Intramolecular H-bonding and boiling point??

[premed08]

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I just came across a question on kaplan diag#5 Q#20. Although I got the question right, the explanation says INTRAmolecular H-bonding has nothing to do with the boiling point..is this true??I though if a molecule is capable of Intramolecular H-bonding, it would have a lower boiling point cause it would have less intermolecular H-bonding..

is this true??

 

[GoldShadow]

Intramolecular H-bonds would not prevent a molecule from participating in intermolecular H-bonding. Intramolecular H-bonds would, however, stabilize the molecule, and would affect things such as its heat of combustion or heat of formation.

 

[premed08]

Intramolecular H-bonds would not prevent a molecule from participating in intermolecular H-bonding. Intramolecular H-bonds would, however, stabilize the molecule, and would affect things such as its heat of combustion or heat of formation.

I don't think that's true. For example take para-nitrophenol and ortho-nitrophenol; which one would have a lower boiling point? ortho cause it can have intramolecular H-bonding and therefore it will have intermolecular h-bonding to a lesser degree..

 

[StIGMA]

intermolecular H-bonding would still be favored to increase the entropy of the system (higher the temp, the more it would bond with itself (ie: think gas) / lower the temp, more it would bond with other molecules (ie: think solid))

Boiling point would not be affected greatly because the intermolecular H-bonds do exist, and are favorable at liquid temperatures, and must be broken to vaporize the molecule.

Edit: Take my explanation with a grain of salt - this explanation only supports kaplan's answer, if it is true.

At least one exception to Kaplan's answer: when intramolecular bonding affects the overall shape of the molecular (ex: protein) to where residues that would be able to H-bond are not exposed to the aqueous phase.

 

[supafield]

I just came across a question on kaplan diag#5 Q#20. Although I got the question right, the explanation says INTRAmolecular H-bonding has nothing to do with the boiling point..is this true??I though if a molecule is capable of Intramolecular H-bonding, it would have a lower boiling point cause it would have less intermolecular H-bonding..

is this true??

That's how I learned it.

 

[radon222]

If a molecule can make intrAmolecular H -bonds then it is going to have less intermolecular H-bonding. Therefore it would have a lower BP than expected. I am assuming that all else is equal.

An above poster provides a correct example of this.