The crystal and molecular structure of saccharin (o-sulphobenzoic imide)

Abstract

Crystals of saccharin, o-[graphic omitted], have been shown by three-dimensional X-ray methods to be monoclinic, space group P2₁/c, a= 9·563, b= 6·913, c= 11·822Å, β= 103° 51′. The final parameters were obtained by a least-squares refinement with the structure amplitudes of 1609 intensities collected with a linear diffractometer. The final R was 0·052. Standard deviations for bond lengths (0·003 Å) and angles (0·2°) involving the heavy atoms are an order of magnitude larger in the case of hydrogen atoms. Significant and symmetrical in-plane distortions were observed in the benzene ring, and strain in the five-membered ring results in large angular distortions. Despite this, the maximum out-of-plane bending, except for the oxygen atoms at sulphur, is only 0·014 Å for the heavy atoms. As in many imides, strong N–H ⋯ O hydrogen-bonds are formed across centres of symmetry, the planes of the two participating imide groups being separated by no more than 0·032 Å. The packing arrangement is discussed.