sentences:  The compound is classified as an alkylbenzene.It is one of three isomers of tetramethylbenzene, the other two being prehnitene (1,2,3,4-tetramethylbenzene) and isodurene (1,2,3,5-tetramethylbenzene).Durene has an unusually high melting point (79.2 °C), reflecting its high molecular symmetry.