1983
DOI: 10.1002/9780470171936.ch5
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Secondary Deuterium Isotope Effects on Reactions Proceeding Through Carbocations

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Cited by 25 publications
(11 citation statements)
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“…The observed effect on k cat establishes that chemistry is significantly rate determining for the enzyme. Moreover, the magnitude of the isotope effect is consistent with considerable C−H bond cleavage in the transition state (Scheme b or 1d), but would be unprecedentedly large for a β-secondary effect in an ion pair mechanism (Scheme c) . The somewhat smaller isotope effect observed on k cat / K m indicates a significant forward commitment to catalysis for IPL …”
mentioning
confidence: 66%
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“…The observed effect on k cat establishes that chemistry is significantly rate determining for the enzyme. Moreover, the magnitude of the isotope effect is consistent with considerable C−H bond cleavage in the transition state (Scheme b or 1d), but would be unprecedentedly large for a β-secondary effect in an ion pair mechanism (Scheme c) . The somewhat smaller isotope effect observed on k cat / K m indicates a significant forward commitment to catalysis for IPL …”
mentioning
confidence: 66%
“…Moreover, the magnitude of the isotope effect is consistent with considerable C-H bond cleavage in the transition state (Scheme 1b or 1d), but would be unprecedentedly large for a β-secondary effect in an ion pair mechanism (Scheme 1c). 11 The somewhat smaller isotope effect observed on k cat /K m indicates a significant forward commitment to catalysis for IPL. 12 The fate of the deuterium atom at C2 was determined directly by 2 H NMR spectroscopy.…”
mentioning
confidence: 93%
“…While, it is too small to represent a primary kinetic isotope effect, the observed KIE is notably higher than k H / k D = 1.00−1.04 as found by Singleton and Hang for a stepwise ene reaction. Also, hyperconjugation cannot explain a k H / k D = 1.17, though it is generally accepted as the major contributor to β-deuterium secondary kinetic isotope effects for reactions with radicaloid transition states and for equilibrium isotope effects involving radicals. 15b, To understand this discrepancy, we have analyzed the bona fide diradical C 2 −C 6 cyclization of 1 (R 1 = Ph, R 2 = R 3 = H) as described in a computational study by Engels ).…”
Section: Resultsmentioning
confidence: 99%
“…As a result, a typical secondary KIE was observed since the k H / k D = 1.19 (see Supporting Information). It suggests that a carbocation intermediate should be involved in this reaction and the C−H bond cleavage is not the rate-determining step . With these results in hand, a plausible mechanism for this catalytic coupling reaction is depicted in Scheme .…”
mentioning
confidence: 96%