Direct measurement of singlet methylene removal rates by organic species containing the - O - and > C = O moieties

The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene ¹CH₂ (ã ¹A₁) with dimethyl ether (CH₃OCH₃), acetaldehyde (CH₃CHO), acetone (CH₃COCH₃), acetic acid (CH₃CO₂H), methyl formate (HCO₂CH₃), acetic anhydride (CH₃CO₂COCH₃), and dimethyl carbonate (CH₃OCO₂CH₃). The removal rate constants were found to be (1.80 ± 0.22), (2.81 ± 0.35), (4.48 ± 0.35), (5.71 ± 0.40), (2.82 ± 0.32), (5.27 ± 0.71) and (2.68 ± 0.28) × 10^-10 cm³ molecule^-1 s^-1, respectively. Removal rate constants for the molecules containing the > C=O moiety are considerably greater than those for the corresponding alkanes, but the removal rate constant for dimethyl ether is significantly less than that for the alkane analogue, propane. Removal rate constants were also remeasured for ethane (C₂H₆), ethene (C₂H₄) and methanol (CH₃OH) and found to be (1.95 ± 0.48), (2.46 ± 0.23) and (3.69 ± 0.37) × 10^-10 cm³ molecule^-1 s^-1, respectively.