MS analysis of biindenylidenes

Biindenylidene isomers are components of pyrolysis oils. The mass spectra were recorded and the fragmentation of the following biindenylidene isomers (E)-2,3,2’,3’-tetrahydro- [1,1’]biindenylidene (Z)-2,3,2’,3’-tetrahydro-[1,1’]biindenylidene 1,3,1’,3’-tetrahydro-[2,2’]biindenylidene and 2,3,1’,3’-tetrahydro-[1,2’]biindenylidene, as well as of spiro[1,1a,6,6a-tetrahydrocyclopropa [a]indene-1,1’-2’,3’-dihydro-1’H-indene]is discussed.