The group which increases the electron density at mcta position are called as rneta directors.
For example:
-NO2 . -CN, -CHO, -COOH. -SO3H etc.
Let us consider the directive influence of aldehydic (- CHO) group. Benzaldehyde is a resonence hybrid of the following structures.
In these resonance structures, the positive charge residue is present on the ring structure. It is quite evident that resonance deLocalises the positive charge on the atoms of the ring, making the ring less electron rich than henzene. Here overall electron density of benzene ring decreases due to -I effect of’ -CHO group, thereby deactivating the henzene for electrophilic atlack. However resonating structures shows that electron density is more at meto position as compared to ortho and para positions. Flence -CHO group is a ineta -director and a deactivator.
