Complexations, amino acids, copper sulfate

Figure 8.43 Separation of enantiomers using complexation chromatography. A, Separation of alkyloxiranes on a 42 m x 0.2S mm I.O. open tubular column coated with 0.06 M Mn(II) bis-3-(pentafluoro-propionyl)-IR-camphorate in OV-ioi at 40 C. B, Separation of D,L-amino acids by reversed-phase liquid chromatography using a mobile phase containing 0.005 M L-histidine methyl ester and 0.0025 M copper sulfate in an ammonium acetate buffer at pH 5.5. A stepwise gradient using increasing amounts of acetonitrile was used for this separation.

Aspartic and glutamic acids were not retained in a buffer solution without a counter-ion however, these acids were retained by the addition of octyl sulfate to the eluent, as seen in Figure 4.12. These amino acids can form a complex with copper ions and will be retained on the stationary phase. The addition of both a counter-ion and copper ions further increased the retention and made possible... 

The effects of leucaena and mimosine on nonruminants can be reduced to some extent by diet supplementation with ferrous sulfates. Mimosine forms a complex with iron, which is excreted in the feces. Zinc supplementation has reduced the toxicity in cattle and it is believed that copper and zinc ions bind more strongly to mimosine than most other amino acids. 

Type IV includes chiral phases that usually interact with the enantiomeric analytes through the formation of metal complexes. There are usually used to separate amino acid enantiomers. These types of phases are also called ligand exchange phases. The transient diastereomeric complexes are ternary metal complexes between a transitional metal (usually Cu +), an amino acid enantiomeric analyte, and another compound immobilized on the CSP which is able to undergo complexation with the transitional metal (see also the ligand exchange section. Section 22.5). The two enantiomers are separated based on the difference in the stability constant of the two diastereomeric species. The mobile phases used to separate such enantiomeric analytes are usually aqueous solutions of copper (II) salts such as copper sulfate or copper acetate. To modulate the retention, several parameters—such as the pH of the mobile phase, the concentration of the copper ion, or the addition of an organic modifier such as acetonitrile or methanol in the mobile phase—can be varied. 

Underivatized amino acids form complexes with copper(II). A variety of copper(II)-trapped phases have been developed for the enantiosepara-tion of amino acids. N-Salicylidene-(J )-2-amino-l,2-6is(2-buto Q -5-fe/t-bu(yl-phenyl)-3-phenyl-l-propanol was coated on an octadecyl-bonded silica gel column and copper sulfate solution was used as the eluent. The structure was constructed using the Molecular Editor program and optimized by MM2 calculations. The optimization was performed as the energy change was less than 10 kcal mol. The molecular weight of the chiral phase was 1449, and the final and van der Waals energies were 77.04 and —8.77 kcal mol, respectively. 

The recommended daily dietary doses of copper are 0.4-0.7 mg for children under 1 year, 0.7-2.0 mg for children aged 1 to 10 years, 1.5-2.5 mg for adolescents and 1.5-3.0 mg for adults. Resorption of copper and its retention in the body depend on the chemical form in which this element is present in the diet. Experiments on laboratory animals have shown a higher utilisation of copper in the form of neutral and anionic complexes contained in plant material than in the form of copper sulfate. Availability of copper increases the presence of proteins and amino acids in the diet. Also, carboxylic and hydroxycarboxylic acids stimulate resorption of copper. In contrast, higher doses of ascorbic acid, fructose, molybdenum, sulfur compounds and zinc significantly reduce the resorption of copper. Ascorbic acid reduces cupric compounds to slightly soluble cuprous compounds. The effect of phytic acid and dietary fibre on copper resorption is, in comparison with the effect of these components in zinc, less pronounced. 

Kim et al. published an assay based on UV-Vis spectrometry [149]. As shown in Scheme 29.17a the a-amino acid produced during the reaction was stained with a solution containing CuSO /MeOH, forming a blue-colored copper ion complex, which can be quantified at 595 nm, whereas other substrates like amines, p-amino acids, a-keto acids, or ketones showed no color after adding the CuSO /MeOH solution. A major drawback of this method is the color complex, formed by a-amino acids in a phosphate buffer with cupric sulfate also absorbing at 595 nm. Hence, sufficient dialysis of the enzyme or the crude cell extracts has to be conducted. 

The major problem of these diazotizations is oxidation of the initial aminophenols by nitrous acid to the corresponding quinones. Easily oxidized amines, in particular aminonaphthols, are therefore commonly diazotized in a weakly acidic medium (pH 3, so-called neutral diazotization) or in the presence of zinc or copper salts. This process, which is due to Sandmeyer, is important in the manufacture of diazo components for metal complex dyes, in particular those derived from l-amino-2-naphthol-4-sulfonic acid. Kozlov and Volodarskii (1969) measured the rates of diazotization of l-amino-2-naphthol-4-sulfonic acid in the presence of one equivalent of 13 different sulfates, chlorides, and nitrates of di- and trivalent metal ions (Cu2+, Sn2+, Zn2+, Mg2+, Fe2 +, Fe3+, Al3+, etc.). The rates are first-order with respect to the added salts. The highest rate is that in the presence of Cu2+. The anions also have a catalytic effect (CuCl2 > Cu(N03)2 > CuS04). The mechanistic basis of this metal ion catalysis is not yet clear. 

Diels-Alder reactions are one of the most famous examples which are accderated by a Lewis acid. Various water-stable Lewis adds such as Ln(OTf)3,1371 methylrhenium trioxide,1381 copper nitrate,1391 copper bis(dodecyl sulfate) (4b),1401 indium chloride,1411 and bismuth triflate1421 have been used for Diels-Alder and aza-Diels-Alder reactions in water. Furthermore, a catalytic asymmetric Dids-Alder reaction in water using a copper complex of an amino... 

In demethylative coppering to give the bis-copper complex 22 [74592-99-7] (3 Na, Li salt) [36], the sodium salt of the disazo compound made by coupling of bis-diazotized 3,3 -dimethoxy-4,4 -diaminodiphenyl with two equivalents of 8-amino-l-hydroxynaphthalene-3,6-disulfonic acid in alkaline medium is dissolved in water by adding diethanolamine. An ammonia alkaline copper(n) sulfate solution made from CuS04-5 H20 and of ammonia are added. The mixture is heated at 80-90 °C for 14 h. The solution is then cooled to 40 °C and the bis-coppered dye 22 salted out with sodium chloride. It dyes cotton in lightfast blue shades. 

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