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Posts posted by UC

  1. I recently did a synthesis that involved heating benzaldehyde and pyrrole in refluxing propionic acid. Just...no. Very fortunately, the solvent was not butyric acid instead. I'll take my prize, now.


    I rather like the smell of dimethyl maleate, though it has a pretty low vapor pressure so I didn't know it smelled good until I spilled a drop on a glove and walked around wondering what that nice smell was for half an hour.

  2. A small amount of variation happens sometimes. It probably has more to do with the instrument shimming and proper referencing than anything else. Concentration of sample may also be an issue as various kinds of intermolecular bonding change chemical shifts.


    I'd say if you have:


    1) the right number of peaks

    2) roughly appropriate ratios of integration area/peak height (integration is better, but sometimes things overlap a bit) for proton spectra (this goes down the toilet for carbon). I say roughly appropriate, because different protons have different relaxation times and the integration/height ultimately comes down to instrument paramaters versus these relaxation times. As an example, phenolic hydrogens consistently come up "short" with a relative integration of about 0.6 on the NMR I usually use. I could increase the signal collection time and the integration would increase to ~1.0 relative to other hydrogens, but it's not worth it unless it's for publishing.

    3) roughly proper locations


    Then, you're fine.

  3. The thing I least like about the forums is that the same stupid questions and topics come up time and time again. At some point you stop replying to the threads because you know there really isn't any point - you are just talking to a brick wall.


    But I don't suppose there is much the mods can do about that complaint...


    Not until we get a punch-in-the-face-via-internet feature up and running. Our top scientists are working feverishly on this, I promise.

  4. If you only consider enthalpy (that's changes in bond strength) then yes, endothermic reactions are easy to reverse. However, for a reaction to occur, the change in Gibbs free energy has to be negative. This depends on the change in enthalpy and entropy.




    If the enthalpy is positive (i.e. endothermic) then the change in entropy (S) has to be very positive to overcome this.


    So if a reaction is endothermic, there has to be a large increase in the disorder of the system to make it work.


    Fixed that for you.

  5. Cold temperatures mean a lack of molecular kinetic energy. Temperature is molecular kinetic energy in fact. So anything spinning rapidly when cold is just ridiculous, unless it spins even more rapidly when hot. Similarly ridiculous is something releasing energy when cold for the same reasons.


    Secondly, why would spinning cause something to polarize? I'm apparently missing a chunk of logic here, because that makes no sense.


    Hydrogen gas is indeed susceptible to becoming an instantaneous or induced dipole, as are all other bonds for that matter. However, these have nothing to do with spinning or emitting energy.

  6. You can just buy ethyl lactate by the quart in some hardware stores. It's touted as a green/renewable paint stripper I believe. You'd have to cleave the ester, such as with NaOH, but such a solution, if lacking excess NaOH would be fine for preparing metal lactates.

  7. The acid in just supporting electrolyte for a battery. Any salt should work, but because chloride ion is fairly corrosive try something like sodium sulfate or trisodium phosphate.


    I think you'll get a higher voltage out of these cells if you construct something like a copper-zinc cell with copper sulfate electrolyte. That should manage about 1V. Feel free to stack as many in series and parallel as necessary to ramp up the voltage and amperage.


    This may interest you: http://www.periodictable.com/PopularScience/2007/02/1/Scan.small.jpg

  8. The word you're looking for is methoxy.


    However, you're going to want to look at your numbering again, unless there are other substituents you didn't mention. There's a way to name that with lower numbers, which is always preferable.

  9. You can buy it. It's the only ingredient in oxiclean or the cheaper knock off store brands. It's nothing but an addition compound between sodium carbonate and hydrogen peroxide. You need a source of either anhydrous or very concentrated hydrogen peroxide to prepare it, so no, 3% won't come anywhere near working.

  10. No, and you have not made any appreciable quantity of peracetic acid either. All you've done is to add an oxidizer that can convert copper metal to copper (II) ions. When you typically think of metals dissolving in acid, the reaction generally looks like this one:


    [ce] Mg (s) + 2HCl (aq) -> H2 + MgCl2 (aq) [/ce]


    The metal is oxidized by the acidic proton (solvated as hydronium ion) of the acid, forming a metal cation and hydrogen gas.


    Copper doesn't work in that reaction. Copper lies below hydrogen on a galvanic series. If you could appropriately apply hydrogen gas pressure to a copper ion solution (good luck), the reaction would actually go backward to make the metal and acid. Hydrogen peroxide and oxygen are both capable of oxidizing the copper metal. They're stronger oxidants than hydronium ion. Notice that no hydrogen gas has formed, but [ce] H2O2 [/ce] is reduced to water.


    [ce] Cu + H2O2 + 2HOAc -> Cu(OAc)2 + 2H2O [/ce]

  11. Well technically O2 is blue...but you can only really see it in the condensed phase. Other than that, neon will change colour is you pass an electrical current through it (i.e. neon lights)


    So will almost all gases. http://en.wikipedia.org/wiki/Gas-discharge_lamp


    I know that chromyl chloride vapor is red, but chances are you don't want a volatile hexavalent chromium compound around. I imagine other colored volatile transition metal compounds behave similarly.

  12. Definitely not. Homework is to help you learn. Basically, you are paying to worsen your education, and doing so unethically. I would recommend a study group: you get the benefits of help if you need it, and instead of paying money to random people, you also make friends. It's also superior as they frequently help you learn how to solve the problem rather than just do it for you.


    Also, delete the link; it looks spammy. When you visit a forum for the first time, you would do well to avoid putting in a link to anything commercial. And welcome to SFN.


    That would be because it is spam. Someone is getting crafty. This is the second "online tutor" post recently, complete with links.

  13. It says to not use it for more than a week because it damages tissues it contacts. H2O2 works because it's fantastic at making radicals and oxidizing things. The same reason it kills bacteria is how it kills your cells.


    The stabilizers are typically small amounts of acidic phosphate salts/phosphoric acid or extremely low levels of stannic oxide, neither of which are vaguely harmful.


    Food grade H2O2 simply has lower transition metal ion content than cheaper grades. Without stabilizer, hydrogen peroxide rapidly degrades on it's own to water and oxygen gas.

  14. first off what is methylated spirits and how hard is it to get a hold of and how do you crystalize aspirin?


    1) google is your friend

    2) I prefer acetone for crystallizing aspirin. Buy uncoated, extra strength store brand aspirin. Crush the tablets, add acetone, and place in a bath of hot water somewhere with good ventilation (acetone stinks (isn't great to breathe) and the fumes are quite flammable). If your water was boiling recently and you have enough, the acetone will boil. remove the flask after a minute or two and filter while still hot to remove the binders, which don't dissolve. Do this in small portions so it doesn't crystallize in the filter, if you have a lot. Place the flask back in the hot water between filtering portions to keep it hot if you do this. Place the liquid in a clean glass dish somewhere with good ventilation and cover loosely with thin cloth or paper towel to keep dust out but allow acetone vapor to escape. As the liquid cools and then additional acetone evaporates at room temp, crystals of aspirin grow. They are quite lovely and grow fairly large if you don't disturb the dish.

  15. That would appear to be what is commonly referred to as a typo. The majority of cobalt complexes you will find have a Co(III) ion at the core, and if that - in your equation was actually a +, the +2 charge would make perfect sense.


    What reference is this from?

  16. The type of crystals you're thinking about, such as quartz, cannot reasonably be grown at home. In high pressure superheated water saturated with a carrier salt, they can dissolve slightly. Part of the reactor tube is kept cooler and there, the material is less soluble and crystallizes out. The solution can then go dissolve more of the crystal in the hot part of the tube. repeat, repeat for a week and you have synthetic quartz.


    However, as I said, this isn't very feasible at home. One you can try (though you won't be able to save the crystals because they're too fragile) is to mix a soluble calcium salt with a soluble sulfate salt. Filter off the calcium sulfate that crystallizes out, place the liquid in a jar, and let it sit undisturbed. Not all of the calcium sulfate crystallizes out immediately, and long, thin needle-like crystals will separate over the next few days if all goes well.


    However, this isn't terribly interesting. The water-soluble salts have more or less a monopoly on all the lovely colors.

  17. No such thing as a perpetual motion device (unless you'd like to add energy constantly). You could, I suppose picture a ball moving through a perfect vacuum at a constant velocity forever, but what's the point of that. If it interacts with anything, it will lose energy.

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