Phthalic Anhydride → Dihydrochloride trihydrate

Participants

Reaction Steps

A mixture of phthalic anhydride (5.92 g.), N,N,N',N'-tetramethyl-m-phenylenediamine (6.56 g.), zinc chloride (5.40 g.) and chlorobenzene (70 ml.) was heated under reflux for 3 hours. The chlorobenzene was decanted and the residue was air-dried. A solution of the residue in dilute hydrochloric acid (10%, 20 ml. plus 20 ml. of water) was diluted with more water (20 ml.), affording 2-(2,4-bis(dimethylamino)benzoyl)benzoic acid (II: Y'2 = Y'4 = (CH3)2N, Z4 = Z'5 = Z'6 = Z7 = H) dihydrochloride trihydrate (4 g., m.p. 136°-141° C.; after recrystallization from ethanol, m.p. 140°-141° C.). In another preparation the free base (m.p. 165°-168° C.) was obtained under less acidic conditions (pH 4 -6).

Provenance & Evidence