Theoretical in-Solution Conformational/Tautomeric Analyses for Chain Systems with Conjugated Double Bonds Involving Nitrogen(s).

ABSTRACT: Conformational/tautomeric transformations for X=CH-CH=Y structures (X = CH2, O, NH and Y = NH) have been studied in the gas phase, in dichloromethane and in aqueous solutions. The paper is a continuation of a former study where s-cis/s-trans conformational equilibria were predicted for analogues. The s-trans conformation is preferred for the present molecules in the gas phase on the basis of its lowest internal free energy as calculated at the B97D/aug-cc-pvqz and CCSD(T)CBS (coupled-cluster singles and doubles with non-iterative triples extrapolated to the complete basis set) levels. Transition state barriers are of 29-36 kJ/mol for rotations about the central C-C bonds. In solution, an s-trans form is still favored on the basis of its considerably lower internal free energy compared with

SUBMITTER: Nagy PI 

PROVIDER: S-EPMC4463675 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature