Hydrolysis phenyl esters

Hydrolysis. Place 2 ml. of the ester in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, or use the reflux-distillation apparatus shown in Fig. 38, p. 63. Add about 20 ml. of 10% aqueous NaOH solution, and some fragments of unglazed porcelain, and reflux gently for 20-30 minutes. (Note that methyl oxalate is hydrolysed rapidly by water alone. Phenyl esters on the other hand hydrolyse comparatively slowly even with hot NaOH solution, and should be heated... 

The experimental details already given for the detection and characterisation of aliphatic esters (determination of saponification equivalents h3 diolysis Section 111,106) apply equally to aromatic esters. A sfight modification in the procediu-e for isolating the products of hydrolysis is necessary for i)henolic (or phenyl) esters since the alkaline solution will contain hoth the alkali phenate and the alkali salt of the organic acid upon acidification, both the phenol and the acid will be hberated. Two methods may be used for separating the phenol and the acid ... 

A. Pentoses.—t-Ascorbic acid 2- and 3-phosphates, together with their phosphate esters, give a characteristic colour with ferric chloride and this colour reaction has been used in a study of the hydrolysis of L-ascorbic acid 3-phosphate (58). The acid-catalysed, pseudo-firsi-order hydrolysis proceeds with P—O bond fission, as does the bromine oxidation of its phenyl ester. Both of these observations can be rationalized if (58) is... 

The formation of phenyl esters from boronic acid and phenyhnagnesium bromide in THF is a fast liquid reaction involving contacting of two reactants, Rj (boronic acid) and R2 (phenyhnagnesium bromide), dissolved in the same solvent to yield a liquid mixture [48,108], This mixture is post-processed by a fast hydrolysis. This step was performed conventionally in a batch mode. 

Perhaps the most informative studies (Anvia and Bowden, 1990) of leaving groups are of the alkaline hydrolysis of 3-substituted phenyl 2-acetyl- and 2-benzoyl-benzoates [20], The Hammett reaction constants p are ca. 0.50 and 1.48 for the 2-acetyl and 2-benzoyl esters respectively, as. shown in Table 2. These were compared with various limiting models in a similar manner to the effective charge model (Williams, 1984,1992). This comparison indicates that all simple phenyl esters of the latter types hydrolyse by a mechanism... 

The hydrolysis of sulfate monoesters has been studied increasingly in relation to sulfate group transfer in vivo. In general, the rate-enhancing effect on the sulfate cleavage is small even with hydroxamate- or imidazole-functionalized cationic micelles which are extremely effective for the hydrolysis of phenyl esters. Recently, Kunitake and Sakamoto (1979a) found that zwitterionic hydroxamate [47] cleaved 2,4-dinitrophenyl sulfate effectively in cationic and... 

Simple alkyl or aryl thioesters are commonly assayed as substrates of hydrolases, witness the hydrolysis of phenyl thioesters by horse serum carbox-ylesterase [150], For most substrates investigated, e.g., phenyl thioacetate, phenyl thiopropionate, and phenyl thiobutyrate (7.66, R = Me, Et, and Bu, respectively), kcat values were found, which were a few times larger than those of corresponding nitrophenyl esters, whereas the affinities were lower by approximately one order of magnitude. Methyl and phenyl esters of various linear thioacids were also found to be good substrates of mammalian liver carboxylesterases and serum cholinesterases [151]. 

C. Altomare, A. Carotti, S. Cellamare, M. Ferappi, R. Cagiano, G. Renna, QSAR Analysis of Chemical and Serum-Catalyzed Hydrolysis of Phenyl Ester Prodrugs of Nipecotic Acid , Int. J. Pharm. 1988, 48, 91 -102. 

Hammett substituent constant, effect of cyclo-amyloses on, in hydrolysis of phenyl esters, 23 222... 

Phenylcyclopentadiene, cyclization, 28 294 Phenylcyclopentane, cyclization, 28 294 Phenylcyclopentene, cyclization, 28 294 Phenyl esters, hydrolysis of, catalytic action of, catalytic action of cycloamyloses on, 23 222... 

Gruhn and Bender (2P) attached a hydroxamate group (8) to a secondary hydroxyl in an attempt to attain rapid turnover of catalyst in phenyl ester hydrolysis. The catalytic rate of the cycloamylose-hydroxamate adduct was compared to the rates brought about by (9) free in solution. Relative to the... 

In chymotrypsin and other serine proteases the imidazole moiety of histidine acts as a general base not as a nucleophile as is probably the case in the catalysis of activated phenyl ester hydrolysis by (26). With this idea in mind, Kiefer et al. 40) studied the hydrolysis of 4-nitrocatechol sulfate in the presence of (26) since aryl sulfatase, the corresponding enzyme, has imidazole at the active center. Dramatic results were obtained. The substrate, nitrocatechol sulfate, is very stable in water at room temperature. Even the presence of 2M imidazole does not produce detectable hydrolysis. In contrast (26) cleaves the substrate at 20°C. Michaelis-Menten kinetics were obtained the second-order rate constant for catalysis by (26) is 10 times... 

Neighbouring-group participation in the hydrolysis of esters and amides has been reviewed. The effects of urea, Na+ and Li+ on the intramolecular general-base-catalysed glycolysis of phenyl salicylate (217) in glycol-acetonitrile solvent at constant water concentration have been reported. ... 

Effect of Structure on Carboxyl Group Participation in Hydrolysis of Phenyl Esters (Bruice and Pandit, 1960b)... 

Hubbard and Kirsch (1972) have recently proposed that histidine may act as a nucleophile in a-chymotrypsin acylation reactions of esters having a good leaving group (jO-nitrophenol). This suggestion was based on a similarity in p-value for acylation by p-substituted nitrophenyl and dinitrophenyl benzoates and nucleophilic attack on these compounds by imidazole, in contrast with less positive p-values for hydroxide ion catalysis. Hammett p-values for hydrolysis of substituted phenyl esters are given in Table 6 and show little apparent trend. The values for hydroxide ion and alcoholate ions are... 

By the hydrolysis of esters 81a-c, the corresponding acids 83a-c were formed. The 2-[3-(trifluoromethyl)phenyl]-4//-furo[3,2-7]pyrrole-5-carboxylic acid 83a was decarboxylated in acetic anhydride to 4-acetyl-2-[3-(trifluoromethyl)-phenyl]furo[3,2-7]pyrrole 84 (see 10.01.05.1.2, Scheme 7). 

Kirsch et al. (1968) investigated the base-catalyzed hydrolysis of 24 meta- and para-disubstituted benzoic acid phenyl esters in acetonitrile/water (1 2) at 25°C ... 

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