A study of the reaction of alcohols with bromine and silver salts

The oxidation of alcohols with bromine and silver salts was studied and the synthetic use of this reaction was evaluated. Thus with bromine, silver salts and in the absence of light, 2-cyclohexylcyclohexanol was oxidized to dodecahydrodibenzofuran and 2-cyclohexylethanol was converted to octahydrobenzofuran. The spiro compound, 1-oxa-spiro (4,5) decane, was obtained from two different alcohols, 1-cyclohexyl-3-propanol and 1-propyl-1-cyclohexanol. Two different bicyclic ethers, 1-methyl-8-oxabicyclo (3,2,1) octane and 1-methyl-9-oxabicyclo (4,2,1) -nonane were obtained from two alcohols; namely: 1-methyl-1-cycloheptanol and 1-methyl-1-cyclooctanol. Two new spiro ketal isomers, cis and trans-2,2,9-trimethyl-1,6-dioxaspiro (4,4) nonane were produced when 1,7-dimethyl-3,7-octadiol was reacted with silver carbonate and bromine. Two other new spiro ketals were synthesized in this research; they were 2,2,9-trimethyl-7-propyl-1,6-dioxaspiro (4,4) nonane and 2,2,9-trimethyl-7-ethyl-1,6-dioxaspiro (4,4) nonane. When 2-ethyl-1,3-hexadiol was treated with bromine and silver carbonate, 2-ethyl-1-hexen-3-one was formed. The dihydric alcohol, 2,5-hexadiol yielded 2,5-hexadione. When 1-methyl-2-cyclohexylcyclohexanol was reacted with silver acetate, the starting alcohol was recovered and 8% of 1-methyl-2-cyclohexylcyclohexene was formed. When 2-cyclohexylcyclohexanol reacted with silver trifluoroacetate, 2-cyclohexylcyclohexanone was the major product and no ether was detected. The results of the present study showed that maximum yields of ethers were formed from mono-alcohols when silver acetate in pentane was used, while with diols, ether formation was favored when silver carbonate in chloroform was used. The results support an ionic mechanism involving the hydroxyl group of the substrate. In both cases, alkenes and brominated alkanes, were detected as by products. Spectral data (infrared, nuclear magnetic resonance and mass spectrometry) was determined for the new compounds. The reaction intermediates were studied by either ultra-iolet spectroscopy or gas chromatography.