Are carboxylic acids strong?

1 Answer
Nov 12, 2015

Generally no.


The strength of acids is gauged according to the completion of the following acid/base reaction:

#HA + H_2O rightleftharpoons H_3O^+ + A^-#.

For strong acids, the equilibrium lies strongly to the right. For weak acids the point of equilibrium lies to the left. For saturated carboxylic acids the equilibrium lies to the left, and #pK_a# values are reasonably high: cf. formic acid, #3.75#, acetic acid #4.74#. Halogen or fluoride substitution on the alkyl group can depress these values; this is largely an entropy phenomenon, as the halogen can help delocalize the negative charge of the conjugate base upon dissociation.