Hyponitrous acid is a chemical compound with formula or HON=NOH. It is an isomer of
nitramide
Nitramide is a chemical compound with the molecular formula H2NNO2. Organyl derivatives of nitramide, RNHNO2 are termed nitroamines, and are widely used as explosives: examples include RDX and HMX. It is an isomer of hyponitrous acid.
Struct ...
, H
2N−NO
2; and a formal dimer of
azanone
Nitroxyl (common name) or azanone (IUPAC name) is the chemical compound HNO. It is well known in the gas phase. Nitroxyl can be formed as a short-lived intermediate in the solution phase. The conjugate base, NO−, nitroxide anion, is the reduced ...
, HNO.
Hyponitrous acid forms two series of
salts
In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively c ...
, the
hyponitrite
In chemistry, hyponitrite may refer to the anion ( N=NOsup>2−), or to any ionic compound that contains it. In organic chemistry, it may also refer to the group −O−N=N−O−, or any organic compound with the generic formula R1−O−N=N� ...
s containing the
N=NOsup>2− anion, and the "acid hyponitrites" containing the
ON=NOsup>− anion.
Structure and properties
There are two possible structures of hyponitrous acid, ''trans'' and ''cis''. ''trans''-Hyponitrous acid forms white crystals that are explosive when dry. In aqueous solution, it is a weak acid (p''K''
a1 = 7.21, p''K''
a2 = 11.54), and decomposes to
nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has ...
and water with a half life of 16 days at 25 °C at pH 1–3:
: → +
Since this reaction is not reversible, should not be considered as the anhydride of .
The ''cis'' acid is not known,
but its
sodium salt
Sodium salts are salts composed of a sodium cation and the conjugate base anion of some inorganic or organic acids. They can be formed by the neutralization of such acids with sodium hydroxide.
Categorization
Sodium salts can be categorized ...
can be obtained.
Preparation
Hyponitrous acid (''trans'') can be prepared from
silver(I) hyponitrite and anhydrous
HCl in
ether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...
:
: + 2 HCl → + 2 AgCl
Spectroscopic data indicate a ''trans'' configuration for the resulting acid.
It can also be synthesized from
hydroxylamine
Hydroxylamine is an inorganic compound with the formula . The material is a white crystalline, hygroscopic compound.Greenwood and Earnshaw. ''Chemistry of the Elements.'' 2nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431–43 ...
and
nitrous acid
Nitrous acid (molecular formula ) is a weak and monoprotic acid known only in solution, in the gas phase and in the form of nitrite () salts. Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagent ...
:
: + → +
Biological aspects
In
enzymology, a
hyponitrite reductase is an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
that
catalyzes the
chemical reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
: + 2 NADH + 2 ↔ 2 + 2 NAD
+
References
{{Nitrogen compounds
Hydrogen compounds
Nitrogen oxoacids