A Computational Study of the Thermolysis of B-Hydroxy Ketones in Gas Phase and in m-Xylene Solution

HENAO DIANA; MURILLO JULIANA; RUIZ PABLO; QUIJANO JAIRO; MEJÍA BARBARA; CASTAÑEDA LINA; NOTARIO RAFAEL

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY

JOHN WILEY & SONS LTD

Año: 2012 p. 1 - 6

0894-3230

Theoretical calculations at the M05-2X/6-31+G(d) level of theory have beencarried out in order to explore the nature of the mechanism of the thermaldecomposition reactions of the β−hydroxy ketones, 4-hydroxy-2-butanone, 4-hydroxy-2-pentanone, and 4-hydroxy-2-methyl-2-pentanone, in the gas phaseand in m-xylene solution. The mechanism proposed is a one-step processproceeding through a six-membered cyclic transition state.A reasonable agreement between experimental and calculated activationparameters and rate constants has been obtained, tertiary:secondary:primaryalcohol rate constant relation being calculated, at 503.15 K, as 5.9:4.7:1.0 in mxylenesolution and 44.1:5.0:1.0 in the gas phase, comparing with theexperimental values, 3.7:1.3:1.0 and 13.5:3.2:1.0, respectively.The progress of the thermal decomposition reactions of β−hydroxy ketones hasbeen followed by means of the Wiberg bond indices.