“…The most efficacious leaving
groups are conjugate bases of moderate to strong acids, e.g., sulfates, 85d,93 phosphates 7,9u,82−85,99 (thiophosphate), 100,111 carboxylates, 7b,9u,85a−85c,93−95,97b,97c,112 phenolates, 9u,93 and thiolates. 111,113 In general, quantum yields monotonically
decrease with an increase in the acid leaving group’s p K a (Table 4), conforming
to a Brønsted leaving group relationship (β LG ), which correlates the pHP release rate constant with the K a of the leaving group.…”