Sodium nitrite is an air-sensitive and hygroscopic solid with both reducing and oxidizing properties. It is commonly used as a reagent and catalyst in synthetic organic chemistry. It is decomposed by acids (even weak acids) with the evolution of a brown mixture of nitrogen oxides (NO_x).

Sodium nitrite can be used as a reagent in:      

• In the conversion of amines into diazo compounds, which are used as key precursors to many dyes, such as diazo dyes.      
• Nef reaction and Abidi transformations.      
• The C–C bond cleavage reaction in the presence of TFA under aerobic conditions.      
• The oxidative carbonitration of alkenes in the presence of K₂S₂O₈.

It can also be used as a nitrating agent in organic synthesis.
It is used in direct C-H nitration, ipso-nitration, and nitration via transition metal-catalyzed cross-coupling reaction. NaNO₂ is also used as a co-catalyst for catalytic oxidation of alcohols under aerobic, solvent-free conditions.

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