Ab initio study of the S/sub N/2 reactions of OH/sup -/ and OOH/sup -/ with CH/sub 3/Cl

Journal Article · Wed Apr 15 00:00:00 EDT 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00242a018· OSTI ID:6804077

Evanseck, J D; Blake, J F; Jorgensen, W L

Ab initio molecular orbital calculations have been used to determine energy profiles for the S/sub N/2 reactions of hydroxide and hydroperoxide anions with methyl chloride. Geometry optimizations were carried out at the Hartree-Fock level with the 6-31 +G(d) basis set. These calculations were supplemented by computations of the correlation energy with second and third-order Moeller-Plesset theory. Though the reactions are exothermic by 40-50 kcal/mol, both are found to have the double-well energy surfaces characteristic of gas-phase S/sub N/2 reactions. At the Hartree-Fock level the central barrier heights are 2.9 and 4.1 kcal/mol for OH/sup -/ and OOH/sup -/, and the transition states are 12.4 and 9.7 kcal/mol lower in energy than the reactants. Electron correlation raises the barrier by 2.1 kcal/mol for OH/sup -/, but it has much larger effects on the overall exothermicities. Vibrational energy changes are found to be less than 1.5 kcal/mol up to the transition state. The geometrical results for the ion-molecule complexes and transition states are discussed and show a somewhat later transition state for the reaction with hydroperoxide ion. The results are consistent with experimental observations including the lower reactivity of OOH/sup -/ than OH/sup -/ in the gas phase. Experimental and theoretical data are also combined to consider energy profiles for S/sub N/2 reactions in aqueous solution.

• Research Organization: Purdue Univ., West Lafayette, IN
• OSTI ID: 6804077
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:8; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
ANIONS
CHARGED PARTICLES
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
DATA
ENERGY LEVELS
EXCITED STATES
FLUIDS
GASES
HALOGENATED ALIPHATIC HYDROCARBONS
HARTREE-FOCK METHOD
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
HYDROXIDES
INFORMATION
IONS
METHYL CHLORIDE
MOLECULAR ORBITAL METHOD
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXYGEN COMPOUNDS
PEROXIDES
POTENTIALS
THEORETICAL DATA
VIBRATIONAL STATES