I'm imagining a strong base like NaNH2 attacking the adjacent carbon of the ether, giving the oxygen a lone pair and forming an alkoxide. NH3 has a pKa of 36 while an alcohols (conjugate acid of alkoxides) have a pKa of around 15 so shouldn't this be favorable?

  • $\begingroup$ Do you mean to say that after abstracting a hydrogen from the alpha carbon, you would conjugate that and end up with an alkene+ an alkoxide? $\endgroup$ – Yusuf Hasan Feb 23 '20 at 19:35
  • 1
    $\begingroup$ They can, it just so happens that in many cases a really strong base is needed. Alcoholate-anion is a very shitty leaving group, so something mild like sodium amide won't work normally. Diethyl ether, for example, requires alkyllithium to be cleaved. The products are lithium ethilate and ethylene. $\endgroup$ – permeakra Feb 23 '20 at 19:51
  • $\begingroup$ Yes, like permeakra said, basic cleavage be a whole lot of trouble. It's much easier to stick to our usual acidic ethereal cleavage with HI $\endgroup$ – Yusuf Hasan Feb 23 '20 at 19:55
  • 3
    $\begingroup$ Sodamide is not actually a great nucleophile but is a very strong base. It is fair more likely to remove a beta proton causing alkene formation by elimination of alkoxide $\endgroup$ – Waylander Feb 23 '20 at 21:38
  • 1
    $\begingroup$ Adding on to Waylander's point as to why it is so, the antibonding orbital of the C-H sigma bond is a hard electrophilic centre, while the antibonding of the C-O sigma bond is comparatively softer. NaNH2 would be categorized as a chemically hard species due to it's high charge density, hence it will go for the C-H bond more than the C-O one $\endgroup$ – Yusuf Hasan Feb 24 '20 at 2:53

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.