1,2-dimethylbenzene，OX

O-xylene appears as a colorless watery liquid with a sweet odor. Less dense than water. Insoluble in water. Irritating vapor. (USCG, 1999) O-xylene is a xylene substituted by methyl groups at positions 1 and 2.

生产苯酐（邻苯二甲酸酐，PA）、染料、杀虫剂等的化工原料。邻二甲苯衍生物是邻苯二甲醛，可用于制备邻苯二甲酸酯增塑剂。其中邻二甲苯90%左右用于生产苯酐。亦可用作航空汽油添加剂。是杀菌剂灭锈胺、四氯苯肽和除草剂苄嘧磺隆的原料。