Halogens are deactivating but ‘o, p’ directive. Give reasons.
Answers
Halogens are weakly deactivating ortho-para directing groups. This abnormal behaviour of halogens can be explained by the fact that halogen being more electronegative than carbon, withdraw electrons through inductive effect thereby deactivating the ring towards electrophilic substitution. On the other hand, halogens have lone pairs of electrons also, due to which they are capable of sharing them with benzene ring and can accommodate positive charge.
The negative inductive effect of halogen overshadows the resonance effect and causes net electron withdrawal leading to deactivation of all positions. But this deactivation is less for ortho and para positions than for the meta position. Reactivity is thus controlled by the strong negative inductive effect whereas the weaker resonance effect controls the directive influence.
Various resonance forms of positively charged intermediates for ortho,para and meta-attack make it clear that attack at ortho and para positions places the positive charge on the carbon atom adjacent to halogen which is a tertiary carbon hence contributes to more stability. (Tertiary carbocation is more stable than secondary and primary.)
Halogen atom also takes place in delocalization of positive charge which give additional resonating forms in ortho and para attack. (More resonating structures favour stability)
if you are satisfy with my ans then mark me as a brainlist
if there is something wrong then kindly rectify it
Answer:
Ortho-para directing groups are poorly deactivated by halogens. Halogens' unusual behaviour can be attributed to the fact that they are more electronegative than carbon, which causes them to remove electrons through the inductive effect and deactivate the ring in favour of electrophilic substitution .
Explanation:
Ortho-para directing groups are poorly deactivated by halogens. Halogens' unusual behaviour can be attributed to the fact that they are more electronegative than carbon, which causes them to remove electrons through the inductive effect and deactivate the ring in favour of electrophilic substitution .
Halogens, on the other hand, also possess lone pairs of electrons, which enables them to share them with the benzene ring and tolerate positive charge.
Halogen's detrimental inductive action overpowers the resonance effect and results in net electron withdrawal, which deactivates all locations. However, the ortho and para locations experience less deactivation than the meta position. Thus, the strong negative inductive impact regulates reactivity while the smaller resonant effect regulates the directional influence.
#SPJ2