A quantum-chemical study of the C{sub 2}H{sub 3}F{sub 2}{sup +} and C{sub 2}H{sub 3}Cl{sub 2}{sup +} isomers and their interconversion. CBS-QB3 proton affinities of difluoroethenes and dichloroethenes

Journal Article · Thu Sep 30 04:00:00 EDT 1999 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp9915477· OSTI ID:20001131

Frash, M V; Hopkinson, A C; Bohme, D K

Potential energy surfaces of the C{sub 2}H{sub 3}X{sub 2}{sup +} isomers and proton affinities of dihaloethenes C{sub 2}H{sub 2}X{sub 2} (X = F, Cl) were computed at the B3LYP/6-31++G(d,p), MP2/6-311++G(d,p), and CBS-QB3 levels. The classical 1,1-dihaloethyl cations Ch{sub 3}CX{sub 2}{sup +} represent global minima for the C{sub 2}H{sub 3}X{sub 2}{sup +} isomers. Other minima located are classical, 1,2-dihaloethyl cations, the chloroethylchloronium (Cl-bridged) cation, halogen-protonated cis-1,2-, trans-1,2-, and 1,1-dihaloethenes, and ion-dipole complexes of the CH{sub 2}=CX{sup +} cation with the HX molecule. the classical 2,2-dihaloethyl cations, as well as H-bridged cations, are at first-order saddle points. The fluoroethylfluoronium cation is not at a stationary point. Transition states were located and activation energies computed for isomerization (1) of the trans-1, 2-difluoroethyl cation to the 1,1-difluoroethyl cation,(2) of the cis-1,2-difluoroethyl cation to its trans rotamer, (3) of the chloronium cation to the 1,1-dichloroethyl cation, (4) of the cis-1,2-dichloroethyl cation to the chloronium cation, and (5) of the halogen-protonated dihaloethenes to carbon-protonated isomers. Protonation of dihaloethenes at carbon is more favorable than protonation at halogen. The best estimates at CBS-QB3 for proton affinities (in kcal/mol) are as follows: 1,1-C{sub 2}H{sub 2}F{sub 2}, 171.1; cis-1,2-C{sub 2}H{sub 2}F{sub 2}, 152.9; trans-1,2-C{sub 2}H{sub 2}F{sub 2}, 151.9; 1,1-C{sub 2}H{sub 2}Cl{sub 2}, 176.0; cis-1,2-C{sub 2}H{sub 2}Cl{sub 2}, 159.7; trans-1,2-C{sub 2}H{sub 2}-Cl{sub 2}, 162.0.

• Research Organization: York Univ., North York, Ontario (CA)
• OSTI ID: 20001131
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 39 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CATIONS
CHLORINE
ETHANE
ETHYLENE
FLUORINE
HALOGEN COMPOUNDS
ISOMERS
MATHEMATICAL MODELS