Résumé : ARRHENIUS parameters have been determined (a) for the solvolysis of 1‐,3‐ and 4‐chloromethylpyrene in different solvents (Table 11) and (b) for the S,2 reaction of 1‐ and 4‐chloromethylpyrene with KI in acetone (Table IV). Taking into account previous results, it is shown that 3‐chloromethylpyrene has an apparently abnormally high rate constant in solvolysis reactions. Copyright © 1959 Verlag GmbH & Co. KGaA, Weinheim