Also called limonene, 1- methyl -4-( 1- methyl vinyl) cyclohexene, right? -1, 8- diene, Melaleuca terpene, terpene DL- exists in citronella oil, pine needle oil, vanilla oil and turpentine. These three substances are colorless, oily and transparent liquids. It smells of fresh oranges and lemons. The relative molecular mass is 136.24.