3272-32-0Relevant academic research and scientific papers
Substituent Effects on the C-C Bond Strength, 19. Geminal Substituent Effects, 10. Radical Stabilization Enthalpies of α,α-Bis(methoxycarbonyl)alkyl and Tris(methoxycarbonyl)methyl Radicals
Rakus, Klaus,Verevkin, Sergey P.,Keller, Manfred,Beckhaus, Hans-Dieter,Ruechardt, Christoph
, p. 1483 - 1494 (2007/10/02)
Heats of formation ΔH0f(g) were determined from enthalpies of combustion ΔH0f(c) and enthalpies of vaporization ΔH0vap or sublimation ΔH0sub for the eight substituted methanetricarboxylates 2a-h.From these data and from previously determined enthalpies of formation ΔH0f of substituted malonic esters new thermochemical group increments were derived.From these increments and from the recently published improved increments for carboxylic acid esters the gem. interaction enthalpies of two and three COOR groups were calculated.The radical stabilization enthalpies RSE of α,α-bis(methoxycarbonyl)alkyl (18.2 kJ mol-1, 1a) and tris(methoxycarbonyl)methyl radicals (5.2 kJ mol-1, 1b) were derived from kinetic data obtained by means of our previously developed protocol.They were corrected for the gem. interaction energies of the ester groups in the ground state and are satisfactorily explained by an additive stabilizing effect for the ester substituents and by dipolar substituent interactions in the radicals.The dipolar energies were taken from MM2 calculations. - Keywords: Enthalpies of formation / Geminal substituents, energetic interaction of / Bond cleavage, C-C, kinetics of / Radicals, stabilization of / Increments, thermochemical, of esters
