4nitrobenzenesulfonamide

4-nitrobenzenes, or para-nitrobenzenes, refer to a broad class of disubstituted benzene derivatives in which a nitro group (-NO2) is located at the 4-position relative to another substituent on the ring. The term describes compounds where two substituents occupy opposite sides of the benzene ring, such as 4-nitroaniline or 4-nitrobenzaldehyde.

Common examples include 4-nitroaniline (4-aminonitrobenzene), 4-nitrobenzoic acid, 4-nitrobenzaldehyde, 4-nitrotoluene, and 4-nitroanisole. These compounds illustrate the versatility of the para relationship: the nitro group is para to a second functional group such as amino, carboxyl, aldehyde, methyl, or methoxy. The nitro group is strongly deactivating and electron-withdrawing, influencing reactivity and color in many derivatives.

Preparation typically involves nitration of an activated benzene substrate (such as anisole, toluene, or anilines) followed by separation of the desired para isomer from ortho/para mixtures. Directing effects of existing substituents guide the nitration outcome, though mixtures are common and purification is often required.

Applications of 4-nitrobenzenes span dyes, pigments, polymers, and pharmaceuticals. For example, 4-nitroaniline is a key intermediate in azo dye synthesis, while 4-nitrobenzoic acid derivatives serve in pharmaceutical manufacturing and as building blocks for specialty chemicals.

Safety considerations are important: nitro compounds can be toxic and potentially energetic under certain conditions. Reactions involving nitration are typically exothermic and must be conducted with appropriate controls, protective equipment, and waste handling.