Evidence for Concerted Transfer of Hydrogen from Tetralin to Coal Based on Kinetic Isotope Effects

Article abstract of DOI:10.1021/jo00195a018

The H/D kinetic isotope effects for the reaction of subbituminous coal with tetralin-d₁₂, tetralin-1,1,4,4-d₄, and tetralin-2,2,3,3-d₄ are respectively 3.7, 2.0, and 2.0.This pattern is consistent with concerted transfer of a pair of hydrogen atoms from the 1- and 2-positions.It does not result from exchange of hydrogen in unreacted tetralin and is difficult to explain as an anomalous secondary effect.The H/D kinetic isotope effects for 1,2-dihydronaphthalene-d₁₀ and -1,1,3-d₃ are 2.7 and 1.1.The latter appears to be a typical secondary effect.The rate determining step is thought to be transfer of a single hydrogen from the 2-position, probably as hydride ion.The activation volume for 1,2-dihydronaphthalene is -23mL mol.This result is consistent with the proposed mechanism or almost any other bimolecular mechanism.