ELECTRON-IMPACT INDUCED SYNTHESIS OF BENZO 2,1-B-3,4-B' DITHIOPHENE

The photochemical behaviour of cis and trans 1,2-bis(2-bromo-3-thienyl)ethene has been separately studied with respect to cyclization to benzo[2,1-b:3,4-b']dithiophene (BDT). The gc/ms analysis of the mother liquors of the two isomers photoreaction shows the opposite direction of isomerization followed by production of intractable materials resulting by the radical breaking of one of the two C-Br bonds on the thiophene moiety. On the contrary, in EI mass spectrometry both the isomers give rise to fragment ions at m/z 190 studied and compared to BDT with the aid of mass analysed ion kinetic energy spectrometry and collisional spectroscopy.