Model calculations of kinetic isotope effects for the solvolysis of neopentyl arenesulfonates

Journal Article · Wed Apr 07 04:00:00 EST 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00371a005· OSTI ID:5146065

Yamataka, H; Ando, T

Model calculations of ..cap alpha..-/sup 14/C, ..beta..-/sup 14/C, ..gamma..-/sup 14/C, ..cap alpha..-D/sub 2/, and ..gamma..-D/sub 3/ kinetic isotope effects in the acetolysis of neopentyl arenesulfonate were carried out for two possible pathways, concerted (k/sub ..delta../) and stepwise (k/sub c/). In the k/sub ..delta../ transition state (TS), four bond orders, n/sub ..cap alpha..-0/, n/sub ..cap alpha..-..beta../, n/sub ..beta..-..gamma../, and n/sup ..cap alpha..-..gamma../, were taken as independent parameters which define the model, whereas in the k/sub c/ model, n/sub ..cap alpha..-0/, n/sub ..cap alpha..-..beta../, n/sub ..beta..-..gamma../, and n/sub ..gamma..-H/ were taken as the parameters; other geometrical parameters and diagonal force constants were related to these four parameters by empirical expressions. One or more off-diagonal force constants were used to generate the reaction-coordiate frequency. The calculations suggested that the reaction proceeds via the k/sub ..delta../ pathway whose TS has a weak but significant ..cap alpha..-..gamma.. interaction; the alternative k/sub c/ pathway was shown to be less probable. The k/sub ..delta../ TS structure determined was then compared with that of the 2-methyl-2-phenylpropyl (neophyl) solvolysis. The calculated k/sub ..delta../ TS of the neopentyl solvolysis has (1) a stronger C/sub ..cap alpha../-O bond, (2) a stronger C/sub ..cap alpha../-C/sub ..beta../ bond, (3) a weaker C/sub ..beta../-C/sub ..gamma../ bond, and (4) a weaker C/sub ..cap alpha../-C/sub ..gamma../ bond than the TS of the neophyl solvolysis has. The results were interpreted in terms of the difference in the migrating group, methyl vs. phenyl, and it was concluded that the major mode of neighboring group participation by the phenyl is bridging whereas that by the methyl is hyperconjugation.

• Research Organization: Osaka Univ., Suita, Japan
• OSTI ID: 5146065
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 104:7; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ACETOLYSIS
AROMATICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14
CARBON ISOTOPES
CHEMICAL REACTIONS
DATA
DECOMPOSITION
DEUTERIUM
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
HYDROGEN ISOTOPES
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
MATHEMATICAL MODELS
NITRO COMPOUNDS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
RADIOISOTOPES
REACTION KINETICS
SOLVOLYSIS
STABLE ISOTOPES
SULFONATES
YEARS LIVING RADIOISOTOPES