Distribution of diaromatic nitrogen bases in crude oils

Azanaphthalene derivatives were identified in 9 petroleum samples. In all investigated crude oils; the number of alkyl substituents was found to extend up to C₉ with a maximum most often for C₆; unsubstituted parent compounds are absent. Two distinct types of azanaphthalenes occur: solely methylated derivatives which are abundant in most crude oils of Cretaceous or Miocene ages, and compounds bearing alkyl chains of up to 4 carbon atoms, with a majority of 8-isopropyl quinoline derivatives, which dominate in a California crude oil of Pliocene age.