Estimation of gas-phase rate coefficients for the reactions of a series of α,β-unsaturated esters with OH, NO_3, O_3 and Cl

摘要

Rate coefficients for reactions of a series of α, β-unsaturated esters with OH and NO_3 radicals, O_3 and Cl atoms have been estimated using different methods: i.e., physico-chemical correlations and Structure Activity Relationships (SARs). In this study new correlations to estimate rate coefficients have been proposed (only for α,β-unsaturated esters): log(k_(NO_3)) = (13.9 ± 2.8) + (2.75 ± 0.26) × log (k_(OH)); log (k_(OH)) = (4.93 ± 1.14) + (1.60 ± 0.12) × log (k_(Cl)); ln(k_(OH)/cm~3 molecule~1 s~1 = (1.71 ± 0.21) × E_(HOMO)/eV = (6.25 ± 2.24); ln(k_(NO_3)/cm~3 molecule~1 s~1) -(5.94 ± 0.35) × E_(HOMO)/ eV + (27.87 ± 3.65); ln(k_(O_3)/cm~3 molecule~1 s~1) = (2.20 ± 0.63) × E_(HOMO)/eV = (16.75 ± 6.65) and ln(k_(Cl)/cm~3 molecule~1 s~1) = (0.21 ± 0.23) × (E_(HOMO))/eV (19.8 ± 2.4). The group reactivity factors necessary to estimate the rate coefficients by SAR methods have also been calculated for a series of α,β-unsaturated esters for the first time: f(-C(O)O(CH_2)_3CH_3), f(-C(O)O(CH_2)_5CH_3), f(-C(O) OCH_2CH(CH_2CH_3)CH_2CH_2CH_2CH_3) for reactions with the NO_3 radical, OH radical and O_3. Furthermore, f(-C(O)OCH_3), f(-C(O)OCH_2CH_3), f(-C(O)O(CH_2)_3CH_3), f(-C(O)OCH_2CH_2CH_2CH_2CH_2CH_3), f(-C(O) OCH_2CH(CH_2CH_3)CH_2CH_2CH_2CH_3) for reactions with chlorine atoms have been estimated. The results show that for NO_3 and OH radicals these methods are generally satisfactory. In the case of Cl atoms, all methods used in this study reproduce the rate coefficient within a factor of 1.5. In general the best method for estimating the rate coefficient of α,β-unsaturated esters with the main atmospheric oxidants is the correlation of In k versus E_(HOMO).