Spectroscopic studies on carbonium ions derived from biacene (1,1′-biacenaphthenylidene) and acenaphthylene

Abstract

Biacene (I) was dissolved in concentrated sulphuric acid yielding a carbonium ion (X) as a result of protonation. This cation rapidly oxidised to form the proton adduct of dinaphthylenebutadiene (III). The same reactions took place when methylene dichloride solutions of SnCl₄ or AlCl₃ were used as solvents, provided that traces of water and oxygen were also present. Acenaphthylene was protonated by all of these acidic solvents: by the use of high dilution techniques the consequent polymerisation was limited to the formation of a dimeric cation which also was rapidly oxidised to the proton adduct of dinaphthylenebutadiene.