Hydrogen bonding in amines

Hydrogen bonding does not occur between tertiary amines 

Hydrogen bonding can occur between all amines and water 

Intermolecular and/or intramolecular hydrogen bonding effects are shown by most amines under suitable conditions. As with the hydroxyl group, no attempt will be made to review all the work — especially in the overtone region — which has been carried out in this connection, as a number of excellent reviews already exist [25, 26, 62], but a general indication of the conditions under which frequency shifts may be expected, and of the extent to which they are likely to occur, is given below. 

NH groups are also capable of interacting with alcohols [29] and 

Intramolecular bonds. In alcohols one of the commonest cases of intramolecular bonding arises with conjugated systems containing the group C—C=C, such as salicylic acid and acetyl- 

Cromwell et al. [32] have found that 3-amino-a/3-unsaturated ketones show chelation effects, but in this case a considerable shift of the NH frequency is reported, as no NH bands could be observed in the materials examined, and it was concluded that they were coincident with the CH stretching bands near 3000 cm . The position is further complicated in these cases by their observation that a smaller but still appreciable carbonyl shift occurs in four compounds in which the amino-group is fully substituted and unable to form hydrogen bonds. The suggestion has been made that in these 

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For hydrates, the question is, to what extent does the nitrogen atom lone pair contribute to hydrogen bonding in amine hydrates Hydrogen bonding is expected to explain the difference between gaseous and solid ammonia couplings. 

Hydrogen bonding In amines modifies both symmetric and antisymmetric N—H str bands. In dilute solutions free N—H str can be seen near 3500 cm. N—H def occurs around 1600 cm. ... 

As with other hydrogen bonded compounds, stronger hydrogen bonding in amine salts (I < Br" < Cl ) lowers hydrogen stretching frequencies but raises deformation frequencies (and their overtones). 

Amines have lower boiling points than alcohols because nitrogen is less electronegative than oxygen. As a result the N—H bond is less polar than the O—H bond, and the N—H—N hydrogen bond in amines is weaker than the O—H—O hydrogen bond in alcohols. 

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