Second-order rate constants ($k_{HOO}$?) have been measured spectrophotometrically for nucleophilic substitution reactions of Y-substituted phenyl benzenesulfonates (1a-g) with $HOO^-$ ion in $H_2O$ at $25.0;{pm};0.1;{^{circ}C}$. The Br$phi$nsted-type plot is linear with ${eta}_{lg}$ = ?0.73. The Hammett plot correlated with with ${sigma}^-$ constants results in much better linearity than ${sigma}^o$ constants, indicating that expulsion of the leaving group occurs in the rate-determining step (RDS) either in a stepwise mechanism or in a concerted pathway. However, a stepwise mechanism in which departure of the leaving group occurs in the RDS has been excluded since $HOO^-$ ion is more basic and a poorer leaving group than the leaving Y-substituted phenoxide ions. Thus, the reactions of 1a-g with $HOO^-$ ion have been concluded to proceed through a concerted mechanism. The $alpha$-nucleophile $HOO^-$ ion is more reactive than its reference nucleophile $OH^-$ ion although the former is ca. 4 p$K_a$ units less basic than the latter (i.e., the $alpha$-effect). TS stabilization through intramolecular H-bonding interaction has been suggested to be irresponsible for the $alpha$-effect shown by $HOO^-$ ion, since the magnitude of the $alpha$-effect is independent of the electronic nature of substituent Y in the leaving group. GS destabilization through desolvation of $HOO^-$ ion has been concluded to be responsible for the $alpha$-effect found in the this study.