Ester, alkaline hydrolysis

N-Heterocyclics la 252 lb 268 Hexachlorocyclohexane lb 227 Hexachlorocyclohexane isomers lb 211 Hexacyanoferrate(II) anions lb 307 Hexacyanoferrate(ni) anions lb 307 n-Hexadecanol esters, alkaline hydrolysis la 63... 

The Darzens reaction of isatin with ethyl chloroacetate yields glycidic esters. Alkaline hydrolysis of the glycidic esters yields indole-2,3-dicarboxylic and indole-3-carboxylic acids in a 6 1 proportion. The isolation of two isomeric glycidic esters, and the fact that both produce the indolecarboxylic acids in the same proportion led to a mechanistic proposal for the formation of the later through a common intermediate439 (Scheme 101). 

Derivatives of the 2-phenyl-1,3,4-oxadiazole-5-carboxylic acids give the usual reactions of acids on careful treatment.103 Thus the alcoholysis of the 5-acid chlorides with methanol or ethanol leads to the corresponding ester. Alkaline hydrolysis at 30° produces the carboxylic acid which on warming is decarboxylated to 2-phenyl-1,3,4-oxadiazole. Even a slight increase in the severity of the reaction conditions produces ring cleavage.103 The alkaline hydrolysis of 2-phenyl-5-(p-cyanophenyl)-1,3,4-oxadiazole with addition of H202 leads to 2-phenyl-5-(p-carboxamidophenyl)-1,3,4-oxadiazole.23... 

Polystyrene, (soluble), incorporating an acid chloride group Polymer-saccharide (C-6) ester". Alkaline hydrolysis (NaOMe-Dioxane) C-1 Bromide viacw-1,2-orthoester Guthrie er a/., 1971, 1973... 

It is frequently advisable in the routine examination of an ester, and before any derivatives are considered, to determine the saponification equivalent of the ester. In order to ensure that complete hydrolysis takes place in a comparatively short time, the quantitative saponi fication is conducted with a standardised alcoholic solution of caustic alkali—preferably potassium hydroxide since the potassium salts of organic acids are usuaUy more soluble than the sodium salts. A knowledge of the b.p. and the saponification equivalent of the unknown ester would provide the basis for a fairly accurate approximation of the size of the ester molecule. It must, however, be borne in mind that certain structures may effect the values of the equivalent thus aliphatic halo genated esters may consume alkali because of hydrolysis of part of the halogen during the determination, nitro esters may be reduced by the alkaline hydrolysis medium, etc. 

The first was proposed by Iraoto and Otsuji (511) and Otsuji et al (512) and concerned the pK of substituted 2-, 4-, and 5-carboxylic acids and the alkaline hydrolysis rate k of their respective ethyl esters (259, 260, and 261, where Y = Et). When Hammett cr , values were used for... 

Poly(acrylic acid) and Poly(methacrylic acid). Poly(acryHc acid) (8) (PAA) may be prepared by polymerization of the monomer with conventional free-radical initiators using the monomer either undiluted (36) (with cross-linker for superadsorber appHcations) or in aqueous solution. Photochemical polymerization (sensitized by benzoin) of methyl acrylate in ethanol solution at —78° C provides a syndiotactic form (37) that can be hydrolyzed to syndiotactic PAA. From academic studies, alkaline hydrolysis of the methyl ester requires a lower time than acid hydrolysis of the polymeric ester, and can lead to oxidative degradation of the polymer (38). Po1y(meth acrylic acid) (PMAA) (9) is prepared only by the direct polymerization of the acid monomer it is not readily obtained by the hydrolysis of methyl methacrylate. 

Under conditions of extreme acidity or alkalinity, acryhc ester polymers can be made to hydroly2e to poly(acryhc acid) or an acid salt and the corresponding alcohol. However, acryhc polymers and copolymers have a greater resistance to both acidic and alkaline hydrolysis than competitive poly(vinyl acetate) and vinyl acetate copolymers. Even poly(methyl acrylate), the most readily hydroly2ed polymer of the series, is more resistant to alkah than poly(vinyl acetate) (57). Butyl acrylate copolymers are more hydrolytically stable than ethyl acrylate copolymers (58). 

Displacement reactions with oxygen nucleophiles are of potential commercial interest. Alkaline hydrolysis provides 2-fluoro-6-hydroxypyridine [55758-32-2], a precursor to 6-fluoropyridyl phosphoms ester insecticides (410—412). Other oxygen nucleophiles such as bisphenol A and hydroquinone have been used to form aryl—pyridine copolymers (413). 

Carboxyhc acid ester, carbamate, organophosphate, and urea hydrolysis are important acid/base-catalyzed reactions. Typically, pesticides that are susceptible to chemical hydrolysis are also susceptible to biological hydrolysis the products of chemical vs biological hydrolysis are generally identical (see eqs. 8, 11, 13, and 14). Consequentiy, the two types of reactions can only be distinguished based on sterile controls or kinetic studies. As a general rule, carboxyhc acid esters, carbamates, and organophosphates are more susceptible to alkaline hydrolysis (24), whereas sulfonylureas are more susceptible to acid hydrolysis (25). 

At room temperature, ca 60 wt % ethylene oxide is needed to solubilize the fatty acids. Surface activity of the ethoxylates is moderate and less than that of alcohol or alkylphenol ethoxylates (84). The ethoxylates are low foamers, a useful property in certain appHcations. Emulsification is the most important function. Its importance is reflected in the wide range of lipophilic solubiHties available in the commercial products. Like all organic esters, fatty acid ethoxylates are susceptible to acid and alkaline hydrolysis. 

The most successful of these products contain high ratios of VP to DMAEMA and are partially quatemized with diethyl sulfate (Polyquaternium 11) (142—144). They afford very hard, clear, lustrous, nonflaking films on the hair that are easily removed by shampooing. More recendy, copolymers with methyl vinyl imidazoliiim chloride (Polyquaternium 16) (145) or MAPTAC (methacrylamidopropyltrimethyl ammonium chloride) (Polyquaternium 28) have been introduced. Replacement of the ester group in DMAEMA with an amide analog as in Polyquaternium 28 results in a resin resistant to alkaline hydrolysis and hence greater utility in alkaline permanent-wave and bleach formulations (see Quaternary ammonium compounds). 

Seb cic Acid. Sebacic acid [111-20-6] C QH gO, is an important intermediate in the manufacture of polyamide resins (see Polyamides). It has an estimated demand worldwide of approximately 20,000 t/yr. The alkaline hydrolysis of castor oil (qv), which historically has shown some wide fluctuations in price, is the conventional method of preparation. Because of these price fluctuations, there have been years of considerable interest in an electrochemical route to sebacic acid based on adipic acid [124-04-9] (qv) as the starting material. The electrochemical step involves the Kolbn-type or Brown-Walker reaction where anodic coupling of the monomethyl ester of adipic acid forms dimethyl sebacate [106-79-6]. The three steps in the reaction sequence from adipic acid to sebacic acid are as follows ... 

Pyridazinecarboxamides are prepared from the corresponding esters or acid chlorides with ammonia or amines or by partial hydrolysis of cyanopyridazines. Pyridazinecarboxamides with a variety of substituents are easily dehydrated to nitriles with phosphorus oxychloride and are converted into the corresponding acids by acid or alkaline hydrolysis. They undergo Hofmann degradation to give the corresponding amines, while in the case of two ortho carboxamide groups pyrimidopyridazines are formed. 

In fact, most pyrimidinecarboxylic acids are made by hydrolysis of the corresponding esters, nitriles or sometimes amides, many of which can be made more easily by primary synthesis than can the acids themselves. Thus, pyrimidine-5-carboxylic acid may be made by alkaline hydrolysis of its ethyl ester (62JOC2264) and pyrimidin-5-ylacetic acid (789 ... 

The adamantoate ester is formed selectively from a primary hydroxyl group (e.g., from the 5 -OH in a ribonucleoside) by reaction with adamantoyl chloride, Pyr (20°, 16 h). It is cleaved by alkaline hydrolysis (0.25 N NaOH, 20 min), but is stable to milder alkaline hydrolysis (e.g., NH3, MeOH), conditions that cleave an acetate ester. ... 

The crotonate esters, prepared to protect a primary hydroxyl group in nucleosides, are cleaved by hydrazi ne (MeOH, Pyr, 2 h). The methoxycrotonate is 100-fold more reactive to hydrazinolysis and 2-fold less reactive to alkaline hydrolysis than the corresponding acetate. ... 

The TCBOC group is stable to the alkaline hydrolysis of methyl esters and to the acidic hydrolysis of r-butyl esters. It is rapidly cleaved by the supemucleophile lithium cobalt(I)phthalocyanine, by zinc in acetic acid, and by cobalt phthalocy-anine (0.1 eq., NaBH4, EtOH, 77-90% yield). 

Other derivatives can be prepared by reaction of the alcohol with an acid anhydride. For example, phthalic or 3-nitrophthalic anhydride (I mol) and the alcohol (Imol) are refluxed for half to one hour in a non-hydroxylic solvent, e.g. toluene or alcohol-free chloroform, and then cooled. The phthalate ester crystallises out, is precipitated by the addition of low boiling petroleum ether or is isolated by ev toration of the solvent. It is recrystallised from water, 50% aqueous ethanol, toluene or low boiling petroleum ether. Such an ester has a characteristic melting point and the alcohol can be recovered by acid or alkaline hydrolysis. 

In the ease of a seeond order reaetion, an example is the alkaline hydrolysis of an ester as represented by the following equation ... 

The data given in the table for corynanthine are due to Foumeau and Fiore. Raymond-Hamet later found that corynanthine on alkaline hydrolysis gave a dextrorotatory acid, which Scholz confirmed and identified its methyl ester as yohimbine and suggested that corynanthine is a stereoisomeride of yohimbine. Fourneau and Benoit have confirmed that corynanthine on acid hydrolysis gives 1-corynanthic acid (m.p. 284°, [a]i) — 85-9° pyridine), but on alkaline hydrolysis, even in the cold, some racemisation occurs and the resulting acid is of low lasvo-rotation. They also point out that both yohimbine and corynanthine yield yohimbone on dehydrogenation cf., p. 504) and are probably stereoiso-merides. 

Monocrotaline on alkaline hydrolysis yields retronecine and monocrotic acid, CjHijOg, b.p. 145-6°/18 mm., [a]p 0°, which forms a p-bromo-phenacylester, m.p. 78°,and a methyl ester, b.p. 94-6°/18 mm., characterised by a 2 4-dinitrophenylhydrazone, m.p. 95-6° see below). The acid gives the iodoform reaction and is oxidised by sodium hypobromite to a mixture of dl- and mcso-aa -dimethylsuccinic acids (I). These and other reactions show that monocrotic acid is a -dimethyllaevulic acid (II) and this has been eonfirmed by comparison with a synthetic specimen of the acid. The methyl ester of the synthetie acid forms a mixture of 2 4-dinitrophenylhydrazones, m.p. 108-9° and 121-2°, into which the analogous produet, m.p. 95-6°, first made from methyl monocrotate see above), has also been separated. 

Poethke shows that on alkaline hydrolysis protoveratrine yields acetic, Z-methylethylacetic and methylethylglycollic acids and the alkamine protoverine. It is therefore a triacyl ester of protoverine. 

On alkaline hydrolysis coumingic acid and coumingine yield cassaic acid, C2QH39O4, for which and its derivatives somewhat different [cf. p. 728) constants are now recorded, viz., acid, m.p. 223-4°, [a] ° — 123° (EtOH) methyl ester, m.p. 188-9°, [a] ° — 124° (EtOH) acetyl derivative of... 

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