# Why is the trimethylammonium group a stronger electron withdrawing group than the nitro group?

I was working on a question that basically boils down to deciding whether the nitro group ($$\ce{-NO2}$$) or the trimethylammonium group ($$\ce{-N+(CH3)3}$$) on a benzene ring, is a stronger electron withdrawing group (EWG).

The solution says that the trimethylammonium group is a stronger EWG since it has an overall positive charge, while the nitro group is overall neutral.

But I am getting confused here. Why should the nitro group be neutral? The $$\ce{N}$$ atom has 4 bonds (a single bond to an oxygen atom, a double bond to another oxygen atom, and another bond to the carbon of the ring), so the $$\ce{N}$$ atom in $$\ce{NO2}$$ should also have a positive charge?

Further I analysed that since $$\ce{O}$$ is more electronegative than $$\ce{N}$$, it tries to shift the $$\pi$$ electrons of the double bond towards itself, hence increasing the electrophilicity of the nitrogen of $$\ce{NO2}$$, while in the trimethyl amino group, the $$\ce{N}$$ being the more electronegative atom gets electrons donated to it due to the +I effect of the three $$\ce{CH3}$$ groups, thus reducing the electrophilicity of $$\ce{N}$$. So $$\ce{-NO2}$$ should be a stronger EWG than $$\ce{-N+(CH3)3}$$.

Where am I going wrong?

• You are confusing the way the nitro group is drawn with a partial +ve charge on the N for an actual charge. It is not charged, this is just a convenient way of modelling it. The NMe3 group has an actual overall charge. – Waylander May 23 at 14:39
• @Waylander, Sorry for the late reply, but does it mean that the $NMe_3$ group exists with the ring as an ion? Like $Na^+Cl^-$? – WTS May 25 at 6:07
• Yes, there will be an anion associated with this such as Cl- – Waylander May 25 at 7:14