SUBSTITUENT EFFECTS AND ARYL PARTICIPATION IN BETA-(SYN-9-BENZONORBORNENYL) ETHYL P-BROMOBENZENESULFONATE SOLVOLYSES

A series of 6-substituted β-(syn-9-benzonorbornenyl)ethyl brosylates (Ia-e-OBs), the unsubstituted anti isomer (Ila-OBs), and the syn-propyl homolog (IX-OBs) were synthesized. The acetolysis of unsubstituted Ia-OBs proceeds 20 times as fast at 100° as that of Ila-OBs and yields mainly a mixture of several benzhydrindanyl derivatives formed with rearrangements. The effects of the 6 substituents on the over-all rates, kOCH/kNO, amount to a factor of 146, and those on the anchimerically assisted rates, kΔ, are well correlated by the modified Hammett relationship, log (kΔ/kΔ0) = 1/2ρ;(σp+ + σm+), with ρ =–2.88. These are discussed as evidence for remote aryl participation under a constant steric factor. In contrast, the acetolyses of Ila-OBs and IX-OBs showed neither rate enhancement nor rearrangement. © 1968, American Chemical Society. All rights reserved.