C6H5NH3

C6H5NH3 is the anilinium cation, the protonated form of aniline (C6H5NH2). In chemical salts it exists as the C6H8N+ cation paired with various counteranions such as chloride, sulfate, tetrafluoroborate, or hexafluorophosphate. The cation is the conjugate acid of the weak base aniline.

Protonation converts the amine into a positively charged ammonium center. The conjugate acid has a pKa around 4.6, so in aqueous solution the C6H5NH3+ form is favored at acidic pH, whereas at neutral or basic pH the unprotonated aniline predominates. This behavior is central to acid–base chemistry in organic synthesis and purification.

Structurally, the nitrogen in C6H5NH3+ is bonded to the phenyl ring and to three hydrogens, giving roughly tetrahedral geometry. The positive charge is localized mainly on nitrogen but is stabilized by solvation; resonance with the benzene ring is limited compared with neutral amino groups.

Anilinium salts are common in organic synthesis and industry as reagents and intermediates; the salt form can influence solubility, crystallinity, and reactivity. The C6H5NH3+/C6H5NH2 system serves as a standard example of protonation equilibria for an aromatic amine. Safety considerations for anilinium salts include corrosivity and potential toxicity; appropriate handling and disposal practices should be followed.