Nonempirical (Gaussian ab initio) geometry optimization was performed on a number of isomeric C2NH6 + ions. Two levels of approximation (STO-3G minimal and 4-31G extended basis set) were in agreement in support of the experimental finding that the protonated Schiff-base isomers are the most stable ones on the C2NH6 + surface. In general, those ions possessing a resonance contribution with a filled octet were found to be the most stable ones. Barriers to CH3- or NH3- rotation were predicted to be nearly 1 kcal/mol irrespective of basis set. The results allowed estimation of the proton affinities of some C2NH5 isomers. The imine tautomer (CH3CH=NH) was found to be slightly more basic than the enamine (CH2=CHNH2). The estimated intrinsic basicities (4-31G calculations) were similar to that of pyridine.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry