Reactivity of selected volatile organic compounds (VOCs) toward the sulfate radical (SO4-)

Rate constants for a series of alcohols, ethers, and esters toward the sulf ate radical (SO4-) have been directly determined using a laser photolysis s et-up in which the radical was produced by the photodissociation of peroxod isulfate anions. The sulfate radical concentration was monitored by followi ng its optical absorption by means of time resolved spectroscopy techniques . At room temperature the following rate constants were derived: methanol ( (1.6 +/- 0.2) x 10(7) M-1 s(-1)); ethanol ((7.8 +/- 1.2) x 10(7) M-1 s(-1)) ; tert-butanol ((8.9 +/- 0.3) x 10(5) M-1 s(-1)); diethyl ether ((1.8 +/- 0 .1) x 10(8) M-1 s(-1)); MTBE ((3.13 +/- 0.02) x 10(7) M-1 s(-1)); tetrahydr ofuran (THF) ((2.3 +/- 0.2) x 10(8) M-1 s(-1)); hydrated formaldehyde ((1.4 +/- 0.2) x 10(7) M-1 s(-1)); hydrated glyoxal ((2.4 +/- 0.2) x 10(7) M-1 s (-1)); dimethyl malonate (CH3OC(O)CH2C(O)OCH3) ((1.28 +/- 0.02) x 10(6) M-1 s(-1)); and dimethyl succinate (CH3OC(O)CH2CH2C(O)OCH3) ((1.37 +/- 0.08) x 10(6) M-1 s(-1)) where the errors represent 2 sigma. For the two latter sp ecies, we also measured the temperature dependence of the corresponding rat e constants. A correlation of these kinetics with the bond dissociation ene rgy is also presented and discussed. (C) 2001 John Wiley & Sons, Inc.