Strain criteria for alkenes: Two different manifestations

Abstract

Criteria that have been used to describe alkene strain can be divided into energetic and geometrical criteria. An overview of strain criteria from both groups is given, and altogether, 16 different criteria have been calculated with the DFT M062X/TZVP method for several strained alkene series. Factor analysis was used to judge whether these strain criteria measure the same underlying phenomena. The factor analysis showed that for systematically substituted ethene derivatives (series A) all the studied criteria were describing the same thing. The factor analysis showed that for series B, where the double bonds geometry is fixed with a cyclic backbone, at least two different criteria (e.g. gas-phase basicity and hydrogenation reaction enthalpy) are needed to describe the overall strain. We propose that these two different expressions of strain describe strain related to reactivity and thermodynamics. Those two strains were well-correlated in the first series.