Rate constants for the gas-phase reactions of the OH radical with selected carbamates and lactates

Using a relative rate, method, rate constants have been measured for the gas-phase reactions of the volatile. carbamates CH3NHC(O)OCH3, CH3NHC(O)OCH2CH3, CH3CH2NHC(O)OCH3 and CH3CH2NHC(O)OCH2CH3, and the lactates CH3CH(OH)C(O)OCH3, and CH3CH(OH)C(O))OCH2CH3 with the OH radical at 296 +/- 2 K of (in units of 10(-12) cm(3) molecule(-1) s(-1)) 4.3 +/- 1.2, 8.3 +/- 2.2, 10.5 +/- 2.9, 14.4 +/- 3.7, 2.8 +/- 0.8, and 3.9 +/- 1.1, respectively, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. Rate constants were also measured for the reactions of the carbamates with NO3 radicals and O-3, with respective NO3 radical and O-3 reaction rate constants (in cm(3) molecule(-1) s(-1) units) of CH3NHC(O)OCH3, (8.5 +/- 3.2) x 10(-16) and <4 x 10(-20); CH3NHC(O)OCH2CH3, (9.4 +/- 3.5) x 10(-16) and <4 x 10(-20); CH3CH2NHC(O)OCH3, (1.8 +/- 0.8) x 10(-15) and <6 x 10(-20); and CH3CH2NHC(O)OCH2CH3, (2.6 +/- 1.3) x 10(-15) and <3 x 10(-20). The OH radical reaction rate constants for the carbamates have been used to extend a previously developed estimation method to carbamates of the structure R(1)NHC(O)OR(2) (where R(1) acid R(2) are alkyl groups only), allowing OH radical reaction rate constants and hence tropospheric lifetimes to be calculated for carbamates used in agriculture for which experimental data are not available.