Raman, infrared and 13 C NMR studies on betaine–sulfamic acid (2:1) crystal and its hydrogen bonds

The betaine–sulfamic acid (2:1) crystal complex has been investigated by infrared and Raman experiments in polarized light and by cross‐polarization magic angle spinning 13 C NMR. Very short and symmetric hydrogen bonds formed by acidic protons and betaine carboxylate groups (—COO—H—OOC—) + are characterized by the Raman tensor α′(R) available from Raman symmetric stretching vibrations of the carboxylic groups and by the 13 C shielding tensor σ of these groups. The principal components of the both tensors were found as to be strongly related: σ ii = 93.12 + 0.125α′(R) ii . The sulfamate NH 2 group reorientation was characterized by Raman bandshape analysis at different temperatures. The energy of very weak O· · ·H—N—H· · ·O hydrogen bonds between the sulfamate and betaine moieties was characterized in this way. Copyright © 2003 John Wiley & Sons, Ltd.