AAMC 4, Solubility Question

[davcro]

Why doesn't the carboxylic acid groups on camphoric acid hydrogen bond with 4-aminobenzoic acid, thus increasing the melting point?

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[mcloaf]

There will still be some hydrogen bonding, but that won't necessarily increase the melting point. The issue is whether or not any hydrogen bonding between 4-AB and camphoric will be stronger or weaker than the h-bonding of just pure 4-AB. Generally pure substances pack together better and bond more tightly, so while the camphoric acid will hydrogen bond with 4-AB, this bonding won't be as strong as if your sample contained only 4-AB and will thus lower the melting point.

 

[MedPR]

Why doesn't the carboxylic acid groups on camphoric acid hydrogen bond with 4-aminobenzoic acid, thus increasing the melting point?

Mixtures must have a melting point between the mp of the two pure substances.

 

[TXKnight]

Mixtures must have a melting point between the mp of the two pure substances.

This. Don't you love TBR?

 

[MedPR]

This. Don't you love TBR?

Yea, it's nice having tons of shortcuts!

 

[411309]

this was something they drilled into us during o chem labs. So many agonizingly boring melt points we had to take...

 

[pfaction]

I didn't even say that, a pure compound with impurities always has BP elevation, MP depression, VP depression. A and D don't make sense, and a "small percentage" isn't numerical, so B.

 

[davcro]

Got it, thanks everyone!