C6H4NH2

C6H4NH2 is not a standard, widely used molecular formula for a single defined compound. It may be encountered as an incomplete or shorthand way to discuss an amino-substituted benzene, but the conventional formula for the simplest member of this class is aniline (aminobenzene), which is C6H7N and often written as C6H5NH2. The notation C6H4NH2 is not a common representation for a specific pure substance in standard chemical nomenclature, and its meaning can be ambiguous without further context.

Aminobenzenes, or anilines, are derivatives of benzene in which one hydrogen on the ring is replaced by an amino group (NH2). The amino substituent is an electron-donating group via resonance and strongly activates the ring toward electrophilic substitution, especially at the ortho and para positions relative to the NH2 group. The amine is basic; the conjugate acid has a pKa around 4.6, and aniline itself has a pKb around 9.4. In practice, this basicity and reactivity govern many of its applications and handling considerations.

Mono-substituted benzene amines are primarily represented by aniline (C6H7N). They are important in industry as precursors for dyes, polymers, and various as well as rubber processing aids. Aniline and related compounds are used to produce a wide range of azo dyes, polyurethane foams, and heavyweight chemicals. Safety concerns include irritation of skin, eyes, and respiratory tissues; anilines are toxic and can cause methemoglobinemia with sufficient exposure, so they are handled under controlled conditions with appropriate protective equipment and ventilation.

Diaminobenzenes, with formula C6H4(NH2)2, form another related class (phenylenediamines) and serve as precursors in dye chemistry, polymer science, and specialty chemicals. Three isomeric forms exist: o-, m-, and p-phenylenediamine, each with distinct reactivity and applications.