Hydrolysis in aqueous solution

Aniline hydrochloride, being a salt formed from a very weak base and a strong acid, undergoes considerable hydrolysis in aqueous solution to aniline... 

The AsF ion is very stable toward hydrolysis in aqueous solution. It is not hydroly2ed by boiling a strongly basic solution almost to dryness (26), although it is hydroly2ed in sulfuric acid (27) or in boiling perchloric acid (26). The hydrolysis of AsF in concentrated sulfuric acid (27) and in base (28) at 193—222°C is first order in AsF . The hydrolysis of AsF in alkaline solution is slower than either PF or SbF . ... 

Poly(MA-CDA) was synthesized as described previously by a free radical copolymerization followed by hydrolysis in aqueous solution. By the fractional precipita- n of the copolymerization product (MW = 14,200, MW/Mn = 3.1) different average-molecular weight po-ly(M A-CDA)s with narrow polydispersity were obtained as shown in Table 2. 

These share tendencies to behave as one-equivalent oxidants with redox potentials in the range 1.0 to 2.0 V and to undergo hydrolysis in aqueous solution above pH 2. They form complexes with anions, e.g. sulphate, which make their reactivity dependent on the nature of the medium both from the point of redox potential and of ligand displacement (Table 11). 

Then again, if the hydrolysis in aqueous solution of the alkyl halide, RHal, is found to follow the rate equation,... 

Sulfo-LC-SMPT is not as stable as SMPT. The sulfo-NHS ester is more susceptible to hydrolysis in aqueous solutions and the pyridyl disulfide group is more easily reduced to the free sulfhydryl. Stock solutions of sulfo-LC-SMPT may be prepared in water, but should be used immediately to prevent loss of amine coupling ability. 

Figure 2.1 Three types of fluorophenyl esters have been used for coupling to amine-containing molecules. The PFP and TFP esters are relatively hydrophobic and typically have better stability toward hydrolysis in aqueous solution than NHS esters. The STP ester is water-soluble due to the negatively charged sulfonate group, and it provides better solubility to associated crosslinkers or bioconjugation reagents similar to that of a sulfo-NHS ester group.

Fluorophenyl esters react with amine-containing molecules at slightly alkaline pH values to give the same amide bond linkages as NHS esters (Reaction 15). However, in most cases, the fluorophenyl ester compound will display better stability toward hydrolysis in aqueous solution. It has been reported that a TFP ester has over twice the half-life in basic pH buffers (pH 8) than a corresponding NHS ester on the same compound (Molecular Probes). 

The NHS ester compounds are sensitive to hydrolysis in aqueous solution, and they likely will hydrolyze faster than more hydrophobic biotinylation compounds due to their hydrophilic-ity. If a stock solution is made at a higher concentration to facilitate the addition of a small amount to a reaction solution, the initial solution should be made in a water-miscible organic solvent that is dried with a molecular sieve. Suitable solvents include DMAC, DMSO, or DMF. If using DMF, use only highly pure solvent, as it may contain amines that can react with the NHS ester groups (Figure 18.13). 

These prodrugs underwent spontaneous hydrolysis in aqueous solution. The mechanism of reaction (Fig. 11.10) was postulated to involve nucleophilic hydration of the C=N bond to yield an intermediate carbinolamine. The latter breaks down with loss of the dialkylamine to form an Af4-formyl intermediate, which, in turn, hydrolyzes to the active agent (11.68, Fig. 11.10). The hydrolysis of these prodrugs followed pseudo-first-order kinetics with tm values at pH 7.4 and 37° that were mostly influenced by the steric properties of the dialkylamino group. Thus, tm values were ca. 4, 9 - 10, 14 -15, and 48 - 52 h for R = Me, Et, Pr, and i-Pr, respectively. Interestingly, the rates of hydrolysis were decreased in human serum, indicating protective... 

The fact that Kj TcClg] significantly differs from K2[ReClg] in its instability toward hydrolysis in aqueous solutions , may also be utilized for a separation of technetium from rhenium. 

The following wash steps should be completed in the cold as quickly as possible, since the A-hydroxysuccinamide reactive groups of Affi-gel 10 will undergo gradual hydrolysis in aqueous solutions at neutral pH. Washing should be accomplished in <20 min. 

Formation of hydroxo-bridged complexes by hydrolysis in aqueous solution is, not surprisingly, the most common preparative method. As a rule, such reactions give quite complex product mixtures containing species with different nuclearities, each of which may be present in many isomeric forms. The fact that most of the preparative procedures employed lead to the isolation of one single and pure isomer probably more often reflects favorable solubility properties rather than stereospecificity. In some cases ion-exchange chromatography has been used to isolate the polynuclear species, but systematic analysis of hydrolysis mixtures by this technique has been reported for only a few systems. 

Base catalysis—hydrolysis. Pohl studied the hydrolysis in aqueous solutions of a series of trialkoxysilanes of R Si(OCH,CH,OCH,), structures in which R was an alkyl or a substituted alkyl group [42]. The reactions were followed using an extraction/quenching technique. Silanes were studied at concentrations ranging from 0.001 to 0.03 M and pHs adjusted from 7 to 9. The hydrolysis was found to be first order in silane. The order in water was not determined because the reactions were carried out in a large excess of water (water was the solvent). The rate constants for the hydroxide anion catalyzed hydrolysis reactions and reaction half-lives are reported in Table 1. 

The maleimide group of MPBH is adjacent to an aromatic ring and thus may exhibit instability to hydrolysis in aqueous solutions, especially at alkaline pH. Hydrolysis... 

Acetal (4) undergoes 5 N 1 hydrolysis in aqueous solution at high pH, it is easily monitored via the /7-nitrophcnoxidc chromophore produced.3 The reaction has been used to probe hydration effects in co-solvents alcohols, ammo acids, and peptides— the last two as models for such effects in enzymes. Primary alcohols retard the reaction in proportion to their carbon number, but the ammo acids and peptides show more complex effects, which are interpreted in tenns of interactions between the overlapping hydration shells of the amino and carboxylate groups. 

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