Extensive hydrolysis

The extensive hydrolysis of protactinium in its V oxidation state makes the chemical investigation of protactinium extremely difficult. Ions of protactinium(V) must be held in solution as complexes, eg, with fluoride ion, to prevent hydrolysis. 

A number of salts of the monofluoro- and hexafluorophosphoric acids are known and some are commercially important. The salts of difluorophosphoric acid are typically less stable toward hydrolysis and are less well characterized. Sodium monofluorophosphate [7631-97-2] the most widely used dentifrice additive for the reduction of tooth decay, is best known (see Dentifrices). Several hexafluorophosphates can be prepared by neutralization of the appropriate base using hexafluorophosphoric acid. The monofluorophosphates are usually prepared by other methods (57) because neutralization of the acid usually results in extensive hydrolysis. 

Silver Carbonate. Silver carbonate, Ag2C02, is produced by the addition of an alkaline carbonate solution to a concentrated solution of silver nitrate. The pH and temperature of the reaction must be carefully controlled to prevent the formation of silver oxide. A suspension of Ag2C02 is slightly basic because of the extensive hydrolysis of the ions present. Heating soHd Ag2C02 to 218°C gives Ag20 and CO2. 

A variety of solvents have been used successfully. Extensive hydrolysis or alcoholysis may accompany reduction in aqueous or alcoholic solvent, attack presumably occurring on the intermediate vinyl ether (SS). 

Nari, J. Noat, G. Ricard, J. 1991. Pectin methylesterase, metal ions and plant cell-wall extension. Hydrolysis of pectin by plant cell-wall pectin methylesterase. Eur. J. Biochem. 279 343-350. 

Weigh out 2 mg of sulfo-SMCC and add it to the above solution. Mix gently to dissolve. To aid in measuring the exact quantity of crosslinker, a concentrated stock solution may be made in water (or DMSO) and an aliquot equal to 2 mg transferred to the reaction solution. If a stock solution is made, it should be dissolved rapidly and used immediately to prevent extensive hydrolysis of the active ester. As a general guideline of addition for a particular protein activation, the use of a 40- to 80-fold molar excess of crosslinker over the amount of protein present usually results in good activation levels. 

Use of a higher temperature (280 °C) at the final stage results in more extensive hydrolysis, with the amino group also being replaced by a hydroxy group, leading to the formation of naphthalene-1,8-diol-3,6-disulphonic acid (chromotropic acid). 

Similarly, the addition of substrate to hydrolysis mixtures that had reached stages of very slow rates of change with dialysis resulted in extensive hydrolysis of the added substrate. Comparisons showed that the new substrate was hydrolyzed to practically the same extent in the same time as the original substrate.41 These findings show not only that active amylase was present but that no appreciable inactivation of the amylase had taken place in the dialyzing hydrolysis mixtures when the... 

Upon extensive hydrolysis of starch by either of these enzymes, only small differences were observed in the concentrations of the products or in the average degrees of polymerization of the dextrins. These comparisons were made for equivalent stages of hydrolyses and are not necessarily related to the rates of the hydrolysis of starch by these two amylases. 

Studies of the rate of the hydrolysis of dextrins isolated from a reaction mixture after the extensive hydrolysis of starch by maltase-free malted barley alpha amylase, led Myrback11 to conclude that the flattening of the reaction curves with this amylase is not due to equilibrium between the amylase and the products of the hydrolysis. As indicated above, similar conclusions have been reached for pancreatic amylase and for the amylase of Aspergillus oryzae.41,7a... 

Experiment.—Dissolve 1 c.c. of nitromethane in water and test the solution with litmus paper. Then add some phenolphthalein and, drop by drop from a burette, OliV-sodium hydroxide solution. Before a permanent pink colour develops about 2 c.c. of the alkali will be added—a sign that an acid, aci-nitromethane, H2C NOOH, has been formed from the neutral nitromethane. A small sample of this solution gives with ferric chloride a blood-red colour, characteristic of aci-nitro-compounds. The salts of the oci-compound undergo extensive hydrolysis. This is shown by further addition of 0-1 N-alkali which produces a deep red colour. If 10 c.c. of alkali were added and 5 c.c. of 0-1 JV-hydrochloric acid are now run in the solution is decolorised because the liberated oci-compound restricts the hydrolysis of its salt. But the conversion of H2C N02H into H3C.N02 proceeds so rapidly that the red colour reappears in a few moments. 

Phosphorylation of phenolate anions with dimethyl phosphorochloridothionate in water-dichloromethane systems normally gives large amounts of dithiopyrophos-phate because of extensive hydrolysis of the phosphorus chloride, but in the presence of tetrabutylammonium salts and 1 % imidazole, phosphorylation of the phenolate anion is complete. The explanation lies in an evident combination of activation of acylating agent (by imidazole) and of nucleophile (by phase-transfer catalysis).71... 

A mono-fluorinated alkene has recently been oxidised to the corresponding ketone by RuCyaq. Na(IO )/CgHj3-CH3CN. Hydrolysis of the CF unit to C=0 did not occur in contrast neutral aq. I nO gave no ketone but there was extensive hydrolysis, c/ 1.11... 

More important is the substitution of leaving groups in ortho positions to the diazonium moiety by water when other activating substituents are present on the aromatic ring. For example, 2-bromo-3,4,6-trifluoro- or 3,4,6-trifluoro-2-nitroaniline cannot be diazotized in water without extensive hydrolysis of the 2-substituent giving 4.193 This drawback can be overcome, to give 5, by performing the diazotization in acetone at — 20°C.3 193 194... 

Ether was dried and deoxygenated by distillation from sodium benzophenone ketyl under nitrogen just prior to use. Experience has shown that the quality of reagent 2 is most directly affected by 1) failure to control conversion to the triacetate and 2) exposure to moisture during filtration and other manipulations performed during isolation of the periodinane. Extensive hydrolysis of 2 was observed when washing with ether was conducted in a humid environment. 

A similar preparative procedure was used to isolate tetrahedral complexes of bidentate donors (L = bipy or phen) [VL2](SCN)3. However, complexes of vanadium(lll) chloride or bromide with these same bidentate donors have stoichiometries depending on conditions.199 With excess of bipy or phen, complexes [VX JX were obtained. In EtOH or in MeCN two series of complexes were isolated. VC13LL (L = bipy or phen L = EtOH or MeCN) and [VC12L2]+ + [VCUL]-. In the reaction of vanadium(III) with phenanthroline202 203 or bipyridine204 there is evidence for extensive hydrolysis. Spectrophotometry was used to estimate the equilibrium constant (Kcq = 0.43) for the reaction in equation (7). 03... 

However, T. Urbahski and Berlowski [40] have not confirmed this observation and in fact they report that either of these substances give products of more or less the same viscosity. This could occur in consequence of extensive hydrolysis during nitration. 

Downey (1980) reasoned that although milk lipoprotein lipase is present in sufficient amounts to cause extensive hydrolysis and potential marked flavor impairment, this does not happen in practice for the following reasons (1) the fat globule membrane separates the milk fat from the enzyme, whose activity is further diminished by (2) its occlusion by casein micelles (Downey and Murphy 1975) and by (3) the possible presence in milk of inhibitors of lipolysis (Deeth and Fitz-Gerald 1975). The presence in milk of activators and their relative concentration may also determine whether milk will be spontaneously rancid or not (Jellema 1975 Driessen and Stadhouders 1974A Murphy et al. 1979 Anderson 1979). 

A soln of 130 (0.17 g, 0.34 mmol) and TFA (2.0 mL, 26 mmol) in CH2CI2 (4mL) was stirred at rt for 3h. The volatiles were removed in vacuo, and the residue was dissolved in H20 (15 mL). The resulting soln was frozen and lyophilized to give 131 as a mixture of diastereomers, and as a cream colored hygroscopic powder yield 151 mg (97%) mp 89-92°C. Attempted further purification via RP-chromatography on Sephadex LH-20, with H20 as the mobile phase, resulted in extensive hydrolysis to free glutamic acid and benzoin, as determined by isolation and coelution with authentic samples on TLC. 

The redox chemistry of the actinide elements, especially plutonium, is complex (Katz et al., 1980). Disproportionation reactions are especially important for the +4 and +5 oxidation states. Some of the equilibria are kinetically slow and irreversible. All transuranium elements undergo extensive hydrolysis with the +4 cations reacting most readily due to their large charge/radius ratio. Pu (IV) hydrolyzes extensively in acid solution and forms polymers. The polymers are of colloidal dimensions and are a serious problem in nuclear fuel reprocessing. 

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