Glycolic acid metal complexes

Glycolic acid is the simplest of these hydroxy acids. Metal complexes of this ligand with a wide variety of metal ions have been studied14-16,90-96 and their stereochemistry reviewed.86,871... 

In acidic solution, the degradation results in the formation of furfural, furfuryl alcohol, 2-furoic acid, 3-hydroxyfurfural, furoin, 2-methyl-3,8-dihydroxychroman, ethylglyoxal, and several condensation products (36). Many metals, especially copper, cataly2e the oxidation of L-ascorbic acid. Oxalic acid and copper form a chelate complex which prevents the ascorbic acid-copper-complex formation and therefore oxalic acid inhibits effectively the oxidation of L-ascorbic acid. L-Ascorbic acid can also be stabilized with metaphosphoric acid, amino acids, 8-hydroxyquinoline, glycols, sugars, and trichloracetic acid (38). Another catalytic reaction which accounts for loss of L-ascorbic acid occurs with enzymes, eg, L-ascorbic acid oxidase, a copper protein-containing enzyme. 

A mixture of Pt(ll) and metallic Pt in an aqueous medium was shown to oxidize ethane to yield acetic and glycolic acids. A series of deuterium-exchange processes enabled a complex mechanism to be elucidated metallic platinum catalyzes the oxidation of intermediate alcohols to acid products, whereas the Pt(ll) salt activates the initial alkene (Scheme 7X29... 

The hexitols form the typical derivatives of alcohols and glycols— esters, ethers, acetals and ketals, and metallic complexes. Because of the multiplicity of reactive groups and because of stereoisomerism, the number of theoretically possible derivatives of a given type is enormous. For example, D-mannitol on reacting with a mono reagent such as an etherifying agent or an acid, can form 35 different compounds ... 

Ethylenediaminetetraacetic acid, analogs, complexes of, 3 277 chelation by, 3 276-277 cobalt complex of, 3 281 complexes, 3 277-278 formation constant of, 3 273-274 -nickel, 3 17-18 stability of, 3 266-267 reaction with metal ions, 3 62 Ethylene dibromide, irradiation of, 5 196 4,5-Ethylenedithio-1,3-dithiole-2-thione based supramolecular complexes, 46 200-204 Ethylene glycol, 32 4... 

Reactions. Because it contains both a carboxyl and a primary hydroxyl group, glycolic- acid can react as an acid or an alcohol or both. Thus some of the important reactions it can undergo are esterification, umidation. salt formation, and complexation with metal ions, which lead to many of its uses. As a fairly strong acid it can liberate gases (often toxici when il reacts wilh Ihe corresponding salts. 

Nishiyama, N., Yokoyama, M., Aoyagi, T., Okano, T., Sakurai, Y. and Kataoka, K. (1999) Preparation and characterization of self-assembled polymer-metal complex micelle from cis-dichlorodiammineplatinum(II) and poly(ethylene glycol)-poly(, -aspartic acid) block copolymer in an aqueous medium. Langmuir, 15, 377-383. 

Zr S bonds are rather weak. For example, zirconium, unlike other metals, does not form complexes with thiogly-colic acid, whereas with glycolic acid the triglycolatozirconic acid derivatives H3[Zr(0H)(0CH2C02)3] are formed. Nevertheless, insertion (see Insertion) of CS2 into a metalnitrogen... 

Periodic acid is a versatile oxidant since, depending on pH, the redox potential for the periodate-iodate couple varies from 0.7 V in aqueous basic media to 1.6 V in aqueous acidic media.Based on this observation, Villemin and Ricard devised an oxidative cleavage of glycols, in which mcjo-l,2-diphenyl-1,2-ethanediol was oxidized by periodic acid on alumina to benzaldehyde in 82% yield in aqueous ethanol (90% ethanol) at room temperature in 26 h. The same supported oxidant converted aromatics into quinones. In the presence of transition metal complexes (Mn ), a-arylalkenes suffer oxidative cleavage to aldehydes. For example, tran.r-stilbene gives benzaldehyde at room temperature. 

Chelators such as EDTA, nitrilotriacetic acid (NTA), 1,2-aminocyclohexane 7V,7V,7V ,N7-tetraacetic (DCyTA), and ethylene glycol-bis(2-aminoethyl)-(V,(V, 7V ,7V -tetraacetic acid (EGTA) have been studied extensively and are well summarized (Peters, 1999). Chelator concentration and reaction pH influence metal complexation and the success of removal from soils. Sun et al. (2001) observed that batch extraction methods result in 1 1 molar extraction ratios of EDTA/metal (Pb, Cd, Zn, Cu) and reveal which metal is more or less soluble in EDTA solutions. Column leaching studies, however, relate the elution patterns and recalcitrance of the metals to desorption and dissolution by EDTA. There is concern over the detrimental effects on soil quality from using chelators because of their biotoxicity, persistence in soil environment, and their removal of beneficial micro-and macronutrients, which leave the washed soil infertile for revegetation when it is backfilled. 

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