Hydrolysis 780 table

The substitution on the C-atom is by contrast of great effect on the rate of hydrolysis. Table X gives the half-life values for the fission... 

When ATP acts as a phosphate donor to form those compounds of lower free energy of hydrolysis (Table 10-1), the ph osphate group is invariably converted to one of low energy, eg. 

The relevance of the palladium-catalyzed amidocarbonylation for natural product synthesis has been demonstrated with the multi gram-scale preparation of the central amino acid of chloropeptin I ((S)-3,5-dichloro-4-hydroxyphenylglycine) as well as methionine and p-chlorophenyl alanine via the combination of amidocarbonylation and enzymatic hydrolysis (Table 4) [44]. 

In the case of carboxylesterase-catalyzed hydrolysis (Table 8.1), the Michaelis constant consistently indicated relatively low affinity for the enzyme, with a variation between substrates of one order of magnitude. Even less variation was seen in the maximal velocity of the reaction. It is interesting to note that, for the four compounds where comparisons are possible, a direct relationship exists between the rate of hydrolysis in plasma and the Vmax of carboxylesterase hydrolysis, suggesting comparable catalytic mechanisms. 

A similar type of intramolecular reaction was achieved with basic carbamates of4-hydroxyanisole (8.134, X = MeO, n = 2 or 3, Fig. 8.10) [171]. The drug itself is a clinically effective melanocytotoxic agent. Intramolecular nucleophilic attack again resulted in cyclization-elimination, the pro-moiety being recovered as an imidazolidinone (Fig. 8.10, n = 2). In the series examined, the compounds were stable at pH 4, and became more reactive at higher pH values. At pH 7.4 and 37°, chain length and substitution at the two N-atoms had a marked influence on the f1/2 values for hydrolysis (Table 8.10). First, it is clear that a shorter chain (Fig. 8.10, n = 2) favors intramolecular attack, but a decrease in tm values for hydrolysis for three compared... 

In acid catalysis (HCl), the variation in pH of the medium affects the yield of oligoorganylsilsesquioxanes to a lesser extent than in the case of alkaline catalysis. Base catalysts are used in the synthesis of oligosilsesquioxanes mainly in the thermolysis of the primary products of XSiYj hydrolysis (Table 1). The most efficient catalysts, in this case, are those which are readily decomposed upon heating to give inactive products For example, the use of tetraethylammonium 32,45) trimethyl-benzyl ammonium 23.37,41) triethylamine hydroxides has proved successful. 

The peculiar observation that particular combinations of 6-glucosidases from various related species, or combinations of 6-glucosidases and substrate substitutes, frequently prevented expected hydrolysis (Table li), gave the first indication that the interaction of plant enzymes could be of importance in the Passiflora-Heliconius system. The same inhibitory interaction has since been observed in insect-plant glucosidase combinations (17). 

Standard hydrolysis is performed with 6M HC1 at 110°C for 24 hJ2 But the method can be varied in terms of acids used, temperature, and time, as well as in the mode of gas- or liquid-phase hydrolysis (Table 1). Time-dependent hydrolysis is required to determine the exact stoichiometry for unstable amino acids as well as for particular sequences difficult to hydrolyze. Tryptophan, methionine, cystine, tyrosine, serine, and threonine are known to be degraded at an extent of >50, >50, >30, >20, >10, and >5%, respectively.141 Therefore, performing standard hydrolysis for 24, 48, and 72 h, and extrapolation to zero time of hydrolysis allows for better quantitation of these unstable amino acids, whereas extrapolation... 

The synthesis of 2-alkoxymethylpteridines (antiallergic compounds) has also been achieved by the Taylor synthesis <1996EJM273> (Scheme 31). The 3-aminopyrazine-2-carboxamide 163 reacted with orthoesters to give 2-alkoxymethylpteridine derivative 164. Alternatively, 164 was synthesized by condensing 3-aminopyrazine-2-car-bonitrile 165 with the acetoxyamidine 166 followed by the base hydrolysis (Table 9). 

Examples of these forms of ions are to be found in the chemistry of the transition elements and the main group elements that can exist in higher oxidation states. As may be inferred from equations (3.26) and (3.27), alkaline conditions encourage hydrolysis, so that the form an ion takes depends on the pH of the solution. Highly acid conditions tend to depress the tendency of an ion to undergo hydrolysis. Table 3.7 contains some examples of ions of different form, the form depending upon the oxidation state of the central element, vanadium. 

Although the musk fragrances and biocides often are released to the aquatic environment, many of them may be transported to other media, including the atmosphere. As discussed above, the processes in the atmosphere are all chemical degradation processes and the ability for a chemical to reach the atmosphere will depend on the Henry s law constant (Hc). In addition, some of these products may be susceptible to chemical hydrolysis. Table 16.5 lists the musk fragrances and biocide compounds along with the Henry s law constant estimated by EPISuite... 

Acetals are usually easy to cleave by acid-catalyzed transacetalization or hydrolysis (Table 3.40). Dithioacetals, on the other hand, tend to be more resistant to hydrolysis, but cleavage can be achieved by treatment with mercury(II) salts or by oxidation with either [bis(trifluoroacetoxy)iodo]benzene [723] or periodic acid [724]. Use of the latter reagent can, however, also lead to the conversion of methyl ketones into iodo-methyl ketones [721],... 

The hydrolysis of 4-nitrophenyl acetate in the presence of the macrocyclic complex [Co([15)aneN5)OH)]2+ (41) is somewhat faster201 than the [Co(NH3)5OH]2+-promoted hydrolysis (Table 18). 

In agreement with this hypothesis is the remarkable low rate constant with a never-dried beech sulphite dissolving pulp compared with the dried sample at identical conditions of aqueous acid hydrolysis (Table VI). 

A comparison of a TFA hydrolysis with a sulfuric acid hydrolysis (Table I) demonstrates that all sugars—but not glucose—are obtained in higher yield with TFA than with sulfuric acid this is evidence for the controlled action of TFA. 

The spiro ketal derivatives studied by Giusti 105> are remarkably uniform in their behavior toward acid hydrolysis (Table 17). Ring opening usually occurs at the site of the less-substituted carbon and, in all cases, the ester is the sole product. The overwhelming preference shown by cyclopropanone ethylene ketals for path b) in Scheme 28 may be attributed to (a) the reversibility of path a) due to rapid intramolecular ketalization at the incipient Ci-carbonium ion 131 (R = CH2CH2OH) and (b) the stability of the intermediate dioxocarbonium ion 131 a generated in path 6).106>... 

Under the pH and temperature conditions of natural waters, the various 2-chloro-, 2-methylthio-, and 2-methoxy-.v-triazine herbicides are generally considered to be stable in solution between pH 5 and pH 9, stable in neutral, weakly acidic and weakly alkaline media, and stable to hydrolysis at 20°C in neutral, weakly acidic, and weakly alkaline media (Pesticide Manual, 1997). Metribuzin, metamitron, and hexazinone are also considered to be stable under these conditions (Pesticide Manual, 1997). Such hydrolytic stability of the triazine herbicides is supported by hydrolysis studies (Rhodes, 1980 Widmer et al., 1993 Noblet et al, 1996 Hequet et al, 1997) that indicate either very slow rates of hydrolysis or no measurable hydrolysis (Table 23.3) under these conditions. 

Since we selected cement as our solidification matrix, it is also desirable to use an iodine compound which is resistant to hydrolysis. Tables III and IV also include solubility data for the hydroxide analogs of the low solutility iodides and iodates, respectively. 

From the Hg-containing alcohol in Figure 3.38 and NaBH4 one can obtain the Hg-free alcohol. The overall result is a hydration of the C=C double bond. According to the nomenclature of Section 3.3.3, its regioselectivity corresponds to a Markovnikov addition. It is complementary to the regioselectivity of the reaction sequence hydro-boration/oxidation/hydrolysis (Table 3.1). The latter sequence would have converted the same olefin regioselectively into the primary instead of the secondary alcohol. 

Alkali-induced deacetylation and hydrolysis of the uronic acid group of xylans proceed readily under alkaline pulping conditions and contribute significantly to xylan redeposition onto the fibers. The galactose side chain in galactoglucomannans is fairly resistant to alkaline hydrolysis (Table 2). Wood xylans are much more stable than glucomannans under alkaline conditions [34]. 

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