What is the reason for the boiling point of benzene-1,4-diol being higher than that of benzene-1,3-diol?



Both have hydrogen bonds. I think it is due to quinol's symmetry but can't point out exactly why this is the case.

  • $\begingroup$ Can you take a guess? Have you not been provided with other examples? chemistry.stackexchange.com/help/how-to-ask $\endgroup$
    – Buck Thorn
    Aug 7 '21 at 10:41
  • $\begingroup$ see chemistry.stackexchange.com/questions/112078/… $\endgroup$
    – Lalit
    Aug 7 '21 at 13:43
  • 1
    $\begingroup$ @Lllt: Not related question. None of these two can make intramolecular hydrogen bonding. $\endgroup$ Aug 7 '21 at 17:26
  • $\begingroup$ @MathewMahindaratne I think benzene 1,3 diol can do so $\endgroup$
    – Lalit
    Aug 7 '21 at 17:28
  • $\begingroup$ symmetry makes it have a lot less dipole moment than resorcinol. I think this has to do with larger surface area of quinol leading to higher Vander Waal forces. $\endgroup$ Aug 9 '21 at 4:40

Benzene-1,4-diol has a boiling point of 287°C and Benzene-1,3-diol has a boiling point of 277°C and Benzene-1,2-diol has a boiling point of 245.5°C. This could be attributed to the ease of formation of 2 intermolecular hydrogen bonds with the 2 hydroxy groups of these molecules increasing when the hydroxy groups are placed apart, to minimise steric hindrance and repulsion. Benzene-1,4-diol could form intermolecular hydrogen bonds with more stability than Benzene-1,3-diol or Benzene-1,2-diol as these two will get destabilised by steric repulsion when large groups have to reach nearer to form hydrogen bonds.

Thus, the extent of intermolecular hydrogen bonding in : Benzene-1,4-diol > Benzene-1,3-diol > Benzene-1,2-diol

To overcome this attraction, more energy is needed. Hence the same is the order of their Boiling Points.

  • $\begingroup$ Is that good enough of a reason for a 10°C rise? $\endgroup$ Aug 10 '21 at 11:27

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.