Notable Substituent Effects on the Rate Constant of Thermal Denitrogenation of Cyclic Azoalkanes : Strong Evidence for a Stepwise Denitrogenation Mechanism
AustJChem_63_1615.pdf 220 KB
The thermal denitrogenation rates (k) of a series of 7,7-dimethoxy-1,4-diaryl-2,3-diazabicyclo[2.2.1] hept-2-ene derivatives 2 with a variety of aryl groups (p-CNC6H4, C6H5, p-MeC6H4, p-MeOC6H4) were determined to investigate the denitrogenation mechanism. A linear correlation (r=0.988) between the relative rate-constant (log k(rel)) of the denitrogenation reaction and Arnold's sigma(.)(alpha) parameter for benzylic-type radical-stabilization was observed. However, the relative rate-constant was not correlated with the substituent effect on the lifetime of the resulting singlet diradicals DR2. These results indicate that the rate-determining step of denitrogenation of 7,7-dimethoxy-2,3-diazabicyclo[2.2.1] hept-2-ene derivatives involves stepwise C-N bond cleavage.
Australian Journal of Chemistry
|date of issued||
Copyright (c) 2010 CSIRO
Graduate School of Science