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Nitrous acid (molecular formula H
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
N
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
O
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
2) is a weak and monobasic acid
Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
 known only in solution
Solution

In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent....
 and in the form of nitrite
Nitrite

The nitrite ion is NO2-. The anion is bent, being isoelectronic with ozone. More generally, a nitrite compound is either a Salt or an ester of nitrous acid....
 salts.

Nitrous acid is used to make diazides
Diazo

Diazo refers to a type of organic compound that has two linked nitrogen compounds. The general formula is R2C=N2. The simplest example of a diazo compound is diazomethane....
 from amines; this occurs by nucleophilic attack of the amine onto the nitrite
Nitrite

The nitrite ion is NO2-. The anion is bent, being isoelectronic with ozone. More generally, a nitrite compound is either a Salt or an ester of nitrous acid....
, reprotonation by the surrounding solvent, and double-elimination of water. The diazide can then be liberated as a carbene
Carbene

In chemistry, a carbene is a highly reactive organic molecule containing a carbon atom with six valence electrons and having the general formula: R1R2C: ....
.

he gas phase, the planar nitrous acid molecule can adopt both a cis and a trans form.






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Nitrous acid (molecular formula H
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
N
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
O
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
2) is a weak and monobasic acid
Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
 known only in solution
Solution

In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent....
 and in the form of nitrite
Nitrite

The nitrite ion is NO2-. The anion is bent, being isoelectronic with ozone. More generally, a nitrite compound is either a Salt or an ester of nitrous acid....
 salts.

Nitrous acid is used to make diazides
Diazo

Diazo refers to a type of organic compound that has two linked nitrogen compounds. The general formula is R2C=N2. The simplest example of a diazo compound is diazomethane....
 from amines; this occurs by nucleophilic attack of the amine onto the nitrite
Nitrite

The nitrite ion is NO2-. The anion is bent, being isoelectronic with ozone. More generally, a nitrite compound is either a Salt or an ester of nitrous acid....
, reprotonation by the surrounding solvent, and double-elimination of water. The diazide can then be liberated as a carbene
Carbene

In chemistry, a carbene is a highly reactive organic molecule containing a carbon atom with six valence electrons and having the general formula: R1R2C: ....
.

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
Infrared spectroscopy

Infrared spectroscopy is the subset of spectroscopy that deals with the infrared region of the electromagnetic spectrum. It covers a range of techniques, the most common being a form of absorption spectroscopy....
 indicate it is more stable
Gibbs free energy

In thermodynamics, the Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating Work obtainable from an isothermal, Isobaric process thermodynamic system....
 by around 2.3 kJ mol-1.

dimensions of the trans form
(from the microwave spectrum
Rotational spectroscopy

Rotational spectroscopy or microwave spectroscopy studies the Absorption and Emission electromagnetic radiation by molecules associated with a corresponding change in the Rigid rotor#Quantum mechanical rigid rotor quantum number of the molecule....
)
model
Ball-and-stick model

Ball-and-stick models and space-filling models are three-dimensional space or spatial molecular models which serve to display the structure of chemical products and chemical substance or biomolecules....
 of the trans form
cis form


Preparation

Nitrous acid can be prepared by adding any mineral acid to sodium nitrite
Sodium nitrite

Sodium nitrite, with chemical formula SodiumNitrogenOxygen2, is used as a colour retention agent and preservative in meats and fish....
.

Decomposition

Nitrous acid rapidly decomposes into nitrogen dioxide
Nitrogen dioxide

Nitrogen dioxide is the chemical compound with the chemical formula NitrogenOxygen2. One of several nitrogen oxides, NO2 is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year....
, nitric oxide
Nitric oxide

Nitric oxide or nitrogen monoxide is a chemical compound with chemical formula NitrogenOxygen. This gas is an important signaling molecule in the body of mammals, including humans, and is an extremely important intermediate in the chemical industry....
, and water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
 when in solution.

2HNO2 ? NO2 + NO + H2O


It also decomposes into nitric acid
Nitric acid

Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosion and toxic strong acid that can cause severe burns....
 and nitrous oxide
Nitrous oxide

Nitrous oxide, commonly known as "laughing gas", is a chemical compound with the chemical formula Nitrogen2Oxygen. At room temperature, it is a colorless Flammability gas, with a pleasant, slightly sweet odor and taste....
 and water.

4HNO2 ? 2HNO3 + N2O + H2O


Chemistry

Nitrous acid is used to prepare diazonium salts:
HNO2 + Ar
Aryl

In the context of organic molecules, aryl refers to any functional group or substituent derived from a simple aromatic ring, may it be phenyl, thiophene, indole, etc ....
NH2 + H+ ? ArN2+ + 2 H2O
Such salts are widely is used in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
, e.g., for the Sandmeyer reaction
Sandmeyer reaction

The Sandmeyer reaction is a chemical reaction used to synthesize aryl halides from aryl diazonium salts. It is named after the Swiss chemist Traugott Sandmeyer....
 and in the preparation azo dyes, brightly-colored compounds that are the basis of a qualitative test for aniline
Aniline

Aniline, phenylamine or aminobenzene is an organic compound with the Chemical formula C6H7N. It is the simplest and one of the most important aromatic amines, being used as a precursor to more complex chemicals....
s. Nitrous acid is used to destroy toxic and potentially-explosive sodium azide
Sodium azide

Sodium azide is the chemical compound with the chemical formula NaN3. This colourless azide salt is a common reagent in organic synthesis, and it is a component in many car airbag systems....
. For most purposes, nitrous acid is usually formed in situ by the action of mineral acid on sodium nitrite
Sodium nitrite

Sodium nitrite, with chemical formula SodiumNitrogenOxygen2, is used as a colour retention agent and preservative in meats and fish....
:

NaNO2 + HCl ? HNO2 + NaCl
2 NaN3 + 2 HNO2 ? 3 N2 + 2 NO + 2 NaOH


Atmosphere of the earth

Nitrous acid is involved in the ozone
Ozone

Ozone or trioxygen is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic O2....
 budget of the lower atmosphere
Atmosphere

An atmosphere is a layer of gases that may surround a material body of sufficient mass, by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low....
: the troposphere
Troposphere

The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its water vapor and particulate....
. The heterogenous
Heterogenous

In genetics, heterogenous is an adjective used to describe something derived from a different individual or species.The word may also be used as an alternative spelling for Heterogeneous ....
 reaction of nitrous oxide
Nitrous oxide

Nitrous oxide, commonly known as "laughing gas", is a chemical compound with the chemical formula Nitrogen2Oxygen. At room temperature, it is a colorless Flammability gas, with a pleasant, slightly sweet odor and taste....
 (NO2) and water produces nitrous acid. When this reaction takes place on the surface of atmospheric aerosol
Aerosol

Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are smoke, oceanic haze, air pollution, smog and CS gas....
s, product readily photolyses to hydroxyl
Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
 radical
Radical (chemistry)

In chemistry, radicals are atoms, molecules or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly chemical reaction, so radicals are likely to take part in chemical reactions....
s.

See also

  • Demjanov rearrangement
    Demjanov rearrangement

    The Demjanov rearrangement is the chemical reaction of primary amines with nitrous acid to give rearranged alcohols. Both ring enlargement or contraction can occur....
  • Nitric acid
    Nitric acid

    Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosion and toxic strong acid that can cause severe burns....
     (H
    Hydrogen

    Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
    N
    Nitrogen

    Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
    O
    Oxygen

    Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
    3)
  • Tiffeneau-Demjanov rearrangement
    Tiffeneau-Demjanov rearrangement

    The Tiffeneau-Demjanov rearrangement the chemical reaction of 1-aminomethyl-cycloalkanols with nitrous acid to form an enlarged cycloketone....