Mandelate esters exhibit spasmolytic activity (they act as muscle relaxants). The nature of the alkyl group (R)

Question:

Mandelate esters exhibit spasmolytic activity (they act as muscle relaxants). The nature of the alkyl group (R) greatly affects potency. Research indicates that the optimal potency is achieved when R is a nine-carbon chain (a nonyl group). Explain why nonyl mandelate is more potent than either octyl mandelate or decyl mandelate.

OH Mandelate esters (R = alkyl chain)