Alkalinity, hydrolysis

Fats are hydrolysed to glycerol and fatty acids by boiling with acids and alkalis, by superheated steam and by the action of lipases. If alkalis are used for hydrolysis, the fatty acids combine with the alkalis to form soaps. Alkaline hydrolysis is therefore sometimes called saponification. 

Hammen equation A correlation between the structure and reactivity in the side chain derivatives of aromatic compounds. Its derivation follows from many comparisons between rate constants for various reactions and the equilibrium constants for other reactions, or other functions of molecules which can be measured (e g. the i.r. carbonyl group stretching frequency). For example the dissociation constants of a series of para substituted (O2N —, MeO —, Cl —, etc.) benzoic acids correlate with the rate constant k for the alkaline hydrolysis of para substituted benzyl chlorides. If log Kq is plotted against log k, the data fall on a straight line. Similar results are obtained for meta substituted derivatives but not for orthosubstituted derivatives. 

Prepared by heating p-nitrochlorobenzene with concentrated aqueous ammonia in an autoclave at 170°C. It is also prepared by alkaline hydrolysis of p-nitroacetanilide or by nitrating and hydrolysing benzylideneaniline. 

Hydrolysis of Acetanilide. Anilides in general, such as acetanilide and benzanilide (p. 245), may be hydrolysed by caustic alkalis or by acids. Alkaline hydrolysis, however, is usually very slow, and therefore... 

Amides (except urea and thiourea), imides and nitriles, after the above alkaline hydrolysis, give derivatives similarly to those from the alkaline solution obtained from ammonium salts (p. 360). (A) If the original compound is aromatic, acidification of the cold solution deposits the crystalline acid. (B) The cold solution, when carefully neutralised (p. 332) and treated with benzylthiuronium chloride, deposits the thiuromum salt. 

Note. The treatment of amides with. nitrous add, to obtain the free acid more rapidly than by alkaline hydrolysis, is in general inadvisable when preparing the thiuronium salts.)... 

If the amide is an N-(mono- or di)-substituted amide, or the imide an N-substituted imide, the above alkaline hydrolysis will give a solution... 

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. 

Method 2 (Alkaline hydrolysis). Use a solution of 15 g. of p-bromo-acetanihde in 30 ml. of boiling ethyl alcohol, and add a solution of 7 5 g. of potassium hydroxide in 10 ml. of water. Reflux for 40 minutes, dilute with 120 ml. of water, and distil vmtil 75 ml. of distillate (alcohol and water) are collected pour the residue into 150 ml, of cold water. 

Benzoyl compounds are readily hydrolysed by heating with about 70 per cent, sulphuric acid (alkaline hydrolysis is very slow for anilides) ... 

Acetylene is also protected as propargyl alcohol (300)[2H], which is depro-tected by hydrolysis with a base, or oxidation with MnOi and alkaline hydrolysis. Sometimes, propargyl alcohols are isomerized to enals. Propargyl alcohol (300) reacts with 3-chloropyridazine (301) and EtiNH to give 3-diethylami-noindolizine (303) in one step via the enal 302[2I2]. Similarly, propargyl alcohol reacts with 2-halopyridines and secondary amines. 2-Methyl-3-butyn-2-ol (304) is another masked acetylene, and is unmasked by treatment with KOH or NaOH in butanol[205,206,213-2l5] or in situ with a phase-transfer cata-lyst[2l6]. 

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... 

Another approach to 2-aminothiazole derivatives was recently developed by Zbiral and Hengstberger (667, 700) thus the condensation of )3-acylvinylphosphonium salts (248) with thiourea affords the thiazolyl-methylphosphonium salt (249) via an acyclic intermediate analogous to the Hantzsch s synthesis. Final alkaline hydrolysis of 249 furnishes the 2-aminothiazoles (250) (Scheme 127) (700). 

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. 

Hydrolysis in neutral aqueous solutions proceeds slowly at room temperature and more rapidly at acidic conditions and elevated temperatures. The hydrolysis—esterification reaction is reversible. Under alkaline conditions hydrolysis is rapid and irreversible. Heating the alkaline hydrolysis product at 200—250°C gives 4,4 -oxydibutyric acid [7423-25-8] after acidification (148). 

Alkaline hydrolysis of polyacrylamide can be expressed in terms of three rate constants, and where the subscript indicates the number of... 

Anionic and nonionic polyacrylamides effectively remove suspended soHds such as silt and clay from potable water. SuppHers provide special grades which meet EPA/FDA regulations for residual acrylamides. A recent pubHcation (102) states that hydrolyzed polyacrylamides with narrow interchain charge distributions provide better performance in flocculation of clay. These polymers were prepared by alkaline hydrolysis. (See Flocculating agents.)... 

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). 

Ergonovine (100, R = NHCH(CH3)CH2 0H) was found to yield lysergic acid (100, R = OH) and (+)-2-aminopropanol on alkaline hydrolysis during the early analysis of its stmcture (66) and these two components can be recombined to regenerate the alkaloid. Salts of ergonovine with, for example, malic acid are apparently the dmgs of choice in the control and treatment of postpartum hemorrhage. 

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). 

The presence of water in the carbonylation mixture makes it possible to halt the reaction after the second group migration (step 2). Oxidation of the intermediate boraglycol yields the corresponding ketone, and alkaline hydrolysis affords the secondary alcohol, R HOH. A blocking group of low... 

Hydrolysis. The first effect of either acid hydrolysis or alkaline hydrolysis (saponification) is the removal of the fatty acids. The saponification value of commercial lecithin is 196. Further decomposition into glycerol, phosphoric acid, and head groups (ie, choline, ethanolamine, etc) may foUow prolonged heating. Lecithin may also be hydrolyzed by enzymes. 

By the aLkaU fusion or alkaline hydrolysis under pressure of the appropriate naphthalenedisulfonic or naphthalenetrisulfonic acid or hydroxynaphthalenedisulfonic acid. 

By the alkaline hydrolysis of the sultone formed on boiling an aqueous solution of the diazonium salt of S-amino-l-naphthalenesulfonic acid or its appropriate derivatives. 

Many other polymerization processes have been patented, but only some of them appear to be developed or under development ia 1996. One large-scale process uses an acid montmorrillonite clay and acetic anhydride (209) another process uses strong perfiuorosulfonic acid reski catalysts (170,210). The polymerization product ia these processes is a poly(tetramethylene ether) with acetate end groups, which have to be removed by alkaline hydrolysis (211) or hydrogenolysis (212). If necessary, the product is then neutralized, eg, with phosphoric acid (213), and the salts removed by filtration. Instead of montmorrillonite clay, other acidic catalysts can be used, such as EuUer s earth or zeoHtes (214—216). 

There are four processes for industrial production of ahyl alcohol. One is alkaline hydrolysis of ahyl chloride (1). In this process, the amount of ahyl chloride, 20 wt % aqueous NaOH solution, water, and steam are controhed as they are added to the reactor and the hydrolysis is carried out at 150 °C, 1.4 MPa (203 psi) and pH 10—12. Under these conditions, conversion of ahyl chloride is 97—98%, and ahyl alcohol is selectively produced in 92—93% yield. The main by-products are diahyl ether and a small amount of high boiling point substance. The alkaU concentration and pH value are important factors. At high alkah concentrations, the amount of by-product, diahyl ether, increases and at low concentrations, conversion of ahyl chloride does not increase. 

Isomer separation beyond physical fractional crystallization has been accompHshed by derivatization using methyl formate to make /V-formyl derivatives and acetic anhydride to prepare the corresponding acetamides (1). Alkaline hydrolysis regenerates the analytically pure amine configurational isomers. 

The deterruination of amino acids in proteins requires pretreatment by either acid or alkaline hydrolysis. However, L-tryptophan is decomposed by acid, and the racemi2ation of several amino acids takes place during alkaline hydrolysis. Moreover, it is very difficult to confirm the presence of cysteine in either case. The use of methanesulfonic acid (18) and mercaptoethanesulfonic acid (19) as the protein hydroly2ing reagent to prevent decomposition of L-tryptophan and L-cysteine is recommended. En2ymatic hydrolysis of proteins has been studied (20). 

A/-(4-Hydroxyphenyl)glycine can be prepared from 4-aminophenol and chloracetic acid (199,200) or by alkaline hydrolysis of the corresponding nitrile with subsequent elimination of ammonia (201). 

Sulfaguanidine is prepared by condensation of Ai-acetylsulfanilyl chloride with guanidine ia presence of alkali. The A/ -acetyl group is removed by acid or alkaline hydrolysis. 

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