AgNO2 and KNO2
The crucial difference: Formation of Nitroalkanes vs Alkyl Nitrites.
By chemca Team • Updated Jan 2026
Like the cyanide ion ($CN^-$), the nitrite ion ($NO_2^-$) is an Ambident Nucleophile. It can attack through Nitrogen to form Nitroalkanes or through Oxygen to form Alkyl Nitrites. The product depends entirely on the nature of the reagent used ($AgNO_2$ vs $KNO_2$).
1. Reaction with Potassium Nitrite ($KNO_2$)
Formation of Alkyl Nitrites
When an alkyl halide reacts with $KNO_2$ (or $NaNO_2$), the major product is Alkyl Nitrite ($R-ONO$).
$$ R-X + KNO_2 \xrightarrow{\Delta} \underset{\text{Alkyl Nitrite}}{R-O-N=O} + KX $$
Reasoning (Ionic Mechanism):
- $KNO_2$ is an Ionic Compound ($K^+ O-N=O^-$).
- In solution, the bond between K and O breaks easily.
- The negative charge resides on the Oxygen atom.
- Oxygen acts as the nucleophile and attacks the alkyl group, forming the $C-O$ bond.
2. Reaction with Silver Nitrite ($AgNO_2$)
Formation of Nitroalkanes
When an alkyl halide reacts with $AgNO_2$, the major product is Nitroalkane ($R-NO_2$).
$$ R-X + AgNO_2 \xrightarrow{C_2H_5OH, \Delta} \underset{\text{Nitroalkane}}{R-N(=O)-O^-} + AgX $$
Reasoning (Covalent Mechanism):
- The $Ag-O$ bond in $AgNO_2$ is predominantly Covalent.
- The oxygen atom is not free to attack.
- Nucleophilic attack occurs through the lone pair of electrons on the Nitrogen atom.
- Since the $C-N$ bond is stronger than the $C-O$ bond (and N is less electronegative, donating electrons easily), the nitro compound is formed.
3. Quick Comparison
| Reagent | Bond Nature | Nucleophilic Atom | Product |
|---|---|---|---|
| $KNO_2 / NaNO_2$ | Ionic | Oxygen | Alkyl Nitrite ($R-ONO$) |
| $AgNO_2$ | Covalent | Nitrogen | Nitroalkane ($R-NO_2$) |
4. Reactions of Products (Differentiation)
How to distinguish?
Nitroalkanes and Alkyl Nitrites show different chemical behaviors upon reduction.
A. Reduction of Nitroalkanes ($R-NO_2$):
Yields Primary Amines ($R-NH_2$).
Yields Primary Amines ($R-NH_2$).
$$ R-NO_2 + 6[H] \xrightarrow{Sn/HCl} R-NH_2 + 2H_2O $$
B. Reduction of Alkyl Nitrites ($R-ONO$):
Yields Alcohols ($R-OH$) and Ammonia.
Yields Alcohols ($R-OH$) and Ammonia.
$$ R-O-N=O + 6[H] \xrightarrow{Sn/HCl} R-OH + NH_3 + H_2O $$
Knowledge Check
Test your understanding of Ambident Nucleophiles
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