Experimental rate coefficient for the reaction of OH radical with (Z)-3-HEXENE at 298K

BARBOSA, THAÍS DA SILVA ; PEIRONE, SILVINA A.; ARANGUREN-ABRATE, JUAN P.; BARRERA, JAVIER A.; LANE, SILVIA I.; ARBILLA, GRACIELA; BAUERFELDT, GLAUCO FAVILLA

Congreso; 13th IGAC Science Conference on Atmospheric Chemistry; 2014

The volatile organic compounds (VOCs) are emitted into the troposphereby both biogenic and anthropogenic sources, playing an important role inatmospheric chemistry. VOCs reactions lead to a complex series of chemical andphysical transformations which result in the formation of ozone and oxygenatedcompounds. It is now well recognized that a wide variety of volatilenon-methane organic compounds are emitted into the atmosphere from vegetation,mainly by forests 1. Hexenol and other unsaturated alcohols aremainly emitted by vegetation. Other unsaturated compounds are of anthropogenicorigin, such as hexenes. These compounds are used in the production ofpolymers. The main goal of this work was the study of OH radical + (Z)-3-hexenereaction for a further comparison with its alcohol homologue. The kinetics of the reaction at 298 K and atmospheric pressure wasinvestigated using the relative rate method. The experimental set-up at INFIQC(Argentine) consisted of an 200 L Teflon bag located in a wooden box with theinternal walls covered with aluminum foil, and operated at atmospheric pressureand 298 K. OH radicals were produced by the photolysis of H2O2 at254 nm using five germicide lamps. The mixtures of (Z)-3-hexene and referencecompounds with H2O2 were stable in the dark whenleft in the chamber for about 2 h. Moreover, no photolysis of (Z)-3-hexene orreferences was observed. Photolysiswas carried out in steps of 2 min, and thetotal time of photolysis varied from 2 to 12 min. Periodically, gas sampleswere removed from the Teflon bag using calibrated gas syringes and analyzedusing the GC-FID. Relative rate coefficients were determined by comparing therate coefficients for the reaction of OH radicals with the target compound tothat with three reference compounds (cyclohexene, 2-buten-1-ol and allylether). The mean value for the second-order rate coefficient was (0.6±0.1) x 10-10cm3 molécule-1 s-1 ingood agreement with the previous reported value 2.