# Why does the trimethylammonium cation have a larger -I effect than the ammonium cation?

Why does $\ce{N(CH_3)_3^+}$ have a larger $-I$ effect than $\ce{NH_3^+}$?

Since the methyl group is good at donating electrons it would stabilize the charge on nitrogen atom, decreasing its potential to withdraw electrons hence its $-I$ effect.

I can't figure out why its the other way around. Can someone help me understand this?

• Are the groups in a gaseous phase or in a polar solvent..? The choice of phases in case of these groups changes everything. – Mitchell Feb 22 '17 at 8:27
• @BhavyaSharma nothing as such is mentioned in the question. The question just wants me to find the group with highest -I effect – oshhh Feb 22 '17 at 8:41
• Methyl groups donate inductively only into empty-p-orbital cations (e.g. carbenium ions). Ammonium cations cannot profit from that stabilisation. – Jan Feb 22 '17 at 23:34
• @Jan Oh I didn't know that, thank you! So basically inductive effect from methyl or hydrogen groups doesn't operate here. Then what is the factor that influences the stability of these ions? – oshhh Feb 23 '17 at 8:54