Strain effects in phenyl substituted methanes. Geminal interactions between phenyl and electron-withdrawing cyano substituent in benzylcyanides

Abstract

The standard (po= 0.1 MPa) molar enthalpies of formation ΔfHmo(l) atT= 298.15 K were determined by means of combustion calorimetry for benzylcyanide, α -methyl-benzylcyanide, α -ethyl-benzylcyanide, and α, α - dimethyl-benzylcyanide. The standard molar enthalpies of vaporization of these compounds were obtained from the temperature dependence of the vapor pressure measured in a flow system. Resulting values ofΔfHmo (g) were obtained atT= 298.15 K and used to derive strain enthalpies of benzylcyanides. The strain effects were discussed in terms of deviations ofΔfHmo (g) from the group additivity rules. These values provide a further improvement on the group-contribution methodology for estimation of the thermodynamic properties of organic compounds.