OH-initiated degradation of a series of hexenols in the troposphere. Rate coefficients at 298Â K and 1Â atm

- First reactivity study of OH-atmospheric oxidation of unsaturated hexenols.
- Relative kinetics and products identification by SPME-GC-FID-MS at 298 K and 1 atm.
- Reactivity trends developed in terms of substitution effects.
- EHOMO calculations of alcohols correlated with their rate coefficients.
- Atmospheric lifetimes of hexenols determined and possible impact assessed.

The kinetics of the reactions of OH radicals with three C6 unsaturated alcohols at 298 K and atmospheric pressure were investigated using solid phase microextraction (SPME) with GC-FID detection of organic compounds. Rate coefficients (in cm3 molecule−1 s−1) of k1(OH + (E)-CH2OHCHCH(CH2)2CH3) = (1.0 ± 0.3) × 10−10, k2(OH + (E)-CH2OHCH2CHCHCH2CH3) = (1.2 ± 0.2) × 10−10 and k3(OH + (Z)-CH2OHCH2CHCHCH2CH3) = (1.4 ± 0.3) × 10−10 were obtained by the relative rate method using methyl methacrylate and (E)-2-buten-1-ol as references. Rate coefficients were compared with previous determinations and reactivity trends were developed and rationalized in terms of the effect and position of substituents in the unsaturated alcohol. A correlation between the reactivity of unsaturated alcohols toward OH radicals and the energy of the HOMO of the unsaturated alcohol is presented.Additionally, product identification under atmospheric conditions was performed for the first time for these unsaturated C6 alcohols by the GC-MS technique. Butanal was observed as the main degradation product of OH with (E)-2-hexen-1-ol, in accordance with the decomposition of the 2,3-hydroxyalcoxy radicals formed. On the basis of our kinetic measurements, tropospheric lifetimes of the studied unsaturated compounds are estimated.

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