Diazepines. Part XIII. Relative reactivities of positions 5 and 6 in electrophilic substitution reactions of 2,3-dihydro-1,4-diazepinium salts measured by deuterium exchange kinetics

Kinetics and activation parameters have been measured for deuteriation at position 6 of 2,3-dihydro-5,7-dimethyl-1,4-diazepinium perchlorate by deuteriosulphuric acid in deuterium oxide, and the data are compared with those for the corresponding deuteriation catalysed by primary phosphate ions. In contrast, protons at positions 5 and 7 in two other diazepines were only slightly affected by dilute deuteriosulphuric acid. In anhydrous deuteriotrifluoroacetic acid protons at positions 5 and 7 were completely unaffected. The relative reactivities of positions 6 and 5 (or 7) are discussed. The ratio of the reactivities is 109 and the difference in activation energies is 61 kJ mol–1.