3DMet B00354 Molar mass 62.0282 g/mol | Formula H2N2O2 Appearance white crystals | |
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Hyponitrous acid is a chemical compound with formula H
2N
2O
2 or HON=NOH. It is an isomer of nitramide, H2N−NO2.
Contents
Hyponitrous acid forms two series of salts, the hyponitrites containing the [ON=NO]2− anion, and the "acid hyponitrites" containing the [HON=NO]− 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 (pKa1 = 7.21, pKa2 = 11.54) , and decomposes to nitrous oxide and water with a half life of 16 days at 25 °C at pH 1–3:
H2N
2O
2 → H
2O + N
2O
Since this reaction is not reversible, N
2O should not be considered as the anhydride of H
2N
2O
2.
The cis acid is not known, but its sodium salt can be obtained.
Preparation
Hyponitrous acid (trans) can be prepared from silver(I) hyponitrite and anhydrous HCl in ether:
Ag2N
2O
2 + 2 HCl → H
2N
2O
2 + 2 AgCl
Spectroscopic data indicate a trans configuration for the resulting acid.
Biological aspects
In enzymology, a hyponitrite reductase is an enzyme that catalyzes the chemical reaction
H2N
2O
2 + 2 NADH + 2 H+
↔ 2 NH
2OH + 2 NAD+