IR spectra and structure of 2-{5,5-dimethyl-3-[(2-phenyl)vinyl]cyclohex-2-enylidene}-malononitrile and its potassium cyanide and sodium methoxide carbanionic adducts: Experimental and B3LYP theoretical studies

A combined IR experimental/B3LYP computational approach was applied to follow the formation and isomerization of potassium cyanide and sodium methoxide carbanionic adducts of 2-{5,5-dimethyl-3-[(2-phenyl)vinyl]cyclohex-2-enylidene}-malononitrile 1. A very good agreement was found between theoretical and experimental IR data about neutral compound 1. In agreement between theory and experiment, 1 forms β-, δ-, and ζ-adducts with the above mentioned nucleophiles. Structural changes and energy differences between various adducts and their diastereoisomers, have also been studied. According to the computations, the chemical driving force in the β → δ and δ → ζ isomerization is the higher stability of the corresponding adducts by c.a. 10 kJ mol−1 and c.a. 30 kJ mol−1, respectively.