Gas-phase reaction of methyl isothiocyanate and methyl isocyanate with hydroxyl radicals under static relative rate conditions.
Gaseous methyl isothiocyanate (MITC), the principal breakdown product of the soil fumigant metam sodium (sodium N-methyldithiocarbamate), is an inhalation exposure concern to persons living near treated areas. Inhalation exposure also involves gaseous methyl isocyanate (MIC), a highly reactive and toxic transformation product of MITC. In this work, gas-phase hydroxyl (OH) radical reaction rate constants of MITC and MIC have been determined using a static relative rate technique under controlled laboratory conditions. The rate constants obtained are 15.36 × 10(-12) cm(3) molecule(-1) s(-1) for MITC and 3.62 × 10(-12) cm(3) molecule(-1) s(-1) for MIC. The average half-lives of MITC and MIC in the atmosphere are estimated to be 15.7 and 66.5 h, respectively. The molar conversion of MITC to MIC for OH radical reactions is 67% ± 8%, which indicates that MIC is the primary product of the MITC-OH reaction in the gas phase.
Department of Natural Resources and Environmental Science, University of Nevada, Reno , 1664 North Virginia Street, Reno, Nevada 89557, United States.
Zhou
Z
Lu
Vincent R
VR
Hebert
Glenn C
GC
Miller
D005659:Fungicides, Industrial / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D017953:Isocyanates / Q000737:chemistry*; D017879:Isothiocyanates / Q000737:chemistry*; D007700:Kinetics; D044367:Phase Transition; D012989:Soil Pollutants / Q000737:chemistry
D005659:Fungicides, Industrial; D017953:Isocyanates; D017879:Isothiocyanates; D012989:Soil Pollutants; D017665:Hydroxyl Radical; C008461:methyl isocyanate; C005227:methyl isothiocyanate