6

(Oxolan-2-yl)methanol + H+

I think the ethereal oxygen in THFA gets protonated. Due to greater +I effect, the electron density on it is higher, hence it is more likely to behave as a Lewis base. Consequently, the product formed is pent-2-en-1,5-diol:

(Oxolan-2-yl)methanol + H+ to pent-2-en-1,5-diol

Apparently, this is wrong. What exactly happens here and why my answer is wrong?

andselisk
  • 37,604
  • 14
  • 131
  • 217
chappie
  • 69
  • 2
  • 2
    Cleavage of ethers is rather difficult http://chemistry.stackexchange.com/questions/14860/cleavage-of-ethers – Mithoron Mar 20 '16 at 19:00
  • 3
    Also alcohols are stronger bases than ethers http://chemistry.stackexchange.com/questions/46514/why-is-dimethyloxonium-cation-stronger-acid-than-hydronium/46517?s=2|0.0667#46517 – Mithoron Mar 20 '16 at 19:08
  • but in this case, there is greater +I effect on the ethereal o than on the alcoholic O. Would that not make the electron density on the ethereal oxygen greater? – Daipayan Mukherjee Mar 21 '16 at 12:51

1 Answers1

7

The alcohol group of your educt (tetrahydrofurfuryl alcohol) is protonated, and after subsequent loss of water, the resulting primary carbocation can rearrange to a more stable 6-membered ring cation, which is stabilized by resonance. Initial protonation at the ether oxygen is therefore disfavored, as it will not result in the formation of a similarly stable carbocation (with positive charge adjacent to oxygen). After final deprotonation, 2,3-dihydropyran is obtained.

enter image description here

Jannis Andreska
  • 5,942
  • 6
  • 47
  • 83