Substituenteneffekte auf die CC‐Bindungsstärke, 16. Thermische Stabilität und Bildungsenthalpie von β‐Dicarbonylverbindungen. — Stabilisierung von α,α′‐Diketoalkyl‐Radikalen

Abstract

Substituent Effects on the CC Bond Strength, 16. — Thermal Stability and Enthalpies of Formation of β‐Dicarbonyl Compounds. — Stabilisation Enthalpies of α,α′‐Diketoalkyl Radicals The geminal interactions of the two carbonyl groups in seven β‐diketones of the type 8–9 and 11–13 were estimated from their enthalpies of formation, which were deduced from their heats of combustion and enthalpies of vaporization. The radical stabilisation enthalpies RSE of the α,α′‐diketoalkyl radicals 9–13 were obtained from the enthalpies of activation Δ H ≠ of thermal CC bond cleavage of eight model compounds of the type 9–13 by their comparison with Δ H ≠ of comparable hydrocarbons of similar strain. For non‐cyclic α,α′‐diacyl‐alkyl radicals and six‐membered cyclic ones RSE = 54.8 ± 1.3 kJ mol −1 was determined, which indicates an additive stabilisation by two carbonyl groups.