ISSN:
1573-935X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The photo-initiated oxidation of alcohols by carbon tetrachloride was studied. The main reaction products formed during the irradiation of CCl4 solutions in ethanol with light of λ = 254 nm are chloroform, acetaldehyde, and hexachloroethane. With increase in concentration of CCl4 in the mixture with ethanol from 0.5 to 5 mole/liter, the quantum yields of the formation of CHCl3 and CH3CHO decrease from 9.2 to 4.4 and from 4.3 to 1.4, respectively, while the quantum yield of formation of C2Cl6 increases from 0.38 to 0.68. By using semiconductor photocatalysts (TiO2, TiO2/Pd, CdS), the oxidation of alcohols can be carried by the action of light of the near-UV and visible regions of the spectrum (320 〈 λ 〈 520 nm). When the reaction is carried out photocatalytically, the maximum quantum yields of the formation of CHCl3 and CH3CHO were attained with a palladized TiO2 (0.77 and 0.36, respectively). The initial stage of the mechanism of the photochemical process involves the cleavage of the C-Cl bond with absorption of a quantum of light by the CCl4 molecule, and this is followed by reactions of free radicals. When semiconductor photocatalysts are used, the cleavage of the C-Cl bond occurs either by the action of hydroxyethyl radicals, formed by the reaction of ethanol molecules with valence zone “holes” of the semiconductor (in the case of TiO2), or electrons of the semiconductor conductivity zone (in the case of CdS).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00534442
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