Part I. The experimental basis

Quantum tunneling in chemical reactions 28 Quantum tunneling in solution reactions 29 

Quantum tunneling in enzyme-catalyzed reactions early indications 35 The rule of the geometric mean ( no isotope effects on isotope effects ) 36 The Swain-Schaad relationship 36 

The normal temperature dependence of isotope effects (see Chart 1) 37 

Secondary isotope effects measure transition-state structure 37 Quantum tunneling in enzyme-catalyzed reactions breakthroughs 42 

2 Experimental phenomenology of quantum tunneling in enzyme-catalyzed 

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Part I. The experimental basis, 39, 27 Isotope effects, hydrogen, in aromatic substitution reactions, 2, 163... 

Ionic dissociation of carbon-carbon a-bonds in hydrocarbons and the formation of authentic hydrocarbon salts, 30, 173 Ionization potentials, 4, 31 Ion-pairing effects in carbanion reactions, 15, 153 Ions, organic, charge density-NMR chemical shift correlations, 11, 125 Isomerization, permutational, of pentavalent phosphorus compounds, 9, 25 Isotope effects and quantum tunneling in enzyme-catalyzed hydrogen transfer. Part I. The experimental basis, 39, 27... 

It is shown that the simplified calculational scheme discussed in Parts I and II of this series accomodates the total body of inexact and often self-contradictory experimental information almost as well as might reasonably be expected of any computational method. Some possibly systematic discrepancies in the reported experimental C-J pressures are discussed on the basis of methods used to carry out and interpret the measurements in the various laboratories. 

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