摘要:
Electronic effects in the third step of the Criegee mechanism of ozonolysis, i.e., the reaction of a carbonyl oxide with a carbonyl compound, were studied by using a non-ozone source of carbonyl oxides as well as by an ozonolysis method. Benzophenone oxide, produced by photosensitized oxidation of diphenyldiazomethane or ozonolysis of tetraphenylethylene, was reacted with a series of para-substituted benzaldehydes. The relative rates of triaryl ozonide formation were treated with the Hammett relationship to give rho = 0.48 or 0.76, respectively, for the photooxidation and ozonolysis reactions. These results indicate that electron-withdrawing substituents in the aldehyde increase the rate of ozonide formation and are consistent with those reported earlier by Kuczkowski and co-workers for stilbene ozonide and with the long held view that ozonide formation involves reaction of a dipolar carbonyl oxide with the carbonyl partner.