Benjamin, Inc. ISBN This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format. Basicity The degree of basicity of amides is very much less than that of aliphatic amines. Contributors and Attributions John D. Instead, the actual structure is somewhere in between the structures shown. It can be thought of as some average of these structures.
Why is this resonance system better? A qualitative argument is that the O, which is very electronegative, draws electrons toward it. In this case, it draws electrons from the lone pair of the N. The resonance system shown in Figure 2 is based on measurements of the properties of amides.
That is, detailed study of amides shows that the properties are better explained by Figure 2 than by Figure 1. As examples:. Hence the more R groups the amine has, the more basic it is. So lone pair on nitrogen is less available for donation and ammonia is less basic than amines. The lone pair of nitrogen is delocalised into the pi electron system of benzene.
This makes the lone pair less available for donation and hence phenylamine is less basic than ammonia. The lone pair on nitrogen is delocalised extensively into the acid group, between both electronegative atoms oxygen and nitrogen.
0コメント