INTRAmolecular forces on boiling point/melting point

[ahs4n]

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We know intermolecular forces increase boiling point and melting but what do intramolecular forces do for the bp and mp?

 

[12345a]

http://lmgtfy.com/?q=intramolecular+forces+and+boiling+melting+point

third one from the top

 

[loveoforganic]

I don't get how you can predict MP's unless you're given some very drastic examples. Maybe QofQuimica can weigh in on this, but I was under the impression MP was based on lattice structure, which essentially doesn't correlate with anything we can observe with molecular structure - it has to be determined experimentally, or at least with a powerful computer app that runs packing simulations.

 

[sv3]

Most of the melting pt questions I've seen have to do with colligative properties. There were some regarding different types of organic compunds and structures that you need to be careful about (cis vs trans). But just based on an intramolecular interaction is a question i have yet to see.....

 

[QofQuimica]

You don't break intramolecular bonds (within the compound) when you melt something unless it is decomposing, which can happen if you heat organic compounds high enough. Ditto for boiling. I wrote a post a while back about intramolecular versus intermolecular forces that you can find in the organic chemistry thread link in the sticky for this forum. Also there is one on MP and BP. The link that 12345a posted is good too.

 

[kobe200LATE]

boiling point and melting point are primarily dependent on INTERmolecular forces so if anything, so increased INTRAmolecular forces might actually lower the melting point/boiling point if they result in lower INTERmolecular forces.

 

[sv3]

boiling point and melting point are primarily dependent on INTERmolecular forces so if anything, so increased INTRAmolecular forces might actually lower the melting point/boiling point if they result in lower INTERmolecular forces.

how would that happen? any examples? (only one i can think of is a h-bonding within a molecule, thus decreasing h-bonds across molecules)

 

[ahs4n]

One of the early AAMC tests had a intramolecular problem, and it actually lowered either the boiling or melting point...I'm not sure..but this is why I'm trying to ask.

And, that AP link does nothing to help...I know the diffrence between the types...I just can't put a finger on what intramolecular forces would do bp/mp

 

[12345a]

yeah, i didn't mean to reference the AP link...i guess this thread bumped the page I wanted down to a 2nd or 3rd page on the google search 😀.