FTIR PRODUCT STUDY OF THE OH-RADICAL INITIATED REACTIONS OF Z-3-HEPTENOL AND E-3-HEXENOL UNDER NOx-FREE CONDITIONS

R. GIBILISCO, I. BEJAN, I. BARNES, P. WIESEN, M. B. BLANCO, M.A. TERUEL

Conferencia; ATMOSPHERIC CHEMICAL MECHANISMS; 2014

High fluxes of (Z)-3-hepten-1-ol and (E)-3-hexen-1-ol have been observed after the wounding of plants, during the drying plants and also after pathogen attack making these compounds an important fraction of the total OVOCs emitted by vegetation. It is also known that they have a potential use as biopesticides for the control of plagues. Product studies have been performed on the OH-radical initiated photodegradation of (Z)-3-hepten-1-ol and (E)-3-hexen-1- in order to help determine the potential contribution of these unsaturated alcohols to the formation of secondary pollutants such as ozone and oxygenates. This work represents the first study of the OH radical-initiated degradation of these unsaturated alcohols under NOx free conditions. The reactions where carried out in a 1080 L quartz-glass environmental chamber at 298  2 K and atmospheric pressure of synthetic air using in situ FTIR spectroscopy to monitor the reactants and products. Butanal with a yield of (32.7±2.4) % has been observed in the reaction of OH with (Z)-3-hepten-1-ol; and propanal with a yield of (35.3±5.1) % from the reaction of OH with (E)-3-hexen-1-ol. In both cases secondary reactions led to the formation of carbon monoxide and formic acid. The observed reaction products are in line with a mechanism involving mainly addition of the OH radical to the double bond. The 2,3-hydroxyalkoxy radicals formed in the OH addition step can decompose to give the observed aldehydes, however, a significant fraction can also react by isomerization involving an intermediate six membered transition state and a 1,5-H atom leading to the formation of other products.