The pH dependences of the second-order rate constants and the primary kinetic isotope effects for hydride-transfer reactions from an acid-stable NADH model compound, 10- methylacridan (AcrH 2), to a series of p-benzoquinone derivatives (Q) in H 2 O–EtOH (5: 1 v/v) have revealed that the hydride transfer proceeds via acid-catalyzed electron-transfer from AcrH 2 to Q.
