Propargyl halides, solvolysis

Allenyl cations have been generated by solvolysis of allenic derivatives, by photolysis of allenyl halides and by reaction of metal salts with allenyl and propargyl halides. This review will delineate these reactions. The related butatrienyl cations are not many and they will be only briefly described. 

Jacobs and Fenton (202) were the first to suggest the possible intermediacy of ion 242 in the hydrolysis of trisubstituted allenyl halides to give the corresponding propargyl alcohols as products. A detailed and elegant study of the solvolysis of a series of triarylchloroallenes, 243, has recently been carried out by Schiavelli and co-workers (203). Excellent first-order kinetics... 

In spite of the favourable steric arrangement, propargyl cations, although more stable than vinyl and ethyl cations, are less stable than allyl cations. This is indicated by the ionization potentials of the simple parent radicals, 8-25 and 8-16 eV (Lossing, 1963) respectively, and by the lower (by a factor of ca. 104) rate of unimolecular solvolysis in ethanol-water 4 1 of propargyl (174) than of allyl halides (175) (Burawoy and... 

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