0
$\begingroup$

In the 3d conformation of 1,2,4,5 - benzenetetrol, how could i determine the direction to which hydrogen atoms of hydroxyl groups would point? and if there were tertiary butyl groups in positions 3 & 6 would it be more stable for hydrogen atoms to point in the direction away from t-butyl groups as a matter of steric hindrance ?

1,2,4,5-benzenetetrol!

Source

$\endgroup$
5
  • 4
    $\begingroup$ Consider whether there would be hydrogen bonding between the OH groups $\endgroup$ – Waylander Mar 22 '20 at 10:23
  • $\begingroup$ @Waylander well this may partially answer the first half of the question, but if i needed this molecule in the stable form which you mean then it would be better to do the reaction in low temperature in order to preserve hydrogen bonds $\endgroup$ – mohamed Mar 22 '20 at 11:43
  • $\begingroup$ @Waylander but it is not a one molecule it is present with other molecules so which forces will win intramolecular hydrogen bonding or intermolecular hydrogen bonding $\endgroup$ – mohamed Mar 22 '20 at 11:45
  • $\begingroup$ Intra pretty much always wins over inter $\endgroup$ – Waylander Mar 22 '20 at 11:54
  • $\begingroup$ @Waylander so i suppose that that the conformation would be like 'swastika' symbol, but what would happen if there were t-butyl in 3 and 6 position? $\endgroup$ – mohamed Mar 22 '20 at 13:09
2
$\begingroup$

The melting point of 1,2,4,5-benzenetetrol is 210C (https://www.chemicalbook.com/ProductChemicalPropertiesCB41307665_EN.htm), so there is very probably significant intermolecular attraction between molecules, probably in three dimensions, which would involve the hydrogens pointing up and/or down, and not in-plane.

For a crystal structure, https://pubchem.ncbi.nlm.nih.gov/compound/1_2_4_5-Benzenetetrol suggests that 3 hydroxyls are planar while one is as out of plane as you would expect for cyclohexanol. Believe it or not. (I don't believe it.)

The (predicted) NMR spectrum shows two peaks, one very sharp for the aromatic protons, the other fairly sharp for the hydroxyls, but no experimental data seems to be available. The sharpness of the predicted spectrum suggests that the prediction is that free rotation is likely in solution.

$\endgroup$
3
  • $\begingroup$ do you know how to force the hydrogen bonds to stick to a specific direction? $\endgroup$ – mohamed Mar 26 '20 at 11:00
  • $\begingroup$ I'll take a wild guess (because I don't "know"). If you can find a substrate where you get strictly monolayer adsorption, it is likely that the adhesive forces would be thru the electrons of the aromatic system plus oxygens, so the hydrogens would be pointing away from the adsorbent (which could be graphite or graphene). Now if the adsorbent had a polar surface, like clay, the hydrogens might be preferentially attracted. But i am not aware of any method that could prove the orientation. $\endgroup$ – James Gaidis Mar 26 '20 at 13:52
  • $\begingroup$ what about steric hindrance (i mean by putting t-butyl in 3,6 position ) wouldn't that push the hydrogen of hydroxyl groups away from t-butyl and also prevent the formation of strong intermolecular hydrogen bonds ? $\endgroup$ – mohamed Mar 26 '20 at 16:07

Your Answer

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

Not the answer you're looking for? Browse other questions tagged or ask your own question.