Febuary 28, 2006
Well, to make things clear I might have to start from the begining on this. It all started several months ago when I was reading "Technical Bulletin Reaction Solvent Dimethyl Sulfoxide" an excelent resource that can be easily found online, it was released as a PDF and can be downloaded by anyone. Anyway, on pages 51 and 52 of the PDF several decarboxylation reactions are mentioned on different substrates. The main conclusion to be drawn from them though is that decarboxylation reactions occur more readily in DMSO then under most other conditions. And upon learning this I figured that maybe I could decarboxylate benzoic acid.
So, I made some benzoic acid from sodium benzoate and added it into DMSO. Approximately 100 grams of benzoic acid was added to a round bottom and 70 ml of DMSO was added. To my suprize the benzoic acid seemed to be fairly soluble in the DMSO. So, I put it on the hotplate, attached a condenser, and hit it with some heat from the hotplate. After some time it started boiling and some distllatate came over. The problem though was that it brought with it a peculiar smell. Something like the DMSO itself. The stillhead was in the 80 °C neighbor hood, consistent with benzene actually coming over and much below the boiling point of DMSO so I tried to ignore it. But it was a strong stink. So, I added some water. My hope being that the azeotrope with benzene would pull it out of the reaction mixture and additionally that it might help the reaction as some of the proceess described in the bulletin used 70% DMSO solutions.
After adding it though there was a massive gas release. I don't think it did anything constructive though. The stillhead temperature shot up to 100 °C and stayed there as the water continued to distill over. Something did distill over. Likely the fraction before the water was added floated on the top of the water. Being that it was insoluble in water eliminated DMSO from the possibilities and that coupled with the stillhead temperature at the begining pointed to benzene being the distillate.
Still, what were the fumes? Lots of carbon dioxide or some kind of gas was being produced contiuilly because if the apparatus was closed by my finger it would rapidly build pressure. So I knew somthing was going on. I would like to repeat this in the future to try and acheive more reproduceable results and get a feel for what is being produced.
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