24 September 2009 (UTC)

Except that water does contain non-trivial amounts of hydrogen ions free in solution. See Autoionization of water. These are small, but as with any equilibrium situation, per Le Chatelier's principle, once removed via reaction with sodium, they will be nearly instantly replaced; the equilibrium kinetics almost certainly faster than the reaction kinetics. So the radical need not form on H2O, since there will always be some readily availible hydrogen ions to accept the electron to form the radical. If you want to understand why the transfer of the electron from sodium to hydrogen is so exothermic, see the Molar ionization energies of the elements, where the first ionization energy of hydrogen is 1312.0 kJ/mol while it is 495.8 kJ/mol for sodium. Now these are "gas phase" ionization energies, and the presence of water as a solvent is going to be a mitigating factor for this reaction, but I still expect the electron transfer from sodium to hydrogen, by any mechanism, to be massively thermodynamic. --Jayron32 04:24, 24 September 2009 (UTC)

Okay, so I can rule out the HOH*- x HOH*- mechanism.... would the reaction slow down as you accumulate more hydroxide ... I mean, the pH of the solution would increase, resulting in less H+ to go around, e.g. there is both less reagent and more basic product . (Le Chatelier double whammy?) Suppose I had 95% THF, 4% LDA, and 1% water (by molarity). Now I add in some sodium metal. What would happen?

Oops, forgot that LDA reacts almost irreversibly with water. Ummm... I add pyridine instead? John Riemann Soong (talk) 04:39, 24 September 2009 (UTC)

How about concentrated NaOH solution - does it react slower - yes.83.100.251.196 (talk) 17:09, 24 September 2009 (UTC)

Is that because pre-existing Na+ and OH- inhibits production of more Na+ and OH- (par le principe du Chatelier) or is it because NaOH reduces H+ concentration? That's why I wanted to use pyridine -- to explore a pH-dependent effect. John Riemann Soong (talk) 22:38, 24 September 2009 (UTC)

Lower H+ concentration is one factor, as is higher Na+ concentration in solution. Both are examples of Le Chatelier's principle since increased H+ affects OH- (a product of the reaction) concentration in aqueous solution - however that principle specifically is about equilibrium rather than rate - however the two are linked - for the same reaction.

At higher concentrations other factors come in - like higher viscosity of conc NaOH aq, as well as lower absolute H2O concentration.83.100.251.196 (talk) 03:01, 25 September 2009 (UTC)

The other thing that disturbs me is that H3O* radicals have to "find" each other, which seems sort of improbable, but I suppose rapid proton transfer helps this somewhat? The thing though, I expect that with concentration of 10^-15 * 10^-15 (that's a rough reaction probability rate of 10^-30!), that rapid transfer only partially mitigates the slowness of such a reaction ... it still happens in a blink of an eye, but it would actually seem slower than most other "rapid" reactions, allowing us to significantly slow the reaction under creative conditions? John Riemann Soong (talk) 04:34, 24 September 2009 (UTC)

I don't think electron transfer to "H+" is as likely as electron transfer to "H20" in plain water - (see below) - just because of the low concentration. However in an acidic solution I expect the H+'s will react first. Typically we don't add sodium to acid.. Because we don't get many volunteers..83.100.251.196 (talk) 17:13, 24 September 2009 (UTC)

I have some further questions, since I suddenly am guessing that inhibiting radical formation would dramatically undermine sodium's reactivity. I think some heat catalyses the formation of more radicals, which helps autocatalyse the reaction (as the reaction gets hotter more radicals get formed/propagated).

So I have two hypotheses:

• Adding peroxide would dramatically increase the reactivity of the reaction by catalysing the amount of OH* radical available in solution at any one time (plus, it wouldn't be an anion radical, which might help it a bit react with other anion radicals).
• Doing the reaction in say, a cold solution of -50C (or -78 C? that number seems fun) THF and water. (I assume the THF would keep the water from freezing.) The reaction slows much more than a simple Q10 trend (or the T term in the Arrhenius equation) would predict, because of the inhibition of radical propagation.

Can someone comment? John Riemann Soong (talk) 04:08, 24 September 2009 (UTC)

OK, after all of this discussion, I actually bothered to do a search. this article discusses mass spectrometric analysis of sodium-water solvation clusters formed during the sodium-water reaction. Not sure of the depth of detail you want here, but if you read that article, especially the "background" section, it may likely contain the information you seek, or at least references to said information. here is anothr article on a similar subject. --Jayron32 04:43, 24 September 2009 (UTC)

Sodium definately transfers a single electron at a time - but remember that sodium is typically added in bulk - ie you've got Na's next to Na's - so transferring two electrons isn't a problem. For a little more clarity consider the reaction of alkali metals with liquid ammonia at very low temperatures - the intial (isolateable) product is M+(solvated by ammonia) and 'electrons' [1], only at higher temperatures does the 'free electron' actually reduce and react with ammonia to give amide NH2- it can be expected to be similar for water. Additionally it can be expected that the first step is single electron transfer driven by the very thermodynamically favourable solvation of M+

I don't think radicals will actually catalyse the reaction - it looks like radical combination is a final step, not the beginning step. also I don't think peroxide will act as a catalyst - on the surface of Na the peroxide can be converted to two -O^- in one step with no radical intermediates. Also HOH^·- + RO-OR >>> ROH + OH^- + RO· note there is no net increase in number of radicals (However clearly hydrogen peroxide will be more reactive with sodium...)

I'd suggest something like this:

Nan  bulk surface + HOH >>> [Nan bulk]+[HOH]·- still bound to surface

2 ( "Na+ [HOH]·-" bound to surface ) >>> H2 +2NaOHdissolves

It's possible to believe that H· could separate at the surface and migrate across the surface to another radical or radical anion for further reaction

Also what is "Q10 trend" ?83.100.251.196 (talk) 16:30, 24 September 2009 (UTC)

There's an alternative 'in solution' reaction that can be suggested:

Na+[HOH]·- + HOH >>> Na+HO- + OH· + H2
OH· + Na+[HOH]·- >>> Na+HO- + H2O

83.100.251.196 (talk) 16:55, 24 September 2009 (UTC)

It should be worth investigating "hydrated electrons" - the formulation [HOH]^·- may be a simplification (as H30+ is a simplification) [2] - it's definately possible that the initial reaction of Na with water is formation of Na+ and 'hydrated electrons' followed by various other processes - Many references eg [3] suggest that the solvated electron reacts with water to form hydroxide and H atoms - however I prefer my formulation above in which hydroxyl radicals are formed - until I find something that proves that to be wrong.83.100.251.196 (talk) 17:35, 24 September 2009 (UTC)

lability of alkyne protons and NMR

Would an alkyne proton be a sharp peak in proton NMR? Since amine and alcohol protons show a wide peak, do alkyne protons undergo labile exchange as well? Like if I placed an alkyne in say some deuterium water (or perhaps deuterium methanol to increase solubility), would I see the alkyne proton replaced by deuterium on NMR? John Riemann Soong (talk) 03:40, 24 September 2009 (UTC)

Read the article on Alkynes, especially the section on Reactions specific for terminal alkynes. The C-H bond on a terminal alkyne is relatively weak, making such terminal alkynes a relatively good weak acid. The pKa lies somewhere between the alcohol hydrogen and the amine hydrogen, which means such a hydrogen will behave chemically somewhere between that of alcohols and amines, and should undergo deuterium exchange. --Jayron32 03:47, 24 September 2009 (UTC)

Yeah I remember covering that in my first semester lol. But what I don't get is that my NMR interpreting table seems to imply that alkyne protons have more shielded peaks than hydrocarbons (and seem just as sharp apparently) because of that anisotropy thing -- that is, alkyne protons apparently aren't labile. Are they labile, or are they not? Is my NMR guide just wrong? John Riemann Soong (talk) 03:55, 24 September 2009 (UTC)

Our Chemical shift article, and also any good orgo text, will discuss the origins of the deshielding effects of various groups. Any good text will also have numerous examples of actual NMR spectra for you to see exactly whether their correlation tables are reasonable. I never rule out textbook-mistakes, but I always cross-check with other sources before thinking "mistake" is the likely explanation for something I don't understand. DMacks (talk) 04:32, 24 September 2009 (UTC)

(EC) No, while they DO undergo deuterium exchange, they are NOT labile. That is because lability is due exclusively to hydrogen bonding; the relatively strong hydrogen bonding in alcohols and amines means that protons are essentially shuffled around freely between neighboring molecules. With alkynes, there is no hydrogen bonding, so neighboring alkyne molecules will not exchange protons. The deuterium exchange with alkynes will only occur with a relatively labile base, such as say water or methanol or ethanol. If you added, say, deuterated acetylene to another non-deutrated terminal alkyne, I would expect no deuterium exchange. --Jayron32 04:34, 24 September 2009 (UTC)

Okay, I noted that the pKa of ammonia (and the rest of the amine family) was 35 (10 more than an alkyne!), and yet I wondered why it still gets such wide peaks on NMR! Hmm ... isn't the electron rich triple bond in alkynes a good H+ acceptor? Or no? (The pi cloud is too delocalised?) Simple water (and not hydroxide) is good enough to induce proton exchange? Seems good enough for me...so would an alkyne proton in an alcohol-aqueous solution show up as a sharp peak on NMR? John Riemann Soong (talk) 04:44, 24 September 2009 (UTC)

Yes. Google is your friend. I just typed in "Proton NMR of Acetylene" and this was hit #1. Here is propyne's proton NMR. I would describe the alkynal proton as producing a "sharp" peak on each of these spectra. --Jayron32 04:56, 24 September 2009 (UTC)

Quite sharp indeed. As Jayron32 said, you need hydrogen bonding to get wide peaks; alkynes simply don't do that. And actually, alkynes are generally less reactive to electrophilic attacks than alkenes. Tim Song (talk) 05:03, 24 September 2009 (UTC)

Yeah, isn't that what I said? Alkynes are less reactive at room temp to halogens, etc. So anyway, doesn't it depend on the solvent? I guess this alkyne was dissolved in TMS (what a great protic solvent!) ... but what if some methanol were added too? Also, if a product with a hydroxyl group was sufficiently dilute in TMS, would the lack of hydrogen bonding resharpen the hydroxyl proton peak? John Riemann Soong (talk) 05:06, 24 September 2009 (UTC)

Tetramethylsilane is not the solvent, its added as a dopant to the sample to act as a standard. The solvent is usually something like carbon tetrachloride or Deuterated chloroform. --Jayron32 05:12, 24 September 2009 (UTC)

Oh okay. What if you used a protic solvent? John Riemann Soong (talk) 05:21, 24 September 2009 (UTC)

And so as not to get signal strength issues, perhaps deuterated methanol or dilute methanol in 95% THF? John Riemann Soong (talk) 05:29, 24 September 2009 (UTC)

Well, that sounds great. What I would do if I were you is to approach the professor in charge of the NMR machine at your school, and ask him. If he knows the answer, he'd likely tell you. If there is an open time slot on the NMR, he may even let you run your own samples. --Jayron32 17:00, 24 September 2009 (UTC)

For lability a low activation energy is needed - lone pairs on N or O allow this since a concerted 'H swap' can occur ie simultaneous exchange of H's with no high energy O^- intermediate. Alkynes lack a lone pair, and so lack the ability to do this concerted reaction. Thus they are much less labile than the corresponding OH or NH compounds. (even for the same acidity...)83.100.251.196 (talk) 17:03, 24 September 2009 (UTC)

Consider this reaction:

  H   Ha                     H   Ha
   \ /                        \   \
    O   O             >>>      O   O     
       / \                      \   \
      Hb   H                    Hb   H

(looks better in 3d) - two arrows required - swaps Ha and Hb - in 3d it's easier to see that the two H20 can be arranged so that the product is formed so that the bond angles are still 109degrees - no strain. Also note that the starting product is already part of the way to the product via hydrogen bonds.

However for the exchange with alkynes - it's impossible to get this conformation - there is only one position for the terminal CH (in a straightline) - so such a concerted reaction would produce a highly strained (bent) alkynes (before relaxation) - thus much higher energy, and much less likely to occur. 83.100.251.196 (talk) 17:58, 24 September 2009 (UTC)

Another way to consider it: pKa is a thermodynamic equilibrium measurement, whereas broadening and exchangeability on the NMR timescale is a kinetic effect. That's a more formal dichotomy for the explanation that the exchange is "hard to do" without H-bonding or similar mechanistic possibilities even if "eventually" it would be likely to occur. DMacks (talk) 18:09, 24 September 2009 (UTC)

What's actually happening MO-wise? I'm now really what happens with a 4-membered transition state in this proton exchange to the molecular orbitals ... after all, "lone pairs" don't really exist in MO theory. John Riemann Soong (talk) 23:17, 24 September 2009 (UTC)

It's really the same - the electron density is still there - the orbtils can be considered to remain the same - there is no movement of electrons (except minor pertubations) - what does move is the protons in H - they cross a small energy barrier (the potential graph vs distance is W shaped) - and end up inside an identical potential well as they experience before. Someone else might want to clarify this.83.100.251.196 (talk) 00:30, 25 September 2009 (UTC)

can strong acid transform one type of alcohol into another?

I thought of this issue a while ago, but say you start out with 1-butanol or something. I'm purposely reacting it at high heat in aqueous solution with sulfuric acid to rehydrate the first alkene product. So now I would get 2-butanol as a major product, right?

So now, I start out with say, 4-methylcyclohexanol. I add H2SO4 + HOH (and any important surfactants). If I left the reaction running long enough, would I eventually get 2-methylcyclohexanol as a major product? The thing is, the hydration has to occur at least twice (at different positions), so I would get a "migration" of the double bond of the alkene intermediate around the ring? Also, if you dehydrate 3-methylcyclohexanol, what is the major product? Both would depend on secondary carbocation formation -- without hyperconjugative stabilisation, would the double bond prefer to be furthest away from the electron-donating methyl group as possible? What would the effect size (based on (de)stabilisation energy) be?

Also, seeing as I would have a pretty interesting reaction sequence, how would someone determine the relative abundance of the final equilibrium products? (Assuming the system was closed and no water was distilled in the rxn.)

John Riemann Soong (talk) 05:40, 24 September 2009 (UTC)

Assuming your equilibriating methylcyclohexanols - you'd get a fairly broad mixture of 1,2,3 and 4methylcyclohexanols. I'd expect the 2. 3 and 4 isomers to be in about the same amounts. But I'd expect slightly more of the 1methylcyclohexanol.

Also consider that a very small amount of 1(hydroxymethyl) cyclohexanol should be formed to..

The reaction products should be exactly the same for 3methylcyclohexanol if left long enough.

Because you're reacting for a long time the relative proportions of the products should depend on the thermodynamic stabilities of the products, (tertiary>secondary>primary see enthalpies of formation of isomers, or enthalpies of combustion of isomers for proof)

Also consider side reactions - one springs to mind - reaction of carbocation with alcohol to make ether.

"how would someone determine the relative abundance of the final equilibrium products?" - did you mean experimentally or theoretically. Theoretically there are many ways - mostly based on ways of estimating bond strengths in different enviroments - either theoretical, or from spectra, or extrapolated from known examples eg methanol,ethanol,propanol,butanol series83.100.251.196 (talk) 14:43, 24 September 2009 (UTC)

Or set up a bunch of equations with the delta G's. The tertiary is preferred by much; the primary I think we can safely ignore. Tim Song (talk) 19:22, 24 September 2009 (UTC)

Actually for the elimination reaction involving 3-methylcyclohexanol I was thinking the equilibrium product after 1 run (okay let's use phosphoric acid for this one particular inquiry). Basically, since both double bond positions would involve two secondary carbons, which would be more stable? Also, in 1(hydroxymethyl)-cyclohexanol, one of the carbons involved in the double bond is primary, but the other is tertiary, so wouldn't it make it an interesting competitor to the other "double secondary" alkenes? (Also here the double bond is attached to the ring, and not on the ring, so that might improve ring strain.)

Would there be any models to predict the amount of product after 1 cycle, 2 cycles, 50 cycles etc. (assuming idealised conditions and 100% conversion of the initial reagent into cyclohexene). How many cycles would it take for thermodynamic equilibrium to be 85% achieved? John Riemann Soong (talk) 21:55, 24 September 2009 (UTC)

RR'C=CH2 vs RHC=CHR' see [4] cis but2ene combustion 2534kJ/mol isobutene (2methylpropene) 2524kJmol - also see enthalpies of formation [5] this means (CH3)₂C=CH2 is more stable than cis CH3CH=CHCH3. I'm not sure if this extends to exo-cycloalkenes (though I don;t see why not - but note they are in general more kinetically reactive for the usual reasons)

1st cycle, 2nd cycle isn't something we can (easily) do - for any reaction A >> B as soon as some B is formed it can start to do the reactions B >> C and B >> A etc - the relative proportions at time t can be calculated (or estimated) through solving differential equations - needed are the rate constants for each step.83.100.251.196 (talk) 00:23, 25 September 2009 (UTC)

Side reactions ... interesting. Would the ether product actually eventually accumulate, since it seems less reversible? John Riemann Soong (talk) 22:11, 24 September 2009 (UTC)

The products appear in order of their thermodynamic stabilities - it's a curiousity that needs explaining therefor that for a reaction

  A >>> B rate constant k1

and the reverse reaction

  B >>> A rate constant k2 

that at equilibrium k2[B]=k1[A] and so [B]/[A] = k1/k2 = the equilibrium constant - a relationship between kinetics and thermodynamics...(there should be an article on this but I can't find it)83.100.251.196 (talk) 00:23, 25 September 2009 (UTC)

It's kinda shocking that equilibrium constant spends so much time doing heavy math derivations but seems to only discuss it in terms of starting/product concentration ratios, never forward/backward rate constants. Rate equation is a little better. Our whole series of Chemical equilibrium articles appears to have the same problem: target audience of college-level with lots of for a concept that does not require lots of math to understand and is taught in high school. There's no Simple Wikipddia article for any of this either. Please fix! DMacks (talk) 15:37, 26 September 2009 (UTC)

History of large SI prefixes

Hi. Does anyone know to which unit was the prefix Giga- applied in its first documented usage? Also, when was the first time the term Gigabyte was used? Thanks. -- Meni Rosenfeld (talk) 06:23, 24 September 2009 (UTC)

I don't know when the "giga-" prefix was first used. It was only standardized in 1960, but it had certainly been in use long before that. "gigabyte" has been a standard term pretty much as long as we've had bytes because the word 'byte' was coined in 1956, along with 'kilobyte' to mean 1024 bytes - which established the convention of (mis-)using metric prefixes for power-of-two numbers when talking about bytes. Although that was four years before SI was standardized, it was long after modern SI prefixes were in common scientific use. The choice to use Latin prefixes for smaller units (milli-, micro-) and Greek prefixes for big units (kilo-, mega-) was made sometime in the 1700's - so the choice of 'giga-' was essentially made back then - even if nobody knew it at the time! But whether anyone actually USED those terms is hard to say. When I was studying for my cybernetics degree back in the mid-1970's, the idea that you could have a gigabyte was a remote future possibility. Computers had kilobytes of memory and megabytes of disk and tape storage space. Perhaps someone might be talking about a roomful of magnetic tapes and use the word "gigabyte" - but it's unlikely. The word was almost certainly used by SOMEONE in the 1950's and 1960's - but more like in a joke - "You have so many punched-cards stacked up in your office, you'll soon be hitting a gigabyte!!". Of course nowadays, you're supposed to say 'gibibyte' instead of 'gigabyte' in order to avoid the 1024/1000 confusion...I don't know anyone who does that! Incidentally, the power-of-two version of the SI prefixes is not restricted to bits and bytes - it is also applied in communications technology to prefix words like 'baud' and 'erlang' (the first being a unit of data bandwidth, the second being a telephony unit relating to the number of telephone conversations that can be simultaneously made). SteveBaker (talk) 12:30, 24 September 2009 (UTC)

For what it's worth, the OED's earliest citation for this use of giga- in English is from the "Compt. Rend. de la 14me Conf. (Internat. Union of Chem.)" in 1947: "The following prefixes to abbreviations for the names of units should be used … G  giga-  10⁹ × ." The earliest citation for the prefix's actual occurrence in a word is from 1960—a use of gigacycles in a discussion of frequencies. Deor (talk) 16:16, 24 September 2009 (UTC)

It's hard to believe that the first "actual occurrence in a word" for "giga-" was in 1960 when the SI standard containing the "giga-" prefix also came out in 1960. It must have been used for years before that - if only because the SI folks took several years to nail down the standard...so they must have been using it at least a year or two before 1960. But (as I said before) the convention to use Latin prefixes for small units and Greek for large units meant that "giga-" was presumably the "pre-ordained" choice at least 150 years before the SI people actually wrote it down. SteveBaker (talk) 17:26, 24 September 2009 (UTC)

The Greek word that giga- comes from simply means "giant"; it has no numerical significance in Greek, so it wasn't really preordained that its root would come to be used as a numerical prefix denoting 10⁹. (Similarly, the words that mega- and tera- come from mean "large" and "monster" respectively; the ancient Greeks had no specific names for numbers greater than 10,000.) Since the OED is dependent on printed sources and only on sources in English, it's quite possible that giga- words were in oral use in English before 1960 or that they were in printed use in other languages before then or that earlier printed uses have escaped the lexicographers' notice. It's also possible, however, that few scientists felt the need for terms denoting such magnitudes even after the prefix was agreed on. It may be significant that the earliest recorded uses in words are in gigacycles, gigawatts (1964), and gigahertz (1966), since the related topics seem to be exactly the ones in which names for such large units would have been useful at the time. Deor (talk) 18:12, 24 September 2009 (UTC)

Actually, there are two different "Gigabytes" depending on the context. If you are dealing with longterm solid-state storage like hard drives and flash memory, then a gigabyte = 1000³ (1,000,000,000) bytes. If you are dealing with chip memory like RAM, then a gigabyte = 1024³ (1,073,741,824) bytes. There's been a movement among pedants to get people to use the term "Gibibytes" to refer to the latter (binary) definition, but this has never caught on in any common usage, so under most usages, we are stuck with the dual meanings. --Jayron32 16:53, 24 September 2009 (UTC)

Thank you for crystallizing in 3 words the "movement" behind popularizing the godawful term "gibibyte". You are correct — it is a movement among pedants. Let us all move along, and ignore the pedants. Comet Tuttle (talk) 17:35, 24 September 2009 (UTC)

It might be a bit pedantic, but by using the label gigabyte, the hard drive manufacturers are in fact selling 7% short weight! Googlemeister (talk) 19:43, 24 September 2009 (UTC)

It's more than just pedantry. There is genuine confusion caused (noteably by hard disk manufacturers) - and there is really no reason not to have the world of computers brought into line with the rest of the scientific community. We've seen spectacular failures due to people NOT using SI units - and it's only a matter of time until the 1000/1024 confusion bites us. The trouble is that when we only had kilobytes, the error was just 2.4% - when we moved to megabytes, the error grew to 4.8% - at gigabytes, the error is now 7.3%. As we have larger and larger numbers, the discrepancy between the SI usage of those prefixes and that of computer users is growing. Terabyte hard drives already exist - and now the error is 10%! At petabytes, the error is 13%.

Quick! Answer me this: How many bits per second is 56kbits per second? How many bytes are there in 8kbits?

If this error were limited to bits and bytes - we could probably get away with it - but when you talk about a 10Mbit/second communications interface - is that the same thing as a 10Mbaud raw binary data channel? Yes, it is. If you have 10Mbits of memory and you try to transmit them down a 10Mbit/second link will it happen in one second? No! Bits (of memory) use the 1024 convention and bits (of communications bandwidth) use the 1000 convention. It's a god-awful mess. So a bold move is needed to fix this - and the sensible thing to do is to stick rigidly to the SI standard where we use powers of 1000 - and invent a new word for powers of 1024. Now, we can talk about 10Mibits of memory being sent down a 10Mbit data linl

We lost a very expensive and important Mars probe due to the very unsubtle error of confusing SI and US units - how long until we have a disaster of similar cost and embarrassment due to the vastly more likely confusing of 10Mbits (memory) with 10Mbits (communications) ? Or 100Gbytes (hard disk) with 100Gbytes (RAM). We have to learn by our mistakes - and if that means a bit of pedantry - then so be it. One man's "pedantry" is another man's "adherence to rational standards".

SteveBaker (talk) 00:56, 25 September 2009 (UTC)

I agree completely with Steve. In fact the motivation for this question was an attempt to build a case against the usage of "gigabyte" in the binary sense. -- Meni Rosenfeld (talk) 09:18, 25 September 2009 (UTC)

A book from 1970 uses gigabyte,[6] and so does this German computer magazine from 1981:[7]. Fences&Windows 16:54, 24 September 2009 (UTC)

Ok, Thanks for all the replies. -- Meni Rosenfeld (talk) 19:48, 24 September 2009 (UTC)

Not what you asked, but depending on how old you are, you may or may not remember that the giga- prefix used to be pronounced with the first g soft (as in j). You can probably still find this in dictionaries, and in the original Back to the Future. I don't know how exactly the hard g caught on. --Trovatore (talk) 21:53, 24 September 2009 (UTC)

I'm quite old - but I never heard the soft 'j' sound before "Back to the Future". I was in school (just) when the SI standard was announced - it's always been the hard 'g' sound. I kinda suspect the 'j' sound is an American thing. SteveBaker (talk) 00:56, 25 September 2009 (UTC)

Where I live we always pronounce it with a 'j'. I have only heard it with a hard 'g' a few times on television. -- Meni Rosenfeld (talk) 09:18, 25 September 2009 (UTC)

My old Webster's, published in 1961, has no words at all with the prefix "giga" except for variants on "gigantic", which of course starts with a "j" sound but followed by a long "i", although it seems to me I've heard people say it with a short "i" sometimes - as with that variant on "giga-". →Baseball Bugs ^{What's up, Doc?} carrots 09:38, 25 September 2009 (UTC)

Force and gravity

A 80kg woman stands on a scale in an elevator. when it starts to move, the scale reads 700N. (i) is the elevator moving up or down?

(ii) what is the elevators acceleration?

Which science class is this question coming from? Also, being an American, my scale doesn't have N's, it only has LB's. What's an N? →Baseball Bugs ^{What's up, Doc?} carrots 06:56, 24 September 2009 (UTC) P.S. N meaning "Newtons", right? It's been a long time since physics class. →Baseball Bugs ^{What's up, Doc?} carrots 07:25, 24 September 2009 (UTC)

Probably the first physics class on mechanics. In physics we use SI, so yeah, the N stands for Newtons which is the basic unit for force. Oddly enough, the pound (lbf) is also a unit of force, and not mass as people commonly assume. Jkasd 07:29, 24 September 2009 (UTC)

The pound-force is a unit of force, yes. The pound mass is a unit of mass. --Trovatore (talk) 09:03, 24 September 2009 (UTC)

I have a vague recollection that the English System unit of mass is the "slug". If your mass adds up to too many slugs, you might be sluggish. →Baseball Bugs ^{What's up, Doc?} carrots 08:19, 24 September 2009 (UTC)

Indeed: slug (mass). Jkasd 08:15, 24 September 2009 (UTC)

Yep. A slug is equivalent to 32 pounds. A Stone is equivalent to 14 pounds. So the subject in question is about 175 pounds, or about 5.5 slugs, or about 13 stone. →Baseball Bugs ^{What's up, Doc?} carrots 08:19, 24 September 2009 (UTC)

It really has been a long time. If I'm reading the Newton (unit) article correctly, 1 kilogram to 10 newtons is used as a rough estimate, actually 1 to 9.80665. So 80 kilograms would equate to about 785 newtons. So if it's only 700 newtons, that would indicate the elevator is descending, right? Beyond that, I give up. →Baseball Bugs ^{What's up, Doc?} carrots 08:25, 24 September 2009 (UTC)

Well, their weight in pounds actually changes during the acceleration, while their mass in slugs remains constant throughout. (assuming they don't eat or breathe or take into account general relativity...) Also, since this is almost certainly homework, let's wait until they at least show some effort before we do the problem for them. Jkasd 08:28, 24 September 2009 (UTC)

However, the mass in pounds also remains the same. --Trovatore (talk) 09:03, 24 September 2009 (UTC)

So an extra-credit question would be, what if they start out holding a McDonald's Angusburger in their hand and slowly consume it while the elevator moves up and/or down? →Baseball Bugs ^{What's up, Doc?} carrots 08:32, 24 September 2009 (UTC)

Well in that case, a special sort of scale would be needed to measure only the woman's mass, and not anything else. You might even have to take into account such things as the rate of mastication. Jkasd 08:36, 24 September 2009 (UTC)

Hey, let's not delve into her private life or what she does alone on elevators. However, if she started holding the burger and then ate it, I would think her overall mass would be constant. We're assuming the 80 kilograms is her body plus whatever she's wearing or holding. In fact, despite the disparagement, I'm guessing she herself is only about 50 kilograms and the rest is shopping bags full of jewelry. And, apparently, angusburgers. →Baseball Bugs ^{What's up, Doc?} carrots 08:46, 24 September 2009 (UTC)

Mastication = chewing. Jkasd 04:57, 25 September 2009 (UTC)

Try reading the article on acceleration. Also, Newton's laws of motion, especially the second one, may prove useful. If you show some effort towards trying to figure out the problem, we can help you more specifically. Jkasd 07:22, 24 September 2009 (UTC)

Regardless of the above, the only reason a woman would stand on a scale in an elevator would be to convince herself that, for a moment at least, she is a bit lighter. Therefore she sends the elevator down. Unless of course this stupidity has also led her to press the wrong button. How she managed to acquire a scale graduated in Newtons is another question.--Shantavira|^{feed me} 07:38, 24 September 2009 (UTC)

I don't think that your statements will help the OP's understanding, and may even detract from it. Since helping others understand is, as I know it, the primary function of the reference desk, I think you should perhaps retract your comments, or at least make it clear you are joking. Jkasd 08:02, 24 September 2009 (UTC)

Agree with Jkasd here. Shantavira's response is potentially offensive and is unlikely to help the OP. The change in a weight scale in a lift is a not uncommon concept in physics and while it's generally a thought experiment, I'm sure quite a number of people do it each year and there's no reason why a woman can't be interested in physics. Also it's possible e.g. the woman is anorexic and is trying to convince herself she doesn't need to put on weight or perhaps she's using it as a motivational device to stop herself putting on weight. Finally the person who set the question is generally unlikely to consider such issues so it could be either way when it comes to the actual question. Nil Einne (talk) 10:04, 24 September 2009 (UTC)

F=m*a means that Weight = mass * gravity. What's the woman's weight when the lift isn't moving? Is 700 N more or less than her normal weight?

Think about when you're in a lift. When you accelerate upwards, do you feel heavier (more weight than normal) or lighter (less weight than normal)?

The total acceleration is the acceleration of the lift and the acceleration due to gravity. F = m * (a + g). Rearrange to find a and put in the numbers, but make sure you get the signs right, because F, a and g are vectors (they have direction). AlmostReadytoFly (talk) 09:15, 24 September 2009 (UTC)

Yes, but up-down velocity also plays a role. If the elevator had no acceleration but was in a constant speed free-fall, the woman would be weightless, relative to the elevator on which the scale in placed. So, how do we add velocity to that equation ? Specifically, how can we determine how much of the apparent weight reduction is due to downward acceleration and how much is due to downward velocity ? You could even have an upward moving elevator which has arrived at it's destination and is decelerating (that is, accelerating downward), to arrive at a weight of 700N. Thus, I'm plain inclined to think that neither part of this Q can be answered with the info provided. Perhaps if we knew the range of speeds at which the elevator travels and the range of acceleration, we may be able to come up with one or more answers. StuRat (talk) 13:11, 24 September 2009 (UTC)

Yes, we can. You've made a few mistakes in your arguments, Stu... First, an object can't be in "constant speed free fall", cause that's not free fall. Free fall means an acceleration of 9.8m/s² downwards. If it goes down with a constant speed, th reading will be her actual weight, ie, when measured in her house.
Since the weight is reduced, the elevator is definitely accelerating down. Since it has just started moving, it is going down.
Now, Since the weight loss is 100N, the acceleration has caused a weight reduction of 784-700=84N. Now 84=m*a, therefore a = 1.05m/s². This is the acceleration with which the elevator is moving downwards... Rkr1991 ^{(Wanna chat?)} 13:26, 24 September 2009 (UTC)

(after edit conflict) Agreed. StuRat is (unusually) writing nonsense. Velocity doesn't come into the argument! Only acceleration of the lift (relative to the building) is significant here. The question would be unanswerable except that it says "when it starts to move" so we can deduce that the initial acceleration is downwards, and so the lift must be going down. Dbfirs 13:33, 24 September 2009 (UTC)

Oops, I think the problem is my the definition of "acceleration". I was only thinking of acceleration due to the elevator's motor, but there's also acceleration due to gravity to consider. So, I was thinking she could be weightless without any action from the elevator's motor, as if the elevator just dropped. While this is correct, there still is acceleration due to gravity. Upon re-reading the Q, I see they didn't specify why the elevator was accelerating, only what it's accel was. Also, I was confusing two different cases of free-fall. In free-fall without atmosphere, it's correct to say the object is accelerating at one g. In the case where there is atmosphere, and terminal velocity has been reached, then there's no acceleration, but the weight of the lady in the elevator would be normal (other than the weight lost by messing herself). :-) StuRat (talk) 15:36, 24 September 2009 (UTC)

A Newton is 102 gram. Either you learned that or (in the US) probably didn't. So before the elevator moves the scale reads 80 x 0.102 = 785N. When the elevator accelerates down the reading reduces by 85N. Applying Newton's 2nd law F (N) = m (kg) a (sec^-2) shows that the downward acceleration is 85 / 80 = 1.1 meters per second per second, to 2 sig. fig. accuracy.Cuddlyable3 (talk) 15:10, 24 September 2009 (UTC)

A Newton is not any number of grams. Grams measure mass and Newtons measure force. The force of gravity at the earth's surface at sea level makes it so that 102 grams of material will be pulled downward with a force of 1 Newton. --Jayron32 16:48, 24 September 2009 (UTC)

Jayron32, how many elevators with 80kg women standing in them do you know that are not on planet earth ? Just a round figure will do. Cuddlyable3 (talk) 18:54, 24 September 2009 (UTC)

Are you saying that 800N Women have round figures? I know 800N sounds a little chunky...but...well...really? SteveBaker (talk) 23:29, 24 September 2009 (UTC)

But it is a common mistake in an early physics class to confuse weight with mass, so we need to be absolutely clear for the sake of the OP's understanding. Jkasd 19:06, 24 September 2009 (UTC)

How many 80kg women standing on scales that measure in Newtons in elevators do you know that are on planet earth? :) Rckrone (talk) 22:06, 24 September 2009 (UTC)

Snows all year round

The map shows areas of the US with permafrost where snow can lie all year without melting.Cuddlyable3 (talk) 15:41, 24 September 2009 (UTC)

What are the parts of the US that snows all year round? --Reticuli88 (talk) 13:02, 24 September 2009 (UTC)

Probably only in northern Alaska or very high altitudes (e.g. the Rockies). --98.217.14.211 (talk) 13:49, 24 September 2009 (UTC)

In much of Canada it can snow any month of the year, but typically doesn't. I would suspect that's the same with a lot of northern US states, specifically Montana, North Dakota etc. Is that what you mean? TastyCakes (talk) 16:18, 24 September 2009 (UTC)

I had a friend who died in Colorado when his car slid off the road during a snowstorm in July. And Colorado is pretty far south. In the high Rockies, it can snow on any day of the year; though I am not sure of anywhere in the lower 48 where there will be snow on the ground all 365 days of the year. Even in Barrow, Alaska there is not year-round snow on the ground. --Jayron32 16:35, 24 September 2009 (UTC)

Snow line. Sagittarian Milky Way (talk) 17:03, 24 September 2009 (UTC)

There are literally hundreds of places in the Rockies, Sierra Nevada, Cascades, and Olympic range where snow sticks all year round. The southernmost that I'm aware of are in central California in Sequoia National Park. Looie496 (talk) 18:26, 24 September 2009 (UTC)

Science Lab Cleaner

I am a new Science teacher in a Jr./Sr. High school. What type of cleaner I should use to scrub beakers and other equipment after use in the lab? Answer needs to be safe for student use, please. —Preceding unsigned comment added by Mleisy (talk • contribs)

What was in them? If they were used for aqueous reactions, then hot water is a good start (and might even be completely sufficient). Alconox is a standard series of cleansers for glassware. DMacks (talk) 15:07, 24 September 2009 (UTC)

The cleaner you should use is called a lab technician.--CruelSea (talk) 15:21, 24 September 2009 (UTC)

If you are new to practical science teaching then for the safety of students and yourself you must be properly aware of how to store and handle (not literally!) dangerous chemicals such as undiluted acids (e.g. never add water to sulphuric acide), phosphorus and mercury; precautions such as using a hood to protect against fumes; which reactions can be explosive and how to avoid risks of poisoning, scalding or electric shocks.Cuddlyable3 (talk) 15:34, 24 September 2009 (UTC)

I agree with Cuddlyable -- it's pretty important to get adequate training yourself before trying to teach a practical lab course. You could try the National Science Teachers Association for more information. --- Medical geneticist (talk) 16:06, 24 September 2009 (UTC)

I also agree. If you have to come here to ask such basic questions then you aren't ready to be a science teacher. Don't do any practical exercises with your classes until you have learned basic lab safety. --Tango (talk) 16:30, 24 September 2009 (UTC)

I used to use Alconox for cleaning glassware. I also used it to scrub down counters and stuff, although I think there's better things for that. I never had a problem with it, and I'm sure there are other similar products. TastyCakes (talk) 16:22, 24 September 2009 (UTC)

I'll second alconox. That stuff will clean the white off of rice. It's good stuff. IIRC, they make a hand-washing version and an automatic dishwasher version that works well too. --Jayron32 16:32, 24 September 2009 (UTC)

According to the MSDS it contains ~10% sodium carbonate , as well as sodium phosphate - that's a strongly caustic solution - and would make a potential 'emergency' if splashed in the eye. What I don't understand is how the MSDS passes it off as 'may cause eye irritation'. Goggles would be absolutely necessary for this. It is strongly basic enough to be classed as corrosive.

The intention seems to get something safe for students to use - why not soap solution, "fairy liquid" or similar non-branded products, plus hot and cold water.

Alconox MSDS says pH of a 1% aqueous solution is 9.5. That's pretty tame! Mix up a large batch and give out containers of the solution (similar form to dish detergent or some other squeeze bottle?). That way they have a safe-to-handle liquid instead of the heavy-duty concentrated solid. As a bonus, they'll use much less of it (save $). If a few-% is the standard solution, that's only a few grains of solid per washing, but students have a habit of dumping on the soap. DMacks (talk) 13:48, 30 September 2009 (UTC)

Torque Practice Problems

Attempting to lift a 450-lb rock, a 180-lb person stand on the end of a 5-foot pry bar. Hint: The pivot of the pry bar is 4 feet from the end. Can the person lift it?

I know Torque is (force)(Lever Length)

but I do not know where to begin.

Accdude92 (talk) (sign) 17:11, 24 September 2009 (UTC)

For it to move, the torque on the side of the bar with the person standing on it must be greater than the side with the rock (or the bar bends or breaks or something!). Under normal gravity, the force due to a one pound mass is one lbf (pound-force) - so the force on each end is equal to the weight on that end. So if you know the distance of each weight from the fulcrum (pivot) you can calculate the two torques and compare them. SteveBaker (talk) 17:17, 24 September 2009 (UTC)

Enlarged nostrils

We don't pick our noses.Cuddlyable3 (talk) 18:38, 24 September 2009 (UTC)

Does excessive nosepicking contribute to enlargement in the nostrils in any way? This is not a personal medical question, rather more of a curiosity question, owing to the fact that nosepicking is a relatively common, albeit bad, habit amongst a large part of the worlds population. I hope the question made sense enough to answer it. Thank you!

No. Lamarck was wrong. ~ Amory (user • talk • contribs) 18:52, 24 September 2009 (UTC)

This has nothing to do with Lamarckism, or its being incorrect. Nobody has asked whether the acquired characteristics are hereditary. Acquired characteristics are real (if you exercise your arm, it will get stronger), just not genetically transmissible. --Mr.98 (talk) 19:44, 24 September 2009 (UTC)

This doesn't relate to Lamarckism. It is possible to enlarge the nostrils by constantly stretching them, but it seems extremely unlikely that nosepicking could do it. (And regarding the picture, see this Google Image search.) Looie496 (talk) 19:10, 24 September 2009 (UTC)

I felt inheritance was implied since the image was used to apply the concept to an entire species. ~ Amory (user • talk • contribs) 03:40, 25 September 2009 (UTC)

This is not advice to experiment with self modification of body parts, since injury could easily result. Some tribes or peoples insert round objects into slits cut in the lips, or in the earlobes to achieve "beauty" by their standards. Over time, the tissue stretches to amazing extents. So nostril enlargement seems quite possible. Goatse could probably have stretched his nostrils to an amazing extent, had he set his mind and fingers to it. Edison (talk) 21:16, 24 September 2009 (UTC)

Is nose-picking bad? Obviously it's frowned upon in Western culture, but does anyone have any info on whether it's harmful (or maybe even beneficial)? Rckrone (talk) 00:35, 25 September 2009 (UTC) I should've just consulted the nose-picking article... Rckrone (talk) 00:38, 25 September 2009 (UTC)

Nose picking is frowned upon, because the boogers (boogies for Brits) on the fingers are considered disgusting. But it allows easier breathing by reducing the constriction of the nasal passages due to crusted mucous. A Neti pot is a somewhat splashy way of achieving the same goal of ridding the nasal passages of deposits. Edison (talk) 03:19, 25 September 2009 (UTC)

Minor correction: it's bogies (singular bogey [8], pronounced with oʊ). A boogie is what you blame it on. AlmostReadytoFly (talk) 07:26, 25 September 2009 (UTC)

is the goverment out to get us?

up for discussion.

iv allways been interested in government conspiracies, and lately iv heard from a person that reads up on all the crap going on with the economy (in the U.S.) . He showed me in a paper, on a discustion, a politic mentioned that we would be out of this recession if we lost a third of the population and i cant help but think what if thay used the swine flu as a way to kill off how ever many people thay want or need to get out of the recession by giving out false vaccines? and if thats the case, then all thay would have to do is sell a true vaccine at a higher price. with the way healthcare is calapsing, all the lower class residents may not be able to afford it. it would be an easy way to kill off poor residence leaving a population of much wealthier people. do you think the U.S. Government would go that far? DanielTrox

No, that seems pretty silly to me. TastyCakes (talk) 17:51, 24 September 2009 (UTC)

That is ridiculous. Even if it would work, they would never do it, and it wouldn't work. If you wipe out a third of the population the economy would completely collapse, it wouldn't recover faster. You can't have an economy without a workforce and a workforce needs to include people doing a wide range of jobs, from street sweeping to bank managing. Even if they could wipe out 1/3 of the population while maintaining per-capita GDP, the country's total GDP would inevitably drop, making the US less influential on the international stage, economically, politically and militarily. --Tango (talk) 17:57, 24 September 2009 (UTC)

well even if its not a likely scenario, its still interesting to think about. Its good to hear the opinion of some one more educated in Government. DanielTrox

This is the reference desk, not a forum or soapbox. --Mark PEA (talk) 18:08, 24 September 2009 (UTC)

The custom here is that nonsense is in small font at the end of a section. Small != Big. End != Beginning. Cuddlyable3 (talk) 18:32, 24 September 2009 (UTC)

Uh, broken window fallacy anyone? More citizens always means more GDP, less citizens always means less GDP. More workers means more GDP. Note that it's far better to have 200 million people with 10% unemployment than it is to have 30 million people with 2% unemployment. In the first case, it just means you're using resources inefficiently. Killing off citizens to get yourself out of a "recession" is like not drinking water in a desert because you know you'll sweat a great deal of it. John Riemann Soong (talk) 18:37, 24 September 2009 (UTC)

Unless of course the third wiped out are the social security and medicare hogging, old aged pensioner types or the chronically unemployed ;) TastyCakes (talk) 19:50, 24 September 2009 (UTC)

If a third of the population fell into those categories, you might have a point, but I wouldn't include OAPs - they often do useful voluntary work (babysitting grandchildren, for example) and they are consumers, so stimulate productivity in other people. --Tango (talk) 19:55, 24 September 2009 (UTC)

There are a lot of problems with the idea. From an economic standpoint, it doesn't work out well—killing off a third of the population would cripple, not stimulate the economy.

From a governance standpoint, it doesn't work out well either. In a democratic government, politicians are mostly interested in things they can point to as something they did, or avoiding things that will later be used as ammunition against them. This particular event would satisfy neither—even if the conspiracy was kept secret, the politicians would not benefit. They'd be accused of grossly mismanaging the outbreak, and even if the economy DID bounce back at a much later date, they would never be able to take credit for it. If it did leak out in any way (and there are many ways that could happen), then they'd be treated like Stalinists.

How would it leak out? Well, it doesn't take many independent researchers to see if a vaccine doesn't work in an outbreak, and to check the vaccine itself to see if that's the problem.

In short: the possibility of exposure is high, the possibility of actually benefitting is low. That's a recipe for not doing it. Now, there are always exceptions—our governmental figures are often less rational about such things than we'd imagine (Nixon provides great examples of this, where his personal psychology got in the way of making the rational political decision). Still, in the absence of ANY evidence that this sort of thing would be going on, I can see NO reason to even entertain it as a realistic possibility.

Be aware—there are people "out to get you." There are people who want to hook you on addictive products, take your money, are happy to ruin your lives and health in the meantime. They have immense political influence and are able to spend literally billions of dollars lobbying our politicians and pushing their bills through Congress. They are probably a far greater threat to the idea of democracy, and to your personal livelihoods and freedoms, than any government conspiracy. --Mr.98 (talk) 19:37, 24 September 2009 (UTC)

anouther thing i was wandering about is this whole, "Obama is getting the power to shut off everyones access to the internet" thing. i know its supost to be in terms with national security, but is'nt that a little to much? also i read in a news paper that he wants to make USS troops to police the people of America with automatice weapons. whats that all about? sure its suport to be for protection, it seem a little strange to me.

The first would be censorship, and I doubt it's increasing under the new president's administration. There is very minimal censorship in the United States. Perhaps somebody has convoluted the debate about network neutrality with censorship; there are legitimate concerns about the telecommunications technology, but it's much more subtle than "turning off the internet." Your second question appears to be about martial law; this is also very uncommon in the United States, and I doubt it is increasing under the new administration. You might find the articles about these topics informative; it will help you make up your own mind about whether these phenomena are actually a problem in our present society. The general consensus of most people seems to be that these are not real problems; but fringe groups tend to lay out such claims about every government and president - not just the Obama administration. Nimur (talk) 20:57, 24 September 2009 (UTC)

The first isn't strictly censorship, but it's certainly an issue that's still very much theoretical. There's a proposed Senate bill that would give the government some sort of emergency powers over private networks. The rationale isn't clear, the scope isn't clear, and in any event, untold numbers of stupid bills get proposed every year and die quiet deaths in committee (or earlier). — Lomn 21:04, 24 September 2009 (UTC)

If the consequences of the Black Death are anything to go by, wiping out 1/3 of your population using an infection isn't a great policy. It exacerbated recession, and lead to persecution and peasant revolts. Fences&Windows 21:04, 24 September 2009 (UTC) p.s. Original poster, the government is out to get you. Lock all the doors, pull the curtains closed, turn off the television and the lights, and firmly put on your tin-foil hat. Fences&Windows 21:07, 24 September 2009 (UTC)

As I understand it, it created a labor shortage, and that's usually good for the people. →Baseball Bugs ^{What's up, Doc?} carrots 23:11, 24 September 2009 (UTC)

Not really. Yes, it increases wages, but that extra money has to come from somewhere - ie. prices go up. It's just inflation, it isn't really good for anyone (unless you have lots of debts, I suppose). --Tango (talk) 23:36, 24 September 2009 (UTC)

If nothing else, it likely made the gene pool stronger. →Baseball Bugs ^{What's up, Doc?} carrots 23:40, 24 September 2009 (UTC)

Actually it makes the gene pool smaller, which generally means it is weaker. Yes, you'll have better overall immunity to that particular disease, but that's the only improvement, really. There will be a small number of people with other congenital medical problems that die that wouldn't have done had they not had those problems, but that's too small a number to make any real difference. I think the reduction in diversity would be more significant. --Tango (talk) 00:02, 25 September 2009 (UTC)

Some major misunderstandings of economics here, and also, failure to account for opportunity cost. A labor shortage isn't good for anyone in the long run. It's good if you're a particularly bad worker and you couldn't find a job before, but labor shortage means the economy produces less. The economy produces less => the economy is poorer. There's less food to go around. In the long-run, there's no such thing as a "labor oversupply", and all labor is useful (unless you're so parasitic that your productivity is less than your criminal parasitism). The only issue is how to allocate it. The minimum wage however, makes it hard for underproductive workers to find jobs. Of course the minimum wage didn't exist back then John Riemann Soong (talk) 00:33, 25 September 2009 (UTC)

And all because they tried to kill all the cats because they were witches. Poetic justice. →Baseball Bugs ^{What's up, Doc?} carrots 00:41, 25 September 2009 (UTC)

According to Pyongyang: A Journey in North Korea, the North Korean government, while not providing adequate medical care, has stated that the country's "natural" population size is smaller than its current one. There may be a better source for this claim than a (non-fictional) graphic novel. AlmostReadytoFly (talk) 07:48, 25 September 2009 (UTC)

According to our article on the 1918 flu pandemic, that particular virus only managed to infect about third of the population of the United States, and only killed about 0.5%. Swine flu is milder and there was no vaccine in 1918. Even if you wanted to kill off this number of people I don't think you could do it with swine flu. Hut 8.5 14:04, 25 September 2009 (UTC)

well just in case im going to lock all my door and i have a years worth of food under my bed. take that America! DanielTrox

Is that because you never made your mini hotplate? Nil Einne (talk) 20:50, 25 September 2009 (UTC)

LMFAO Talk Shugoːː 18:12, 30 September 2009 (UTC)

Annulenes vs. cycloalkanes

I'm quite confused by the fact IUPAC organic nomenclature apparently makes it compulsory to use annulenes in polycyclic compounds, as I fail to understand the ambiguities alluded to here and here (this probably has to do with how unwiledy the online material is to consult).This policy results in the central ring in Butriptyline being treated as containing double bounds which must be "removed", a rather counterintuitive approach to me.

I'm also confused by the way even a simple single-bound fusion of a cycloheptane and naphthalene must be described as a 7,8,9,10-tetrahydro-6H-cyclohepta[b]naphthalene according to the online tool even though it seems to me that cyclohepta- clearly implies there cannot be double bounds unique to that ring to begin with! (Why not to use annulenes there too, anyway?) Circeus (talk) 18:45, 24 September 2009 (UTC)

I'm not sure I follow what question you are meaning to ask, but the prefix for seven is "hepta-" and not "hept-". The a is dropped before vowels by convention, but if it does not precede a vowel, then the "hepta-" is correct, and does not imply a single- or double- bonding situation in any manner. --Jayron32 18:48, 24 September 2009 (UTC)

Okay, but it still confuses me awfully that the ring is assumed to be maxed in double bounds, but named as an otherwise unqualified cycloheptane: putting two double bounds results in 6H-cyclohepta- being the prefix, which is only possible with the assumption that the ring requires a stated hydrogen (I think that is the proper term), which a mere cycloheptane ring certainly doesn't. Circeus (talk) 19:09, 24 September 2009 (UTC)

<Sympathy>I agree - it contains anachronistic, unintuitive elements for anything other than the simplest compounds - full of legacy components.

However connnectivity lists aren't suitable for searching (because they can be constructed in various combinations of ways depending on how you lable the atoms, (and there isn't a simple way to decide which atom gets to be No.1 , No.2 in an abitrary structure.. International Chemical Identifier is an example - you still need to know which order to lable the atoms.

The best bet would be to always use an assigned ID ie CAS registry number - however nobody does that - they're not memorable, and very old literature doesn't have them.

There is no real logic to it, which is the simplist explanation.83.100.251.196 (talk) 20:02, 24 September 2009 (UTC)

<more sympathy>I agree about labelling a saturated ring as an anullene and then adding H's seems silly.83.100.251.196 (talk) 20:03, 24 September 2009 (UTC)

My problem is truly about treating the ring as if it were an annulene bt WITHOUT actually calling it one in the name. Circeus (talk) 21:36, 24 September 2009 (UTC)

To restate my first question: can somebody explain to me the ambiguity that requires the use of the name "10,11-dihydro-5H-dibenzo[a,d][7]annulene" for the ring system in butriptyline instead of the far more straightforward and transparent dibenzo [a,d]cycloheptane? Circeus (talk) 21:36, 24 September 2009 (UTC)

:Wouldn't "dibenzo" imply, or be easily confused, with a benzyl-type attachement, which is not at ALL what is going on in that ring system... --Jayron32 03:43, 25 September 2009 (UTC) nm. not sure what I was thinking. --Jayron32 03:44, 25 September 2009 (UTC)

The deal is, the "cycloheptane" ring is not saturated; its created by a "methyl" and an "ethyl" bridging groups between the two benzene rings. In fact, 4 of the 7 carbons in the "cycloheptyl" section are sp2 carbons. That's pretty unsaturated if you ask me. --Jayron32 03:47, 25 September 2009 (UTC)

It would make sense if they had interacting pi systems -- but nope! John Riemann Soong (talk) 04:10, 25 September 2009 (UTC)

Such facts make no difference in naming here. IUPAC naming is not meant to be convenient or handy, just scrupulously consistant and unambiguous. The deal is, if you follow the name given, you should get the resulting structure, regardless of whether or not one could conceivably come up with a "simpler" name. I am not sure the "a" "d" connection convention applies to anything EXCEPT annulenes, there are completely different naming conventions for Bicyclic molecules, using numbers and not letters. I don't think that you can assign letters to cyclohexyl the same way you could [7]annulene. That may be part of the problem. --Jayron32 04:21, 25 September 2009 (UTC)

Actually, now that I look at it, the problem is indeed what you describe ("I don't think that you can assign letters to cycloheptyl the same way you could [7]annulene."). Rule 21.5 which covers this locant type has to do with "polycyclic hydrocarbons with maximum number of non-cumulative double bonds", so indeed (according to the rules) to use that format at all one would have to start from an Annulene. Circeus (talk) 06:26, 25 September 2009 (UTC)

Re-opening my refrigerator door

Normally the door on my refrigerator takes about 5 lb. of force to open. At times, depending on how many seconds have passed since I closed it, a considerably larger force is needed. Just now I tried to open the door about five seconds after I closed it, and I had to use 15 - 20 lb. of force. Is air pressure differential causing this, or is something else going on?

I have a side-by-side refrigerator/freezer and there are valves between the fridge and freezer compartments to allow for more efficient cooling (or so says the owners manual). WHat I have found is that if I open and close the freezer, it will "suck some air" out of the fridge and make it much harder to open the fridge. This may be similar to what is happening in your situation. --Jayron32 19:33, 24 September 2009 (UTC)

Is this a refrigerator with a mechanical latch or a plastic strip magnet to hold the door shut? Cuddlyable3 (talk) 19:36, 24 September 2009 (UTC)

My refrigerator is a side-by-side model with magnetic strip (I haven't seen a mechanical latch refrigerator in decades - are they still made?)

I think not - paranoia about children locking themselves inside the refrigerator has largely chased the "locking" or "latching" refrigerators off the market. Nimur (talk) 21:00, 24 September 2009 (UTC)

You open the door, and the cold air falls out, warm air moves in. Close door and the air cools and the pressure drops - hence the door is harder to open. I have a similar problem in the lab with a -40°C freezer - easy to open then if you want to open it again in a few minutes - it's virtually impossible unless one eases back the seal at a corner.  Ronhjones  ^(Talk) 21:05, 24 September 2009 (UTC)

(edit conflict) PV=NRT is the gas law. Some back of the envelope calculations, with an implausible result: When the box is opened, room temp air replaces the chilled air. The door closes easily because the pressures inside and outside are the same. The air inside experiences a pressure drop due to the temperature drop, from perhaps 293 k to 277 k for a typical refrigerator (70 F to 40 F), which should produce a 5% pressure drop due to a 5% drop in absolute temperature. If the door is 32 inches feet by 36 inches, then there is a pressure differential on the door of 1152 square inches times 5% of 14.7 pounds per square inch, so that 846 pounds is the pressure differential on the door. This seems way too high. The refrigerator has a vent or drain to allow pressure equalization, and the air does not fully warm up to room temp while the door is open, nor does it cool to the refrigerator temp before the vent tube has done its work, which may account for the smaller pressure reported. I get a more impressive result with my deep freeze, which has a larger door and is at zero F. Edison (talk) 21:08, 24 September 2009 (UTC)

I suspect (without proof) that it's actually the magnetic seal that's doing this. After you close the door, it sometimes takes several seconds for the magnetic strips to align themselves - sometimes they do this perfectly (resulting in a door that's hard to open) sometimes imperfectly - making it a lot easier. SteveBaker (talk) 21:42, 24 September 2009 (UTC)

No Edison is right, it is the temp contracting air from the room. Apart from my intuition I have a spare switched off (so warm) freezer and fridge in the stables and I cannot get either to go into hard to open mode, on top of which when my (cold) upright freezer in the house does it I can get rid of the phenomenon immediately by breaking the air seal at a point and the huge sucking noise is notfrom a magnetic strip. --BozMo talk 21:55, 24 September 2009 (UTC)

This sure seems like a simple problem to fix. A little pin-hole would allow the pressure to equalize without any significant impact on energy efficiency. StuRat (talk) 01:53, 25 September 2009 (UTC)

Would a hole the size of a pin really accomplish anything? I would think something that small would make no detectable difference, if any difference at all, not to mention that a pin-sized hole would likely not be maintained by the cushiony material that serves as the gasket, so to speak, of the door. DRosenbach ^{(Talk | Contribs)} 12:41, 25 September 2009 (UTC)

Have you ever noticed how airplane windows have three small pin holes near the bottom ? I believe this is to allow pressure to equalize between the passenger compartment and the area between the inner window and the outer, pressure-proof window. I doubt if air pressure changes occur nearly as fast in a freezer as in an airplane (would your ears pop if placed inside a freezer ?). Also, I didn't say that the pin hole needed to be in the gasket, it could be drilled in the side anywhere that won't rupture the coolant lines. StuRat (talk) 15:34, 25 September 2009 (UTC)

Most refrigerators with freezer compartments have a drain to a sump from which the icemelt from the automatic defrost is evaporated. This allows gradual pressure equalization, like a pinhole would. When the door closes after being open for a long while, I hear bubbling in the drain system as outside air enters. The fact that the door is opened by pulling on one side likely makes it easier to fight the atmospheric pressure being slightly greater than the pressure inside, compared to if one had to pull on the center of the door. Edison (talk) 15:17, 25 September 2009 (UTC)

When I had this problem with an old (now defunct) deep-freezer, I glued a piece of rigid plastic to the magnetic gasket at hand height. Pulling on this allowed air to enter and made the door easy to open. Dbfirs 12:09, 26 September 2009 (UTC)

Uranium hexafluoride

Here's an odd one - I saw several UF6 containers (big ones on lorries) going to rotterdam from england. Type UN2978. Does it have any uses - what would the dutch do with it? (Perhaps they were empty?). Where would it be going? and why? So many questions.83.100.251.196 (talk) 20:07, 24 September 2009 (UTC)

Uranium hexafluoride gas is used in the purification of uranium, because it is a low-boiling compound, and easy to turn into a gas, you can seperate out the different isotopes of uranium (U-235 and U-238) relatively easily using gas centrifuge techniques. Since the Dutch have both power-producing and research level reactors, see List_of_nuclear_reactors#Netherlands, there are any number of reasons why they would be purifying Uranium in this manner. The purification plant may have been in the Netherlands, and the material may have been going to the UK for use in their reactors, or visa-versa (UK purification plant, Dutch reactors) or any number of other possibilities. --Jayron32 20:15, 24 September 2009 (UTC)

The dutch URENCO, french Eurodif and the UK URENCO have enrichment facilities of notable throughput, but from the container it is not clear if the stuff is enriched depleted or normal grade, so it is not clear if it was going or coming from the enrichment. --Stone (talk) 20:23, 24 September 2009 (UTC)

Doesn't UN2978 mean it's useless (except for uranium jewelry, cufflinks etc) [[9]] - does anyone know about UK enrichment flows - I assumed it was all done at sellafield - and stored in the UK.83.100.251.196 (talk) 20:43, 24 September 2009 (UTC)

Not much, but I do know that Urenco, as linked by User:Stone, is actually based near Capenhurst in Cheshire. AlmostReadytoFly (talk) 21:21, 24 September 2009 (UTC)

Was it necessarily going just to the Netherlands? Rotterdam is on the way to Germany, and RWE has contracted fuel reprocessing to UK companies before now (not always with success [10]). AlmostReadytoFly (talk) 21:15, 24 September 2009 (UTC)

The Dutch URENCO facility (on the other end of the country from Rotterdam) is quite a large uranium enrichment facility. You can see its tanks of UF6 from Google Earth—it looks a lot like the U.S. facility at Oak Ridge.

Anyway, UN2978 is listed as "Uranium hexafluoride, fissile excepted or non-fissile". I can't tell if that means it is just unenriched uranium or if it is depleted uranium. I suspect the former as there isn't a whole lot of reason to ship DU (most nuclear countries will have lots of the stuff). --Mr.98 (talk) 02:28, 25 September 2009 (UTC)

Degradation of methylmethacrylates

This is one sentence from a book about dental materials. Dental composites contain such monomeres, as BISGMA, TEGDMA, UDMA. I'm interested in chemical formula of this process mentioned here: Formaldehyde is very likely generated by an oxidation of unsaturated methacrylate groups, such as during polymerization or/and as a degradation product of the oxygen-inhibited surface layer (or oxygen-methacrylate polymer)

Chemical formula of dental composite monomeres

Renaldas Kanarskas (talk) 22:22, 24 September 2009 (UTC)

The reaction sounds like ozonolysis, this link [11] suggests that both Ozone and OH radical (found in air?) can cause this reaction - the formaldehyde seems to come from the =CH₂ groups in unpolymerised methacrylate. I'n not sure that there isn't something else going on as well.83.100.251.196 (talk) 23:12, 24 September 2009 (UTC)

this paper [12] suggests that the peroxide initiator for the polymerisation might also contribute to formaldehyde formation, but this should occur in the polymerised layer, where as this abstract [13] says " A correlation coefficient, r = 0.83, was found between released formaldehyde and the thickness of the unpolymerized surface inhibition layer" - I assume this means that there is a correlation between unpolymerised methacrylate and formaldehyde.83.100.251.196 (talk) 23:31, 24 September 2009 (UTC)

this paper [14] suggests that OH radicals catalyse the oxidation of methacrylate to formaldehyde.83.100.251.196 (talk) 23:31, 24 September 2009 (UTC)

 H2C=CMe-C(O)-O-R-O-C(O)-CMe=CH2 + 4[O]   >>>   2 H2C=O + O=CMe-C(O)-O-R-O-C(O)-CMe=O
  where [O] comes from O2 (promoted by OH radical) , or maybe O3

83.100.251.196 (talk) 23:38, 24 September 2009 (UTC)