Spontaneous reaction alkaline hydrolysis

The synthesis of 4-alkyl-y-butyrolactones 13 and 5-alkyl-<5-valerolactones 14 can be achieved in high enantiomeric excess by alkylation of ethyl 4-oxobutanoate and ethyl 5-oxopentanoate (11, n = 2, 3). The addition of diethylzinc, as well as dimethylzinc, leads to hydroxy esters 12 in high optical purity. When methyl esters instead of ethyl esters are used as substrates, the enantioselectivity of the addition reaction is somewhat lower. Alkaline hydrolysis of the hydroxy esters 12, followed by spontaneous cyclization upon acidification, leads to the corresponding y-butyro- and -valerolactones32. 

A mechanism proposed 87) for the alkaline hydrolysis of tetraethyl pyrophosphate, which is markedly accelerated by HPO e ions, has been substantiated by isotopic labeling 88). The nucleophilic attack by HPOJp on the symmetrical pyrophosphate 131 is considered to lead initially to the unsymmetrical P P1-diethyl pyrophosphate dianion 132 which decomposes spontaneously under the conditions of reaction to give the diethyl phosphate anion and POf 102. The latter reacts with water to form inorganic phosphate and with alcohols suclj as methanol and ethylene glycol to produce alkyl phosphates. 

Although a great deal of interest has been shown in the kinetics of alkaline hydrolysis in DMSO + water mixtures (see below), rather less interest has been shown in the kinetics of spontaneous hydrolysis reactions in TNAN mixtures. 

Interest in the kinetics of alkaline hydrolysis of esters in DMSO + water mixtures was stimulated by the observation that the rate constant often increased gradually as x2 increased. This is observed, for example, in the alkaline hydrolysis of ethyl acetate. For higher esters, e.g. ethyl p-nitrobenzoate, the rate constant drops slightly at low x2 but then rises again until k/k x2 = 0) > 1 (Tommila, 1964). The rate of alkaline hydrolysis of esters of benzoic acid is accelerated when DMSO is added (Tommila and Palenius, 1963), as also is the rate of alkaline hydrolysis of 2,4-dinitrofluorobenzene. In the latter case the effect is less dramatic because the rate constant for spontaneous hydrolysis also increases (Murto and Hiiro, 1964). The rate constants also increase when DMSO is added to aqueous solution for reactions between hydroxide ions and benzyl chloride (Tommila... 

Benzyl- or cinnamyl-triphenylarsonium bromides, upon reaction with aqueous sodium hydroxide at 100 °C, decompose into triphenylarsine oxide and toluene or 2-methyl-styrene, respectively . Since tertiary arsine oxides spontaneously racemize in water , alkaline hydrolysis of arsonium salts of this type cannot be used for the preparation of optically active arsines. 

In contrast to equilibrium peracids, preformed peracids refer to percarboxylic acids that were isolated from the reaction mixture and purified for use in formulations. The development of these peracids offers several challenges due to their susceptibility to alkaline hydrolysis, risk of spontaneous combustion, possible spotting of colored fabric, and poor cost/performance. 

The activity of IF2 in binding fMet-tRNA was measured quantifying the protection conferred by these proteins on the initiator tRNA with respect to spontaneous hydrolysis occurring at alkaline pH (Gualerzi et al., 1991 Petersen et al., 1979). Reaction mixtures (50 pi) in Buffer F contained 22 pM f 35S]Met-tRNA, an appropriate amount of protein that is capable of protecting approximately 80% of the initiator tRNA after 60 min incubation as well as increasing concentrations of the antibiotic to be tested. Samples (20 pi), withdrawn after 0 and 60 min of incubation at 37°, are spotted on Whatman 3MM paper discs for determination of the acid-insoluble radioactivity by the cold TCA procedure, described previously. 

Addition of a nucleophile to the C-6 position of cytosine often results in fascile displacement reactions occurring at the N4 location. With hydroxylamine attack, nucleophilic displacement causes the formation of an N4-hydroxy derivative. A particularly important reaction for bioconjugate chemistry, however, is that of nucleophilic bisulfite addition to the C-6 position. Sulfonation of cytosine can lead to two distinct reaction products. At acid pH wherein the N-3 nitrogen is protonated, bisulfite reaction results in the 6-sulfonate product followed by spontaneous hydrolysis. Raising the pH to alkaline conditions causes effective formation of uracil. If bisulfite addition is done in the presence of a nucleophile, such as a primary amine or hydrazide compound, then transamination at the N4 position can take place instead of hydrolysis (Fig. 38). This is an important mechanism for adding spacer arm functionalities and other small molecules to cytosine-containing oligonucleotides (see Chapter 17, Section 2.1). 

Since the hydrolysis reactions proceed more rapidly at a lower pH, the plating rate is faster at lower KOH concentrations. To avoid spontaneous decomposition of the bath, however, alkalinity of at least 0.1 M must be used. The effect of the KOH concentration on the deposition rate of a borohydride bath is illustrated in Fig. 30. 

The binding of Co + to apo-alkaline phosphatase has been studied by the stopped-flow technique and the process appears to be complex. Three reaction steps were detected, in the millisecond, second, and minute ranges none of these was a bimolecular process but the authors suggest that they might all be associated with enzyme isomerization. The spontaneous hydrolysis of (5) is catalysed by bivalent metal ions and it seems that optimal behaviour depends almost entirely on the cationic radius. 

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