Exchange of Alkanes with Deuterium

Abstract

PREFACE The replacement of hydrogen atoms by deuterium (or tritium) atoms is the simplest catalytic change that can happen to a hydrocarbon; it occurs with sur-prising ease on a number of metal surfaces, and it focuses on the reactivity of C H bonds, ignoring the C C bonds. It has been a popular field of study, and has revealed (as all isotopic labelling studies have) an unsuspected wealth of detail, and a number of mechanistic questions have arisen that have required the study of carefully selected large hydrocarbon molecules whose structures allow only certain pathways to operate. It is one of the paradoxes of heterogeneous catalysis that reactions of larger molecules sometimes give more direct and unambiguous information about reaction mechanisms than smaller molecules are capable of. Studies of such molecules do however illuminate the stereochemical principles governing the chemisorption and reactions of hydrocarbon molecules of all sizes; and the reactions singled out for examination here will be found to occur as part of, or in parallel with, the more profound processes to be met in the following chapters. They therefore deserve careful attention.