Reaction of o-phenylenediamine with diacetyl monoxime: characterisation of the product by solid-state C-13 and N-15 MAS NMR

摘要

2,3-Dimethylquinoxaline (DMQ) and dimethylglyoxime (DMGH(2)) form a 1: 1 hydrogen-bonded complex in the solid state, which is completely dissociated in methanol solution. There are small differences in solid-state C-13 shifts between the separated components DMQ and DMGH(2) and the complex. The changes in N-15 solid-state chemical shifts are more significant: the hydrogen bond imparting a low frequency shift of ca 19 ppm. The effect of direct protonation on the DMQ solid-state N-15 shifts was measured, and the experimental N-15 data correlated with those from GIAO molecular orbital (MO) calculations. Copyright (C) 2006 John Wiley & Sons, Ltd.