Hydrolysis conditions

Oyychlorides. Hydrolysis of TiCl yields a number of products, the composition of which depends on the hydrolysis conditions. In the TiCl —HCl—H2O system, species ranging from Ti(H20) g through TiCl(H20) 3 to TiCl3(H20) , as the acid concentration increases, has been reported (141). 

The physical piopeities of poly(vinyl alcohol) aie highly coiielated with the method of piepaiation. The final piopeities are affected by the polymerization conditions of the parent poly(vinyl acetate), the hydrolysis conditions, drying, and grinding. Further, the term poly(vinyl alcohol) refers to an array of products that can be considered copolymers of vinyl acetate and vinyl alcohol. 

The behavior of penicillins under hydrolysis conditions has been extensively studied e.g. B-49MI51102,71JPS503), and Some of the early work has been summarized in Section 5.11.3.2. Generally, the rate of /3-lactam hydrolysis for various penicillins reaches a minimum between pH 6 and 7, and increases sharply above and below that minimum (74CPB1186). Under basic conditions, hydrolysis rates are relatively insensitive to the 6-substituent, and the product is the relatively stable penicilloate and, at least in some cases, its 5-epimer (Scheme 51) (77JHC503). 

Acetates, benzoates, and cyclic carbonates are stable to these hydrolysis conditions. [Cyclic carbonates are cleaved by more alkaline conditions (e.., dil. NaOH, 20°, 5 min, or aq. Pyr, warm, 15 min, 100% yield).] ... 

Hydrolysis of the resins will produce aldehydic acids at mild concentration of alkali ( N) using more concentrated alkalis (5N) hydroxy acids are produced, probably via the aldehydic acids. Unfortunately most of the work done in order to analyse the lac resin was carried out before the significance of the hydrolysis conditions was fully appreciated. It does, however, appear to be agreed that one of the major constitutents is aleuritie acid (Figure 30.9). 

Even alkyl benzoate esters give only a small amount of exchange imder basic hydrolysis conditions. This means that reversal of the hydroxide addition must be slow relative to the forward breakdown of the tetrahedral intermediate. ... 

The application of the Birch reduction to ethers of estradiol by A. J. Birch opened up the area of 19-norsteroids to intensive research. The major Birch reduction product is an enol ether which affords either a 3-keto-A -or a 3-keto-A -19-norsteroid depending upon the hydrolysis conditions. Various 19-norsteroids have been found to have useful clinical activity compounds (30), (31), and (32) are oral contraceptive agents and compound (33) has been used as an oral anabolic agent. Several of these compounds were prepared on an industrial scale for a number of years by the Birch reduction of estradiol derivatives. 

EtMgBr, Et20, 90% yield. Under these conditions silyl migration is not a problem, as it was when the typical hydrolysis conditions were used. ... 

Subsequently it was found140 that ethyl 2-alkyl-1//-azepine-1-carboxylates can be isolated from a mixture of isomeric 1//-azepines by stirring the mixture with potassium hydroxide in ethanol at room temperature. Apparently, this method, which is limited to 2-alkylated azepines, depends on the slower rate of hydrolysis (and subsequent decomposition of the resulting 1H-azepine-l-carboxylic acid) of the sterically hindered 1-(ethoxycarbonyl) group. Although the yields of l//-azepines are poor (4-7%, vide supra), the method provides access to otherwise difficult to obtain, isomerically pure 2-alkyl-1//-azepines. Under the basic hydrolysis conditions aryl 2-alkyl-l//-azepine-1-carboxylates undergo transesterification to the l-(ethoxycarbonyl) derivatives. 

During the aqueous hydrolysis of dichlorosilanes there is always a very important side reaction. It is the self-condensation of silanols which are formed initially during the hydrolysis. These reactions also give rise to the formation of cyclic siloxanes together with the linear oligomers or polymers (Reaction Scheme III). The amount of cyclic products usually depends on the hydrolysis conditions and the degree of the self-condensation attained as well as concentration considerations. 

The reactivity of T4R4 species remains largely unexplored because of the lack of compounds available for study but the T4[OR]4 (R = Ft, Pr, iPr, mBu, CgH4Me, C18H37) compounds are reported to be reactive under the hydrolysis conditions under which they are prepared, probably to give Tg and T12 species (Figure 4). The reactions of T4 derivatives with functionalized substituents are likely to be dominated by the reactivity of the substituents as has been found in the case of the Tg derivatives described in Section V. 

A complete post-column LC system for the analysis of oxime carbamates using this approach is commercially available (Pickering Laboratories). Alternative post-column hydrolysis conditions 50 X 4.0-mm i.d., 15 p.m, Aminex A-27 column (Bio-Rad), 120°C. 

The sol-gel process to prepare SIO2 glass fibers and T102 films has been reviewed. It has been known that the hydrolysis conditions such as molar ratio of water to alkoxide and reaction temperature are critical to the desired forms of the gel product (fiber, film or bulk). Some properties of the resultant products have been examined. Especially, Ti02 films have been attempted to use as a photoanode for decomposition of water, and their photoelectrochemical properties are described in comparison with the results previously obtained for single crystal and polycrystalline TiC>2, and are discussed in terms of the microstructure of the film. 

The hydrolysis conditions were as follows 10M HCl/glacial acetic acid (ratio 1 1) at 293 K. 

In the world of red colourants, anthraquinones, which are obtained from plants or animals, are the largest group. They can be separated by RPLC due to diverse polarity caused by the presence of various polar groups in their structure. However, forms of identified compounds depend mostly on extraction and hydrolysis conditions. 

Schwartz, R. W. Lakeman, C. D. E. Payne, D. A. 1990. The effects of hydrolysis conditions, and acid and base additions, on the gel-to-ceramic conversion in sol-gel derived PbTi03. In Better Ceramics Through Chemistry IV, edited by Zelinski,... 

Figure 13.1 Degradation of glucosinolates. Hydrolysis is catalyzed by myrosinases and gives rise to different degradation products dependent on the structure of the glucosinolate side chain and the hydrolysis conditions. (I) isothiocyanates, the major product at pH >7 (II) nitriles, the major product at pH <4 (ID) thiocyanates, produced from 2-propenyl-, benzyl-, and 4-methylthiobutylglucosinolates (IV) oxazolidine-2-thiones, produced from glucosinolates with P-hydroxylated side chains, (V) epithionitriles, produced in the presence of epithiospecifier proteins.

To ensure metal oxide growth occurs only on the nanocarbon, careful consideration of the hydrolysis conditions are required. The ideal conditions vary between precursors, nanocarbon, linking mechanism and growth process to such an extent that optimization is required [232],... 

Once correction factors have been determined for a set of hydrolysis conditions, it is only necessary to recheck the correction factors occasionally. However, as will be shown for the case of acid hydrolysis of pectin and galacturonic acid by 2 M trifluoroacetic acid (CF3CO2H), correction factors are only approximate consequently, it is always important to minimize decomposition. 

Both peak IV (fig. 1) and peak V-2 (fig. 2) resemble cross-links in TLC (Rf = 0 in BUOH/HAC/H2O). IV gave one main peak in SCX-HPLC, but V-2 was separated into several fractions with one major peak (fig. 3b). The yields were relatively low compared with that of HP, namely 1.0, and 1.4 pmoles leucine equivalents for IV and V-2, respectively, versus 10.1 for III (HP). This is not due to instability under acid hydrolysis conditions, since 80% of IV and 100% of V-2 survived acid hydrolysis in a preliminary test. 

Racemizations in the crystalline state have a long history. It is known that L-a-amino acids slowly racemize in the solid state [62]. As this also happens in solid proteins the implications are manifold, not only in pure chemistry but also in biochemistry, nutrition, food technology, and geology. Therefore, techniques have been developed to determine the dl ratio of amino acids down to 0.1% and inversion rate constants have been determined under acid hydrolysis conditions [63]. One could think of very slow deamination and readdition of the amine or an enolization mechanism. However, such reactions can also be induced by photolysis or radiolysis from natural sources [64]. 

Lysine is an essential amino acid with an e-amino group on the side chain that can react with various food components. As known, reaction of the e-amine can render lysine nutritionally unavailable reducing the nutritional value of food. While the determination of total lysine is straightforward (it is stable to acid hydrolysis), the determination of available lysine is difficult as lysine adducts are labile to the standard acid hydrolysis. A solution to this problem consists of derivatizing the e-amino group with a chromophore such as l-fluoro-2,4-dinitrobenzene (FDNB) to form a derivate which is stable to optimized hydrolysis conditions [222]. 

The hydrolysis conditions of phosphoamino acids with respect of stability and reproducibility of quantitative determination are discussed by Bylund and Huang (1976). Anal Biochem 73 477). 

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