4-Nitrobenzoic Acid

Basic Information

Physical and Chemical Properties

Chemical Properties

Acidity: It has acidity, and its acidity is stronger than that of benzoic acid. The nitro group (-NO₂) is an electron-withdrawing group, which can enhance the acidity of the carboxyl group (-COOH). It can react with bases to form salts. For example, it reacts with sodium hydroxide to form sodium 4-nitrobenzoate.

Reduction Reaction: The nitro group can undergo a reduction reaction. Under the action of suitable reducing agents such as iron powder/hydrochloric acid, hydrogen/catalyst, etc., the nitro group (-NO₂) can be reduced to an amino group (-NH₂), generating 4-aminobenzoic acid.

Substitution Reaction: The hydrogen atoms on the benzene ring can undergo substitution reactions under certain conditions. For example, in the presence of strong electrophilic reagents and appropriate reaction conditions, halogenation, nitration, etc. may occur at other positions (such as ortho and meta positions) of the benzene ring. However, due to the directing effects of the carboxyl group and the nitro group, the selectivity of the reaction will be affected.

Synthesis Methods

Oxidation Method: Using p-nitrotoluene as the raw material, it is prepared by oxidation reaction. Commonly used oxidants include potassium permanganate, potassium dichromate, etc. Under acidic conditions, p-nitrotoluene is oxidized to 4-nitrobenzoic acid. For example, under the action of potassium permanganate and sulfuric acid, the methyl group of p-nitrotoluene is oxidized to a carboxyl group.

Nitration Method: Starting from benzoic acid, it is synthesized by nitration reaction. Under the action of a mixture of concentrated sulfuric acid and concentrated nitric acid, the benzene ring of benzoic acid undergoes nitration reaction, introducing a nitro group at the para position to generate 4-nitrobenzoic acid. However, the selectivity of this method needs to be optimized by controlling the reaction conditions to minimize the formation of ortho and meta nitration products.

Application Fields

• Medical Field: It is an important intermediate for synthesizing drugs. For example, its derivatives can be used to synthesize local anesthetics, antibacterial drugs, etc. In the molecular structure of some drugs, the structural unit of 4-nitrobenzoic acid can provide specific pharmacological activities or be used to adjust the physical and chemical properties of the drugs.
• Dye Industry: It can be used to synthesize dyes. Due to its having a chromophore (nitro group) and a reactive group (carboxyl group), it can combine with other compounds through chemical reactions to generate dyes with specific colors and dyeing properties, which are used for dyeing textiles, leather, etc.
• Organic Synthesis: As an important intermediate in organic synthesis, it is used to construct complex organic molecules. By performing various chemical conversion reactions on 4-nitrobenzoic acid, such as esterification, amideization, etc., a variety of organic compounds can be synthesized, which are applied in the fields of pesticides, fragrances, polymer materials, etc.

Storage Conditions

It should be in a cool, dry, and well-ventilated warehouse.

Keep away from ignition sources and heat sources, and avoid direct sunlight. Because it is an organic compound, high temperature or ignition sources may cause it to burn.

Store it separately from oxidants, reductants, and alkalis to prevent chemical reactions.