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?

  • 2
    $\begingroup$ Refer to these papers: here, here and here $\endgroup$ Aug 14 '20 at 3:54
  • $\begingroup$ This is a prime example of question that's both badly worded and too broad. $\endgroup$
    – Mithoron
    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:

enter image description here

(Etter, Acc. Chem. Res. 1990, 23, 120-126, doi 10.1021/ar00172a005)

But there is no limit to $p$-substitution to find this motif again, e.g.:

enter image description here

(Holy et al., Collect. Czech. Chem. Commun. 2006, 71, 139-154, doi 10.1135/cccc20060139, researchgate.net)

  • $\begingroup$ But why exactly isn't hydrogen bonding predominant in explaining the 3 specific cases I mentioned in my question. Would really appreciate your help and support. $\endgroup$ Aug 16 '20 at 11:33

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