Question

Is it possible to protonate p-toluic acid with HCL? Trying to determine where my caffenine went during extraction lab. Thinking after adding HCL to naphthalene, caffeine and ptoluic acid...my caffeine and ptoluic acid both became conjugate acids and were extracted together in solution. The original solvent was dimethyl chloride. I'm thinking it may have been possible to protonate the ptoluic acid since the methyl p group is an electron donating group and doesnt assist with helping the carboxylic acid in hiding electrons from protonation. Thoughts?

Answer 1

It is not possible to protonote p-toluic acid with HCl for the reason being the p-toluic acid is allready existing in acidic form and its Pka should be around 4.2 and is a week acid. It can easily donate its proton in the presence of a base.

Addition of HCl, to the mixture of naphthalene, caffeine and p-toluic acid, had facilitated the p-toluic acid to get extracted into organic layer as its solubility in dichloromethane is more than that of water. This should have gone in water if was treated with base such as Sodium Hydroxide as it can easily for sodium salt of p-toluic acid that dissolves in water and has less solubility in organic solvent.