4-Nitrophenol

4-Nitrophenol (also known as p-nitrophenol) is an organic compound with the formula C₆H₅NO₃. It is one of the isomers of nitrophenol, distinguished by the position of the nitro group (NO₂) at the para position relative to the hydroxyl group (OH) on the benzene ring.

Structure and Properties

4-Nitrophenol is a yellow crystalline solid that is soluble in water. It has a melting point of 114 °C and a boiling point of 279 °C. The compound is characterized by its aromatic ring, which is substituted with a hydroxyl group and a nitro group. The presence of the nitro group makes 4-nitrophenol more acidic than phenol, with a pKa of 7.15.

Synthesis

4-Nitrophenol can be synthesized through the nitration of phenol using a mixture of concentrated sulfuric acid and nitric acid. The reaction typically yields a mixture of ortho- and para-nitrophenol, which can be separated by recrystallization or other purification methods.

Applications

4-Nitrophenol is used in various applications, including:

• As a precursor in the synthesis of paracetamol (acetaminophen), a common analgesic and antipyretic.
• In the production of dyes, pesticides, and other chemicals.
• As a pH indicator due to its color change from colorless to yellow as the pH increases.

Toxicity and Safety

4-Nitrophenol is considered toxic and can be harmful if ingested, inhaled, or absorbed through the skin. It can cause irritation to the eyes, skin, and respiratory tract. Prolonged exposure may lead to more severe health effects, including damage to the liver and kidneys. Proper safety precautions, such as the use of personal protective equipment, should be taken when handling this compound.

Environmental Impact

4-Nitrophenol is a pollutant that can be released into the environment through industrial processes. It is known to be toxic to aquatic life and can contribute to environmental pollution. Biodegradation and other remediation techniques are often employed to mitigate its impact.

Also see

• Nitrophenol
• Phenol
• Paracetamol
• Nitration