Modes of dimerization of the alpha-hydroxyamide group

An X-ray diffraction and theoretical study on selected dimeric, mostly cycl ic, hydrogen-bonded structures occurring in the crystals of several (R,R)-t artaric acid derivatives and involving alpha-hydroxyamide moieties is prese nted. The conformational behaviour of the dimers in both isolated and solva ted states is considered theoretically with the use of the RHF/6-311+ +G** method and complete geometry optimization. Solvation effects have been incl uded at the SCRF level and the following models have been employed: Onsager , polarized continuum model, and self-consistent isodensity PCM. All types of dimeric structures observed in the crystals have been obtained as stable local energy minima after complete geometry optimizations. (C) 1998 Elsevi er Science B.V. All rights reserved.