- adipic acid
- aerosol
- alcohol
- alkyl nitrites
- Ammonium nitrite
- aniline
- aryl
- atmosphere
- azo dye
- ball-and-stick model
- carbene
- carbenoid
- diazo
- diazonium salt
- Dinitrogen trioxide
- Gibbs free energy
- heterogeneous
- Hydrogen
- hydroxyl
- ketone
- Nitric acid
- nitrite
- Nitrogen
- Nitrogen dioxide
- nitrogen monoxide
- organic synthesis
- oxime
- Oxygen
- ozone
- photolysis
- Potassium nitrite
- Radical (chemistry)
- Sandmeyer reaction
- sodium azide
- Sodium nitrite
- solution
- troposphere
- Vasodilation
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- acid
- adipic acid
- aerosol
- alcohol
- alkyl nitrites
- Ammonium nitrite
- aniline
- aryl
- atmosphere
- azo dye
- ball-and-stick model
- carbene
- carbenoid
- diazo
- diazonium salt
- Dinitrogen trioxide
- Gibbs free energy
- heterogeneous
- Hydrogen
- hydroxyl
- ketone
- Nitric acid
- nitrite
- Nitrogen
- Nitrogen dioxide
- nitrogen monoxide
- organic synthesis
- oxime
- Oxygen
- ozone
- photolysis
- Potassium nitrite
- Radical (chemistry)
- Sandmeyer reaction
- sodium azide
- Sodium nitrite
- solution
- troposphere
- Vasodilation
size: 1.6Kb
size: 3.4Kb
size: 8.9Kb
size: 5.2Kb
size: 1.8Kb
size: 12.0Kb
size: 2.0Kb
Nitrous acid is used to make diazides from amines; this occurs by nucleophilic attack of the amine onto the nitrite, reprotonation by the surrounding solvent, and double-elimination of water. The diazide can then be liberated to give a carbene or carbenoid.
Structure
In the gas phase, the planar nitrous acid molecule can adopt both a cis and a trans form. The trans form predominates at room temperature, and IR measurements indicate it is more stable by around 2.3 kJ mol−1.{|align="center" class="wikitable" |
Preparation
When cold, dilute solutions of nitrite ion, NO2− are carefully acidified, a light blue solution of nitrous acid is produced. Free nitrous acid is unstable and decomposes rapidly.
Decomposition
In anything other than very dilute, cold solutions, nitrous acid rapidly decomposes into nitrogen dioxide, nitric oxide, and water:
:2 HNO2 → NO2 + NO + H2O
Nitrogen dioxide disproportionates into nitric acid and nitrous acid in aqueous solution:
:2 NO2 + H2O → HNO3 + HNO2
In warm or concentrated solutions, the overall reaction amounts to production of nitric acid, water, and nitric oxide:
:3 HNO2 → HNO3 + 2 NO + H2O
Chemistry
Nitrous acid is used to prepare diazonium salts: :HNO2 + ArNH2 + H+ → ArN2+ + 2 H2Owhere Ar is an aryl group.
Such salts are widely used in organic synthesis, e.g., for the Sandmeyer reaction and in the preparation azo dyes, brightly-colored compounds that are the basis of a qualitative test for anilines. Nitrous acid is used to destroy toxic and potentially-explosive sodium azide. For most purposes, nitrous acid is usually formed in situ by the action of mineral acid on sodium nitrite:
: NaNO2 + HCl → HNO2 + NaCl : 2 NaN3 + 2 HNO2 → 3 N2 + 2 NO + 2 NaOH
Reaction with two α-hydrogen atoms in ketones creates oximes, which may be further oxidized to a carboxylic acid, or reduced to form amines. This process is used in the commercial production of adipic acid.
Nitrous acid reacts rapidly with aliphatic alcohols to produce alkyl nitrites, which are potent vasodilators:
:(CH3)2CH-CH2-CH2-OH + HNO2 → (CH3)2CH-CH2-CH2-ONO + H2O
Atmosphere of the earth
Nitrous acid is involved in the ozone budget of the lower atmosphere: the troposphere. The heterogeneous reaction of nitrogen monoxide (NO) and water produces nitrous acid. When this reaction takes place on the surface of atmospheric aerosols, product readily photolyses to hydroxyl radicals.
See also
References
Category:Nitrogen oxoacids Category:Nitrogen metabolism Category:Oxidizing agents
az:Nitrit turşusu bg:Азотиста киселина ca:Àcid nitrós cs:Kyselina dusitá de:Salpetrige Säure es:Ácido nitroso eo:Nitrita acido fr:Acide nitreux ko:아질산 it:Acido nitroso he:חומצה חנקיתית hu:Salétromossav nl:Waterstofnitriet ja:亜硝酸 no:Salpetersyrling pl:Kwas azotowy(III) pt:Ácido nitroso ro:Acid azotos ru:Азотистая кислота simple:Nitrous acid sk:Kyselina dusitá sl:Dušikasta kislina sh:Azotasta kiselina fi:Typpihapoke sv:Salpetersyrlighet uk:Азотиста кислота zh:亚硝酸This text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.