The infra-red absorption spectra of organic peroxides

Abstract

The infra-red absorption spectra of over thirty organic peroxides have been investigated between 3 and 15/μ. These peroxides, which included several of the lowest members of the series, were mostly studied Jin solution or as pure liquids. The spectra are presented in order to assist in the analysis of combustion products, and to show whether a band can be found which is characteristic of the peroxide group. Almost all the peroxides have a t least one, and often several, bands of medium intensity in the region 10·5 to 12μ. The band at ll·4μ known to be associated with the stretching vibration of the O— O group in hydrogen peroxide, and calculations of the vibration frequencies of the system R— O— O—R also indicate that a corresponding band might be found in this part of the spectrum if the skew structure is maintained. The evidence for the structure is reviewed, and it is concluded that an O— O band exists in the region 10 to 12μ, of medium intensity in hydroperoxides, and weaker in peroxides. These bands are not easy to identify owing to the presence of other bands, whose origins are discussed The hydroxyl stretching frequencies provide evidence regarding association in acyl and alkyl hydroperoxide. Alkyl hydroperoxides appear to have ‘alcohol’-type hydrogen bonds, while acyl hydroperoxides exhibit also another form; this is probably due to chelation, but some dimerization is not excluded.