Melting points of organic acids

Question

Hi!

I found out that benzoic acid has a higher melting point than stearic acid. Why is that?

Can't get any answer from my teacher in Zoom (he signed off for the weekend a little too early), and my book doesn't explain this either..

Thanks in advance

Answer 1

Nice question. Won't answer question for you but will guide you through with discussion and you should be able to deduce your own response.

Both carboxylic acids ..... has that CO2H tail

Benzoic acid is C6H5-CO2H

Stearic acid is C17H35-CO2H

Benzoic acid is cyclic ..... in addition, is a ring ..... doubly special with resonance

Stearic acid is a chain

Is a necklace structural tougher as cyclic or linear?

Have you learned about resonance?

As a ring, there are double bonds vs. single bonds and the resonance kind of looks like a center in a 3-center unit can share that double bond left or right ..... resonating

Physical properties like melting points and boiling points are breaking points.

The tougher the nut, the harder you have to work to crack it

Hope this simple explanation helps you develop your response in more technical terms.

You'll do fine.. :)