Theoretical study on the Br + CH3SCH3 reaction

The multiple‐channel reactions Br + CH3SCH3 → products are investigated by direct dynamics method. The optimized geometries, frequencies, and minimum energy path are all obtained at the MP2/6‐31+G(d,p) level, and energetic information is further refined by the G3(MP2) (single‐point) theory. The rate constants for every reaction channels, Br + CH3SCH3 → CH3SCH2 + HBr (R1), Br + CH3SCH3 → CH3SBr + CH3 (R2), and Br + CH3SCH3 →CH3S + CH3Br (R3), are calculated by canonical variational transition state theory with small‐curvature tunneling correction over the temperature range 200–3000 K. The total rate constants are in good agreement with the available experimental data, and the two‐parameter expression k(T) = 2.68 × 10−12 exp(−1235.24/T) cm3/(molecule s) over the temperature range 200–3000 K is given. Our calculations indicate that hydrogen abstraction channel is the major channel due to the smallest barrier height among three channels considered, and the other two channels to yield CH3SBr + CH3 and CH3S + CH3Br are minor channels over the whole temperature range. © 2007 Wiley Periodicals, Inc. J Comput Chem 2007

[1]  Gordon McFiggans,et al.  Active chlorine release from marine aerosols: Roles for reactive iodine and nitrogen species , 2002 .

[2]  Thanh N. Truong,et al.  Direct Ab Initio Dynamics Methods for Calculating Thermal Rates of Polyatomic Reactions , 1996 .

[3]  Dietmar Heidrich,et al.  The Reaction path in chemistry : current approaches and perspectives , 1995 .

[4]  Ian Barnes,et al.  FT‐IR kinetic and product study of the Br‐initiated oxidation of dimethyl sulfide , 1999 .

[5]  Piotr Piecuch,et al.  A General Reaction Path Dual-Level Direct Dynamics Calculation of the Reaction of Hydroxyl Radical with Dimethyl Sulfide , 2000 .

[6]  Lazar' Mateevich Sverdlov,et al.  Vibrational spectra of polyatomic molecules , 1974 .

[7]  Michael J. Frisch,et al.  A direct MP2 gradient method , 1990 .

[8]  A. Guenther,et al.  Sulfur emissions to the atmosphere from natural sourees , 1992 .

[9]  Masahiro Kawasaki,et al.  Temperature and Pressure Dependence Study of the Reaction of IO Radicals with Dimethyl Sulfide by Cavity Ring-Down Laser Spectroscopy , 2003 .

[10]  Donald G. Truhlar,et al.  Molecular modeling of the kinetic isotope effect for the [1,5]-sigmatropic rearrangement of cis-1,3-pentadiene , 1993 .

[11]  Donald G. Truhlar,et al.  Dual-Level Reaction-Path Dynamics (the /// Approach to VTST with Semiclassical Tunneling). Application to OH + NH3 .fwdarw. H2O + NH2 , 1995 .

[12]  Thanh N. Truong,et al.  Thermal and vibrational‐state selected rates of the CH4+Cl↔HCl+CH3 reaction , 1995 .

[13]  Donald G. Truhlar,et al.  Direct Dynamics Method for the Calculation of Reaction Rates , 1995 .

[14]  Donald G. Truhlar,et al.  POLYRATE 4: A new version of a computer program for the calculation of chemical reaction rates for polyatomics , 1992 .

[15]  N. Jensen,et al.  FT-IR Study of the Kinetics and Products of the Reactions of Dimethylsulphide, Dimethylsulphoxide and Dimethylsulphone with Br and BrO , 2002 .

[16]  Paul H. Wine,et al.  Temperature-dependent kinetics studies of the reactions bromine atom(2P3/2) + hydrogen sulfide .tautm. mercapto + hydrogen bromide and bromine atom(2P3/2) + methanethiol .tautm. methylthiol + hydrogen bromide. Heats of formation of mercapto and methylthio radicals , 1992 .

[17]  J. M. Nicovich,et al.  Temperature-Dependent Kinetics Studies of the Reactions Br(2P3/2) + CH3SCH3 .dblarw. CH3SCH2 + HBr. Heat of Formation of the CH3SCH2 Radical , 1994 .

[18]  Zang-Ho Shon,et al.  Evaluation of the DMS flux and its conversion to SO2 over the southern ocean , 2001 .

[19]  C. F. Cullis,et al.  Atmospheric sulphur: Natural and man-made sources , 1980 .

[20]  B. C. Garrett,et al.  Variational Transition State Theory , 1980 .

[21]  Masahiro Kawasaki,et al.  Cavity Ring-Down Spectroscopic Study of the Reactions of Br Atoms and BrO Radicals with Dimethyl sulfide , 2001 .

[22]  E. D. Cyan.  Handbook of Chemistry and Physics , 1970 .

[23]  Donald G. Truhlar,et al.  A simple approximation for the vibrational partition function of a hindered internal rotation , 1991 .

[24]  A. Kettle,et al.  Flux of dimethylsulfide from the oceans: A comparison of updated data sets and flux models , 2000 .

[25]  Michael J. Frisch,et al.  MP2 energy evaluation by direct methods , 1988 .

[26]  Hugh Coe,et al.  The nitrate radical in the remote marine boundary layer , 2000 .

[27]  Krishnan Raghavachari,et al.  Gaussian-3 theory using reduced Mo/ller-Plesset order , 1999 .

[28]  David J. Cooper,et al.  Estimation of hydroxyl radical concentrations in the marine atmospheric boundary layer using a reactive atmospheric tracer , 1996 .

[29]  Garrett Ito,et al.  Origin of intraplate volcanoes from guyot heights and oceanic paleodepth , 2000 .

[30]  A. Ravishankara,et al.  Atmospheric oxidation of reduced sulfur species , 1991 .

[31]  K. Kuchitsu,et al.  Structure of Free Polyatomic Molecules , 1998 .

[32]  K. C. Ferguson,et al.  Bond dissociation energies from equilibrium studies. Part 4.—The equilibrium Br2+ CH4⇌ HBr + CH3Br. Determination of D(CH3—Br) and ΔH°f(CH3Br, g) , 1973 .

[33]  Wolfgang Demtröder.  Spectra of Polyatomic Molecules , 2007 .

[34]  S. Warren,et al.  Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate , 1987, Nature.

[35]  Donald G. Truhlar,et al.  Statistical thermodynamics of bond torsional modes , 2000 .

[36]  Thanh N. Truong,et al.  Direct ab initio dynamics studies of proton transfer in hydrogen‐bond systems , 1994 .

[37]  Donald G. Truhlar,et al.  Factors Affecting Competitive Ion−Molecule Reactions: ClO- + C2H5Cl and C2D5Cl via E2 and SN2 Channels , 1996 .

[38]  D. C. Clary,et al.  The Theory of Chemical Reaction Dynamics , 1986 .