products of the replacement of hydrogen atoms in the toluene ring, C6H5CH3, by nitro groups, —NO2. The nitrotoluenes that are of commercial significance are shown in Table 1.
|Table 1. Properties of commercial nitrotoluenes|
|Melting point (° C)||Boiling point (° C)||Density (g/cm3)|
|*(α) stable form; (β) unstable form **Temperature (°C)|
|o-Nitrotoluene........||-9.27 (β)*||221.7||1.162 (19)**|
|m-Nitrotoluene .......||16.1||232.6||1.157 (20)|
|2,4,6-Trinitrotoluene …||80.8||Explodes at 280°C||1.55–1.60|
Mononitrotoluenes are produced in the form of a mixture of isomers (56 percent ortho-, 38 percent meta-, and 4 percent para-) by nitration of toluene with a nitrating mixture; o-nitrotoluene and m-nitrotoluene are light-yellow liquids, whereas the para- isomer is a colorless crystalline compound. Mononitrotoluenes are used in the production of toluidines, which are intermediates in the production of azo and sulfur dyes.
Dinitrotoluene is produced mainly by nitration of an industrial mixture of mononitrotoluenes. The product is a yellow, crystalline substance with a solidification point of 50°–54°C; it contains mostly 2,4-dinitrotoluene. The dinitrotoluene product has explosive properties and is used to produce diisocyanates, which are initial materials in the production of polyurethanes; 2,4,6-trinitrotoluene is a high explosive.
Nitrotoluenes are poisonous. For example, the maximum permissible concentration of 2,4-dinitrotoluene in the air in work areas is 1 mg/m3.
REFERENCESOrlova, E. Iu. Khimiia i tekhnologiia brizantnykh vzryvchatykh veshchestv, 2nd ed. Leningrad, 1973.
Vorozhtsov, N. N. Osnovy sinteza promezhutochnykh produktov i krasitelei, 4th ed. Moscow, 1955.