Termólisis de Clorooxoacetato de Etilo en Fase Gas: Comparación con Oxoacetato de Etilo y Detalles del Sistema Estático para el Estudio Cinético / Gas Phase Ethyl ChlorooxoacetateThermolysis: Comparison with Ethyl Oxoacetate and Static System Details for Kinetic Study

• Andreína Alexandra Reyes Yanes Universidad Nacional Mayor de San Marcos, Facultad de Química e Ingeniería Química, Departamento Académico de Fisicoquímica, Ciudad Universitaria- Pabellón B- Calle Germán Amezaga Nº 375, Lima 15081, Perú. http://orcid.org/0000-0003-4603-2318

Palabras clave: termólisis, cinética en fase gas, clorooxoacetato de etilo / thermolysis, gas-phase kinetics, decarbonilation

Resumen

Resumen

La ventaja de los estudios cinéticos en fase gas es que el coeficiente de velocidad no es afectado por superficies, catalizadores ni disolventes que interactúen con el sustrato. La termólisis en fase gas de los ésteres derivados del ácido oxálico ha sido poco estudiada.En esta investigación se realizó el estudio cinético de la descomposición térmica de clorooxoacetato de etilo entre 543–593 K y 76–209 mbar, utilizando un sistema estático de vacío cuyo funcionamiento se describeampliamente. Mediciones de presión total y análisis cromatográfico de productos indicanreaccionesconsecutivas de orden uno, unimoleculares y homogéneas, de decarbonilación del sustrato seguida de la eliminación de etileno, a diferencia de la termólisis de oxoacetato de etilo, que procede por vías paralelas de decarboxilación y decarbonilación.La ecuación de Arrhenius para la reacción estudiada entre 543,2 – 593,1 Kresultó serlog k₁ = (13,22 ± 0,45)–(179,4 ± 4,9) kJ mol^–1 (2,303RT)^–1, y el coeficiente de velocidad a 623 K significativamente mayor que para la decarbonilación del oxoacetato de etilo sugiere que el sustituyente cloro tendría mayor disposición que el hidrógeno de migrar al carbonilo adyacente, formando un estado de transición con enlaces más rígidos.

Abstract

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 orderreactions, unimolecular and homogeneous forsubstrate decarbonylation, followed by ethylene elimination, unlike the ethyl oxoacetatethermolysis, 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 k₁ = (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.

 

https://doi.org/10.22209/rt.v43n3a01

Citas

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