Which of the following will have the lowest pKa?Select answer from the options below4-chlorobutanoic acid2-chlorobutanoic acid3-chlorobuanoic acidbutanoic acid

The pKa of a molecule is determined by the stability of the conjugate base that is formed after it donates a proton. The more stable the conjugate base, the more likely the molecule is to donate a proton, and the lower the pKa.

In the case of chlorobutanoic acids, the chlorine atom is electronegative and can stabilize the negative charge on the conjugate base through inductive effect. The closer the chlorine atom is to the carboxylic acid group, the stronger this effect.

Therefore, 2-chlorobutanoic acid, where the chlorine atom is closest to the carboxylic acid group, will have the most stable conjugate base and the lowest pKa.