The kinetics and mechanism of the reaction of C4H5 (methylpropargyl radical) with O2 were investigated from 296 to 900 K in a tubular reactor coupled to a photoionization mass spectrometer. At room temperature the reaction proceeds by a simple pressure-dependent addition reaction. Between 369 and 409 K the equilibrium C4H5 + O2 ⇄ C4H5O2 was clearly observable and equilibrium constants were measured as a function of temperature. These measurements yielded the values of ΔHo298 (-78±3 kJ mol-1) and ΔSo298 (-122±9 J mol-1 K-1). Above 600 K the rate of reaction of methylpropargyl with O2 is independent of density and increases with temperature with a phenomenological rate constant equal to 6.9×10-14 exp(-10.5 kJ mol-1/RT) cm3 molecule-1 s-1. A mechanism of the C4H5+O2 reaction is proposed which involves initial formation of a C4H5O2 adduct. At temperatures above 600 K, decomposition of the chemically activated adduct competes with redissociation to C4H5+O2. The role of elementary reactions between unsaturated radicals and molecular oxygen in combustion processes is briefly reviewed.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology
- Mechanical Engineering
- Physical and Theoretical Chemistry
- Fluid Flow and Transfer Processes