Protonation

[garytse86]

This is about amines:

The functional groups present are: C=O and NH2

Why does the N get protonated always but not C=O, since the oxygen has more lone pairs and more electronegative than N so shouldnt the oxygen be protonated more easily? I can't think of any good reasons.... please help :confused:

[GCT]

In some cases note that the lone pairs on the oxygen are delocalized, and thus less available in a sense. In some cases, protonation of the nitrogen atom to its corresponding cation will be reinforced by hydrogen bonding of water to the newly formed compound (4 hydrogens in contrast to 3). Also, nitrogen holds its electrons less tightly.

[movies]

An alternate explanation: A positive charge on nitrogen is better than a positive charge on oxygen because nitrogen is less electronegative.

[garytse86]

Thanks. But how can the lone pairs of oxygen be delocalised?