In activation of alcohol by tosyl chloride, why does the chloride ion not displace the poor leaving group?

I think that's because chlorine is a poorer base than that thing which will be formed. But that should not be true considering delocalisation.

Additional Information:

I know this question is unclear because I don’t know the name of the things formed when alkyl group has left the sulphonate ester so please edit this.

  • 2
    $\begingroup$ Chloride can displace the tosylate group if one is not careful in the preparation of the tosylate. Usually, the tosylation is done in the cold. $\endgroup$ – user55119 May 4 '18 at 19:09
  • $\begingroup$ Yeah, it can happen. $\endgroup$ – orthocresol May 4 '18 at 19:10
  • 1
    $\begingroup$ This is particularly observed with tbe std conditions of Et3N/MsCl/DCM for mesylate formation where Cl displacement of the mesylate can lead to significant amounts of the chloride $\endgroup$ – Waylander May 4 '18 at 19:12
  • $\begingroup$ @user55119 Two questions: Even if tosylate gets displaced we get alkyl hallide so that is not bad right? And if the preparation is done in cold due to activation energy barrier rate of displacement will be very slow is that true? $\endgroup$ – vishal mishra May 5 '18 at 5:48
  • $\begingroup$ If you are forming the sulfonate to then displace with a nucleophile (or to eliminate) then the presence of chloride is of no significance as it will follow the same pathway, particularly if you add catalytic iodide along with the nucleophile. Cooling should reduce the amount of displacement, but it will also slow the formation of the sulfonate. $\endgroup$ – Waylander May 5 '18 at 23:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.