Theoretical study of the kinetics and mechanism of the decomposition of trifluoromethanol, trichloromethanol, and tribromomethanol in the gas phase.
Ab initio calculations at the G2 level were used in a theoretical analysis of the kinetics of unimolecular and water-accelerated decomposition of the halogenated alcohols CX(3)OH (X = F, Cl, and Br) into CX(2)O and HX. The calculations show that reactions of the unimolecular decomposition of CX(3)OH are of no importance under atmospheric conditions. A considerably lower energy pathway for the decomposition of CX(3)OH is accessible by homogenous reactions between CX(3)OH and water. It is shown that CX(3)OH + H(2)O reactions proceed via the formation of intermediate complexes. The mechanism of the reactions appears to be complex and consists of three consecutive elementary processes. The calculated values of the second-order rate constants are of 2.5 x 10(-21), 2.1 x 10(-19), and 1.2 x 10(-17) cm(3)molecule(-1)s(-1) at 300 K for CF(3)OH + H(2)O, CCl(3)OH + H(2)O, and CBr(3)OH + H(2)O, respectively. The theoretically derived atmospheric lifetimes of the CX(3)OH molecules indicate that the water-mediated decomposition reactions CX(3)OH + H(2)O may be the most efficient process of CF(3)OH, CCl(3)OH, and CBr(3)OH loss in the atmosphere.
Department of Physical Chemistry, Wroclaw Medical University, Wroclaw, Poland.
Katarzyna
K
Brudnik
Dorota
D
Wójcik-Pastuszka
Jerzy T
JT
Jodkowski
Jerzy
J
Leszczynski
D000438:Alcohols / Q000737:chemistry; D003198:Computer Simulation; D054879:Halogenation; D017665:Hydroxyl Radical; D007700:Kinetics; D000432:Methanol / Q000031:analogs & derivatives* / Q000737:chemistry*; D008958:Models, Molecular; D008962:Models, Theoretical
D000438:Alcohols; C534497:tribromomethanol; C534496:trichloromethanol; C534495:trifluoromethanol; D017665:Hydroxyl Radical; D000432:Methanol