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Kinetic isotope effects in Menschutkin-type reaction of benzyl benzenesulfonates with N,N-dimethylanilines. Variation in the transition-state structure

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00319a030· OSTI ID:6549633
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Primary carbon-14 and secondary ..cap alpha..-tritium isotope effects were measured for the Menschutkin-type reaction of m-bromobenzyl-methylene-/sup 14/C X-substituted benzenesulfonates with Y-substituted N,N-dimethylanilines in acetone at 35/sup 0/C (eq 1; Z = m-Br). The large carbon-14 (/sup 12/k//sup 14/k = 1.117-1.151) and small ..cap alpha..-tritium (/sup H/k//sup T/k = 1.026-1.041) isotope effects were consistent with the S/sub N/2 mechanism of the reaction. A monotonous trend was observed when the carbon isotope effects were plotted against the relative rates for varied Xs and a fixed Y (p-CH/sub 3/), while a bell shape was observed for varied Ys and a fixed X (p-Cl). Comparison of the results with those obtained for the unsubstituted benzyl esters indicated that the substitution on the benzyl moiety with the electron-withdrawing m-Br group made the transition state more product-like. Smaller ..cap alpha..-tritium isotope effects for the m-Br series than those for the unsubstituted series verified tighter transition states for the former. The variation in the three-centered S/sub N/2 transition stages caused by the substituents on the leaving group, the nucleophile, as well as the benzyl moiety, is discussed in terms of Thornton's rules and described on a potential energy map. 42 references, 2 figures, 1 table.
Research Organization:
Osaka Univ., Japan
OSTI ID:
6549633
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 106:7; ISSN JACSA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ACETONE
AMINES
AROMATICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BROMINATED AROMATIC HYDROCARBONS
CARBON 14
CARBON ISOTOPES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINATED AROMATIC HYDROCARBONS
COMPARATIVE EVALUATIONS
DATA
DATA ANALYSIS
ESTERS
ETHERS
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
HALOGENATED AROMATIC HYDROCARBONS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
KETONES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
NITRO COMPOUNDS
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ORGANIC BROMINE COMPOUNDS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANIC SOLVENTS
ORGANIC SULFUR COMPOUNDS
RADIOISOTOPES
REACTION KINETICS
SOLVENTS
SULFONIC ACID ESTERS
TRITIUM
TRITIUM COMPOUNDS
YEARS LIVING RADIOISOTOPES