I need mechanism of NR3+ as a meta directing group.

It has positvie charge and must be electron withdrawing....but it has lack of orbitals to donso

Dear student groups.The field effect explanation predicts that these should all be meta directing and deactivating and except for NH3+) this is the case.The NH3+ group is an anomaly, since this group directs meta . The NH2Me+,NH2Me2+ and NMe3+ groups all give more meta than para substitution, the percentage of para product decreasing with the increasing number of methyl groups.IIn this category are ,in approxiamte order of decreasing deactivating ability,NR3+,NO2,CF3,CN,SO3H,CHO,COR,COOH,COOR,CONH2,CCL3,NH3+.Also in this category are all other groups with a positive charges on atoms farther away,since often these are still powerfull -I.Groups that lack an unshared pair on the atom connected to the ring and that are -