Acidic degradations

Urea—Phosphate Type. Phosphoric acid imparts flame resistance to ceUulose (16,17), but acid degradation accompanies this process. This degradation can be minimized by iacorporation of urea [57-13-6]. Ph osph oryl a ting agents for ceUulose iaclude ammonium phosphate [7783-28-0] urea—phosphoric acid, phosphoms trichloride [7719-12-2] and oxychloride [10025-87-3] monophenyl phosphate [701-64-4] phosphoms pentoxide [1314-56-3] and the chlorides of partiaUy esterified phosphoric acids (see Cellulose esters, inorganic). 

HEC hydroxyethyl cellulose nonionic 110 viscosity builder, acid degradable primarily for completion/workover fluids... 

Hydroxyethyl cellulose (HEC), a nonionic thickening agent, is prepared from alkali cellulose and ethylene oxide in the presence of isopropyl alcohol (46). HEC is used in drilling muds, but more commonly in completion fluids where its acid-degradable nature is advantageous. Magnesium oxide stabilizes the viscosity-building action of HEC in salt brines up to 135°C (47). HEC concentrations are ca 0.6—6 kg/m (0.2—21b/bbl). 

Cellulose sulfated usiag sulfamic acid degrades less than if sulfated usiag sulfuric acid (23). Cellulose esters of sulfamic acids are formed by the reaction of sulfamyl haHdes ia the presence of tertiary organic bases (see Cellulose esters). 

Periodic Acid Degradation 17a,20 -Dihydroxy-4,4,6,16a-tetramethyl-pregn-5-en-3-one (0.3 g) is dissolved in 30 ml of methanol and treated with an aqueous solution of 0.25 g of periodic acid in 5 ml of water at room temperature for 17 hr. On dilution with water, the resultant crystals are collected by filtration, washed well with water, and dried to give 0.26 g mp 158-160°. Recrystallization from hexane-acetone gives 0.24 g (90%) of 4,4,6,16a-tetramethylandrost-5-ene-3,17-dione mp 160-161° [aj —6° (CHCI3). 

More More Flow Excess phosphoric acid degrades product. No hazard in work area. — —... 

Intermediates in fatty acid synthesis are linked covalently to the suifhydryl groups of special proteins, the acyl carrier proteins. In contrast, fatty acid breakdown intermediates are bound to the —SH group of coenzyme A. Fatty acid synthesis occurs in the cytosol, whereas fatty acid degradation takes place in mitochondria. 

Amino acid degradation produces cytosolic acetyl-CoA. 

The acetyl-CoA derived from amino acid degradation is normally insufficient for fatty acid biosynthesis, and the acetyl-CoA produced by pyruvate dehydrogenase and by fatty acid oxidation cannot cross the mitochondrial membrane to participate directly in fatty acid synthesis. Instead, acetyl-CoA is linked with oxaloacetate to form citrate, which is transported from the mitochondrial matrix to the cytosol (Figure 25.1). Here it can be converted back into acetyl-CoA and oxaloacetate by ATP-citrate lyase. In this manner, mitochondrial acetyl-CoA becomes the substrate for cytosolic fatty acid synthesis. (Oxaloacetate returns to the mitochondria in the form of either pyruvate or malate, which is then reconverted to acetyl-CoA and oxaloacetate, respectively.)... 

The next three steps—reduction of the /3-carbonyl group to form a /3-alcohol, followed by dehydration and reduction to saturate the chain (Figure 25.7) — look very similar to the fatty acid degradation pathway in reverse. However, there are two crucial differences between fatty acid biosynthesis and fatty acid oxidation (besides the fact that different enzymes are involved) First, the alcohol formed in the first step has the D configuration rather than the L form seen in catabolism, and, second, the reducing coenzyme is NADPH, although NAD and FAD are the oxidants in the catabolic pathway. 

The structure of this compound is confirmed by the preparation of the 1-acetyl derivative, acid degradation to 4-methylquinoxalin-3-one-2-carboxylic acid (12), and alternative synthesis from the acid chloride of (12) and AW -dimethyluread A most unusual cyclization occurs when AW-dimethyl-o-phenylenediamine (15) is treated with alloxan in ethanolic solution this apparently involves an A-methyl group and leads to the formation of the spirobarbituric acid (16). The struc-... 

Tuttle, R. N., and J. H. Bankman, New nondamaging and acid-degradable drilling and completion fluids, SPE Reprint Series Well, completions, SPE, 1978. 

Nitration with concentrated nitric acid degrades chlorins which are sensitive to oxidation. Here nitronium tetrafluoroborate in sulfolane is the reagent of choice. Both mononitrooc-... 

Plutonium(IV) polymer is a product of Pu(IV) hydrolysis and is formed in aqueous solutions at low acid concentrations. Depolymerization generally is accomplished by acid reaction to form ionic Pu(IV), but acid degradation of polymer is strongly dependent on the age of the polymer and the conditions under which the polymer was formed (12). Photoenhancement of Pu(IV) depolymerization was first observed with a freshly prepared polymer material in 0.5 HClOh, Fig. 3 (3 ). Depolymerization proceeded in dark conditions until after 140 h, 18% of the polymer remained. Four rather mild 1-h illuminations of identical samples at 5, 25, 52, and 76 h enhanced the depolymerization rates so that only 1% polymer remained after the fourth light exposure (Fig. 3). 

The Feulgen Nucleai Reaction. Acid Degradation of Sperm Deoxynucleic Acid. Mechanism of the Feulgen Nucleai Reaction, Chong-fu Li, W. G. Overend, and M. Stacey, Nature, 163 (1949) 538-540. 

Inhibition of Hyaluronic Acid Degradation by Dimethyl Sulphoxide, S. A. Barker, S. J. Crews, J. B. Marsters, and M. Stacey, Nature, 207 (1965) 1388-1389. 

Thus, acid-catalyzed hydrolysis of sucrose initially yields D-glucose and a fmctose oxocarbonium ion, which can react with water to form D-fructose and regenerate the H+ catalyst. As a consequence, further acid degradation of sucrose can be described by the action of acids on D-glucose and D-fructose. 

Acetals, nomenclature, 123-124 cyclic, nomenclature, 121-122 Acid degradation, monosaccharides, 457-459 Acid hydrolysis... 

Mills depiction, cyclic monosaccharides, 63 Monosaccharides, see also Aldoses acid degradation, 457-459 alkaline degradation, 449-455 mechanisms, 451... 

Gupta JK, C Jebsen, H Kneifel (1986) Sinapic acid degradation by the yeast Rhodotorula graminis. J Gen Microbiol 132 2793-2799. 

Hofmann KW, H-J Knackmuss, G Heiss (2004) Nitrite elimination and hydrolytic ring cleavage in 2,4,6-trinitrophenol (picric acid) degradation. Appl Environ Microbiol 70 2854-2860. 

Imhoff-Stuckle D, N Pfennig (1983) Isolation and characterization of a nicotinic acid-degrading sulfate-reducing bacterium, Desulfococcus niacini sp. nov. Arch Microbiol 136 194-198. 

Schreiber A, M Hellwig, E Dorn, W Reineke, H-J Knackmuss (1980) Critical reactions in fluorobenzoic acid degradation by Pseudomonas sp. B13 Appl Environ Microbiol 39 58-67. 

Don RH, JM Pemberton (1985) Genetic and physical map of the 2,4-dichlorophenoxyacetic acid-degradative plasmid pJP4. J Bacteriol 161 466-468. 

Greer LE, DR Shelton (1992) Effect of inoculant strain and organic matter content on kinetics of 2,4-dichlorophenoxyacetic acid degradation in soil. Appl Environ Microbiol 58 1459-1465. 

Kamagata Y, RR Fulthorpe, K Tamura, H Takami, LJ Forney, JM Tiedje (1997) Pristine environments harbor a new group of oligotrophic 2,4-dichlorophenoxyacetic acid-degrading bacteria. Appl Environ Microbiol 63 2266-2272. 

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