Ortho-nitrotoluene (2-nitrotoluene) is a pale yellow liquid with a mild aromatic odour, primarily used as an intermediate in the chemical industry. Its significance lies in its role in synthesising various compounds, particularly in dye manufacturing and agricultural chemicals.
Chemical structure and properties
Ortho-nitrotoluene has the chemical formula C₇H₇NO₂ and a molecular weight of 137.14 g/mol. Structurally, it consists of a benzene ring substituted with a methyl group and a nitro group in the ortho position.
At room temperature, it appears as a light yellow to orange clear liquid with a density of approximately 1.17 g/cm³. It has a boiling point of 222°C and a melting point of around -10.4°C. Ortho-nitrotoluene is sparingly soluble in water but exhibits good solubility in organic solvents such as alcohol, ether, and benzene.
Production methods
Industrially, ortho-nitrotoluene is produced through the nitration of toluene using a mixture of concentrated nitric and sulfuric acids. This reaction yields a mixture of mononitrotoluene isomers, predominantly 2-nitrotoluene and 4-nitrotoluene, typically in a 2:1 ratio. The process requires careful temperature control to prevent over-nitration and ensure the desired product yield.
Applications
The primary application of ortho-nitrotoluene is as a precursor to o-toluidine, an intermediate in the production of various azo dyes used for colouring textiles, leather, and paper. Additionally, it serves as a starting material for synthesising agricultural chemicals, rubber accelerators, and other industrial compounds.
Safety and environmental concerns
Ortho-nitrotoluene is classified as hazardous, with potential health risks upon exposure. It can be absorbed through the skin and inhalation, leading to symptoms such as headache, dizziness, and methemoglobinemia—a condition affecting oxygen transport in the blood.
Environmentally, ortho-nitrotoluene poses risks due to its toxicity to aquatic life and potential for long-lasting effects in aquatic environments. It is susceptible to photochemical degradation in water but exhibits low bioaccumulation potential.
Regulatory measures
Given its hazardous nature, the handling and use of ortho-nitrotoluene are subject to stringent regulations. In the United States, it has been added to the Toxics Release Inventory (TRI) list, mandating reporting of its environmental releases. Occupational exposure limits have been established to protect workers, and safety data sheets provide guidelines for safe handling and emergency measures.
A chemical of industrial significance
Ortho-nitrotoluene plays a vital role in the synthesis of dyes and other industrial chemicals. However, its associated health and environmental risks necessitate careful handling, adherence to safety protocols, and compliance with regulatory standards to ensure both human safety and environmental protection.
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