The dimerization of ammonia and amines

The second virial coefficients of ammonia and the vapours of the primary, secondary and tertiary methylamines and ethylamines have been measured at temperatures between 20 and 130° C. The results are interpreted as showing that dimerization occurs with ammonia and with the primary and secondary amines, but not with the tertiary amines. The dimerization is attributed to hydrogen bonding, and the energy of the N—H....N bond is discussed.