Ab initio calculation of I. Infrared intensities of CH[sub 2]F[sub 2]. II. Radical abstraction reactions

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:7165095

Fox, G L

Ab initio molecular orbital theory has been employed to study the molecular properties of CH[sub 2]F[sub 2] and radical abstraction reactions. The dipole moment of CH[sub 2]F[sub 2] is estimated to be 1.90D at the MP2/6-311++G(3d,3p) level, compared to the experimental value of 1.9785 [+-] .0021 D. The average error in the calculated harmonic frequencies is 1.9% at MP2/6-311+G(d,p), and 1.3% at the estimated MP2/6-311++G(3d,3p) level. The average error in the calculated IR intensities is 26 km/mol at HF/6-311++G(3d,p), 7.8 km/mol at MP2/6-311+G(d,p) and 3.1 km/mol at the estimated MP2/6-311++G(3d,3p) level (compared to the observed values for A[sub 2], A[sub 4], A[sub 8], A[sub 1]+A[sub 6], and A[sub 3]+A[sub 7]+A[sub 9]). The reactions CH[sub 3]X + CH[sub 2]Y [yields] CH[sub 2]X + CH[sub 3]Y (X, Y = H,F,Cl,OH,NH[sub 2],CN) have been studied. The Marcus relation can be used to predict barrier heights of cross reactions based on information from identity reactions and the changes in energy for the cross reactions. This method predicts the barrier heights accurately with two exceptions; the average absolute error is 0.98 kcal/mol when compared to the ab initio barrier heights. Charge transfer states have been found to play a significant role in the reactions where X = CN and Y = NH[sub 2] or OH. A similar study was performed on the following reactions: XH + Y [yields] X + HY (X,Y = H,F,Cl,CH[sub 3],NH[sub 2],CN,OH and SH). Again, Marcus theory predicts the barrier heights accurately with five exceptions; the average absolute error is 3.1 kcal/mol. Analysis of these exceptions indicate charge transfer states play a crucial role in several reactions. The reaction F + HF [yields] HF + F has been studied. Most correlated levels of theory predict the transition state to be a highly bent C[sub 2v] symmetry structure, whereas MP2, MP3 and CCD levels predict the C[sub 2v] symmetry structure to be a shallow minimum bound by 0.1-0.4 kcal/mol.

• Research Organization: Wayne State Univ., Detroit, MI (United States)
• OSTI ID: 7165095
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CHEMICAL REACTION KINETICS
MOLECULAR ORBITAL METHOD
CYANIDES
HALOGENATED ALIPHATIC HYDROCARBONS
METHANE
METHANOL
METHYLAMINE
RADICALS
ALCOHOLS
ALKANES
AMINES
CALCULATION METHODS
HYDROCARBONS
HYDROXY COMPOUNDS
KINETICS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
REACTION KINETICS
400201* - Chemical & Physicochemical Properties