Of a carboxylic acid with

The formulated mechanism is supported by the finding that no halogen from the phosphorus trihalide is transferred to the a-carbon of the carboxylic acid. For instance, the reaction of a carboxylic acid with phosphorus tribromide and chlorine yields exclusively an a-chlorinated carboxylic acid. In addition, carboxylic acid derivatives that enolize easily—e.g. acyl halides and anhydrides—do react without a catalyst present. 

The Hunsdiecker reaction is the treatment of the dry silver salt of a carboxylic acid with bromine in carbon tetrachloride. Decarboxylation occurs, and the product isolated is the corresponding organic bromide 16). Since dry silver salts are tedious to prepare, a modification of the reaction discovered by Cristol and Firth (77) is now... 

Esters can also be synthesized by an acid-catalyzed nucleophilic acyl substitution reaction of a carboxylic acid with an alcohol, a process called the Fischer esterification reaction. Unfortunately, the need to use an excess of a liquid alcohol as solvent effectively limits the method to the synthesis of methyl, ethyl, propyl, and butyl esters. 

Acid chlorides are prepared from carboxylic acids by reaction with thionyl chloride (SOCl2), as we saw in the previous section. Similar reaction of a carboxylic acid with phosphorus tribromide (PB ) yields the acid bromide. 

Esters are usually prepared from carboxylic acids by the methods already discussed. Thus, carboxylic acids are converted directly into esters by SK2 reaction of a carboxyfate ion with a primary alkyl halide or by Fischer esterification of a carboxylic acid with an alcohol in the presence of a mineral acid catalyst. In addition, acid chlorides are converted into esters by treatment with an alcohol in the presence of base (Section 21.4). 

Why is the saponification of an ester irreversible In other words, why doesn t treatment of a carboxylic acid with an alkoxide ion yield an ester ... 

Treatment of a carboxylic acid with triJluoroacctic anhydride leads to an unsymmetrical anhydride that rapidly reacts with alcohol to give an ester. 

Fischer esterification reaction (Section 21.3) The acid-catalyzed nucleophilic acyl substitution reaction of a carboxylic acid with an alcohol to yield an ester. 

Hell-Volhard-Zelinskii (HVZ) reaction (Section 22.4) The reaction of a carboxylic acid with Br2 and phosphorus to give an -bromo carboxylic acid. 

Reaction of a carboxylic acid with an alkoxide ion gives the carboxylate ion. 

Treatment of a carboxylic acid with the strong base NaOH harms the sodium salt of the acid. With acetic acid, the acid-base reaction is... 

Ketones can also be obtained by treatment of the lithium salt of a carboxylic acid with an alkyllithium reagent (16-31). For an indirect way to convert carboxylic esters to ketones, see 16-33. 

Reaction of a silver salt of a carboxylic acid with bromine is called the Hunsdiecker... 

We will now explore each aspect of this two-step process. In the first step, a peroxyacid (RCO3H), sometimes called a per-acid, reacts with the alkene. Compare the structure of a carboxylic acid with the structure of a peroxy acid ... 

In the first part of this activity, you will prepare a polyester. As the name polyester implies, this polymer contains many ester functional groups. One technique for preparing an ester is by the reaction of a carboxylic acid with an alcohol. RCOOH + R OH —> RCOOR + H20... 

Much more important than these reactions, however, are the reactions of CDI and its analogues with carboxylic acids, leading to AAacylazoles, from which (by acyl transfer) esters, amides, peptides, hydrazides, hydroxamic acids, as well as anhydrides and various C-acylation products may be obtained. The potential of these and other reactions will be shown in the following chapters. In most of these reactions it is not necessary to isolate the intermediate AAacylazoles. Instead, in the normal procedure the appropriate nucleophile reactant (an alcohol in the ester synthesis, or an amino acid in the peptide synthesis) is added to a solution of an AAacylimidazole, formed by reaction of a carboxylic acid with CDI. Thus, CDI and its analogues offer an especially convenient vehicle for activation of... 

The reaction of a carboxylic acid with N,Af -carbonyldiimidazolellH33 (abbreviated as CDI), forming an imidazolide as the first step followed by alcoholysis or phenolysis of the imidazolide (second step), constitutes a synthesis of esters that differs from most other methods by virtue of its particularly mild reaction conditions.t41,[5] It may be conducted in two separate steps with isolation of the carboxylic acid imidazolide, but more frequently the synthesis is carried out as a one-pot reaction without isolation of the intermediate. Equimolar amounts of carboxylic acid, alcohol, and CDI are allowed to react in anhydrous tetrahydrofuran, benzene, trichloromethane, dichloromethane, dimethylformamide, or nitromethane to give the ester in high yield. The solvents should be anhydrous because of the moisture sensitivity of CDI (see Chapter 2). Even such unusual solvent as supercritical carbon dioxide at a pressure of 3000 psi and a temperature of 36-68 °C has been used for esterification with azolides.[6]... 

Salicylic acid (Fig. 13.4.2) is an example of a carboxylic acid with the general formula R-COOH. In this class of organic compounds the carbonyl functionality... 

FIGURE 6.10 The side chain of histidine is readily acylated (A) by activated residues. The imidazolide produced is an activated species similar to the intermediate generated by reaction (B) of a carboxylic acid with coupling reagent carbonyldiimidazole. (Staab, 1956). Imida-zolides acylate amino and hydroxyl groups. Isomerization of histidyl during activation results from abstraction (C) of the a-proton by the 7t-nitrogen. 

Exchanging the hydroxyl group of a carboxylic acid with a different group produces a carboxylic acid derivative. In the following investigation, you will react two carboxylic acids with primary alcohols to produce different organic compounds. 

The reaction of a carboxylic acid with an alcohol to form an ester is called an esterification reaction. An esterification reaction is one type of condensation reaction. In a similar type of condensation reaction, an amide can be formed from a carboxylic acid and an amine, but this process is slightly longer and will not be discussed here. 

Treating the dianion of a carboxylic acid with an alkyl nitrate leads to an a-nitrocarboxylic acid which readily undergoes decarboxylation to the corresponding nitroalkane. This method is particularly useful for the synthesis of arylnitromethanes containing electron-donating groups. ... 

The hydrolysis of an ester to alcohol and acid (1) and the esterification of a carboxylic acid with an alcohol (2) are shown here as an example of the Sn2 mechanism. Both reactions are made easier by the marked polarity of the C=0 double bond. In the form of ester hydrolysis shown here, a proton is removed from a water molecule by the catalytic effect of the base B. The resulting strongly nucleophilic OH ion attacks the positively charged carbonyl C of the ester (la), and an unstable sp -hybridized transition state is produced. From this, either water is eliminated (2b) and the ester re-forms, or the alcohol ROH is eliminated (1b) and the free acid results. In esterification (2), the same steps take place in reverse. 

The interaction of a carboxylic acid with ammonia or an amine may form an amide. The amide derived from ammonia has an -NH2 group attached to the... 

The formation of an acyl halide involves the reaction of a carboxylic acid with a halogen source. The common halogen sources tire compounds like PX3, PXj, ClOCCOCl (oxalyl chloride), or SO.V2> where. Y is a halogen. The most commonly used acyl halides are the chlorides, and the simplistic reaction is RCOOH —> RCOCl. Figure 12-15 illustrates the mechanism using thionyl... 

The reaction of a carboxylic acid with sodium hydroxide (NaOH) produces the sodium salt of the carboxylic acid. The sodium salt then reacts with an acid chloride to form the anhydride. Figure 12-16 illustrates the final step in this process. In this reaction, the carboxylate ion behaves as a nucleophile and attacks the carbonyl Ccirbon atom of the acid chloride. The reaction of a carboxylic acid with sodium hydroxide also generates water, which, if not removed, reacts with the acid chloride and lowers the yield of the reaction. 

Amides contain an acid portion and an amine portion. However, unlike the formation of an ester, the reaction of a carboxylic acid with an cimine is not an efficient method for preparing an amide, because, as you see in this section, the simple reaction of an acid (carboxylic acid) with a base (amine) causes interference. Fortunately, methods similar to many of the other ester synthesis methods are useful in the synthesis of amides. 

Preparation of acid chlorides The best way to make acid chlorides is the reaction of a carboxylic acid with either thionyl chloride (SOCI2) or oxalyl chloride (COCl)2 in the presence of a base (pyridine). The mechanism of formation of acid chloride is similar to the reaction of alcohol with SOCI2. 

Compositions and functions of typical commercial products in the 2-alkyl-l-(2-hydroxyethyl)-2-imidazolines series are given in Table 29. 2-Alkyl-l-(2-hydroxyethyl)-2-imidazolines are used in hydrocarbon and aqueous systems as antistatic agents, corrosion inhibitors, detergents, emulsifiers, softeners, and viscosity builders. They are prepared by heating the salt of a carboxylic acid with (2-hydroxyethyl)ethylenediamine at 150—160°C to form a substituted amide 1 mol water is eliminated to form the substituted imidazoline with further heating at 180—200°C. Substituted imidazolines yield three series of cationic surfactants by ethoxylation to form more hydrophilic products quatemization with benzyl chloride, dimethyl sulfate, and other alkyl halides and oxidation with hydrogen peroxide to amine oxides. 

Reaction of a silver salt of a carboxylic acid with bromine is called the Hunsdiecker reaction438 and is a way of decreasing the length of a carbon chain by one unit.439 The reaction is of... 

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