This paper reports the rate measurements for the reactions of carbanions derived from benzyltriflones, 2, with 4-nitrobenzofuroxan, 4, in methanol, to give anionic σ -adducts. 1 H NMR studies in DMSO-d 6 indicate that the products formed by the reaction of 2 and 4 in the presence of triethylamine are consistent with the products formed by the elimination of trifluoromethylsulfinic acid from σ -adducts, initially formed by a carbanion attack at the 5 position of 4. The low value of β, which is the slope of the linear plot of log k 5 versus pK a , provides evidence for the high steric requirements of the benzyltriflone anions. C 2012 Wiley Periodicals, Inc. Int J Chem Kinet 1-9, 2012