Gas-phase pyrolytic reactions. Part 6. [1] Behavior of ethyl (hetero)arylcarboxylate esters in thermal elimination reactions

Abstract

Rates, Arrhenius parameters, and Hammett substituent constants are obtained for the gas-phase thermal elimination of ethyl benzoate (1) and ethyl 2 -thienyl -(2), 3 -thienyl -(3), 2 -furyl -(4), 3 -furyl -(5), 4 -pyridyl -(6), 3 -pyridyl -(7), and 2 -pyridylcarboxylate (8) esters. The log A/s Ϫ1 and the E a /kJ mol Ϫ1 values of these esters averaged 13.60 and 216.3, respectively. The present results are compared with data previously reported for the corresponding isopropyl and t-butyl analogues, and the findings are rationalized in terms of a plausible transition state for the elimination pathway

Kinetics and mechanism of gas‐phase pyrolysis of N‐aryl‐3‐oxobutanamide ketoanilides, their 2‐arylhydrazono derivatives, and related compounds

“…Each rate constant at a given temperature represents an average of at least three measurements in agreement to within ±2% rate spread. To ensure reliable kinetic results, the pyrolysis of each substrate was followed over 59 ± 12 K temperature range and 94%–98% reaction 6–8,12–16. The Arrhenius log A (s −1 ) and activation energy ( E a , kJ mol − 1 ), and the rate constants ( k , s −1 ) at 450 K for the reactions of the compounds under study are recorded in Table II.…”

Thermo-oxidative-kinetic study of cinnamyl diesters

“…This reaction takes place through a concerted mechanism, where the formation of free radicals, responsible for the generation of multiple pyrolysis products, is not observed [17]. The carboxylic-ester-decomposition reactions, yielding an acid and olefin, are represented by an endothermic process which has very high activation energy (148-213 kJ mol À1 ) depending on the ester structure [21][22][23][24][25][26][27][28][29]. However, the combustion process of organic esters is more complicated due to the influence of oxygen on the decomposition and thus, the production of different-structure free radicals which can further undergo, various subsequent reactions, causing the formation of various structure-intermediate-decomposition species.…”

Theoretical Study on the Pyrolysis of Sulphonyl Oximes in the Gas Phase

“…1,2 Some similar reactions have also been studied for 3-phenylhydrazonopentane-2,4-dione, 3 ethyl (hetero) arylcarboxylate esters, 4 and heterocyclic hydrazone 5 systems experimentally. The common character of these reactions is that they were found to be homegeneous and unimolecular, and follow firstorder rate law.…”