Drunkguy
Hazard to Others
Posts: 172
Registered: 23-12-2005
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Mood: somewhat pissed.
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p-toluene sulfonic acid
Has anyone tried the homebake procedure for this as delineated in Vogel? It looks fairly reasonable, although is the glass fritted funnel really
requisite or can one just employ a regular Buchi?
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not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
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Mood: No Mood
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So long ago that I've forgotten details of how it turned out. More recently I would boil toluene and pass the vapour through H2SO4 heated to 150 to
160 C, and use the Dean-Stark trap setup to recover toluene. At that temperature the para isomer is by far the main product, in the 90 to 98 percent
range with the remainder being o and m and a bit of the disulfonate and di-tolu sulfonone. It gives a high conversion of the H2SO4 to the sulfonic
acid as well, less than 5% of the H2SO4 remains unreacted.
As with Vogel, when enough water had come over I poured the reaction mix into a beaker and let it cool, then add cold water. I didn't do the porous
plate trick, which does work well so don't hesitate to use it, but rather filtered the mass and washed with ice cold concentrated hydrochloric acid,
then dumped it back in the beaker to stir with more HCl for 15 or 20 minutes, filter, wash again. That got most of the sulfuric acid out, and some
to most of the other isomers. For my application I didn't really care about the isomers, as they would function well enough as catalysts too.
Yes, glass filter is advised, you're working with rather strong acids. Harden filter paper might work, but no promises. Chill the funnel to 0 C
before filtering, that helps up the yield a bit.
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