Selenium dibenzoylmethane

Selenium dibenzoylmethane crystallises from benzene as lustrous, pale golden-yellow plates containing 2 molecules of benzene of crystallisation when freed from the latter a pale primrose-yellow powder results, M.pt. 211° C. to a deep yellow liquid. The compound is very sparingly soluble in boiling ethyl acetate, moderately soluble in benzene, but dissolves readily in chloroform. It is not enolic. It is insoluble in 5N sodium hydroxide, but decomposed on warming. It is stable towards 15 per cent, hydrochloric acid it yields an intensely scarlet solution in concentrated sulphuric acid, the colour disappearing on dilution. 

Action of Heat on Selenium bisDibenzoylmethane.—When selenium dibenzoylmethane is melted and maintained at 140° to 145° C. for 30 minutes, dibenzoylmethane is eliminated and an equilibrium represented by the following equation occurs ... 

Cooling and examination of the mixture shows that about 50 per cent, of the original quantity of selenium fosdibenzoylmethane has undergone transformation, and that the dimeric selenium product represented on the right of the equation consists of isoselenium dibenzoylmethane together with a small proportion of selenium dibenzoylmethane. iso Selenium dibenzoylmethane,... 

The intermediate compounds, isoselenium dibenzoylmethane and selenium dibenzoylmethane, when isolated and heated separately above their melting-points yield, as would be expected, identical products, selenium dehydrofo sdibenzoylmethane and selenium ... 

The close genetic relationship between the selenium compounds of dibenzoylmethane is shown in the following scheme ... 

From the ethyl acetate extract mentioned above, cyclotriselenium bisdibenzoylmethane may be isolated by evaporation and extraction of the residue with cold alcohol and ethyl acetate. The product has the formula Se3(C15H1o02)2j reddens at 205° C., and melts at 220° C. with liberation of selenium. It separates from benzene as minute, bright yellow prisms, is almost insoluble in chloroform, and is non-enolic towards ferric chloride. It is decomposed by hydriodic acid in the presence of ether, yielding red selenium and orange diselenium bis-dibenzoylmethane. 

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