Diformyl-2,2-Difuran

To utilize the outstanding thermal stability of the furan ring for the manufacture of high-temperature polymers, it is necessary to provide it with two arms capable of linking with equal or different building block molecules. One way of achieving this is to join two furfural molecules at the 5-position in forming difurfural (5,5 -diformyl-2,2 -difuran)  

It was known that this can be accomplished by UV irradiation of bromofurfural [76]  

The special feature of Burger s process is the observation that after complete consumption of the bromofurfural, the formation of difurfural continues indefinitely. Thus, after a start with bromofurfural, a continuous addition of furfural results in a continuous precipitation of solid difurfural (melting point 264.5 C), which can be removed continuously by sedimentation or filtration. By contrast, if the process is started without the bromofurfural, no difurfural is formed. 

As in many photochemical processes, the mechanism at work is not firmly established, but application of known principles seems to indicate the following sequence of events  

Reaction (3) is documented in the literature [78] where it is said to take place when HBr is irradiated with 253.7 nm. In Burger s medium pressure mercury arc lamp, this wavelength is strongly represented. Reaction (3) regenerates bromine radicals, thus creating a steady state population of this species, so that the formation of furfural radicals by hydrogen abstraction can continue even after all of the bromofiirfural has disappeared. 

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Difurfural (5,5 -diformyl-2,2 -difuran) with 6 conjugated double bonds is yellow. 

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