Unstable complex

The simplest type of enzymatic reaction involves only a single reactant or substrate. The substrate forms an unstable complex with the enzyme that decomposes to give the product species or, alternatively, to generate the substrate. 

Transition state (Section 5.9) An activated complex between reactants, representing the highest energy point on a reaction curve. Transition states are unstable complexes that can t be isolated. 

We examined the possibility of a direct formation of two C-C bonds by reaction of a carbanion with [Fe(arene)2]2+ in which the arene bears methyl groups. We could indeed repeat Hellings s experiments but found that mesitylene was the only aromatic allowing this possibility in reasonable yields. With p-xylene, a low yield of an unstable complex was obtained corresponding to double nucleophilic attack of phenyllithium on the same ring in spite of the bulk of the methyl groups [23]. Eq. (4) ... 

Perfluorosuccinamide-Lithium Aluminum Hydride (Danger of Explosion). In an attempt to reduce perfluorosuccinamide to the corresponding diamine, it was added to an ether soln of lithium aluminum hydride in a nitrogen atm. Hydrolysis was then attempted, but as a second drop of w was added, a violent expln and ether fire resulted. It was shown that the diamide and the lithium aluminum hydride reacted to give an unstable complex which detonated at room temp Ref T.S. Reid G.H. Smith, C EN 29,3042 (1951) CA 46, 3279 (1952)... 

Stable complex known +, unstable complex known But see Table IV and Section B,l,a. 

Hexamethylenediamine forms unstable complexes with iodine or iodoform that detonate when they are heated at 138 and 178°C respectively... 

For preparative chromatography, the main goal is the recovery of pure mixture components. Therefore, the localization of separated bands is an important issue. The localization of bands directly on plates in daylight (for colored substances) or mostly in UV light is more convenient. The majority of adsorbents and commercially available precoated plates have a flnorescent indicator, e.g., silica gel 60 F254 -t 366. In several cases, separated bands may be localized in iodine vapors if snbstances form only unstable complexes. Brown or yellow zones produced in this way shonld be immediately outlined. 

An AOX-free alternative [316] is impregnation with 4 g/1 hydrogen peroxide, 8 g/1 urea and 2 g/1 nonionic wetting agent, then treatment for 60 minutes at 95 °C, pH 8 and 20 1 liquor ratio [316]. This results in a bleached fabric with excellent wettability and without serious fibre degradation. The urea interacts with hydrogen peroxide to form an unstable complex, which then decomposes to form hydroxyl and perhydroxyl radicals, according to Scheme 10.28 [316]. Urea exhibits undesirable environmental characteristics in some respects, however. 

Protein functional groups able to react with anhydrides include the oc-amines at the N-terminals, the s-amine of lysine side chains, cysteine sulfhydryl groups, the phenolate ion of tyrosine residues, and the imidazolyl ring of histidines. However, acylation of cysteine, tyrosine, and histidine side chains forms unstable complexes that are easily reversible to regenerate the original group. Only amine functionalities of proteins are stable to acylation with anhydride reagents (Fraenkel-Conrat, 1959 Smyth, 1967). 

The halides Mc SnCl4 have reversible CV responses and in CPE yield inorganic Sn(II), MeHgCl and unidentified compounds including unstable complexes of the formula... 

In enzyme catalyzed reactions the inhibitor may interact in various ways either reversibly or irreversibly. In irreversible inhibition, the inhibitor associates with enzyme and block the active site of the enzyme or form a unstable complex with enzyme and thus retards the rate of reaction. 

Warning is given that sodium sulfite may not remove all peroxidic compounds if peroxyacids are present, with which it can form undetectable, but unstable, complex peroxides [19], Peroxide test strips may not be sufficiently reliable as the sole means of testing for presence of peroxides in a wide range of peroxidisable liquids. It was recommended that an additional test (potassium iodide-acetic acid) should be used unless it is certain that the test strips will give a positive result with a particular peroxide-containing liquid [20],... 

Speed and improved quahty are also important. In the analysis of quinizarin in gas oil, transfer to the automatic regime immediately improved performance. Manual solvent extraction is a very boring task. An analyst, in an attempt to relieve the monotony, will set up a series of extractions in parallel. However, the sodium salt of the quinizarin is an unstable complex. Inevitably, variable times are taken for the solvent extraction, which leads to variable product development and imprecise results. Automation accurately sets the time for the extraction, removes this area of variability and provides consistent and rehable results. 

Prolonged treatment of manganese carbonyl with azulenes gives unstable complexes of the type [Mn2(CO)6(azulene)2], the structures of which are uncertain (29). 

Substituted cyclopentadienones react with iron carbonyls to form stable, diamagnetic 7r-co triplexes of the type [Fe(CO)3(cyclopentadienone)] (215). The proposed structure is shown in (XX). These complexes undergo reactions typical of metal carbonyls, e.g., displacement of carbon monoxide by tertiary phosphines, but the carbonyl group of the ligand does not show reactions characteristic of a keto-group. These complexes are also formed by interaction of acetylenes with iron carbonyls (see Section VI,C). Interaction of tetracyclone and Fe3(CO)i2 gives unstable complexes which contain the sandwich anion [Fe(tetracyclone)2]2 analogous to the anion (XXV) (215). 

There is evidence that an unstable complex is formed when rhodium(III) chloride is treated with ethylene at high pressure (97). 

Slade and Jonassen (192) treated ethyleneplatinous chloride, [Pt2Cl4-(C2H4)2], with butadiene, and obtained an unstable complex to which they ascribed the chlorine-bridged structure (XXXIV), on the evidence that its infrared spectrum showed a weak absorption at 1608 cm-1 due to the free double bond of each butadiene molecule. 

Mono-olefins (un) react with solid copper(I) halides to form unstable complexes of the type [CuX(un)] (X = Cl, Br), which dissociate into their constituents above 0° (67, 138). Dienes (e.g., butadiene, isoprene, pipery-lene, bicyclo[2,2,l]hepta-2,5-diene, and cyclopolyolefins) form more stable complexes of the type [Cu2X2(diene)J (1,63, 67,138,192), in which a copper atom is attached to each C C bond industrial processes to separate dienes from mono-olefins and paraffins are based on this difference in stability (8). Complexes of the type [Cu(un)]+, [CuCl(un)], and [CuCl2(un)] have been shown to exist in dilute acid solution (15, 67, 138). 

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