The pKa of 2-chlorobutanoic acid is 2.84 and that of 4-chlorobutanoic acid is 4.52. How many times larger is the acid dissociation constant of 2-chlorobutanoic acid than that of 4-chlorobutanoic acid? Give the answer to the nearest integer.

Numerical answer type, tolerance 0.5.

Answer: 48

K_{a} = 1 0^{- p K_{a}}

, so the ratio is

1 0^{4.52 - 2.84} = 1 0^{1.68} \approx 47.86

. The nearest integer is 48. The chlorine on the alpha carbon exerts a much stronger

- I

effect than the one on the gamma carbon.