Fig. 1.
Schematic TRS of the reverse reaction (aldehyde to alcohol) showing 1°–2° coupling. The hydrogens are black, the carbons are gray, the oxygen is red, and the three heavy atoms define the blue plane. Traditional models of tunneling and coupled motion proposed that the reaction coordinate involved motion of all three hydrogens (shown with arrows). The model presented here parameterized the out-of-plane bending angles of the benzyl substrate and nicotinamide cofactor, θs and θc, respectively, in order to obtain a symmetric double-well potential along the H-transfer coordinate.