Prismane

• Ladenburg benzene
• Tetracycloparaffins [ 2.2.0.02,6.03,5 ] hexane

Colorless, highly explosive liquid

Liquid

Template: Infobox chemical / molecular formula search available

Prismane or Ladenburg benzene, molecular formula C6H6, is another name for the connection tetracycloparaffins [ 2.2.0.02,6.03,5 ] hexane. The name has connected through their prism structure.

The structure was originally proposed by Albert Ladenburg for the benzene molecule, however, turned out to be false. The hydrocarbon prismane corresponding to the then proposed structure, was first produced synthetically in 1973.

Prismane is under considerable ring strain and is about 377 kJ / mol higher in energy than benzene. Nevertheless, even prismane is metastable at room temperature. Robert B. Woodward and Roald Hoffmann discovered, which is contrary to the rearrangement of prismane to benzene: the conservation of orbital symmetry ( Woodward -Hoffmann rules ). Woodward and Hoffmann [ received for this theory Nobel prize in 1981, at a time when Woodward (Nobel Prize 1965) had already died ], prismane designated as a " raging tiger, it is impossible to break out of his cage paper. "

Prismane is a colorless, volatile and explosive liquid.

Synthesis

Prismane as valence isomer of benzene can be produced by photochemical transformations of benzene:

An alternative synthesis of prismane also starts from benzvalene (1). Is converted to benzvalene ,5- dione ( PTAD ) with the compound 4-phenyl -1 ,2,4- triazoline -3, which is the so far known reactive dienophile. The reaction is a stepwise Diels -Alder -like reaction with a carbenium ion as a reactive intermediate. The adduct of 2 is hydrolyzed in a basic medium and then treated with copper ( II) chloride. The neutralization with a strong base gives the crystalline azo compound 3 in 65 % yield. The photolysis of 3 results cyclized elimination of nitrogen a diradical which then prismane (4).