Which of the following carboxylic acids will yield the least amount of protons in an aqueous solution?

2-methylbutanoic acid 

The carboxylic acid that will yield the least amount of protons in solution will be the least acidic molecule. Chloro substituents are electron withdrawing which makes the molecule more acidic by stabilizing the conjugate base anion. A carboxylic acid with a longer carbon chain is less acidic due to the greater induction of electrons destabilizing the conjugate base anion. A carboxylic acid with alkyl branching is less acidic due to the greater induction of electrons destabilizing the conjugate base anion. The molecule, 2-methylbutanoic acid, has the most alkyl branching of the provided answer choices.