Mechanism and kinetic study on the gas-phase reactions of OH radical with carbamate insecticide isoprocarb

As one of the most important carbamate insecticides, isoprocarb [2-(1-methylethyl) phenyl methylcarbamate, MIPC] is widely used in agricultural and cotton spraying. The atmospheric chemical reaction mechanism and kinetics of MIPC with OH radical have been researched using the density functional theory in this paper. The study shows that OH radical is more easily added to the C atoms of aromatic ring than to carbon-oxygen double bond, while the H atom is abstracted more difficulty from –CONH– group and aromatic ring than from the –CH3– group and the –CH– group. At room temperature, the total rate constant of MIPC with OH radical is about 5.1 × 10−12 cm3 molecule−l s−l. OH radical addition reaction and H atom abstraction reaction are both important for the OH-initiated reaction of MIPC. The energy-rich adducts (MIPC-OH) and the MIPCʹs radical isomers are open-shell activated radicals and can be further oxidized in the atmosphere.