Ethylenediaminetetraacetic acid (English spelling)

Japanese: エチレンジアミン四酢酸 - えちれんじあみんしさくさん(英語表記)ethylenediaminetetraacetic acid
Ethylenediaminetetraacetic acid (English spelling)

Also known as ethylenediaminetetraacetic acid, abbreviated as EDTA. A colorless crystalline powder.

When ethylenediamine and sodium chloroacetate are reacted by heating in a sodium hydroxide solution and hydrochloric acid is added, a precipitate is obtained. It is sparingly soluble in water, but soluble in 5% or more inorganic acids. It is insoluble in ethanol (ethyl alcohol) and ether. It dissolves in alkaline solutions as a tetrabasic acid, forming mono- to tetraalkali salts depending on the amount of alkali. It forms stable water-soluble chelate compounds with almost all metal ions. The chelate structures vary from those in which EDTA is coordinated to the metal as a hexadentate ligand, to those in which it is a pentadentate, tetradentate, or bidentate ligand (the abbreviation EDTA is used when it is a ligand). Its ability to form stable water-soluble chelates has a wide range of applications.

(1) Removal and inactivation of harmful metals contained in rubber, vegetable oil, medicines, food, etc. (heavy metal antagonists)
(2) Hard water softener, boiler cleaner
(3) Medical applications include X-ray contrast medium, removal of kidney stones, and prevention of blood clotting (anticoagulant).
(4) In analytical chemistry, it is used as a chelating titration reagent for various metal ions, a colorimetric reagent, a masking agent, and for separating rare earth element ions.

[Manabu Yamamoto]

[References] | Ethylenediamine | Chelating compounds | Chelometric titrations | Metal indicators | Anticoagulants | Reagents | Heavy metal antagonists | Ligands | Colorimetric analysis [Supplementary material] | Ethylenediaminetetraacetic acid (Data Note)
Chelate structure diagram
EDTA coordinated to a metal as a hexadentate ligand ©Shogakukan ">

Chelate structure diagram


Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

エチレンジアミンテトラ酢酸ともいい、EDTAと略称される。無色の結晶性粉末。

 エチレンジアミンとクロロ酢酸ナトリウムとを水酸化ナトリウム溶液中で加熱反応させ、塩酸を加えると沈殿として得られる。水には難溶であるが、5%以上の無機酸には可溶。エタノール(エチルアルコール)、エーテルには不溶。アルカリ性溶液には四塩基酸として溶け、アルカリの量に応じて一ないし四アルカリ塩を生成する。ほとんどすべての金属イオンと水溶性の安定なキレート化合物をつくる。キレートの構造はEDTAが六座配位子として金属に配位したものから、五座、四座、二座配位子となったものまで多様である(配位子のときはedtaの略号が用いられる)。水溶性の安定なキレートをつくることを利用して、広範な用途がある。

(1)ゴム、植物油、医薬、食品などに含まれる有害金属の除去、不活性化(重金属拮抗薬)
(2)硬水の軟化剤、ボイラーの清浄剤
(3)医学への応用としてX線造影剤、腎臓(じんぞう)結石の除去、血液の凝固防止(抗凝血薬)など
(4)分析化学への応用として、各種金属イオンのキレート滴定試薬、比色分析用試薬、マスキング剤、希土類元素イオンの分離
などに用いられている。

[山本 学]

[参照項目] | エチレンジアミン | キレート化合物 | キレート滴定 | 金属指示薬 | 抗凝血薬 | 試薬 | 重金属拮抗薬 | 配位子 | 比色分析[補完資料] | エチレンジアミン四酢酸(データノート)
キレートの構造図
EDTAが六座配位子として金属に配位したもの©Shogakukan">

キレートの構造図


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