Meta Directors Deactivating groups slow down electrophilic aromatic substitutions and direct the substituents to the meta position. The only exceptions are the halogens that deactivate the aromatic ring yet directing the electrophile to the ortho and para positions.
Resonating structure of nitrobenzene shows +ve charge develops in ortho and para positions. If the opposite is observed, the substituent is called a meta directing group. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, … So, electron deficient electrophile always attacks at meta position.
Image Source: google images. Thus, the methyl group is an ortho, para directing group. – Deactivators (not halogens) are meta-directing. Ortho, para directing groups are electron-donating groups; meta directing groups are electron-withdrawing groups.
We call the substituents which lead to this result “meta- directors”. Examples of meta– directors include nitriles, carbonyl compounds (such as aldehydes, ketones, and esters), sulfones, electron-deficient alkyl groups, nitro groups, and alkylammoniums. – Deactivators (halogens) are ortho-para directing. Type 3- Alkyl groups are ortho, para-directing groups. Ortho, para directing groups are electron-donating groups; meta directing groups are electron-withdrawing groups. The halide ions, which are electron-withdrawing but … Therefore, depending on the character of the initial substituent (R), a subsequent substituent would be placed at the ortho or para position if R is an activator/halogen or at the meta position if it is a deactivator (but not a halogen). The LibreTexts libraries are Powered by MindTouch ® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. As a result, the electron density at meta position is relatively higher than at the ortho and para position. whereas -CX3,- (NR3)+ are meta--directing groups. There is a separate post about this which you can check here. Thus, the nitro group is a meta directing group. The directive influence can easily be decided by drawing the resonating structures of the intermediate after ortho, meta or para - attack and comparing their stabilities.