Why don't carboxylic acids form H-bonds in this formation with the red dots (diagonal) instead of the black dots (horizontal)?

carboxylic acid hydrogen bonding scenarios

I was always taught that H-bonds formed between partially negative and partially positive atoms. I agree that the $\ce{=O}$ carboxyl oxygen is partially negative, so there should be a H-bond there from the partially positive H.

However, the $\ce{O}$ in $\ce{OH}$ is also partially negative. So why aren't the H-bonds denoted with red dots formed?

  • 4
    $\begingroup$ And nobody told you that it goes straight to lone pair? $\endgroup$ – Mithoron Jul 29 at 13:55
  • 1
    $\begingroup$ So, while bifurcated hydrogen bonds do exist, it's not the case here. $\endgroup$ – Mithoron Jul 29 at 15:53
  • 1
    $\begingroup$ You need some degree of orbital overlap. Pretty challenging to overlap at that kind of angle. $\endgroup$ – Josh Mitchell Jul 29 at 16:08
  • 1
    $\begingroup$ In reality in carboxylic acids, there are no double bond and single bond on oxygens. It is a hybrid (e.g., where is the $\ce{^{13}C}$-signal for carboxylic carbonyl in NMR?). $\endgroup$ – Mathew Mahindaratne Jul 29 at 17:52
  • 2
    $\begingroup$ Often times you ignore the stuff that is not as important. It's a simple cartoon after all. $\endgroup$ – Buck Thorn Jul 29 at 20:34

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.