Hydron exchange rates, kexc(M−1s−1), using methanolic sodium methoxide were compared with ΔG°Acid, (kcal mol−1) (gas phase) for 9‐phenylfluorene, C6H5CH(CF3)2, m‐CF3C6H4CH(CF3)2, p‐CF3C6H4CHClCF3, m‐CF3C6H4CHClCF3, 3,5‐(CF3)2C6H3CHClCF3, fluorene and C6F5H. There is a good linear correlation for p‐CF3C6H4CHClCF3, m‐CF3C6H4CHClCF3and 3,5‐(CF3)2C6H3CHClCF3, with the others falling off the line. The fluorinated benzyl compounds and pentafluorobenzene have near‐unity isotope effects and therefore differ from the fluorenyl compounds. Although the acidity and the exchange rates for three of the compounds [9‐phenylfluorene, C6H5CH(CF3)2and p‐CF3C6H4CHClCF3] are similar, the important proton‐transfer step to form a hydrogen‐bonded carbanion intermediate and the subsequent breaking of that weak bond to form a free carbanion in methanol differ significantly for the fluoernyl compound compared with the two fluorinated benzylic compounds. © 1998 John Wiley & Sons, Ltd.