Traces of an alcohol functionalized impurity in a reaction mixture in which the desired product has no alcohol function may well be best removed by treatment with phthalic anhydride, mild hydrolysis of any excess anhydride, and aqueous removal of phthalic acid and the hemi-phthalate of the alcohol impurity by extraction with dilute aqueous ammonium hydroxide from an immiscible organic solvent containing the non-alcohol main product.
This could be cost effective because phthalic anhydride is cheap so the extra work-up cost would be little while the improvement in quality and overall recovery from crystallization of the non-alcohol could easily more than justify it.
The treatment might be useful after oxidation of an alcohol to a aldehyde or ketone; conversion of an alcohol to an ether; pinacol-pinacolone reaction; dehydration of an alcohol to an olefin.
The work could also explore whether some modification could be used to separate an alcohol which is the desired main product from a reaction mixture containing non-alcohol side products. Here at least stoichiometric amount of phthalic anhydride would be necessary to convert all of the desired alcohol to the hemi-phthalate.
The treatment might be useful after reduction of an aldehyde or ketone; to an alcohol; cleavage of an ether; hydroxylation of anything or hydration of an olefin; or hydrolysis of a halide.
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