Abstract: The Brernsted a (I d (ln ku)/d (ln KO)) for an atom-or group-transfer reaction depends on the location of the substitution and the tightness of the transition state (7) as well as the resemblence of the transition state to reactants and products. Within Marcus theory, 7 can be related to rates of symmetrical reactions. These ideas have been successfully applied to hydride transfer between NAD'analogues. A series of 1-benzyl-3- ...