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|Section2= |Section3= }} Hyponitrous acid is the chemical compound H2N2O2. This can be formulated as HON=NOH and is an isomer of nitramide, (H2N−NO2). It forms white crystals that are explosive when dry.〔Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier ISBN 0-12-352651-5〕 Hyponitrous acid is a weak acid (pk1 = 7.21, pK2= 11.54) in aqueous solution and decomposes to N2O and water with a half-life of 16 days at 25 °C at pH 1-3.〔 :H2N2O2→ H2O + N2O Hyponitrous acid forms two series of salts, the "acid hyponitrites" containing ()− anion and hyponitrites containing the ()2− anion.〔 The hyponitrite ion ()2− can be prepared in aqueous solution by two methods. One method uses organic nitrites to synthesize the sodium salt: : RONO + NH2OH + 2 EtONa → Na2N2O2 + ROH + 2 EtOH Another method is by the reduction of sodium nitrite with sodium amalgam: :2 NaNO2 + 4 Na(Hg) + 2 H2O → Na2N2O2 + 4 NaOH + 4 Hg The insoluble silver salt can be precipitated from the solution by the addition of silver nitrate: :Na2N2O2 + 2 AgNO3 → Ag2N2O2 + 2 NaNO3 The free acid is then prepared from silver hyponitrite and anhydrous HCl in ether: :Ag2N2O2 + 2 HCl → H2N2O2 + 2 AgCl There are two possible structures of hyponitrous acid, ''trans'' and ''cis'', and the solid Na2N2O2•5H2O is confirmed to be the ''trans'' form.〔 Spectroscopic data also indicate a ''trans'' configuration of the free acid. The ''cis''-form can be prepared as the sodium salt Na2N2O2 by heating Na2O with gaseous N2O.〔 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「hyponitrous acid」の詳細全文を読む スポンサード リンク
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