spectrum in CDCl3, indicating strong hydrogen bonding. Biaryl amines with an extremely strong intramolecular N−H−N hydrogen bond (δNH ∼13 ppm) were assumed to undergo racemization without cleavage of an N−H−N hydrogen bond, while those with a mediumly strong N−H−N hydrogen bond (δNH ∼11 ppm) are assumed to undergo racemization via cleavage of an N−H−N hydrogen bond. Hydrogen/deuterium exchange of a chiral