The rates of addition of benzenefulphenyl chloride to 62 alkyl substituted allenes have been determined in methylene chloride solution at 24.5°C. The rates of addition span a range of 3.4 × 103 in reactivity. No correlation with the extended Taft equation or variations thereof was found when the rates of all 62 compounds were considered. Partitioned rate constants, wherein each term reflects the relative propensity for attack upon a given π orbital‐lobe of the allenic system, allows one to demonstrate the specific effect of placing an alkyl group in each of three stereochemically distinct positions. Of note is the observation that while the magnitude of the polar effect of an alkyl group changes with the stereochemical location, this magnitude is a constant for methyl, ethyl and isopropyl. The rates reported herein are interpreted in terms of rate‐limiting formation of alkylidenethiiranium ions.