# Why don't dicarboxylic acids show hydrogen bonding in spite of the fact that carboxylic acids exist usually as dimers in polar aprotic solvent? [closed]

I have seen several examples:

1. The fact that maleic acid is more soluble in water than fumaric acid in spite of the fact that it must be able to show intramolecular hydrogen bonding.
2. trans-Cyclopentane-1,2-dicarboxylic acid is more stable than the cis form (cis form should be able to show hydrogen bonding).
3. o-Nitrobenzoic acid is more acidic than the para isomer.

I tried linking point 1 to acidic strength (maleic acid > fumaric acid because of hydrogen bonding in conjugate base) and point 3 to acidic strength (o-nitrophenol < p-nitrophenol)

What am I missing? Something related to the size of the ring?

• Refer to these papers: here, here and here Aug 14 '20 at 3:54
• This is a prime example of question that's both badly worded and too broad. Aug 16 '20 at 23:58

I would like to object the statement dicarboxylic acids would not engage hydrogen bonding. Terephthalic acids ($$\ce{HO2C-C6H4-CO2H}$$) are a prominent example since early attempts to formalize the description of intra- and intermolecular hydrogen bonding in the solid state. Consider the pairing of benzoïc acid and $$p$$-terephthalic acid, sharing the same motif of hydrogen donors and acceptors, described as $$R_2^2(8)$$ in Etter's notation:
But there is no limit to $$p$$-substitution to find this motif again, e.g.: