Hydroxyethyliminodiacetic acid

EDTA begins to decompose at only 400 psig (441 °F, 27.5 bar, 227 °C). However, the initial decomposition products are weaker chelants, hydroxyethyliminodiacetic acid (HEIDA) and iminodiacetic acid (IDA), so chelation still takes place. (Hydrolysis of HEIDA then continues at a much slower rate to produce more IDA and ethylene glycol.) Despite this reversion problem, EDTA is effective and, in practice, is employed at up to 1,200 psig (82.7 bar) and up to 1,500 psig (103.4 bar) when employed as an overlay product. 

Iron can be controlled with certain complexing agents, in particular glucono-5-lactone, citric acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, hydroxyethylethylene diaminetriacetic acid, hydroxyethyliminodiacetic acid, and the salts from the aforementioned compounds. These compounds must be added together with nitrogen-containing compounds such as hydroxylamine salts or hydrazine salts [486,643,1815]. 

In general, chelating agents possess some unique chemical characteristics. The most significant attribute of these chemicals is the high solubility of the free acids in aqueous solutions. Linear core flood tests were used to study the formation of wormholes. Both hydroxyethylethylene diaminetriacetic acid and hydroxyethyliminodiacetic acid produced wormholes in limestone cores when tested at 150° F. However, the efficiency and capacities differ. Because these chemicals have high solubility in the acidic pH range, it was possible to test acidic (pH less than 3.5) formulations [644]. 

During the early sixties Thompson and Loraas (77) reported the formation of mixed complexes of reasonable stability (log K 3.0—5.3) between lanthanide—HEDTA and ligands such as EDDA (N,N -ethylenediaminediacetic acid), HIMDA (N-hydroxyethyliminodiacetic acid) and IMDA (iminodiacetic acid). This observation together with the remarkably large formation constants (72) for the bis-EDDA complexes [log A2 =4.73 (La) 8.48 (Lu)] suggested a coordination number larger than six for the tripositive lanthanide ions in aqueous solution, in view of the fact that mixed chelates of the t5q>e M (HEDTA) (IMDA) axe not formed when M =Co(II), Ni(II) or Cd(II). 

Complexes with IMDA and related ligands.—A series of three substituted aminoacetic acids, IMDA, HIMDA and NTA constitute another set of very interesting ligands. The stability constants of the iminodiacetic acid (IMDA) [ 465], N-hydroxyethyliminodiacetic acid (HIMDA) 466 and nitrilotriacetic acid (NTA) complexes are compared in Table 34. Based on log k values the following trend of stability is noted. The... 

AT-Hydroxyethyliminodiacetic acid (HIMDA) pK 8.72, pK 13.7 (OH). Crystd from water. 

Figure 4, Variation of rate constants for the autoxidation of ascorbic acid as a function of concentration of Cu(ll) chelates at 25°C and - log [H ] of 3.45 EDTA = ethylenediaminetetraacetic acid HEDTA = hy-droxyethylethylenediaminetetraacetic acid NT A = nitrilotriacetic acid HIMDA = hydroxyethyliminodiacetic acid IMDA = iminodiacetic acid.

No appreciable polymerization occurred in concentrated aqueous solutions of La or Nd hydroxonitrilotriacetates but, with the heavier lanthanides, dimerization, via hydroxo bridges, occurred in dilute solution. A series of mixed ligand chelate complexes was obtained with Ho and Er and 5-sulpho-salicylate (ssa) and edta, iV-hydroxyethylethylenediamine-triacetic acid, 1,2-diaminocyclohexanediamine-tetra-acetic acid (YX i.e. [M(Y)(ssa)], and iminodiacetic acetate, hydroxyethyliminodiacetic acid and nitrilotriacetic acid, [M(Y)(ssa)2] with higher carboxylates, no mixed chelate complexes were produced. In the presence of an excess of hydroxyethylethylenediamine triacetic acid (H3A), [Eu(A)(HA)] was formed. Lanthanum(m) formed 1 1 complexes with nitrilotriacetic acid and 8-hydroxyquinoline, or 2-picolinic acid and 8-hydroxyquinoline-5-sulphonic acid. 

Hydroxyethyliminodiacetic acid, disodium salt. See Disodium ethanoldiglycine N-(2-Hydroxyethyl) isooctadecanamide. See Isostearamide MEA... 

Athey, P. S. ef al. "Method for Controlling Alkaline Earth and Transition Metal Scaling with 2-hydroxyethyliminodiacetic acid," U.S. Patent 5,972,868,1999. 

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