An , hydrolysis

The thiazolium is not acidic enough for observing directly solvation of the molecule (or an hydrolysis and subsequent cleavage of the ring) (24) without adding a base, as it is the case for benzoxazolium or benzothiazolium. With the same dilution (10 mole liter ), it is necessary to add sodium ethylate to the solution of 2-methyl-4.5-diphenylthiazolium to observe the equilibrium described above. A new band appears in the UV spectrum at 320 nm that is attributed to the ethoxy derivative by analogy to what has been observed with other benzothiazoliums (26),... 

In an extensive review on abiotic catalysis, Huang (2000) noted that the reactivity of hydrolyzable organic contaminants arises from the presence of electron-deficient (electrophilic) sites within the molecules. Figures 14.2 and 14.3 show the patterns of reactivity in two cases of nucleophihc substitution and monomolecular nucleophilic substitution. The Sj 2 mechanism (nucleophilic substitution) involves attack of the electrophilic sites by OH" or H O, generation of a higher coordination nnmber intermediate, subsequent elimination of the leaving group, and the formation of an hydrolysis product (Fig. 14.2). 

Let us recall the micellar aqueous system, as this procedure is actually the basic one. The chemistry is based on fatty acids, that build micelles in higher pH ranges and vesicles at pH c. 8.0-8.5 (Hargreaves and Deamer, 1978a). The interest in fatty acids lies also in the fact that they are considered possible candidates for the first prebiotic membranes, as will be seen later on. The experimental apparatus is particularly simple, also a reminder of a possible prebiotic situation the water-insoluble ethyl caprylate is overlaid on an aqueous alkaline solution, so that at the macroscopic interphase there is an hydrolysis reaction that produces caprylate ions. The reaction is very slow, as shown in Figure 7.15, but eventually the critical micelle concentration (cmc) is reached in solution, and thus the first caprylate micelles are formed. Aqueous micelles can actually be seen as lipophylic spherical surfaces, to which the lipophylic ethyl caprylate (EC) avidly binds. The efficient molecular dispersion of EC on the micellar surface speeds up its hydrolysis, (a kind of physical micellar catalysis) and caprylate ions are rapidly formed. This results in the formation of more micelles. However, more micelles determine more binding of the water-insoluble EC, with the formation of more and more micelles a typical autocatalytic behavior. The increase in micelle population was directly monitored by fluorescence quenching techniques, as already used in the case of the... 

Because of the reactivity of the chemisorbed groups, an hydrolysis reaction can be carried out not only with water, but also with other molecules such as CH3OH ... 

Decomposition of hypophosphoric acid may be represented as an hydrolysis, thus... 

An alternative transamination procedure described by the author using hydroxylamine as an hydrolysis component is illustrated in Eq. 1 ... 

During the treatment of the reaction mixture, the product can Undergo a transformation the most frequent is an hydrolysis which yields a fi-keto acid ... 

Hydrolysis of Gliadin. An Investigation of the Dicarboxylate Fraction, Including the Isolation of r-Glntamic Acid as an Hydrolysis Product. Biochem. J. 35, 417 (1941). 

The A1i3 precipitates are obtained by diluting concentrate Alia sols prepared by hydrolyzing AlCla-bHaO with NaOH. The concentrates Alia solutions have an A1 concentration of O.IM and an hydrolysis ratio r=(NaOH)/(Al)=2 and 2.5. In r=2, Alia polycations are not aggregated. In r=2.5, 70% of Alia formed small aggregates. 

We have found out that increase in sulphuric acid concentration results in increase of AN hydrolysis rate (AA formation rate) as well as in much lesser increase of polymerization rate. 

Using a similar preparation procedure (adsorption of Pt(NH3)4(N03)2 at pH=9 during 4 hours, followed by washing with water and drying in oven) Yao et al. [7] observed a more pronounced collapse of the MCM-41 structure (AS/S = -80 %) and assigned it to an hydrolysis of the siloxane bonds by hydroxide during the adsorption step ... 

A nucleophilic hydroxide coordinated to one metal ion (terminal coordination) or bridged to both metals (, -hydroxo coordination) is possible both types are present in the X-ray structures. We first consider the possibility that the nucleophile in the reaction is a water molecule coordinated to the Fe + ion of the binuclear metal center. A terminal metal-hydroxo species serving as a nucleophile in an hydrolysis reaction has precedence in model chemistry [62]. The Lewis acidity of the metal, which plays a role by decreasing the pXa of the coordinated water molecule, is more favorable for Fe + than Fe +. The pAaS of water coordinated to aqueous Fe " " and Fe + ate 2.13 and 8.44, respectively, a > 10 -fold difference in acidity [74]. A lower pAa makes it easier to deprotonate to form the hydroxide, the putative nucleophile in the reaction. The loss of activity of Fe -Fe calcineurin upon reduction to the Fe " -Fe + state may therefore reflect the poorer Lewis acidity of Fe + and the requirement for an hydroxide coordinated to the Fe " " ion in the Ml site [35]. 

Having compare destruction behavior of the homopolymer PHB and the copolymer PHBV, we can see that the introduction of hydrophobic entity (HV) into the PHB molecule via copolymerization reveals the hydrolytic stability of PHBV molecules. For PHBV an hydrolysis induction time is the longest among the other polymer systems and over a period of 70 days its weight loss is minimal (<1% wt.) and possibly related with desorption of low-molecular fraction of PHBV presented initially in the samples after biosynthesis and isolation. The kinetic curves in Fig. 5.1 show also that the conversion the parent polymers to their blend PHB-PLA decreases the hydrolysis rate compared to PHB (MW=1000 kDa) even if the second component is a readily hydrolysable polymer PLA (MW=70 kDa). 

Morita-Baylis-Hillman carbonates undergo an hydrolysis in the presence of the asymmetric organocatalyst, hydroquinidine[anthraquinone-l,4-diyl] diether, and Cap2 in aqueous iV,iV-dimethylacetamide, yielding the allylic alcohol Tracer studies using showed that water is the nucleophile in the hydrolysis reaction. It is... 

The most common linkages are esters, anhydrides and acetals. Most likely the chemical degradation will take place through an hydrolysis reaction, the anhydride being the easiest to hydrolyze. A crosslinked polymer will afford more resistance to degradation than linear polymers. Also, a crystalline polymer is less reactive than an amorphous or atactic polymer. 

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