Ab Initio SCF study of the barrier to internal rotation in simple amides

N Vassilev
2017 Bulgarian Chemical Communications   unpublished
The free energies of activation for rotation about the amide C-N bond in R-C(O)NR' 2 (R'=CH 3 , R = CN, N 3 , CC-H, CC-CH 3 ; R'=H, R = C 2 H 5 , CH(CH 3) 2) were calculated at the MP2(fc)/6-31+G*//6-31G* and at the MP2(fc)/6-311++G**//6-311++G** levels of theory and compared with the NMR liquid and gas-phase data. On the basis of results from this and previous studies we generalize that in case of amides and thioamides the nonbonded interactions in ground state (GS) are mainly responsible
more » ... inly responsible for the differences in the rotational barriers and they prevail over the electronic effects of the substitutents.