Structural study of some unsaturated malononitriles using mass spectrometry and theoretical models

Abstract

The study of tautomerism has gained relevance in the scientific community because several cellular processes occur through different tautomeric forms of certain compounds. The percentage of each tautomer in compounds with tautomerism capability depends on numerous factors, such as temperature and solvent polarity, among others; and, by changing the external conditions, equilibrium displacement can be established very quickly. This manuscript deals with nitrile–ketenimine tautomerism in some unsaturated malononitriles. This kind of compounds with two nitrile groups conjugated to a double bound is able to rearrange accessible hydrogens and provide new and complex structures of different functionalities. The authors' motivation for investigating these compounds lies in understanding their tautomeric behavior in solution and gas phases and to predict reaction deportment to then account for the final products obtained. Four unsaturated malononitriles were synthesized to study the substituent effect on equilibrium displacement. Characterization was performed using nuclear magnetic resonance (NMR) and tautomeric equilibrium in gas phase was evaluated by mass spectrometry. Correlation with theoretical calculations was carried out in order to comprehend the system behavior.