Kinetics and mechanism of gas-phase reaction of C[F.sub.3]OC[H.sub.2]C[H.sub.3] with the oh radical--a theoretical study

• Published in: Canadian journal of chemistry pp. 303 - 310
• Main Authors: Rao, Pradeep Kumar, Singh, Hari Ji
• Format: Journal Article
• Language: English
• Published: NRC Research Press 01.03.2015
• Subjects: Analysis; Chemical properties; Chemical reaction, Rate of; Computational chemistry; Coordination compounds; Density functionals; Environmental aspects; Ethers; Methods; Observations; Potential energy; Tunneling (Physics); India
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/cjc-2014-0400

In the present study, the density functional method with recently developed M06 functionals has been used to study the reaction of C[F.sub.3]OC[H.sub.2]C[H.sub.3] with the OH radical. All possible hydrogen abstraction and displacement reaction channels have been modeled. The minimum energy path on the respective potential energy surface and energetics were calculated at the M06-2X/6-311++G(d,p) level of theory. Two different reaction mechanisms were considered: (i) reactant and product complexes called the complex mechanism and (ii) the direct mechanism (reactant [right arrow] transition state → product). Tunneling corrections were made using the Eckart unsymmetrical potential. The overall rate constant calculated by the complex mechanism ([k.sub.eff] = 1.8 x [10.sup.-13] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]) has been found to be in good agreement with the experimentally determined value (1.5 ± 0.25 x [10.sup.-13] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]), while the rate constant calculated by the direct mechanism ([k.sub.D] = 7.6 x [10.sup.-14] [cm.sup.3] [molecule.sup.-1] [s.sup.-1]) is about two times lower than the experimental value. The theoretical studies show that hydrogen atom abstraction from the - C[H.sub.2]- site is the most favorable reaction pathway and the reaction involves prereactive and product complexes before leading to stable product formation.