1
$\begingroup$

I am a high school student learning chemistry and my knowledge of organic chemistry is very limited, so pardon me if I am asking a nonsensical question.

While practicing organic, I came across the following question: enter image description here

Now my thought process was, option A takes place through Sn2 mechanism and if option B must take place it would through Sn1 mechanism. My chemistry teacher told me that if the reacting halide is tertiary, it would prefer Sn1 pathway and a primary halide prefers Sn2 pathway. The answer says option A is correct because Williamson Ether Synthesis follow Sn2 pathway all the time. Why can it not follow Sn1 pathway, under the right circumstances (a polar protic solvent), which would make both reactions feasible. Some of my friends said that an elimination reaction takes place here and Sn1 isn't possible because of the elimination reaction. But why is Sn1 not possible?

$\endgroup$
4
  • 4
    $\begingroup$ Problem doesn't lie in formation of carbocation intermediate. Chlorine could easily be removed. But main problem is that the carbocation we got now would easily lose hydrogen from $β$ carbon in presence of strong base and would form double bond bond. Elimination is highest in tertiary and lowest in primary. Steric hindrance is 2nd reason as 3 alkyl groups would come in way of alkoxide anion. To overcome hindrance it follow sn1 and lose chlorine but now our carbon would be free to form double bond and again we would not get ether. $\endgroup$ Sep 28, 2023 at 11:32
  • $\begingroup$ Ohh, that makes sense, so elimination is more favourable over Sn1 and thus happens much more quickly, but that doesn’t mean that Sn1 isn’t feasible right? Does the Sn1 pathway not take place at all, even under the right conditions? Or is it just less favourable? $\endgroup$ Sep 28, 2023 at 13:36
  • $\begingroup$ Less favourable and accompanied by a lot of alkene formation $\endgroup$
    – Waylander
    Sep 28, 2023 at 14:23
  • $\begingroup$ Ahh okay thanks a lot to both of you. I think I am clear now. I really appreciate your help. Thanks a lot!!! $\endgroup$ Sep 28, 2023 at 17:38

1 Answer 1

1
$\begingroup$

Option A could not be SN1 as that would lead through the formation of a primary carbocation which is too unstable.

However, there might be a mistake in the answers as A isn’t really feasible given that the tert-butoxide is too sterically-hindered to be very nucleophillic, especially when substituting for a large bromide ion.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.