p-Cymene is transparent liquid, found in essential oils, has a tang of terpenes with orange odor or carrot odor. It can be extracted from Dipentene on the reactions of dehydrogenation and disproportionation by Raney nickel or Pd/C as catalyst. In this method, it is easy separating and have a higher yield than alkylation by Toluene. The great quality of p-Cymene used as material to synthesis Tonalide.