Why is there no formation of epoxide when the two OH-groups are on different planes? I do understand the epoxidation mechanism. However, I would be grateful if someone cleared the specific requirements for epoxidation.
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$\begingroup$ Read up on under what conditions SOCl2 reacts with ROH to give RCl. One set of conditions is SN2; another "internal return", i.e., no inversion. $\endgroup$– user55119Commented Jun 30, 2019 at 11:41
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$\begingroup$ In the above mechanism base is seen at the second step which is not the case $\endgroup$– Harshita GracyCommented Sep 11, 2021 at 5:25
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1 Answer
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Thionyl chloride first reacts with the alcohol to form an alkyl chloro sulfite,which gives various stereochemical products as shown here.
Extending this to the current question , alkyl chloro sulfite 2 is formed.${Cl^-}$ attacks in a ${S_N^2}$ mode to give 3.
Base deprotonates 3 to give 4.
Alkoxide and chloride in 4 are in correct trans configuration for a ${S_N^2}$.This results in 5(B in your scheme).
If we take C in your question , and follow the scheme above, 9 is formed.In 9 alkoxide and chloride are not in correct configuration for ${S_N^2}$.Therefore C in your question does not undergo epoxidation.
answered Jun 30, 2019 at 12:45
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2$\begingroup$ Detailed answer but the OP didn't make much of an effort. That is why I offered hints and no answer. Respectfully, I think we should refrain from quickly offering answers when little effort is made by the OP and hints are offered in the comments. Let the OP do some work. $\endgroup$ Commented Jun 30, 2019 at 17:05
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$\begingroup$ @user55119 ,noted,the question was intreasting for an answer. $\endgroup$ Commented Jun 30, 2019 at 17:14