Termólisis de Clorooxoacetato de Etilo en Fase Gas: Comparación con Oxoacetato de Etilo y Detalles del Sistema Estático para el Estudio Cinético

The advantage offered by kinetic studies in the gas phase is that the velocity coefficient is not affected by surfaces, catalysts or solvents that interact with the substrate. So far, gas phase thermolysis of esters derived from oxalic acid have been scarcely studied. In this investigation, the kinetic study of the thermal decomposition of ethyl chlorooxoacetate between 543–593 K and 76–209 mbar was carried out, using a static vacuum system whose operation are widely described. Total pressure measurements and chromatographic products analysis indicates consecutive first order reactions, unimolecular and homogeneous for substrate decarbonylation, followed by ethylene elimination, unlike the ethyl oxoacetate thermolysis, which proceeds by parallel decarboxylation and decarbonylation pathways. Arrhenius equation for the reaction studied between 543.2 – 593.1 K was found to be log k 1 = (13.22 ± 0.45)– (179.4 ± 4.9) kJ mol –1 (2.303RT) –1 and velocity coefficient at 623 K significantly larger than for the decarbonylation of ethyl oxoacetate, suggesting that chlorine substituent would have a greater tendency than hydrogen to migrate to the adjacent carbonyl, forming more rigid bonds transition state