1. The problem statement, all variables and given/known data Problem: I am told that the first mechanism is operative in saponification. 3. The attempt at a solution However, this strikes me as wrong because the first mechanism involves the formation of dianion. Using hydroxide ion to abstract a proton and make that particular dianion seems like a very uphill process energetically. The second mechanism, according to her, is wrong because it involves the formation of a carboxylic acid in basic conditions. And acids should never exist in basic solutions. Er, this seems wrong. First, the acid we're forming isn't the result of some proton abstraction in basic solution. That would be hard - can you imagine abstracting a proton from HO-? Second, the second route seems highly favorable because once you form the -COOH you can deprotonate the -COOH - an energetically favorable move!