A notable example is provided by the phthaleins, which result by the condensation of phthalic anhydride with phenols.
Dorp (Ber.,1874,7,P.578) obtained orthobenzoyl benzoic acid by heating phthalic anhydride with benzene in the presence of aluminium chloride.
Anthragallol is synthetically prepared by the condensation of benAoic and gallic acids with sulphuric acid OH i [[Cooh + I 10h - 2h20+ Hooc /Oh]] or from pyrogallol and phthalic anhydride in the presence of sulphuric acid or zinc chloride.
Phthalimide, C6H4(CO)2NH, is formed by heating phthalic anhydride or chloride in ammonia gas or by molecular rearrangement of ortho-cyanbenzoic acid.
Unlike resorcin it does not give a fluorescein with phthalic anhydride.