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Everything posted by faumember89

  1. Hey guys, I had a couple lectures on group theory this week, but it's only an undergraduate inorganic chemistry class and the whole concept is very abstract and hard for me to grasp, specifically once I get past the basic operations. I understand the basic applications, how to calculate the number of vibrational modes for nonlinear and linear molecules, but my problem is explaining and interpreting character tables. I don't understand what the A, B, etc. are, and I have trouble calculating their values. So my question is, does anyone know of a good resource on the web to assist me? I've looked for some but I was hoping someone on here knows something that has helped them or is just in general very good.
  2. I understand and believe you that THF will be a better solvent for NaOH but I need a solvent in which benzyltriphenylphosphonium chloride and NaOH will be soluble, although there may not be one. I've been looking online and most standard procedures use aqueous 10M NaOH and do the reaction in methylene chloride, but they have some delivery method to get the hydroxide ions into the methylene chloride, something called "aquilat 336" which we don't have in my lab. No, I don't work in Manchester, I'm an undergraduate student at Florida Atlantic University.
  3. Yeah, I was following an experiment my prof gave me and assumed it was catalytic because I didn't really think about the mechanism of reaction, but you guys are definitely right. Gonna try it with THF sometime this week and I'll post some exuberant thanks if all goes well! My next step is to make allenes and cumulated systems via the same procedure, the reaction with benzaldehyde is just a mock-up to get the procedure down and my experimental methods polished. Merged post follows: Consecutive posts mergedI'd like to report that the benzyltriphenylphosphonium chloride is poorly soluble in distilled THF as compared to a similar volume of methylene chloride, and I'm not particularly sure why seeing as I thought most reactions that used DCM as a solvent work even better in THF... I can't even get 0.5g of the ylide salt to dissolve in about 15mL of the THF.
  4. Thanks for the replies, everyone. Do we know for certain that benzyltriphenylphosphonium chloride is soluble in THF? If so, that could help a lot, because it is definitely the case that the NaOH pellets never fully dissolve in the DCM. Oxidation sounds like a definite possibilty towards eliminating the excess benzaldehyde, so I'll look into that as well if I continue to have extra.
  5. Hey everybody, I'm an undergraduate organic chemistry student at FAU, and part of my research is new experimental methods. All that's fine, but my problem is much more basic at the moment. I'm doing a basic Wittig reaction to produce stilbenes, and the reaction is essentially thus: Dissolve a small mass of benzyltriphenylphosphonium chloride in methylene chloride, add in a catalytic amount of solid sodium hydroxide (there is a color change to bright yellow/orange), stir, and then over time add a stoichiometric amount of benzaldehyde. The reaction takes 15-30 minutes as the color fades away, and the products are cis- and trans- stilbenes. My problem is that I keep getting unreacted benzaldehyde in the product, and I don't know how to purify it out. I've tried doing the reaction with a slight excess of benzyltriphenylphosphonium chloride, I've tried letting the reaction run overnight, and no matter what it seems that I keep getting benzaldehyde in the product. Is there something I can do to ensure that all the benzaldehyde reacts? If there's nothing I can do procedurally, is there any technique I can use to purify out the benzaldehyde afterwards? Thanks in advance.
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