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Question

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Correct answer

A,B,C

My thoughts

Correct answer should be A,B. The main role is of the steric hindrance between the halogen atom and the tert-butyl group. So why are we even considering the electronic effects of both the groups? They are common in all the cases.

Further, the answer should be A only as its only the halogen atom changing each time, and hence the steric hindrance due to it. Why are we even considering other factors, as they are common in all the cases?

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The options ABC are correct answers Reason:

  • A: Steric effect of halogens will definitely be taken into account since all 3 halogens are acting on the same compound hence the primary factor which will make the product formed for each case be different is the steric hindrance due to their respective sizes.

  • B: For steric hindrance to be taken into account both atoms need to be bulky and have equal role to play in the first option we affirmed that due to different sizes among halogens there'll be steric hindrance causing different types of products to be formed however that is only true when we have a bulky group( here, tert butyl) providing steric to the group trying to attach(the halogens) to the adjacent c atoms. Hence for us to take steric hindrance as a factor for different products the steric hindrance caused due to the tert-butyl group and halogens is considered

  • C: The substitution of the halogens is taking place due to the +M effect of the -OH group thus option C must be true for us to proceed even a bit and it is the first requirement and only after this would we take into consideration the steric hindrance. In other words the reaction is taking place due to the electron donating effect of the -OH group since it is donating electrons to the ring via mesomeric and not inductive. And the steric hindrance serves so as to differentiate and predict which product will be formed

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  • $\begingroup$ And +I effect of the tert-butyl group? $\endgroup$ – Reeshabh Ranjan Apr 9 '17 at 10:13
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    $\begingroup$ Inductive effect only strengthens or diminishes the effect of the already existing group which is exerting it's mesomeric effect $\endgroup$ – Saakshya Devat Apr 9 '17 at 10:17
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    $\begingroup$ In this case the tert butyl group is increasing the charge circulating in the benzene ring due to the +M of -OH $\endgroup$ – Saakshya Devat Apr 9 '17 at 10:18
  • $\begingroup$ Okay, so wouldn't have it mattered if there had been a mildly deactivating group in place of tert-butyl? $\endgroup$ – Reeshabh Ranjan Apr 9 '17 at 10:41
  • $\begingroup$ No, only the steric effects of the tert butyl matters, if there has been a -CH3 instead of tert butyl, then yes, it wouldn't have mattered. $\endgroup$ – Sawarnik Apr 9 '17 at 14:37

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