Properties
Xylenes encompass three isomers of dimethylbenzene. The isomers are distinguished by the designations ortho- (o-), meta- (m-), and para- (p-), which specify to which carbon atoms (of the benzene ring) the two methyl groups are attached. Counting the carbon atoms from one of the ring carbons bonded to a methyl group, and counting towards the second ring carbon bonded to a methyl group, the o- isomer has the IUPAC name of 1,2-dimethylbenzene, the m- isomer has the IUPAC name of 1,3-dimethylbenzene, and the p- isomer has the IUPAC name of 1,4-dimethylbenzene.
Some chemical and physical properties differ from isomer to isomer. The melting point ranges from −47.87 °C (−54.17 °F) (m-xylene) to 13.26 °C (55.87 °F) (p-xylene). The boiling point for each isomer is around 140 °C (284.00 °F). The density of each is around 0.87 g/mL (7.26 lb/U.S. gallon or 8.72 lb/imp gallon) and thus is less dense than water. Xylene in air can be smelled at 0.08 to 3.7 parts of xylene per million parts of air (ppm) and can begin to be tasted in water at 0.53 to 1.8 ppm.
| Xylene Isomers | ||||
|---|---|---|---|---|
| General | ||||
| Common name | Xylenes | o-Xylene | m-Xylene | p-Xylene |
| Systematic name | Dimethylbenzenes | 1,2-Dimethylbenzene | 1,3-Dimethylbenzene | 1,4-Dimethylbenzene |
| Other names | Xylols | o-Xylol; Orthoxylene |
m-Xylol; Metaxylene |
p-Xylol; Paraxylene |
| Molecular formula | C8H10, C6H4(CH3)2 or C6H4C2H6 | |||
| SMILES | Cc1c(C)cccc1 | Cc1cc(C)ccc1 | Cc1ccc(C)cc1 | |
| Molar mass | 106.16 g/mol | |||
| Appearance | clear, colorless liquid | |||
| CAS number | ||||
| Properties | ||||
| Density and phase | 0.864 g/mL, liquid | 0.88 g/mL, liquid | 0.86 g/mL, liquid | 0.86 g/mL, liquid |
| Solubility in water | practically insoluble | |||
| Soluble in non-polar solvents such as aromatic hydrocarbons | ||||
| Melting point | −47.4 °C (−53.3 °F; 226 K) | −25 °C (−13 °F; 248 K) | −48 °C (−54.4 °F; 225 K) | 13 °C (55.4 °F; 286 K) |
| Boiling point | 138.5 °C (281.3 °F; 412 K) | 144 °C (291.2 °F; 417 K) | 139 °C (282.2 °F; 412 K) | 138 °C (280.4 °F; 411 K) |
| Viscosity | 0.812 cP at 20 °C (68 °F) | 0.62 cP at 20 °C (68 °F) | 0.34 cP at 30 °C (86 °F) | |
| Hazards | ||||
| MSDS | Xylenes | o-Xylene | m-Xylene | p-Xylene |
| EU Classification | Harmful (Xn) | |||
| NFPA 704 | 3 2 0 | |||
| Flash point | 30 °C (86 °F) | 17 °C (63 °F) | 25 °C (77 °F) | 25 °C (77 °F) |
| R/S statement | R10, R20/21, R38: (S2), S25 | |||
| RTECS number | ZE2450000 | ZE2275000 | ZE2625000 | |
| Supplementary data page | ||||
| Structure & properties | n, εr, etc. | |||
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
|||
| Spectral data | UV, IR, NMR, MS | |||
| Related compounds | ||||
| Related aromatic hydrocarbons |
toluene, mesitylene, benzene, ethylbenzene | |||
| Related compounds | xylenols - types of phenols | |||
Xylenes form azeotropes with water and a variety of alcohols. With water the azeotrope consists of 60% xylenes and boils at 90 °C. As with many alkylbenzene compounds, xylenes form complexes with various halocarbons. The complexes of different isomers often have dramatically different properties from each other.
Read more about this topic: Xylene
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