L. Romsted, Jianbing Zhang, Lanzhen Zhuang
Sep 19, 1998
Citations
0
Influential Citations
20
Citations
Journal
Journal of the American Chemical Society
Abstract
The mechanism of dediazoniation of 2,4,6-trimethylbenzenediazonium ion, 1-ArN2+, in concentrated aqueous solutions of acetamide, N-methylacetamide, and N,N-dimethylacetamide (peptide bond models) was probed by a combination of techniques including HPLC, GC/MS, and H218O isotopic labeling. The kinetics and product distributions are completely consistent with the heterolytic dediazoniation mechanism, i.e., rate-determining loss of N2 followed by trapping of the aryl cation intermediate, 1-Ar+, by H2O and the oxygens and nitrogens of the amides. Aryl imidates formed from trapping by amide O hydrolyze rapidly into aryl ester/amine and amide/phenol product pairs. The results were used to estimate the selectivity of 1-Ar+ toward the amide oxygens and nitrogens versus H2O. 1-Ar+ is only 10−40% more selective toward H2O than amide O, but it is more than 10 times more selective toward H2O than the amide N. 1-Ar+ is slightly more selective toward the N of acetamide than N-methylacetamide. However, within the HPLC d...