EDTA is a widely used abbreviation for the chemical compound ethylenediaminetetraacetic acid (and many other names, see table). EDTA refers to the chelating agent with the formula (HO₂CCH₂)₂NCH₂CH₂N(CH₂CO₂H)₂. This amino acid is widely used to sequester di- and trivalent metal ions (Ca²⁺ and Mg²⁺ for example). EDTA binds to metals via four carboxylate and two amine groups. EDTA forms especially strong complexes with Mn(II), Cu(II), Fe(III), Pb (II) and Co(III).

Synthesis

EDTA is mostly synthesised from 1,2-diaminoethane (ethylenediamine), formaldehyde (methanal), water and sodium cyanide. This yields the tetra sodium salt, which can be converted into the acidic forms by acidification.

Pioneering work on the development of EDTA was undertaken by Gerold Schwarzenbach in the 1940s.

Isomer

EDTA exists in different standard forms under different conditions. At very low pH or very acidic condition (fully protonated) H6Y+2 forms exist while at very high pH or very basic condition (fully deprotonated) Y-4 forms are prevalent.

Popular vs. chemical nomenclature

To describe EDTA and its various protonated forms, chemists use a more cumbersome but more precise acronym that distinguishes between EDTA⁴⁻, the conjugate base that is the ligand, and H₄EDTA, the precursor to that ligand.

Synonyms

EDTA is also known as H₄EDTA, diaminoethanetetraacetic acid, edetic acid, edetate, ethylenedinitrilotetraacetic acid, celon A, gluma cleanser, versene acid, nervanaid B acid, nullapon B acid, ethylene diamine tetracetic acid, tetrine acid, trilon BS, vinkeil 100, warkeelate acid, N,N'-1,2-ethanediylbis(N-(carboxymethyl)glycine)edetic acid, YD-30, Dissolvine Z.

Coordination chemistry principles

H₄EDTA forms highly stable coordination compounds that are soluble in water. In these complexes, the ligand is usually either hexa- or pentadentate, EDTA⁴⁻ or HEDTA³⁻, respectively. Such complexes are chiral, and 1⁻ has been resolved into enantiomers.

Uses

In 1999, the annual consumption of EDTA was equivalent to about 35,000 tons in Europe and 50,000 tons in the US.Fact: date=February 2007 The most important uses are:

• Industrial cleaning

complexation of Ca²⁺ and Mg²⁺ ions, binding of heavy metals.

• Detergents

complexation of Ca²⁺ and Mg²⁺ (reduction of water hardness).