The X alpha scattered-wave (X alpha-SW) method was used to calculate the C K x-ray absorption (NEXAFS) spectrum of propane which previously was used as a model system for larger saturated hydrocarbons. The absorption resonances below the ionization threshold are analyzed in detail and characterized with respect to their valence and/or Rydberg-character. The shape resonances above the ionization threshold were investigated by calculating the eigenchannel wave functions involved in the formation of the resonances. The applicability of the results to the spectra of long alkane chains is studied, in particular for the determination of molecular orientation from their polarization dependence.