Acid anhydride esters from

The net effect of this questionable attitude thrust upon FDA was that sucrose esters went into commercial production in Japan rather than in the land of their discovery. In Japan they go into cake mixes as emulsifying agents, and so far they have hurt no one. The process of digestion splits the sucrose ester into fatty acid and invert sugar, compounds that are normally present in the body. More recently I have seen reports that the French are using sucrose esters in animal feeds. The results of experiments synthesizing sucrose esters from acid anhydrides, to be reported later in this symposium, are, naturally, of great interest to me. 

Esters Like acid anhydrides the carbonyl group of an ester is stabilized by elec tron release from oxygen Because there is only one carbonyl group versus two m anhydrides esters are stabilized more and are less reactive than anhydrides... 

The primary and secondary alcohol functionahties have different reactivities, as exemplified by the slower reaction rate for secondary hydroxyls in the formation of esters from acids and alcohols (8). 1,2-Propylene glycol undergoes most of the typical alcohol reactions, such as reaction with a free acid, acyl hahde, or acid anhydride to form an ester reaction with alkaU metal hydroxide to form metal salts and reaction with aldehydes or ketones to form acetals and ketals (9,10). The most important commercial appHcation of propylene glycol is in the manufacture of polyesters by reaction with a dibasic or polybasic acid. 

Geranyl chloride can be prepared from geraniol by the careful use of triphenylphosphine in carbon tetrachloride. Tris(dimethylamino)phosphine reacts with carbon tetrachloride to form the complex (42) which can be used to form the enol esters (43) from acid anhydrides. Similarly, aldehydes form the alkenes (44), and esters or amides of trichloroacetic acid are converted to glycidic esters. ... 

The alkyl group of the salt of the alkylsulphuric acid can also be made available for esterification if the temperature is raised sufficiently. The formation of esters from acid chlorides or anhydrides need only be recalled here. This method also has practical importance. 

The formation of esters from acid chlorides and anhydrides according to the following equation has been discussed ... 

Amides can also be synthesised from acid anhydrides and esters but in general these reactions offer no advantage over acid chlorides because acid anhydrides and esters are less reactive. Moreover, with acid anhydrides, half of the parent carboxylic acid is lost as the leaving group. Thus, acid anhydrides are only used for the synthesis of amides if the acid anhydride is cheap and freely available (e.g. acetic anhydride). 

The unimolecular mechanism is unusual for carbonyl substitution reactions. Those in the last chapter as well as the carbonyl addition reactions in Chapter 6 all had nucleophilic addition to the carbonyl group as the rate-determining step. An example would be the formation of an ester from an anhydride instead of from an acid chloride. 

In Chapter 12 pyridine was often used as a catalyst in carbonyl substitution reactions. It can act in two ways. In making esters from acid chlorides or anhydrides pyridine can act as a nucleophile as well as a convenient solvent. It is a better nucleophile than the alcohol and this nucleophilic catalysis is discussed in Chapter 12 (p. 282). But nonnucleophilic bases also catalyse these reactions. For example, acetate ion catalyses ester formation from acetic anhydride and alcohols. 

A rather unusual solvent system for sucrose, namely, molten chloroacetic acid, was used by Lorand,160 who prepared sucrose esters from palmitic anhydride dissolved in this medium. It is unlikely that the glycosidic link in the sucrose is unaffected under these conditions. 

Substituted-1,3-benzoxathiolium tetrafluoroborates (53 Scheme 25) can be prepared readily from acids, anhydrides, esters and trihalomethyl compounds. The thiolium salts can be reduced easily with NaBH4 in acetonitrile at 0-20 C to give aldehydes in 71-91% overall yields. 

From acid anhydrides (Sections 15.8 and 19.5) Acyl transfer from an acid anhydride to an alcohol is a standard method for the preparation of esters. The reaction is subject to catalysis by either acids (H2SO4) or bases (pyridine). 

Esterification. - A full account has been given of the preparation of esters from acids by formation of mixed anhydrides using a chloroformate in the presence of ca. 10 mol% of DMAP... 

Carboxylic acids are used as intermediates in the preparation of esters, amides, acid anhydrides, and acid chlorides. Esters are formed from carboxylic acids and alcohols when the mixture is heated in the presence of a mineral acid... 

Since sulfuric acid is not particularly soluble in higher-molecular-weight alcohols, it is common to attempt to form esters from acids, which both promote elimination (or substitution, vide supra) and which enjoy such solubility. To this end, and as shown in Equation 8.41, even the acetate (ethanoate) ester (formed from the reaction of alcohol—in this case cyclopentanol—with, e.g., acetic acid [ethanoic acid, CH3CO2H] or acetic anhydride [ethanoic anhydride, (CH3CO)20)] or acetyl chloride [ethanoyl chloride, CH3COCI]), by processes that are discussed further in Chapter 9, can be used to good effect to produce cis- or suprafacial elimination of the elements of acetic acid (ethanoic acid). 

So far, in this section, we have seen that we can make amides from acid halides, from acid anhydrides, or from esters. Now that we know how to make amides, let s explore some important reactions of amides. Specifically, we will explore hydrolysis of amides (under acidic or basic condition). It is worth mentioning that much of biochemistry is dependent on how, when, and why amides will undergo hydrolysis. So, if you plan on taking biochemistry, you should certainly be familiar with the hydrolysis of amides, which can occur under either basic conditions or acidic conditions ... 

Acid derivatives are made directly from acids or by conversion from other acid derivatives depending on their stabihty. The most important are esters (RCOiEt), amides (RCO2NR2), anhydrides (RCOO COR) and add clilorides (RCOCI). Arrange these in an order of stabilily, the most reactive at the top of the list, the most stable at the bottom. 

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