Abstract
The possibility of carbon atom tunneling at cryogenic temperatures for carbene-based ring expansion of adamantane analogues calls for a delicate balance of reactivity to experimentally detect the transpiring reaction. An overly reactive carbene will precipitously decay; an excessively stable carbene will not tunnel. Nevertheless, the factors that affect the quantum-mechanical tunneling (QMT) reactivity-mass, barrier height and width-are strikingly different from the classical "over the barrier" thermal mechanism. Herein, comparisons with experimental values and predictions on measurable rate constants for novel carbene systems are presented by way of small curvature tunneling (SCT) computations. Adamantane, noradamantane and bisnoradamantane have a significantly different C-C bond strain and reactivity, which can be modulated by tinkering with the carbene substituent atom (H, Cl or F) to obtain an observable lifetime of the reactant. The influence of barrier heights and widths, kinetic isotope effects (KIEs), the detection of the tunneling-determining atoms (TDA) and the comparisons with hydrogen-based reactions are discussed with the objective of finding the physical limits for QMT.
Original language | American English |
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Pages (from-to) | 7718-7727 |
Number of pages | 10 |
Journal | Physical Chemistry Chemical Physics |
Volume | 16 |
Issue number | 17 |
DOIs | |
State | Published - 7 May 2014 |
Externally published | Yes |
All Science Journal Classification (ASJC) codes
- General Physics and Astronomy
- Physical and Theoretical Chemistry