Hydrolysis of ester and ether

The main products formed from the hydrolysis of di- -butyl phthalate and ethyl acetate in NCW are the corresponding acids and alcohols. The formation of thermolysis products, such as alkenes and oxides of carbon, is considerably slower in NCW than when performed neat. 

Lesutis et al. have reported the kinetics associated with the hydrolysis of a series of benzoate esters in NCW (Fig. 9.18). Conversion vs time yielded S-shaped curves (Fig. 9.19), which suggested an autocatalytic mechanism. The Aac2 mechanism for acid-catalyzed 

The rates of hydrolysis of a series of substituted anisoles have also been reported. The reactions are shown in Fig. 9.21, and the rate constants, along with the a values, are summarized in Table 9.2. A Hammett plot produces a p value of 2.3 (Fig. 9.22), showing that the mechanism of reaction involves a simple Sn2 displacement by water on the methyl group of the substituted anisole (Fig. 9.23). Finally, the rates of hydrolysis of anisole are found to be substantially faster than that of the more sterically hindered phenetole (Fig. 9.24), consistent with the postulated Sn2 mechanism. 

Hydrolysis reactions have been widely reported in NCW for low-molecular-weight molecules as well as for polymeric materials. Mandoki reported a process for depoly-merizing condensation polymers using NCW without addition of bases or acids. More particularly, polyethylene terephthalate, polybutene terephthalate, nylon 6, and nylon 66 were hydrolytically depolymerized (Fig. 9.25). 

Siskin et al. similarly hydrolyzed polyacrylonitrile to low-molecular-weight oligomeric materials, with the generation of ammonia instead of the toxic hydrogen cyanide formed by conventional thermolysis processes. Holliday et al. reported that triglyceride-based vegetable oils can be hydrolyzed into their fatty acids constituents. The authors studied NCW and SCW. Although the conversion yields are comparable in both medium, NCW 

---

Hydrolysis of esters and ethers, hydrolytic cleavage of C—N single bonds, hydrolytic cleavage of nonaromatic heterocycles, hydration and dehydration at m ultiple bonds, new atomic linkages resulting from dehydration reactions, hydrolytic dehalogenation removal of hydrogen halide molecules, various reactions. 

Tetramethylammonium hydroxide (TMAH) is the most commonly used reagent for THM, and TMAH thermochemolysis has been extensively applied to the characterization of organic natural materials [98,103,104,107,108,124,127,134-138]. Py with TMAH involves the deprotonation of carboxylic acids and the hydrolysis of ester and ether bonds, followed by the formation of tetramethylammonium salts, which are subsequently subjected to thermal dissociation and leads to the formation of the corresponding methyl derivatives. 

Chemically dextrans are similar to one another. The activation energy for acid hydrolysis is about 30-35 Kcal/mol (5j. The C-2 hydroxyls appear to be the most reactive in most Lewis base and acid-type reactions. A wide variety of esters and ethers have been described as well as carbonates and xanthates ( 7,8j. In alkaline solution, dextran forms a varying complex with a number of metal ions (9). 

However, due to the artifacts resulting from oxidation, hydrolysis of esters or ethers, or isomerization of phenolics during pretreatment of wines, as well as due to the low recovery rates of some phenolics, analysis of wine phenolics via direct injection of the filtered wine into the chromatographic column is often selected (80,82-84). For the red wine and musts (80), which were injected directly into the HPLC without sample preparation, a ternary-gradient system was often employed for phenolic compounds. Twenty-two phenolic compounds, including 10 anthocyanins, were analyzed from red wine. The separation of cinnamic acid derivatives (313 nm),... 

There are two main procedures for the derivatization of thesei substances (i) alkaline hydrolysis and derivatization of the products and (ii) derivatization of the intact insecticide. As the products from the hydrolysis are mostly derivatives of phosphorus acid and phenols, the former procedure involves the preparation of esters and ethers of these compounds. In the latter instance derivatives are applied, depending on interfering functional groups present, and further oxidation, reduction and other reactions. 

Saponification.—As we shall see later, this is the kind of reaction which takes place when soap is made from fats and on that account it is termed an action of saponifikation. In this way the acids are obtained as salts from the naturally occurring fats, oils and waxes in which they are present in the form of esters. The hydrolysis of esters or ethereal salts is then the general reaction by which, with the taking up of the elements of water, an ester is reconverted into the two compounds from which it was formed, viz., into an acid and an alcohol. Esterification and hydrolysis or saponification are, therefore, complementary names applying to the reversible reaction effecting the synthesis and decomposition of esters. The reversible character of the reactions of esterification and... 

Catalytic antibodies have been produced to catalyze an impressive variety of chemical reactions. For instance, stable phosphonic esters (or lactones, respectively) have been used as transition state mimics for the hydrolysis of esters and amides [555-557], acyl transfer [558] and lactonization [559] reactions, which all proceed via a tetrahedral carbanionic intermediate. In some instances, the reactions proved to be enantiospecific [560]. Elimination reactions [561, 562], reductions [563], formation and breakage of C-C bonds [564,565] and even photochemical reactions [566] can be catalyzed. The cleavage of an ether [567] and cis-trans isomerization of alkenes have been reported [568]. 

Me3SiI is a useful reagent for cleavage of esters and ethers, work-up with water giving the hydrolysis products. By use of Ni and Rh catalysts bearing chiral phosphine ligands, low to moderate optical induction during hydrosilylation of alkenes and silane reductions of carbonyl compounds have been achieved. Under... 

As early as 1899, 8tieglitz proposed a tetrahedral intermediate for the hydrolysis of an imino ether to an amide. Thns it was clear qnite early that a complicated overall transformation, imino ether to amide, would make more sense as the result of a series of simple steps. The detailed mechanism proposed, althongh reasonable in terms of what was known and believed at the time, wonld no longer be accepted, but the idea of tetrahedral intermediates was clearly in the air. 8tieglitz stated of the aminolysis of an ester that it is now commonly snpposed that the reaction takes place with the formation of an intermediate prodnct as follows referring to work of Lossen. (Note that the favored tautomer of a hydroxamic acid was as yet unknown.)... 

Although the ability of microwaves (MW) to heat water and other polar materials has been known for half a century or more, it was not until 1986 that two groups of researchers independently reported the application of MW heating to organic synthesis. Gedye et al. [1] found that several organic reactions in polar solvents could be performed rapidly and conveniently in closed Teflon vessels in a domestic MW oven. These reactions included the hydrolysis of amides and esters to carboxylic acids, esterification of carboxylic acids with alcohols, oxidation of alkyl benzenes to aromatic carboxylic acids and the conversion of alkyl halides to ethers. 

The effects of metal ions on the alcoholysis and hydrolysis of esters containing crown ether functionalities have also been studied (Cacciapaglia et al., 1989, 1992 Hedderwick et al., 1991a,b). In the former case, transition state binding was considered explicitly, in the same manner as did Ercolani and Mandolini (1990). 

Reports of depolymerization studies carried out by Semiyen and co-workers at the University of York, UK, typically used much longer reaction times (24-72 h) for the depolymerization of PET [27], This group also reported that the titanates were ineffective catalysts for depolymerization, but it is not known whether measures to prevent titanate hydrolysis were taken. The York group also reported that the relative proportions of cyclic oligomers (trimer, tetramer, etc.) altered as the dilution ratio was changed. Similar results were seen with PBT. They have also reported fast-atom bombardment mass spectrometry (FAB-MS), LC-MS, GPC and X-ray crystallography data. The most recent work reports characterization of the cyclic oligomers from six ester and ether ester systems [29],... 

Stott, W.T. McKenna, M.J. (1985) Hydrolysis of several glycol ether acetates and acrylate esters by nasal mucosal carboxylesterase in vitro. Fundam. appl. Toxicol., 5, 399-404... 

Hydrolysis of a methyl ether.1 Treatment of either 1 or 2 with BF3 etherate yields exclusively 3 (aklavinone). One explanation for the result is formation of a cyclic borate ester intermediate involving the C7- and C9-hydroxyl groups. Under similar conditions, trifluoroacetic acid converts either 1 or 2 into an 8 1 mixture of 3 and 7-epi-3. BF3 etherate was also used to convert the C,0-epimer of 2 into 3. 

The simultaneous and selective protection of the two equatorial hydroxyl groups in methyl dihydroquinate [11L1, Scheme 3.111 j as the butane-2,3-diace-tal 111 2 was a key strategic feature in a synthesis of inhibitors of 3-dehydroqui-nate synthase.205 Later in the synthesis, deprotection of intermediate 111.4 required three steps (a) hydrolysis of the trimethylsilyl ether and the butane-2,3-diacetal with trifluoroacetic acid (b) cleavage of the isopropyl phosphonate with bromotrimethylsilane and (c) hydrolysis of the methyl ester with aqueous sodium hydroxide. Compound 111 1 has also been used in the synthesis of inhibitors 3-dehydroquinate dehydratase206 and influenza neuraminadase207-208 as well as shikimic add derivatives.209 210... 

---