W. Smith, K. Raymond
Feb 1, 1980
Citations
0
Influential Citations
25
Citations
Journal
Journal of the American Chemical Society
Abstract
A series of dimeric N-isopropylhydroxamic acids, separated by (CH/sub 2/)/sub n/ units (n = 4,6,8, and 10), have been synthesized from the acid chlorides and N-isopropylhydroxylamine. The structure of the adipoyl derivative (n = 4) has been determined from single-crystal x-ray diffraction data collected by counter methods. In contrast to all previous hydroxamic acids that have been structurally characterized, the planar hydroxamate groups are trans, with C(O)-N and C=O distances similar to those found in amides. Strong intermolecular hydrogen bonds between the hydroxyl and carbonyl groups hold the molecules in pleated planes perpendicular to the b axis and compensate for the loss of the intramolecular hydrogen bond of the cis conformation. The intermolecular hydrogen bonds appear to be stronger than the intramolecular hydrogen bonds of the cis conformation, but the latter are entropically favored in solution. The molecules are located on a center of inversion in the space group Pbca with a = 9.3859(3), b = 18.7156(2), and c = 4180(2)A. Full-matrix least-squares refinement on 1217 independent data with F/sub 0//sup 2/ > 3sigma(F/sub 0//sup 2/) and all atoms (including hydrogen) anistropic led to an R factor of 3.8%.