Secondary inverse isotopic effect: thermal decomposition reaction in ethanol solution of deuterated acetone cyclic diperoxide and acetone diperoxide

KARINA NESPRÍAS; GASTÓN BARRETO; ADRIANA CAÑIZO; NORA EYLER

QUíMICA NOVA

SOC BRASILEIRA QUIMICA

Lugar: San Pablo; Año: 2017

0100-4042

The characterization by mass spectrometry and the kinetic study of the thermal decomposition reaction of deuterated acetone diperoxide (dACDP) and acetone diperoxide (ACDP) were carried out in ethanol solution in the 140-165 ºC temperature range. The kinetic behavior observed in both cases follows a pseudo first order kinetic law up to at least 86 % peroxide conversions. The reactivity of these compounds was compared at different temperatures observing that, under the established experimental conditions, dACDP decomposes ca. 1.2 times faster than ACDP. It can be postulated that both peroxides decompose a little more by the same mechanism with substituent effect. The presence of deuterated substituents probably affects the stability of the tetraoxacyclohexane ring favoring the O-O bond rupture and the formation of the reaction products. A secondary inverse kinetic isotope effect is observed (kH/kD 1) since the bond to isotopically substituted atom in the reactant is not broken in the rate-determining step of the reaction.