Hydrogen bond rearrangements in organic solids. Part 2. Cyclodehydration of o-acetamidobenzamide

Abstract

o-Acetamidobenzamide (I) undergoes a series of thermal solid-state rearrangements in which a polymorphic transformation and cyclodehydration occur to give anhydrous 2-methylquinazol-4-one (IV). The solid-state processes involved in cyclodehydration of (I) have been investigated. An important feature of this reaction sequence is that it occurs in a matrix of hydrogen-bonded molecules. The hydrogen-bonding patterns, which may play a role in directing the solid-state transformations, are used as a probe for understanding the solid-state reaction mechanisms. The X-ray crystal structures of (IV), and its hydrate (III) were solved, and are compared with those of (I). Crystal data: (IV), Pbca, a= 5.081 (6), b= 14.574(7), c= 20.854(3)Å, Z= 8, R_F= 0.075 for 622 reflections [I > 3σ(I)]; (III), P, a= 10.000(3), b= 12.509(4), c= 7.193(3)Å, α= 78.26(3)°, β= 79.05(3)°, γ= 89.87(3)°, Z= 4, R_F= 0.070 for 1 346 reflections [I > 3σ(I)].