Phthalic acid can be converted to phthalimide through a reaction known as the Gabriel synthesis. Here are the steps to prepare phthalimide (pthalamine) from phthalic acid:
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Dissolve phthalic acid in concentrated sulfuric acid to form the corresponding phthalic acid monosulfate.
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Heat the phthalic acid monosulfate with ammonium hydroxide to produce ammonium phthalate.
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React the ammonium phthalate with sodium hypochlorite to form chloramine phthalate.
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Treat chloramine phthalate with ammonia to produce phthalimide.
The overall reaction can be represented as follows:
Phthalic acid + NH3 + NaOCl → Phthalimide + NaCl + H2O
Note that the Gabriel synthesis is a well-known and widely used method for the preparation of primary amines from carboxylic acids.
