TY  - JOUR
A1  - Movahedifar, Fahimeh
A1  - Modarresi-Alam, Ali Reza
A1  - Kleinpeter, Erich
A1  - Schilde, Uwe
T1  - Dynamic H-1-NMR study of unusually high barrier to rotation about the partial C-N double bond in N,N-dimethyl carbamoyl 5-aryloxytetrazoles
JF  - Journal of molecular structure
N2  - The synthesis of new N,N-dimethyl carbamoyl 5-aryloxytetrazoles have been reported. Their dynamic H-1-NMR via rotation about C-N bonds in moiety of urea group [a; CO-NMe2 and b; (2-tetrazolyl)N-CO rotations] in the solvents CDCl3 (223-333 K) and DMSO (298-363 K) is studied. Accordingly, the free energies of activation, obtained 16.5 and 16.9 kcal mol(-1) respectively, attributed to the conformational isomerization about the Me2N-C=O bond (a rotation). Moreover, a and b barrier to rotations in 5-((4-methylphenoxy)-N,N-dimethyl-2H-tetrazole-2-carboxamide (P) also were computed at level of B3LYP using 6-311++G** basis set. The optimized geometry parameters are in good agreement with X-ray structure data. The computation of energy barrier for a and b was determined 16.9 and 2.5 kcal mol(-1), respectively. The former is completely in agreement with the result obtained via dynamic NMR. X-ray structure analysis data demonstrate that just 2-acylated tetrazole was formed in the case of 5-(p-tolyloxy)-N,N-dimethyl-2H-tetrazole-2-carboxamide. X-ray data also revealed a planar trigonal orientation of the Me2N group which is coplanar to carbonyl group with the partial double-bond C-N character. It also demonstrates the synperiplanar position of C=O group with tetrazolyl ring. On average, in solution the plane containing carbonyl bond is almost perpendicular to the plane of the tetrazolyl ring (because of steric effects as confirmed by B3LY12/6-311++G**) while the plane containing Me2N group is coplanar with carbonyl bond which is in contrast with similar urea derivatives and it demonstrates the unusually high rotational energy barrier of these compounds. (C) 2016 Elsevier B.V. All rights reserved.
KW  - Dynamic H-1-NMR
KW  - Carbamoyl tetrazoles
KW  - Barrier to rotation about C-N bond
KW  - pi-Stacking
KW  - B3LYP/6-311++G**
Y1  - 2017
U6  - https://doi.org/10.1016/j.molstruc.2016.12.010
SN  - 0022-2860
SN  - 1872-8014
VL  - 1133
SP  - 244
EP  - 252
PB  - Elsevier
CY  - Amsterdam
ER  -