The solvates of o-acetamidobenzamide

Abstract

A series of six solvates of o-acetamidobenzamide have been prepared and characterized by single crystal X-ray diffraction. With the exception of the chloroform solvate, five of these, the 1-propanol, 1-butanol, 2-butanol, 1,2-dichloroethane, and 1,4-dioxane solvates are isostructural with similar unit cells and atomic positions for the o-acetamidobenzamide molecules. In all cases, the solvent molecules occupy pores within the hydrogen-bonded sheets of o-acetamidobenzamide. These molecules are readily lost when the crystals are exposed to the atmosphere.

Studies on the preparation and crystal polymorphism of 2-acetamidobenzamide and related compounds

“…As a compound which exhibits variable crystal polymorphism based on differences in molecular conformation and hydrogen-bonding pattern between forms, 2-acetamidobenzamide 1 is an attractive subject for molecular-level crystallization control using additives. In our studies on compound 1, behaviour similar to that described by Barnett et al 10 was observed, i.e. for a considerable period the α form was the only crystal form of compound 1 obtained by us under all crystallization conditions attempted.…”

“…Formation of 2-acetamidobenzamide by methods which hinder the formation of the intramolecular hydrogen bond could result in preferential crystallization of the β form. Barnett et al found that the β form was first obtained by them after attempted preparation of the N-deuterated derivative 15 10 , which may be a consequence of disruption of the intramolecular hydrogen bond by the deuteration process. A similar effect could be achieved by temporary in situ replacement of the N−H groups by N-trimethylsilyl groups.…”

“…compound 1 can be recrystallized from a wide range of solvents, there is no consensus in the literature on the best choice of solvent and conditions to obtain either form. For example, Errede et al found that supercooling solutions of acetone or methanol gave fine crystals of the α form and that larger crystals of the β form could be grown from acetone, methanol or aqueous solutions 5 ; while Barnett et al found that the α form could be obtained by slow cooling of hot saturated solutions of water, ethanol, methanol or ethyl acetate 10 . Barnett et al 10 also found that the β form initially proved difficult to obtain, but that once the β form had been obtained it was the form that resulted from many crystallization conditions which had previously given the α form.…”

“…For example, Errede et al found that supercooling solutions of acetone or methanol gave fine crystals of the α form and that larger crystals of the β form could be grown from acetone, methanol or aqueous solutions 5 ; while Barnett et al found that the α form could be obtained by slow cooling of hot saturated solutions of water, ethanol, methanol or ethyl acetate 10 . Barnett et al 10 also found that the β form initially proved difficult to obtain, but that once the β form had been obtained it was the form that resulted from many crystallization conditions which had previously given the α form. As the α form has a melting point of 179−180ºC 9 and a density of 1.325 g cm −3 5,6 ; while the β form has a melting point of 189−190ºC 9 and a density of 1.345 cm −3 5,6 , it would be reasonable to conclude that the β form is likely to be the thermodynamically preferred form, while there may be a kinetic preference for the α form.…”

High-Z′ structures of organic molecules: their diversity and organizing principles

“…Two more have aggregates built from six independent molecules, although one of the two has a somewhat approximate twofold modulation as well. In two structures (CEGBAS, CEGBEW; Barnett et al, 2006) stacking breaks the approximate sixfold symmetry of the hydrogenbonded layers. Four more structures are too complicated to categorize easily.…”