Paratoluenesulfonic acid (aka p-tosic acid)
Added 5.0g toluene (1 equiv), 16.4g 94% H2SO4 (3 equiv) to a 50ml flask. Toluene layer went to the top of the flask. Dropped in a stir bar, fitted with a condenser, started stirring, heated to get a gentle reflux (~110C) of 1 drop/sec. 40 minutes passed and the reflux had stopped, the layer of toluene was gone. Easy reaction, nothing to it!
I added 5ml water down the condenser, allowed the flask to cool slowly to room temp, nice crystals of p-tosic acid form. How do I separate them without a sintered glass buncher funnel? Or, would changing this to 1 equiv H2SO4 make tosic acid? (obviously with some 2- & 3- isomers, but that doesn't matter much as it's just going to be used as an acid catalyst, impurities don't bother me much)