Calculation of carbon-14, chlorine-37, and deuterium kinetic isotope effects in the solvolysis of tert-butyl chloride

Journal Article · Wed May 11 04:00:00 EDT 1977 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00452a031· OSTI ID:7324446

Burton, G W; Sims, L B; Wilson, J C; Fry, A

In the solvolysis of tert-butyl chloride, satisfactory ..cap alpha..-carbon-14, ..beta..-deuterium, and chlorine kinetic isotope effects (KIE) may be calculated for a productlike transition state characterized by bond orders n/sub C Cl/ = 0.2, n/sub C C/ = 1.18, and n/sub C H/ = 0.94, employing a diagonal valence force field, provided that allowance is made for hydrogen-bonded solvation of the developing chloride ion with n/sub Cl H/ approx. 0.05 (approx. 7 kcal/mole hydrogen bonds). The effect of the three solvating molecules appears to be to increase the ''effective'' mass of the incipient chloride ion and to decrease the loss of zero-point energy in going to the transition state. Reaction coordinates more complicated than a simple heterolysis of the carbon-chlorine bond appear to be unnecessary and there is no advantage in employing force fields more complex than a simple valence force field containing only diagonal elements for both the reactant and the transition state model. The structural and bonding features of the proposed transition state are in accord with earlier more qualitative conclusions concerning the polar nature and productlike character of the transition state, and provide a reasonable explanation of the kinetic and equilibrium isotope effects (EIE) for the reaction. An alternative transition state model involving weak solvent nucleophilic assistance provides reasonable calculated values for the KIE, but the EIE strongly suggest the importance of solvation of the leaving group which, together with the hyperconjugation of the ..beta.. hydrogens, provides a preferred explanation of the tert-butyl solvolysis results.

• Research Organization: Univ. of Arkansas, Fayetteville
• OSTI ID: 7324446
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 99:10; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14
CARBON ISOTOPES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
CHLORINE 37
CHLORINE ISOTOPES
DECOMPOSITION
DEUTERIUM
EVEN-EVEN NUCLEI
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN ISOTOPES
INTERMEDIATE STRUCTURE
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
NUMERICAL SOLUTION
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RADIOISOTOPES
REACTION KINETICS
SOLVOLYSIS
STABLE ISOTOPES
YEARS LIVING RADIOISOTOPES