[disillusioned19]

Why is it when, say, an amine group is attached to a benzene ring, the nitrogen group is said to be electron donating, whereas when it is attached to an aliphatic chain it is considered electron withdrawing, like we see with negative inductive effect?

The same could be said of oxygen containing groups as well.

Thanks in advance.

[AWK]

http://en.wikipedia.org/wiki/Inductive_effect
http://en.wikipedia.org/wiki/Mesomeric

[disillusioned19]

http://en.wikipedia.org/wiki/Inductive_effect
http://en.wikipedia.org/wiki/Mesomeric

I guess what you mean by this is that there is no resonance effect in an alkyl chain and so nitrogen cannot donate, only withdraw owing to its higher electronegativity than carbon?

[AWK]

In mesomeric effect it can donate.