Photochemistry of benzoin ethers in solution (in German)
Benzoin alkyl ethers dissociate into benzoyl- and alpha -alkoxybenzyl radicals on absorption of 368nm-light. This alpha -cleavage was demonstrated by ESR-spectroscopic identification of the primary radicals during irradiation. The quantum yield of photofragmentatioh is close to 1 and independent of the nature of the alkyl group, additional alpha -substituents and of the solvent. The quantum yield of beazoin ether consumption is only 0.42, because the starting material is partly reformed by recombination of the primary radicals. Product analysis by means of a GC/MS-combination yielded information on the secondary reactions of the radicals formed when deuterium marked benzoin methyl ethers were irradiated. In the absence of oxygen the benzoyl radicals react by dimerisation to benzil, by reaction with the alcohol used as solvent to form the corresponding benzoic acid ester, and by hydrogen abstraction from the starting material forming beazaldehyde. The alpha -methoxybenzyl radicals react by dimerisation to 1,2-dimethoxy-1,2-diphenylethane selectively. Additionally, highboiling compounds form 20% of the final products. In the presence of oxygen the primary radicals are scavenged leading to peroxy radicals, causing an increase in the quantum yield of starting material consumption. In the secondary reactions the peroxy radicals react to perbenzoic acid, benzoic acid methyl ester, benzaldehyde, and benzaldehyde dimethyl acetal. In oxygen saturated solution the solvent (methanol) is decomposed to formic acid, hydrogen peroxide, performic acid, and formaldehyde. (auth)
- Research Organization:
- Kernforschungszentrum Karlsruhe (F.R. Germany). Inst. fuer Radiochemie
- Sponsoring Organization:
- Sponsor not identified
- NSA Number:
- NSA-29-015147
- OSTI ID:
- 4936654
- Report Number(s):
- KFK--1861
- Country of Publication:
- Germany
- Language:
- German
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