Evaluation of transition state models using chlorine kinetic isotope effects and high resolution vibrational measurements. [Reaction of n-butyl chloride, p-methylbenzyl chloride, or benzyl chloride with thiophenol in methanol]

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1976

OSTI ID:7256990

Julian, R L

A series of possible transition state models for three S/subN//sup 2/ reactions has been evaluated using chlorine leaving group kinetic isotope effects (KIE). For the reaction of n-butyl chloride or benzyl chloride with thiophenol anion in methanol, vibrational analysis of a skeletal ground state model reproduces the measured normal modes of both isotopically substituted molecules to an average error of +-0.03%. A preliminary model for the transition state of the reaction of p-methylbenzyl chloride with thiophenol in methanol is also advanced. Conclusions regarding this model are tentative because experimental measurements are available only at a single temperature. The ground state model also reproduces the measured normal modes to an average error of +-0.03%. all three central transition state models show that the S/sub N//sup 2/-type transition states are not trigonal bipyramids. These models are nonplanar and are more like the reactant structure than the planar trigonal bipyramid. In all three cases the C-Cl bond in the transition state was increased by 2% of its ground state value. The use of Fourier transform infrared spectroscopy enables the measurement of ground state vibrational frequencies and the associated isotopic splittings without isotopically enriched compounds. The measured frequencies and vibrational assignments required for analysis of a skeletal ground state model are presented for methyl, ethyl, n-propyl, n-butyl, t-butyl, benzyl, p-methylbenzyl, and p-nitrobenzyl chloride and bromide as well as for p-methoxybenzyl chloride.

• Research Organization: Wisconsin Univ., Madison (USA)
• OSTI ID: 7256990
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ALCOHOLS
AROMATICS
BOND ANGLE
BOND LENGTHS
CHEMICAL BONDS
CHEMICAL REACTIONS
CHLORINATED AROMATIC HYDROCARBONS
CHLORINE ISOTOPES
ENERGY LEVELS
GROUND STATES
HALOGENATED AROMATIC HYDROCARBONS
HYDROXY COMPOUNDS
ISOTOPE EFFECTS
METHANOL
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS