Revised structure activity parameters derived from new rate coefficient determinations for the reactions of chlorine atoms with a series of seven ketones at 290 K and 1 atm

Abstract

Rate coefficients of Cl atom reactions with several ketones have been investigated at 298K and 1atm using relative rate methods, monitoring substrates with both GC and FTIR and with two reference compounds. The following rate coefficients (1010k/cm3 molecule−1s−1) were obtained: k(2-pentanone)=(1.08±0.05), k(3-pentanone)=(0.89±0.12), k(3-methyl-2-butanone)=(0.68±0.06), k(4-methyl-2-pentanone)=(1.10±0.10), k(5-methyl-2-hexanone)=(1.65±0.14), k(3-methyl-2-pentanone)=(0.94±0.10) and k(3,3-dimethyl-2-butanone)=(0.48±0.05). The results are discussed in terms of Cl reactivity trends and existing literature. k(3-methyl-2-pentanone) and k(3,3-dimethyl-2-butanone) are poorly predicted with current structure activity relationships and revised parameters are proposed. In regions of high [Cl], these reactions can significantly reduce the fraction of ketones reaching the free troposphere.