November 23, 2024, 03:07:33 AM
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I would call our purification a partial success.  When there is a small amount of water present in CDCl3, it usually shows up around 1.6 ppm.  I looked over the H-1 NMR of the starting material, and there is a low, broad peak that might be a polymer.  I am not sure whether I should ignore this signal in the starting material; I plan to buy some more of this starting material soon.
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High School Chemistry Forum / Re: Doubt plastic rubber
« Last post by jonas8732 on November 16, 2024, 11:09:40 AM »
Does any type of fabric protect against drying out of plastic and rubber due to UV lamps or indirect sunlight?

I think electronics use ABS plastic but I don't know what type of rubber they use.
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Good! Isn't 3.6 typical for water? I am very rusty on NMR You could try DMSO-d6 as solvent It looks like poor resolution? You can also heat the sample in the probe. Or use MeO-D4, then the OH, if OH should go away or move. It's strange with a broad signal like that if not OH, it must be a polymer or something that does not dissolve properly? It can not be PEG? It's to up-field?
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High School Chemistry Forum / Re: Ionization energy vs electron affinity
« Last post by Borek on November 16, 2024, 03:34:44 AM »
I have been taught that in general, atoms need energy to remove one electron from it while it releases energy when capturing an electron.

That's for an isolated atom, not interacting with its surroundings. Put Na- between other atoms/molecules, and it will happily get rid of the extra electrons, forcing other things to keep them.
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High School Chemistry Forum / Ionization energy vs electron affinity
« Last post by rentj on November 16, 2024, 03:11:27 AM »
I have been taught that in general, atoms need energy to remove one electron from it while it releases energy when capturing an electron. Then, why does Na atom prefers being Na+ instead of Na-, since the enthalpy of electron capture for sodium is negative (exothermic), and the enthalpy of ionization for sodium is positive (endothermic). Generally, if the enthalpy is negative, the reaction would be spontaneous. Thus, why does Na atom prefer consuming energy (ionization) instead of capturing an electron (electron affinity) which is more spontaneous? Thank you.
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After silica gel chromatography the compound has less mass (now the mass is below theoretical) and looks more crystalline.  The broad peak that overlaps with the PCH2S(O)2 doublet in the H-1 spectrum is smaller, but it is not gone.  There are other low, very broad peaks in several places in the NMR spectrum: 3.3, 1.6 and 0.85 ppm being the most prominent.  I saw something similar before, but I did not give it much thought.  My current thinking is to try the synthesis over again.  If the second batch is impure, then we will develop recrystallization conditions.  I will also give the two NMR spectra (before and after chromatography) a more careful look.
EDT
I added two pdf files.  Each one shows a portion of the H-1 NMR.  One was taken after we stripped with chloroform but before the silica gel column.  The other was taken after the column.
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Yes the sulfone is easy to make, and a new synthesis also occurred to me as possibly being the better choice.  Of course, the same problem may occur twice, whatever it is.  BTW we obtained a H-1 NMR of the starting sulfide, and it looks fine.  We have not yet tried recrystallization, but my bet is that hexanes or heptane would work.

That sounds like very non-polar solvents? I think it will not dissolve in those? I don't know, toluene maybe? If you boil it and let it cool?
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Hint: dilutions don't matter here.
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so the question is: You choose to make a serial dilution of alcohols ie. to make the 2nd dilution from the 1st.  In order to end up with 140mL of 82% AND 52mL of 51%, how many mL of absolute ethanol do you need to make up the 1st solution? (answers to 2 d.p.)

I've never really done these kinda of questions with alcohol involved so i think its the percentages that are throwing me off and i'm kinda confused what the question is asking. how do i go about solving this?
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High School Chemistry Forum / Re: Doubt plastic rubber
« Last post by marquis on November 14, 2024, 12:28:53 PM »
That's the problem.  It depends on the polymers used.  Without knowing more,.only general answers can be given .  For example, it could be continued crosslinking, it could be loss of plasticizer, you get the idea. As a first pass, you can try putting a drop of mineral oil on an unused part of the device.  Work it in.  And give it some time.  It.may or may not work.  And it may or may not work on all of the parts of the electronic device.  For example, one part maybe made of black rubber, where it might work.  On the other hand, a drop of mineral oil on some plastics might not work.  It depends on the type of plastic or rubber.  Also note that sometimes they can be dissolved by oil.  Not likely,.but be careful.  That is why you should only go a small drop at a time.
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