The competition between bimolecular nucleophilc substitution and base-induced elimination is investigated through kinetic isotope effect measurements for gas-phase reactions of RCl+ ClO-(R= methyl, ethyl, isopropyl, and tert-butyl) utilizing a FA-SIFT instrument. The overall reaction rate constants and the kinetic isotope effect for the reaction of C2H5Cl+ ClO-are compared to computational results.[Hu, WP; Truhlar, DGJ Am. Chem. Soc. 1996, 118, 860. ...