Citric reductive

SO2 absorbed with buffered citric acid solution. SO2 reduced with H2S to S. H2S produced on site by reduction of S with steam and methane. 

Contaminants and by-products which are usually present in 2- and 4-aminophenol made by catalytic reduction can be reduced or even removed completely by a variety of procedures. These include treatment with 2-propanol (74), with aUphatic, cycloaUphatic, or aromatic ketones (75), with aromatic amines (76), with toluene or low mass alkyl acetates (77), or with phosphoric acid, hydroxyacetic acid, hydroxypropionic acid, or citric acid (78). In addition, purity may be enhanced by extraction with methylene chloride, chloroform (79), or nitrobenzene (80). 

Reduction. The hydrogenation of citric acid yields 1,2,3-propanetricarboxyhc acid [99-14-9] (5). 

Fool s Gold and the Reductive Citric Add Cycle—The First Metabolic Pathway ... 

The citric acid cycle, a nine-step process, also diverts chemical energy to the production of ATP and the reduction of NAD and FAD. In each step of the citric acid cycle (also known as the Krebs cycle) a glucose metabolite is oxidized while one of the carrier molecules, NAD or FAD, is reduced. Enzymes, nature s chemical catalysts, do a remarkable job of coupling the oxidation and reduction reactions so that energy is transferred with great efficiency. 

Generally, NAD-linked dehydrogenases catalyze ox-idoreduction reactions in the oxidative pathways of metabolism, particularly in glycolysis, in the citric acid cycle, and in the respiratory chain of mitochondria. NADP-linked dehydrogenases are found characteristically in reductive syntheses, as in the extramitochon-drial pathway of fatty acid synthesis and steroid synthesis—and also in the pentose phosphate pathway. 

In some cases enzymes can increase the rate of reaction by up to lO times. Carnell and Roberts (1997) have briefly discussed the scope of biotransformations that are used to make pharmaceuticals like penicillins, cephalosporines, erythromycin, lovastatin, cyclosporin, etc., and for food additives like citric acid, L-glutamate, and L-lysine. A very successful transformation by Zeneca has been that of benzene reduction, with Pseudomonase Putida, to dihydrocatechol and catechol the dihydro derivative is used to produce (+/-) pinitol. Fluorobenzene has been converted to fluorodihydrocatechol, an intermediate for pharmaceuticals. The highly stereo selective Bayer-Villeger reaction has been carried out with genetically engineered S-cerevisvae. Hydrolases have allowed enantioselective, and in some cases regioselective, hydrolysis of racemic esters. 

The surface metabolism hypothesis can also be used to deal with questions on the formation of the first cell structures for example, molecules required for the construction of cell membranes could have been formed via the so-called reductive Krebs cycle (citric acid cycle). 

A carrier molecule containing four carbon atoms (the C4 unit) takes up a C2 unit (the activated acetic acid ), which is introduced into the cycle. The product is a six-carbon molecule (the C6 unit), citric acid, or its salt, citrate. CO2 is cleaved off in a cyclic process, so that a C5 unit is left this loses a further molecule of CO2 to give the C4 unit, oxalacetate. In the living cell, this process involves ten steps, which are catalysed by eight enzymes. However, the purpose of the TCA cycle is not the elimination of CO2, but the provision of reduction equivalents, i.e., of electrons, and... 

Different organic acids, primarily lactic acid, have been successfully used for decontamination of whole livestock carcasses, and the application of different organic acids used for decontamination has also been tested in the fruit and vegetable industry. Organic acids other than lactic acid that are known to have bactericidal effects are acetic, benzoic, citric, malic, propanoic, sorbic, succinic and tartaric acids (Betts and Everis 2005). The antimicrobial action is due to a reduction in the pH in the bacterial environment, disruption of membrane transport, anion accumulation or a reduction in the internal pH in the cell (Busta et al., 2001). Many fruits contain naturally occurring organic acids. Nevertheless, some strains, for example E. coli 0157, are adapted to an acidic environment. Its survival, in combination with its low infective dose, makes it a health hazard for humans. 

Guevremont et al. [117] studied the use of various matrix modifiers in the graphite furnace gas method of determination of cadmium in seawater. These included citric acid, lactic acid, aspartic acid, histidine, and EDTA. The addition of less than 1 mg of any of the compounds to 1 ml seawater significantly decreased matrix interference. Citric acid achieved the highest sensitivity and reduction of interference, with a detection limit of 0.01 pg cadmium per litre. 

FIG. 13 Shrinkage coefficient (volume/initial volume) and redness (a /10) of peach and apricot cubes air dried at 70 °C up to 35% weight reduction without (NT) or following 60-min osmotic dehydration at 25 °C at atmospheric pressure in 60% (w/w) sucrose (SU) or sorbitol (SO) solutions, added with 1% ascorbic acid and 0.5% citric acid (Campolongo, 2002 Riva et al., 2001, 2002). 

Fischer formula, 4 697 a-Ketoxime, reduction, 2 572 Kettle soap making, 22 723, 736-737 Kettle-type reboilers, 79 510 Kevlar, 70 211, 212 79 742 20 79, 399 TD resins in, 22 589 Kevlar fibers, 73 373-376 26 760 Kew laboratories, 77 248—249 Key-and-lock principle, 7 574 Keyword-in-context (KWIC) index, 78 239 KF alumina, 5 337 Kharasch process, 79 114 Kidney, citric acid in, 6 632t Kidney Disease Outcome Quality Initiative (K/DOQI), 26 823 Kidney failure, 26 813 Kidney function, normal, 26 813 Kielselguhr 22 402... 

An acidic bromate solution can oxidize various organic compounds and the reaction is catalyzed by species like cerous and manganous ions that can generate 1-equivalent oxidants with quite positive reduction potential. Belousov (1959) first observed oscillations in Celv]/[Cem] during Ce (III) catalysed oxidation of citric acid by bromate ion. Zhabotinskii made extensive studies of both temporal and spatial oscillations and also demonstrated that instead of Ce (III), weak 1- equivalent reductants like Mn(II) and Fe (II) can also be used. The reaction is called Belousov-Zhabotinskii reaction. This reaction, most studied and best understood, can be represented as... 

Similar photo-induced reductive dissolution to that reported for lepidocrocite in the presence of citric acid has been observed for hematite (a-Fe203) in the presence of S(IV) oxyanions (42) (see Figure 3). As shown in the conceptual model of Faust and Hoffmann (42) in Figure 4, two major pathways may lead to the production of Fe(II)ag i) surface redox reactions, both photochemical and thermal (dark), involving Fe(III)-S(IV) surface complexes (reactions 3 and 4 in Figure 4), and ii) aqueous phase photochemical and thermal redox reactions (reactions 11 and 12 in Figure 4). However, the rate of hematite dissolution (reaction 5) limits the rate at which Fe(II)aq may be produced by aqueous phase pathways (reactions 11 and 12) by limiting the availability of Fe(III)aq for such reactions. The rate of total aqueous iron production (d[Fe(aq)]T/dt = d [Fe(III)aq] +... 

The reduction of benzoic acid at a lead cathode in aqueous sulphuric/citric acids yields the two-electron products benzaldehyde and the four-electron product benzyl alcohol rather than one-electron hydrodimer. In all cases studied by the authors they found that ultrasound favoured the process involving the smaller number of electrons per molecule. This is the opposite of the sonoelectrochemical effect seen in carboxylate electrooxidation [57,59,60] where the process involving the greater number of electrons was favoured by ultrasound. 

The oxidation/reduction reactions that require one of the nicotinamide coenzymes are everywhere in metabolism in the glycolytic pathway, the citric acid cycle, the synthesis and degradation of fatty acids, the synthesis of steroids, and so on. Certain of... 

Reduction Experiments. NEO (100-1000 pmole) was reacted with an excess (10-1000 equivalents) of sodium borohydride, sodium cyanoborohydride or Zn/acid in buffer at pH 8-10, 3-7 or 2-5 respectively. The borohydride and cyanoborohydride reductions were performed with and without added diglyme for 2-40 hours. The Zn was used with hydrochloric, acetic, phthalic or citric acid with... 

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