The 1,4-Dimethylbenzene, also called p-Xylene, is an aromatic hydrocarbon. It is an isomer of xylene. Other isomers include o-xylene and m-xylene. It occurs in two forms, either as colorless liquid with a characteristic aromatic odor at normal temperature, or as colorless crystalline solid below 13 °C. 1,4-Dimethylbenzene which exists in the atomatic tobacco and smoke is non-corrosive to metal. When heating to its decomposition, it decomposes to methane, hydrogen, toluene, couplet toluene and 2,6 - dimethyl anthracene.

Preparation: There is a considerable amount of 1,4-Dimethylbenzene in oil xylene and coal tar xylene. As the difference of boiling point between m-xylene and 1,4-Dimethylbenzene is only 0.75 °C, it can not be separated by distillation method. The current methods in domestic and foreign research are low-temperature crystallization separation, adsorption separation and complexing separation. The yield of low-temperature crystallization separation is 60-70% which is low. But the adsorption separation has relatively high yield and purity.

There is another method which has high purity of 99.9%. In transalkylation reactor, raw material toluene can produce xylene and benzene by alkyl transfer reaction. Part of m-xylene can be isomerized to 1,4-Dimethylbenzene by isomerization reactor. Then after some treatment, people can get the product with by-product m-xylene.

Uses: It is not only used as raw material in the production of polyester fibers and resins, paints, dyes and pesticides, but also used as chromatography standard materials and solvents. On a large scale, 1,4-Dimethylbenzene is used for the manufacture of terephthalic acid for polyester. In addition, it also can be used in organic synthesis. For example: it can react with benzoyl chloride to get 2,5-dimethyl-benzophenone. This reaction needs reagents CS₂ and AlCl₃.

Safty: It has danger of very serious irreversible effects through inhalation, in contact with skin and if swallowed. If you want to contact this product, you must wear suitable protective clothing and gloves. In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.) So 1,4-Dimethylbenzene should be sealed in the container and stored in the cool and dry place which must be away from oxidant.

Other physical properties: (1)ACD/LogP: 3.25; (2)ACD/LogD (pH 5.5): 3.247; (3)ACD/LogD (pH 7.4): 3.247; (4)ACD/BCF (pH 5.5): 173.006; (5)ACD/BCF (pH 7.4): 173.006; (6)ACD/KOC (pH 5.5): 1391.912; (7)ACD/KOC (pH 7.4): 1391.912; (8)Index of Refraction: 1.5; (9)Molar Refractivity: 35.903 cm³; (10)Molar Volume: 121.984 cm³; (11)Surface Tension: 28.791 dyne/cm; (12)Density: 0.87 g/cm³; (13)Flash Point: 27.222 °C; (14)Enthalpy of Vaporization: 35.67 kJ/mol; (15)Boiling Point: 139.61 °C at 760 mmHg; (16)Vapour Pressure: 7.943 mmHg at 25°C.

Data structure conversion:
(1)Canonical SMILES: CC1=CC=C(C=C1)C
(2)InChI: InChI=1S/C8H10/c1-7-3-5-8(2)6-4-7/h3-6H,1-2H3

Toxicity: