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外観
白色の結晶
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性質
ホスホン酸の融点は70.1°Cで、無色の潮解性結晶です。200°Cまで熱すると、分解してとが生じます。
アルカリ塩やカルシウム塩以外は、水に難溶です。酸解離定数はpKa = 1.5と6.79です。
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溶解性
水及びエタノールに極めて溶けやすい。
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解説
ホスホン酸，四面体形の [PHO3]2- を含む二塩基酸。 H3PO3 と書いて，亜リン酸と称していたことがあったが，これは誤称。無色，潮解性結晶，比重 1.65 。還元性が強く，貴金属塩から金属を遊離する。アルカリ塩およびカルシウム塩のほかは水に難溶。なお，ホスホン酸とオルトリン酸とが脱水縮合して生成する酸に相当するものとして次リン酸などが知られている。
ブリタニカ国際大百科事典 小項目事典 ブリタニカ
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用途
塩化ビニル安定剤、有機合成触媒、pH 調整剤、ポリエステルフィルムの表面処理剤、分 析（水銀検出）、還元剤、亜リン酸塩製造（肥料等）.
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構造
ホスホン酸の示性式は、HP(=O)(OH)2と示されます。P-H結合の存在は、一置換塩と二置換塩だけが生成して三置換塩が得られない事実や物理測定から明らかになっています。分子の形は四面体です。
と互変異性体の平衡関係にあります。亜リン酸の化学式はP(OH)3で、ホスホン酸は平衡の中で優位です。
有機リン化学でホスホン酸は、リンと水素の結合とホスホリル基を持つ有機リン化合物の総称です。ホスホン酸の有機誘導体には、リン原子上の水素原子がアルキル基に置換されたアルキルホスホン酸とヒドロキシ基の水素原子がアルキル基に置換されたホスホン酸アルキルが存在します。ホスホン酸アルキルには、1つのみアルキル基が置換したモノエステルと2つともアルキル基が置換したジエステルがあります。
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製法
PCl3 または P3O6 と冷水との反応で生成するが，熱するとリン酸とホスフィンとに不均化反応するホスホン酸。 P4O6＋6H2O→4H3PO3→PH3＋3H3PO4
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合成法
有機ホスホン酸とは、リン原子上の水素原子がアルキル基に置換された誘導体のことです。一般式はR-P(=O)(OH)2と表されます。抗ウイルス薬のホスカルネット (英: foscarnet) は、有機ホスホン酸の一例です。有機ホスホン酸の具体例として、CH3P(O)(OH)2 (メチルホスホン酸) やC6H5P(O)(OH)2 (フェニルホスホン酸) が挙げられます。
亜リン酸トリアルキルエステルは、異性化反応によって自発的に酸素原子からリン原子にアルキル基が移動し、アルキルホスホン酸ジアルキルエステルが生じます。亜リン酸トリエステルとハロゲン化アルキルから、P-アルキルホスホン酸のジエステルを合成可能です。この反応をミカエリス‐アルブーゾフ反応 (英: Michaelis-Arbuzov Reaction) と呼びます。
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説明
Phosphorous acid, H3PO3, is diprotic (readily ionizes
two protons), not triprotic as might be suggested by this
formula. Phosphorous acid is as an intermediate in the
preparation of other phosphorous compounds. Because
preparation and uses of “phosphorous acid” actually
pertain more to the major tautomer, phosphonic acid,
it is more often referred to as “phosphorous acid”. Phosphorous
acid has the chemical formula H3PO3, which is
best expressed as HPO(OH)2 to show its diprotic character.
P(OH)3 (IUPAC: phosphorous acid) has CAS
number 10294-56-1. It has been shown to be a stable
tautomer.
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化学的特性
Phosphorous acid is a white crystalline deliquescent solid that can be prepared by the action of water on phosphorus( III) oxide or phosphorus(III) chloride. It is a dibasic acid producing the anions H2PO3- and HPO3 2- in water. The acid and its salts are slow reducing agents. On warming, phosphonic acid decomposes to phosphine and phosphoric(V) acid. Phosphorus acid is used to prepare phosphite salts. It is usually sold as a 20% aqueous solution.
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物理的性質
White crystalline mass; deliquescent; garlic-like odor; density 1.651 g/cm3 at 21°C; melts at 73.6°C; decomposes at 200°C to phosphine and phosphoric acid; soluble in water, about 310 g/100mL; K1 5.1x10-2 and K2 1.8x10-7; soluble in alcohol.
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使用
Phosphorous acid is used to produce the fertilizer phosphate salt like potassium phosphite, ammonium phosphite and calcium phosphite. It is actively involved in the preparation of phosphites like aminotris(methylenephosphonic acid) (ATMP), 1-hydroxyethane 1,1-diphosphonic acid (HEDP) and 2-phosphonobutane-1,2,4-tricarboxylic Acid (PBTC), which find application in water treatment as a scale or corrosive inhibitor. It is also used in chemical reactions as a reducing agent. Its salt, lead phosphite is used as PVC stabilizer. It is also used as a precursor in the preparation of phosphine and as an intermediate in the preparation of other phosphorus compounds.
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定義
ChEBI: Phosphorous acid is a phosphorus oxoacid. It is a conjugate acid of a dihydrogenphosphite. It is a tautomer of a phosphonic acid.
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主な応用
Phosphorous acid (H3PO3, orthophosphorous acid) may be used as one of the reaction components for the synthesis of the following:
α-aminomethylphosphonic acids via Mannich-Type Multicomponent Reaction
1-aminoalkanephosphonic acids via amidoalkylation followed by hydrolysis
N-protected α-aminophosphonic acids (phospho-isosteres of natural amino acids) via amidoalkylation reaction
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製造方法
Phosphorus acid can be prepared by the reaction of phosphorus trichloride with water: PCl3 + 3H2O → H3PO4 + 3HClThe reaction is violent. Addition of PCl3 should be extremely cautious and slow. The addition can be carried out safely in the presence of concentrated HCl. Alternatively, a stream of air containing PCl3 vapor is passed into icecold water and solid crystals of H3PO4 form. Alternatively, phosphorus acid can be prepared by adding phosphorus trichloride to anhydrous oxalic acid: PCl3 + 3(COOH）2 → H3PO3 + 3CO + 3CO2 + 3HCl In this reaction, all products except H3PO3 escape as gases leaving the liquid acid. Dissolution of phosphorus sesquioxide in water also forms phosphorus acid. When shaken with ice water, phosphorus acid is the only product . P4O6 + 6H2O → 4H3PO3 However, in hot water part of the phosphorus acid disproportionates to phosphoric acid and phosphorus or phosphine.
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一般的な説明
Phosphorous acid appears as a white or yellow crystalline solid (melting point 70.1 deg C) or a solution of the solid. Density 1.651 g /cm3 . Contact may severely irritate skin, eyes, and mucous membranes. Toxic by ingestion, inhalation and skin absorption.
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空気と水の反応
Deliquescent. Absorbs oxygen from the air very readily to form phosphoric acid [Hawley]. Soluble in water.
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反応プロフィール
Phosphorous acid decomposes when heated to form phosphine, a gas that usually ignites spontaneously in air. Absorbs oxygen from the air to form phosphoric acid [Hawley]. Forms yellow deposits in aqueous solution that are spontaneously flammable upon drying. Reacts exothermically with chemical bases (for example: amines and inorganic hydroxides) to form salts. These reactions can generate dangerously large amounts of heat in small spaces. Dissolution in water or dilution of a concentrated solution with additional water may generate significant heat. Reacts in the presence of moisture with active metals, including such structural metals as aluminum and iron, to release hydrogen, a flammable gas. Can initiate the polymerization of certain alkenes. Reacts with cyanide compounds to release gaseous hydrogen cyanide. May generate flammable and/or toxic gases in contact with dithiocarbamates, isocyanates, mercaptans, nitrides, nitriles, sulfides, and strong reducing agents. Additional gas-generating reactions occur with sulfites, nitrites, thiosulfates (to give H2S and SO3), dithionites (to give SO2), and carbonates (to give CO2).
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健康ハザード
TOXIC; inhalation, ingestion or skin contact with material may cause severe injury or death. Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.
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火災危険
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.
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使用用途
ホスホン酸は還元性が強いため、無電解めっきの還元剤としての使用可能です。やの水溶液から、それぞれ銀やを析出させて、メッキを施せます。
P-アルキルホスホン酸ジアルキルエステル (R-P(=O)(OR')2)は、工業的に重要な中間体です。P-アルキルホスホン酸ジアルキルエステルはホーナー・ワズワース・エモンズ反応 (英: Horner–Wadsworth–Emmons reaction) の基質であり、ホーナー・エモンズ試薬と呼ばれ、アルケンの原料になります。ホーナー・エモンズ試薬は、香料や医薬品の原料として、多方面で使用されています。
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工業用途
This collector was developed recently and was used primarily as specific collector for cassiterite
from ores with complex gangue composition.On the basis of the phosphonic acid, Albright and Wilson had developed a range of collectors
mainly for flotation of oxidic minerals (i.e. cassiterite, ilmenite and pyrochlore).
Very little is known about the performance of these collectors. Limited studies conducted
with cassiterite and rutile ores showed that some of these collectors produce voluminous
froth but were very selective.
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安全性プロファイル
Moderately toxic by ingestion. When heated to decomposition at 200℃ it emits toxic fumes of POx and phosphme whch may ignite. See also PHOSPHINE.
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概要
ホスホン酸とは、化学式がH3PO3で表される、酸化数が+3のリンのオキソ酸です。
分子量は82.00g/molで、密度は1.65g/cm3です。の加水分解により得られます。溶液中では亜リン酸 (英: phosphorous acid) との互変異性を示します。
有機リン化学でホスホン酸は、一般式がR-P(=O)(OH)2 (Rは有機基) と示される一連の有機リン化合物の総称です。
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参考文献
R.J. Motekaitis, A.E. Martell, Inorg. Chem., 33, 1032 (1994), DOI: 10.1021/ic00084a011.
