Published:Journal of Chromatographic Science,
ISSN 0021-9665Volume
39, Number 2, February 2001, pp. 45-48
Kinetics
and Mechanism of Gas-Phase Thermolysis Using Headspace-Gas Chromatographic Analysis
Lázaro
F.R. Cafferata and Carlos J. Manzione
LABORATORIO LADECOR, Facultad de Ciencias Exactas, Universidad Nacional de La
Plata, Calle 47 esq. 115, (1900) La Plata, República Argentina
Headspace
gas chromatography is employed in order to study the thermal decomposition reaction
of gaseous di-tert-butyl peroxide (DTBP) in the 130°C to 160°C temperature
range and in the presence of n-hexane as the internal standard and nitrogen
as the carrier gas. The reaction exclusively yields acetone and ethane as products.
First-order kinetics are observed, including when the surface-to-volume ratio
(S/V) of the Pyrex 20-mL vial employed as the reactor is increased by packing
it with silanized glass wool. However, a small increase in the rate constant
values is observed at each temperature, which supports a heterogeneous surface
process in DTBP decomposition. The rate constant’s dependence on the homogeneous
unimolecular decomposition reaction corresponds to the O–O bond rupture
of the DTBP molecule in a stepwise three-stage mechanism. Thus, the relevant
question of the participation of a surface catalytic effect in the DTBP gas-phase
thermolysis can easily be assessed through the procedure described in this work.
In general, this is advantageous for the rapid investigation of the reaction
kinetics of volatile compounds at different temperatures.
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