CRYSTAL AND MOLECULAR STRUCTURE OF N-METHYL-N-T-BUTYL-3-HYDROXYAZETIDINIUM METHANESULFONATE, A NONPLANAR AZETIDINIUM RING

The crystal structure of N-methyl-N-t-butyl-3-hydroxyazetidinium methanesulfonate (HAM) has been determined by Patterson and Fourier methods. The space group= is Pnam, No. 62, having four molecules in the orthorhombic unit cell with a = 21.714, b = 7.608, and c = 7.360 Å. Each molecule is bisected by a mirror plane. The sulfur atom was located in the E2-1 Patterson synthesis, but the contribution of this atom was insufficient to determine the phases for an approximate structure. Superposition methods were used to locate the remaining atoms. The azetidinium ring is found to be buckled by 14 ± 1 ° from a plane which'is perpendicular to the molecular mirror plane. The hydroxy and N-methyl ring substituents lie on the convex side of the ring, while the t-butyl group lies on the concave side. Only one hydrogen-bonding situation is found, and that may be interpreted as a bifurcated hydrogen bond from the hydroxyl hydrogen atom to two of the methanesulfonate oxygen atoms. The ring bond lengths in HAM are close to those of L-azetidine-2-carboxylic acid, and the degree of ring buckling is similar. © 1969, American Chemical Society. All rights reserved.