rate-determining step as the basicity of amines increases. The corresponding Brønsted-type plot for the reactions with secondaryamines is also biphasic with β1 = 0.34, β2 = 0.74, and pKa° = 9.1, indicating that the effect of amine nature on the reaction mechanism and pKa° is insignificant. However, primaryamines have been found to be less reactive than isobasic secondaryamines. The microscopic rate constants
Rate-determining nitrogen inversion in the isomerisation of isoimides to imides and azides to tetrazoles: direct observation of intermediates stabilized by trifluoroethyl groups
作者:Anthony F. Hegarty、Nuala M. Tynan、Suzanne Fergus
DOI:10.1039/b202005j
日期:2002.6.27
N→O acylgroup transfer or cyclisation. The Hammett ρ value (−0.4), obtained for the rearrangement of the imidoyl azides to the tetrazoles, compares well to other systems where the rate-determining step (nitrogen inversion) was similar. Nitrogen inversion in these imine systems is therefore significantly slower (ca. 10-fold relative to an ethyl group) in the presence of the trifluoroethyl group on nitrogen