Ultraviolet and photoelectron spectroscopic studies of aromatic hydrocarbons occurring in hydroformed fuel oil from coal

Abstract

Ultraviolet spectra of fractions of hydroformed creosote oil boiling in the range 140–200°C are reproduced. The aromatic content is shown to consist predominantly of those hydrocarbons which might be expected to derive from the hydrogenation cracking of naphthalene such as indan and normal monoalkyl benzenes. The spectrum of indan has attracted discussion because of its relatively strong absorption in the 260 nm region compared to other polysubstituted alkyl aromatics. The possibility that this arises from the strained nature of the attached saturated five ring system is considered. The effects of increasing alkyl substitution on the excitation energies of the 260 nm transitions are compared with the associated ionization energies obtained by photoelectron spectroscopy. This has been done for the mono up to the completely substituted hexamethyl derivative and is illustrated graphically.