Mechanisms of elimination reactions. XXXIII. Carbon isotope effects in E2 reactions of (2-phenylethyl-2-/sup 14/C)trimethylammonium ion: the role of tunneling
Carbon isotope effects have been determined for the reactions of (2-phenylethyl-2-/sup 14/C)trimethylammonium ion with hydroxide ion in 10, 25, 40, and 60% Me/sub 2/SO-water and with ethoxide ion in dry ethanol. Comparison of these values with earlier results on /sup 13/C isotope effects shows that the relation between the /sup 14/C and /sup 13/C effects is close to that predicted from theory. The magnitudes of the isotope effects suggest significant contributions from tunneling, and this suggestion is supported by temperature-dependence studies that give ..delta..E/sub a/ values too large and A/sub a(12)//A/sub a(14)/ values too small to account for without tunneling. Temperature dependences calculated from the Bell theory of tunneling can be fitted to the experimental data. The results indicate that the semiclassical (without tunneling) carbon isotope effects are small or even inverse and that tunnel corrections make major contributions to the observed isotope effects.
- Research Organization:
- Univ. of Rochester, NY
- OSTI ID:
- 6206035
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 103:12; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ALCOHOLS
AMINES
AMMONIUM COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 13
CARBON 14
CARBON ISOTOPES
CHEMICAL REACTIONS
COMPARATIVE EVALUATIONS
DATA
DMSO
ETHANOL
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
HYDROXIDES
HYDROXY COMPOUNDS
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
QUATERNARY COMPOUNDS
RADIOISOTOPES
STABLE ISOTOPES
SULFOXIDES
WATER
YEARS LIVING RADIOISOTOPES