Hydrolysis saponification

Section 20 11 Ester hydrolysis m basic solution is called saponification and proceeds through the same tetrahedral intermediate (Figure 20 5) as m acid catalyzed hydrolysis Unlike acid catalyzed hydrolysis saponification is irreversible because the carboxylic acid is deprotonated under the reac tion conditions... 

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. 

Mechanism of base-induced ester hydrolysis (saponification). 

Alkaline hydrolysis (saponification) has been used to remove contaminating lipids from fat-rich samples (e.g., pahn oil) and hydrolyze chlorophyll (e.g., green vegetables) and carotenoid esters (e.g., fruits). Xanthophylls, both free and with different degrees of esterification with a mixture of different fatty acids, are typically found in fruits, and saponification allows easier chromatographic separation, identification, and quantification. For this reason, most methods for quantitative carotenoid analysis include a saponification step. 

An alternative procedure involves the release of the fatty acids by alkaline hydrolysis (saponification) by refluxing the extracted sample with dilute alcoholic potassium hydroxide for 1 h. After cooling, adding water and acidifying, the fatty acids are extracted into diethyl ether. The methyl esters can then be prepared by treatment with diazomethane, which may also be used directly on free fatty acids. Saponification is less satisfactory, because it is a lengthy procedure and often results in the loss of lipid components. 

It is prepared by the alkaline hydrolysis (saponification) or alcoholysis (ester interchange) of polyvinyl acetate [Structure (5.2)] as shown in Scheme 5.1. 

Alkylation can be done a second time Ester hydrolysis/saponification, then with... 

Saponification see Hydrolysis Saponification equivalent of an ester, determination of. 392, 1065 Saturated aliphatic hydrocarbons, 233 reactions and characterisation of 234, 1058 table of, 235 ... 

Acid-catalyzed hydrolysis of esters is the reverse of acid-catalyzed ester formation discussed previously. Base-induced ester hydrolysis (saponification) is an irreversible reaction. The initial step is the attack of hydroxide ion at the carbonyl carbon ... 

Treatment of fats or oils with strong bases such as lye (NaOH) or potash (KOH) causes them to undergo hydrolysis (saponification) to form glycerol and the salt of a long-chain fatty acid (soap). 

Mechanism of the base-catalyzed hydrolysis (saponification) of an ester. 

The method applied consists in a prior, basic hydrolysis (saponification) of the oil sample, followed by thin layer chromatography (TLC) fractionation of the classes of compounds, namely hydrocarbons, tocopherols, long-chain aliphatic alcohols, triterpenic alcohols, methyl sterols, sterols and triterpenic dialcohols. This procedure loses all information about the combination of polycyclic triter-penes with fatty acids. 

Alkaline hydrolysis (saponification) can be used to remove interfering lipids and chlorophylls present in plant and food samples, such as... 

This study reports the monocarboxylic fatty acid content of a series of brown coal lithotypes from the Latrobe Valley, Victoria, Australia. We have looked both at the solvent-extractable, or free, fatty acids (which include those extractable as esters or intact lipids) and at those that are released upon hydrolysis (saponification) of the residue after solvent extraction. The latter are presumably bound chemically to the coal matrix (kerogen) and are therefore designated as bound acids. The total acids are taken as the sum of the free and bound acids. 

Soap, which is a mixture of sodium and potassium salts of fatty acids, is produced industrially by hydrolysis (saponification) of animal fat using aqueous sodium hydroxide. 

As glycerol is formed automatically in the hydrolysis, saponification, or transesterification of natural fats and oils as by-product (cfi, Section 3.4.1), the catalytic derivatization of glycerol will also be considered. As it is produced on a large scale in the manufacture of biodiesel, the classical markets for glycerol (Scheme 3.5, left... 

Normally, the Darzens reaction of simple a-halo esters is carried out under anhydrous conditions, since in aqueous media or under phase-transfer catalysis conditions the esters are prone to hydrolysis. Saponification can be largely prevented by using r-butyl esters, but this strategy also poses potential problems, as hydrolysis of the resulting glycidic ester is often the next stage of a synthetic process. Recently, a procedure has been developed in which a-chloro esters are deprotonated by treatment with potassium... 

Acid hydrolysis requires only catalytic amounts of an acid however, for alkaline hydrolysis (saponification) an equimolar amount of alkali is necessary since this is not merely a catalyst but also acts by withdrawing the acid as salt from the equilibrium mixture.47 48... 

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