Amino complexes 4-7 formation

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. 

The blue-violet stain which forms on thin-layer chromatograms when amino acids are stained with ninhydrin is only stable for a short time. It rapidly begins to fade even on cellulose layers. The stability can be appreciably enhanced by complex formation with metal ions [3]. 

The ethylenediamine derivative [31] possesses higher promoting activities than other diamines. This phenomenon may be ascribed to the copromoting effect of the two amino groups on the decomposition of persulfate through a CCT (contact charge transfer complex) formation. So we proposed the initiation mechanism via CCT as the intimate ion pair and deprotonation via CTS (cyclic transition state) as follows ... 

Ferruti, P. and Barbucci, R. Linear Amino Polymers Synthesis, Protonation and Complex Formation. Vol. 58, pp. 59—92. 

Complex formation between palladium(II) and amino acids, peptides and related ligands. L. D. Pettit and M. Bezer, Coord. Chem. Rev., 1985, 61, 97 (90). 

Iron, tris(hexafluoroacetylacetone)-structure, 1,65 Iron, tris(oxalato)-chemical actinometer, 1,409 photoreduction, 1,471 relief-image-forming systems, 6,125 Iron, tris(l,10-phenanthroline)-absorptiometry, 1,549 racemization, 1,466 solid state, 1,467 structure, 1, 64 lron(III) chloride amino acid formation prebiotic systems, 6,871 Iron complexes acetonitrile. 4,1210 acetylacetone, 2,371 amidines... 

Molybdenum hexafluoride. 3,1412 Molybdenum-iron-sulfur complexes, 4,241 Molybdenum oxide amino acid formation prebiotic systems, 6, 872 Molybdenum storage protein microorganisms, 6, 681 Molybdenum telluride, 3, 1431 Molybdenum tetraalkoxides physical properties, 2, 347 Molybdenum tribromide, 3,1330 Molybdenum trichloride, 3,1330 Molybdenum trifluoride, 3, 1330 Molybdenum trihalides, 3, 1330 bond lengths, 3, 1330 magnetic moments, 3,1330 preparation, 3,1330 properties, 3, 1330 structure, 3,1330 Molybdenum triiodide, 3,1330 Molybdenum trioxide complexes, 3, 1379 Molybdenum triselenide, 3, 143)... 

In aqueous solutions at pH 7, there is little evidence of complex formation between [MesSnflV)] and Gly. Potentiometric determination of the formation constants for L-Cys, DL-Ala, and L-His with the same cation indicates that L-Cys binds more strongly than other two amino acids (pKi ca. 10,6, or 5, respectively). Equilibrium and spectroscopic studies on L-Cys and its derivatives (S-methyl-cystein (S-Me-Cys), N-Ac-Cys) and the [Et2Sn(IV)] system showed that these ligands coordinate the metal ion via carboxylic O and the thiolic 5 donor atoms in acidic media. In the case of S-Me-Cys, the formation of a protonated complex MLH was also detected, due to the stabilizing effect of additional thioether coordination. ... 

The palladium(O) complex undergoes first an oxydative addition of the aryl halide. Then a substitution reaction of the halide anion by the amine occurs at the metal. The resulting amino-complex would lose the imine with simultaneous formation of an hydropalladium. A reductive elimination from this 18-electrons complex would give the aromatic hydrocarbon and regenerate at the same time the initial catalyst. 

In contrast to the dihalogens, there are only a few spectral studies of complex formation of halocarbon acceptors in solution. Indeed, the appearance of new absorption bands is observed in the tetrabromomethane solutions with diazabicyclooctene [49,50] and with halide anions [5]. The formation of tetrachloromethane complexes with aromatic donors has been suggested without definitive spectral characterization [51,52]. Moreover, recent spectral measurements of the intermolecular interactions of CBr4 or CHBr3 with alkyl-, amino- and methoxy-substituted benzenes and polycyclic aromatic donors reveal the appearance of new absorption bands only in the case of the strongest donors, viz. Act = 380 nm with tetramethyl-p-phenylendiamine (TMPD) and Act = 300 nm with 9,10-dimethoxy-l,4 5,8-... 

Another important N-donor group is the amide group. Contrary to the basic amino groups, the more acidic amide functions tend to be deprotonated in the complex and therefore operate as a monoanionic donor. Alkaline conditions promote the deprotonation and subsequent complex formation. The amide group is a very useful component of mixed donor sets, such as N2S2 or N3S, as discussed in the next chapter. Whether a pure amide coordination may occur in M(V) complexes has not yet been proved. Tetrapeptides do form Tc(V) complexes [68], apparently without involvement of the carboxyl group. The N-donor atom provided by Schiflf bases plays only a role in mixed donor sets and will be discussed below. 

RRL (Promega) is quickly thawed and placed on ice. Twenty microliter reaction mixtures are prepared containing 70% (v/v) RRL, 0.5 /il amino acid mix (minus methionine), 80 mM KOAc, 1.6 [iM methionine, 1 mM GMP-PNP (for 48S pre-initiation complex) or 0.6 mM cyclo-heximide (for 80S complex formation), and 20 fiM of the small molecule hit under study. 

Nucleophilic displacement of halogen by amines is an important method of introducing amino groups into the anthraquinone ring system. In the Ullmann reaction the displacement is catalysed by metallic copper or by copper ions so that relatively mild conditions can be used. Mechanistic studies suggest that copper(I) ions exert a catalytic effect via complex formation. Derivatives of 1,4-diaminoanthraquinone are of considerable industrial significance. Many compounds are prepared from the reduced form of quinizarin (6.6). 

N-Dealkylation reactions are not restricted to tertiary amines. Secondary amines as well as primary amines can also be dealkylated although both types are less favored than tertiary amines. In the case of primary amines, the lone pair of electrons of the amino group can interact and complex with the Fe3+ of heme. Thus primary amines tend to be inhibitors of P450 activation and for that reason are generally poor substrates. Secondary amines have metabolic properties intermediary between those of tertiary amines and primary amines. They are less-effective inhibitors because of increased steric hindrance to complex formation but are also better substrates because they are less-effective inhibitors and thereby increase the effective concentration of enzyme. 

Organic material can strongly adsorb metal ions the functional groups on their surfaces act as ligands (carboxyl, amino groups etc.) for metal ions. All these functional groups favor the surface complex formation with metals the adsorption reactions are favored at higher pH (Fig. 11.11). 

Hydrogen bonding and complex formation involving compounds with amino, nitroso and nitro groups... 

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