I found this link trying to explain it: Why pyranosides do not mutarotate? however, I don't understand a step of the reasoning.

Why is it that acetalisation needs a stronger acid than for hemi-acetalisation? I was wondering why can't the mechanism be similar to the the one for the mutarotation of glucose as shown below: enter image description here

Couldn't the $\ce{O}$ break the bond, and then instead of forming the aldehyde, rotate the $\ce{O-CH3}$ group and then reform the bond?

  • $\begingroup$ the second step, where the proton is removed by a base, woudn't work for a methyl group. Ether Cleavage needs a strong haloacid such as HI. $\endgroup$ – Aniruddha Deb Sep 2 '20 at 2:43
  • $\begingroup$ @AniruddhaDeb ok, but can't I skip that step and just rotate then whole thing and then reform that bond? $\endgroup$ – John Hon Sep 2 '20 at 2:47
  • 1
    $\begingroup$ You can’t skip a step. You either move along the pathway or you hit a dead end/wall. $\endgroup$ – Jan Sep 2 '20 at 15:12

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