Hydrolysis and Aminolysis

Hydrolysis and Aminolysis. 2-Substituted 3-benzyl-2-thiazolinium salts (226) are partially hydrolysed in water to yield the iS-acylthioalkylammonium salts (227). The action of alkali produces acylaminothiols (228), but this ring-cleavage is reversed on treatment with acid. iV5-Dialkyl-2-thiazolinium salts (230) yield 3-alkylthiazolidin-2-ones, e.g. (231), under these conditions. Among other nucleophilic reactions, the reduction of 

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Alkanesulfonyl halides are not the only alkanesulfonyl derivatives that can undergo substitution by an elimination-addition mechanism. A number of aryl esters of phenylmethanesulfonic acid, PhCH2SOzOAr, undergo alkaline hydrolysis and aminolysis by such a pathway, and study of these reactions has been particularly valuable in providing insight into the detailed mechanism for sulfene formation (Williams et al., 1974 King and Beatson, 1975 Davy et al., 1977). 

R. Mendez, T. Alemany, J. Martin-Villacorta, Catalysis of Hydrolysis and Aminolysis of Non-Classical /3-Lactam Antibiotics by Metal Ions and Metal Chelates , Chem. Pharm. Bull. 1992, 40, 3228-3233. 

J. Martin, R. Mendez, F. Salto, Studies on Clavulanic Acid. Part 2. Catalysis of Hydrolysis and Aminolysis of Clavulanic Acid by Metal Chelates , J. Chem. Soc., Perkin Trans. 2, 1990, 43-46. 

The zinc complex of (HOCH2)3CNH2(tris) is a most effective catalyst for the hydrolysis and aminolysis of benzylpenicillin, 1 and it is suggested that this observation may be of some relevance to the mode of action of zinc-dependent /3-lactamases. 

The iV-acyl group is easily removed in weakly acidic or basic media, especially from those 1 -acylpyrazoles with electron-withdrawing substituents. The kinetics of hydrolysis and aminolysis of variously substituted acylpyrazoles was studied in great detail by Hiittel,102 using ultraviolet spectroscopy. Rate constants were found for both reactions, and an attempt was made to apply Hammett s equation to substituted pyrazoles. 

Figure 1. A simplified representation of the possible process for the papain-catalyzed hydrolysis and aminolysis E, enzyme (papain) S, substrate (protein) ES, Michaelis complex ES, peptidyl enzyme N, nucleophile (amino acid ester) P and P2, products formed from S by hydrolysis ...

Most chemical studies in this field have eoncentrated on the effect of micellar surfactants on reaction rates and only a few attempts have been made to investigate the effect that micelles might have in altering the relative extent of competing reactions. For example, in studying the competitive hydrolysis and aminolysis of aryl sulfates in aqueous solution, Fendler et al. have found [407] that cationic micelles such as cetyl-trimethylammonium bromide (CTABr) are able to alter the balance between S—O bond fission and C—O bond fission as shown in Eq. (5-162). 

All the other half-sandwich complexes in this section derive from the chemistry of ReCp Os and ReCp Cl4 (136). Complex (136) forms an octahedral adduct ReCp Cl4(PMe3), but excess phosphine reduces it to ReCp Cl2(PMe3)2. Hydrolysis and aminolysis form ReCp OCl2and ReCp (NR)Cl2 respectively. Stepwise reductive dehalogenation with Al/HgCl2... 

The familiar substitution reactions of derivatives of carboxylic acids with basic reagents illustrate nucleophihc substitution at aliphatic sp carbons. (Substitution reactions of carboxylic acids, and their derivatives, with acidic reagents are covered in Chapter 4.) The mechanisms of these reactions involve two steps (1) addition of the nucleophile to the carbonyl group and (2) elimination of some other group attached to that carbon. Common examples include the basic hydrolysis and aminolysis of acid chlorides, anhydrides, esters, and amides. 

M.B. Davy et al., Elimination-Addition Mechanisms of Acyl Group Transfer Hydrolysis and Aminolysis of Arylmethanesulphonates, J. Am. Chem. Soc., 1977, 99, 1196. 

The p value corresponds to the nucleophile concentration at which hydrolysis and aminolysis of the acylenzyme proceeds with the same velocity. The advantage of p is that the definition is not based on a particular kinetic scheme. Furthermore, p allows a rapid estimation of the yield of any acyl transfer reaction. A concentration of the nucleophilic amine component [N] p is necessary for peptide formation in high yield. Assuming an equilibrium between the acylenzyme and the acylenzyme-... 

It follows from Eq. (6) that a linear correlation between the partition value p and the nucleophile concentration is obtained. The quotient ks/fe4 corresponds to the ratio of hydrolysis and aminolysis of the EAN complex whereas the term kNk3/k4 is a measure of the nucleophile efficiency. 

Williams and his coworkers have shown that the hydrolysis and aminolysis of aryl toluene-a-sulphonates proceed via a stepwise elimination-addition (ElcB) mechanism (equation 101)137 139. 

To obtain a better understanding of the sigmoid kinetics observed for hydrolysis and aminolysis reactions, as discussed in the previous sections, these reactions were investigated on the nanometer scale by iCFM. In these experiments the force required to pull gold-coated AFM tips functionalized with SAMs of NHS-CIO away from contact with an inert octadecanethiol (ODT) SAM on flat Au(lll) was monitored in real-time during reaction in aqueous NaOH and n-butylamine for hydrolysis and aminolysis, respectively. 

A study of hydrolysis and aminolysis of xanthate esters included the two 6-substituted glucosides (68) and (69) ... 

Polysulfonate co-polymer (sulfonate-car-boxylate co-polymer) n. A family of transparent, thermoplastic polyesters, moldable at 250-300°C, and formed by reaction of a diphenol, generally bisphenol A, with an aromatic disulfonyl chloride and an aliphatic disulfonyl chloride or carboxylic acid chloride. These co-polymers have good electrical and mechanical properties, and excellent resistance to hydrolysis and aminolysis. 

When vesicles are polymerised, the interaction between substrate and vesicle is modified. We therefore expect different reactivities for monomer vesicles and their polymerised counterparts. This hypothesis has been borne out experimentally with regard to hydrolysis and aminolysis of nitrophenylesters. Polymerisation allows better control of reactivity by localising the substrate at different vesicular sites. 

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