For the reaction of a carboxylic acid and organolithium reagents to synthesise a ketone, Clayden's, on p 219, mentions:
Notice that three equivalents of organolithium are needed in this reaction: one to deprotonate the acid, one to deprotonate the hydroxyl group, and one to react with the lithium carboxylate.
It seems to me that "the acid" and "the hydroxyl group" refer to the same thing. A carboxylic acid molecule only has one acidic proton and it belongs to a hydroxyl group. Thus, shouldn't these two terms refer to the same thing and only two equivalences of the organolithium reagent be necessary?
Clayden, J., Greeves, N., & Warren, S. (2012). Organic Chemistry (2nd ed.). New York : Oxford University Press Inc.