7297-77-0Relevant academic research and scientific papers
Tunneling in elimination reactions. Tests of criteria for tunneling predicted by model calculations
Amin, Mohammed,Price, Robin C.,Saunders Jr., William H.
, p. 4467 - 4471 (1990)
Isotope effects in E2 reactions of mixtures of ArCL2CH2X and ArCLTCH2X (L = H or D) were determined by isotope fractionation methods. The temperature dependences of the secondary isotope effects, kHH/
Tunneling in elimination reactions. Structural effects on the secondary β-tritium isotope effect
Lin, Sue,Saunders Jr., William H.
, p. 6107 - 6110 (2007/10/02)
Secondary tritium isotope effects have been determined for the elimination reactions of (2-(p-(trifluoromethyl)-phenyl)ethyl-2-t)- and -2-d-2-t)trimethylammonium bromide (1) (EtO/EtOH), (1-phenylethyl-2-t)- and -2-d2-2-t)-trimethylammonium bromide (2) (t-BuO-/t-BuOH), and (1-phenyl-2-(p-chlorophenyl)ethyl-2-t)- and -2-d-2-t)-trimethylammonium bromide (3) (EtO/EtOH). kHH/kHT values at 50 °C were in the range 1.22-1.27 (errors ± 0.01 or less), with 1 giving the greatest effect. These values are all large enough to suggest significant contributions from tunneling. Studies of the temperature dependences give AaH/AaT values well below unity (0.60-0.90), and the secondary isotope effect is depressed when deuterium rather than protium is the transferred atom, results which also implicate tunneling. It appears that a carbanion-like E2 transition state is especially conducive to tunneling.
