Dynamic 1H NMR study of the barrier to rotation about the C-N bond in primary carbamates and its solvent dependence.
The dynamic 1H NMR study of some primary carbamates in the solvents CDCl3 and CD3COCD3 between 183 and 298 K is reported. The free energies of activation, thus obtained (12.4 to 14.3 kcal mol-1), were attributed to the conformational isomerization about the N-C bond. These barriers to rotation show solvent dependence in contrast to the tertiary analogues and are lower in free energy by ca. 2-3 kcal mol-1.
Modarresi-Alam
Ali Reza
AR
Department of Chemistry, University of Sistan & Baluchestan, Zahedan, Iran. modaresi@hamoon.usb.ac.ir
Najafi
Parisa
P
Rostamizadeh
Mohsen
M
Keykha
Hossein
H
Bijanzadeh
Hamid-Reza
HR
Kleinpeter
Erich
E