Chlorine dioxide absorption spectra

Chlorine dioxide gas is unstable and can rapidly decompose at high concentrations. It also decomposes rapidly to chlorine and oxygen with exposure to mild heat. Chlorine dioxide will decompose upon exposure to sunlight (Vogt et al. 1986). The gas-phase absorption spectrum for chlorine dioxide is the same as in aqueous solution (Kaczur and Cawfield 1993). The primary photochemical reaction of CIO2 in the gas phase corresponds to homolytic scission of one of the chlorine-oxygen bonds (i.e., C102 CIO +... 

Chlorine dioxide is usually analyzed spectrophoto-metrically. Its ultraviolet absorption spectrum has been determined many times (28, 31, 82, 120, 125, 194, 211). It possesses a broad absorption band with a... 

OP-UV spectrometry can be used to measure vapors or gases that have weak absorption characteristics, and therefore, low sensitivities in the IR spectrum. These include such compounds as nitrogen oxides, formaldehyde, ozone, sulfur dioxide, benzene, toluene, and xylenes, and also homonuclear diatomic molecules, such as chlorine. The compounds that can be determined by UV are much fewer (see Table 3.43) than those that are absorbing in the IR spectra. 

The structure —CHC1—CH2—CO—CH2 — was found by Kwei [99] in polyvinylchloride after photo-oxidation. Such j3 chloroketones decompose by the Norrish type I mechanism without loss of chlorine atoms. Hydrogen chloride is obtained only when polyvinylchloride is photo-oxidized above 30°C [98]. It seems that zipper dehydrochlorination plays little role in the reaction occurring on exposure to ultraviolet light at temperatures below 150°C in the presence of air [97], and that hydrogen chloride is mainly a product of thermal decomposition rather than photolysis [98], The following mechanism can be proposed which takes into account the experimental results namely, that chain scission and crosslinking occur simultaneously on irradiation at 253.7 nm [100] and that carbon dioxide is evolved, while an absorption band at 1775 cm-1 (ascribed to peracids) is detected in the infrared spectrum [98]. 

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