Anhydrides carboxylic acid

Carboxylic acids react with acyl chlorides in the presence of pyridine to give carboxylic acid anhydrides. Pyridine deprotonates the carboxylic acid, enhancing its nucleophilidty. 

This method is frequently used in the laboratory for the preparation of anhydrides. The method is quite general and can be used to prepare mixed anhydrides (R R ) or symmetric anhydrides (R = R ). 

Sodium salts of carboxylic acids also react with acyl chlorides to give anhydrides  

Cyclic anhydrides can sometimes be prepared simply by heating the appropriate dicar-boxylic acid. This method succeeds, however, only when anhydride formation leads to a five- or six-membered ring  

When maleic acid is heated to 200°C, it loses water and becomes maleic anhydride. Fumaric acid, a diastereomer of maleic acid, requires a much higher temperature before it dehydrates when it does, it also yields maleic anhydride. Provide an explanation for these observations. 

Liauw et al. [23] found that when dodecenyl succinic anhydride was adsorbed onto aluminum hydroxide at 50 °C, most of the interaction was through acid groups formed by hydrolysis and there was little salt formation, with carboxylate salts appearing only at higher temperatures. Monolayer coverage levels were determined 

Tabtiang and Venables studied the reaction of dodecenyl succinic anhydride with calcium carbonate, using dry blending [10]. They found that the anhydride was largely converted to the carboxylate salt, with htde or no evidence of any remaining anhydride or free acid. The effects in polypropylene were those associated with a noncouphng additive, even when peroxide was present in the coating. 

In 1991, Panasonic found that small quantities of additives such as acetic anhydride (16) and benzoic anhydride (17) can suppress the temperature-dependent increase in resistance, which is considered to be caused by water inside the battery or residual alkali mixed into the active material of the cathode [55]. 

As described in the relevant report, Consequently, by having acid anhydride included in positive electrodes, reduction of the water content or the residual alkali within batteries is made possible with a resultant prevention of the battery performance deterioration occurring at high temperature storage and assumedly caused by the existence of water or residual alkali [55], 

in 1999, Mitsubishi Chemical Corporation discovered that the addition of cyclic carboxylic acid anhydrides, such as succinic anhydride (18) and maleic anhydride (19), suppresses the decomposition of PC even when graphite anodes are used [56], 

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Carboxylic acid anhydrides compounds of the type RCOCR can also serve as sources of acyl cations and m the presence of aluminum chloride acylate benzene One acyl unit of an acid anhydride becomes attached to the benzene ring and the other becomes part of a carboxylic acid... 

Carboxylic acid anhydrides react similarly to acyl chlorides... 

Esterification with carboxylic acid anhydrides (Section 15 8) Car... 

Friedel-Crafts acylation of aromatic compounds (Section 12 7) Acyl chlorides and carboxylic acid anhydrides acylate aromatic rings in the presence of alumi num chloride The reaction is electrophil ic aromatic substitution in which acylium ions are generated and attack the ring... 

In naming carboxylic acid anhydrides in which both acyl groups are the same we simply specify the acid and replace acid by anhydride When the acyl groups are dif ferent they are cited m alphabetical order... 

FIGURE 20 3 An acid cat alyzes the hydrolysis of a carboxylic acid anhydride by increasing the rate of the first stage of the mecha nism The faster the tetra hedral intermediate is formed the faster the rate of hydrolysis... 

Amines are convert ed to amides on reaction with acyl chlorides Other acylating agents such as carboxylic acid anhydrides and esters may also be used but are less reactive... 

Acylatmg agents such as acyl chlorides and carboxylic acid anhydrides can react with phenols either at the aromatic ring (C acylation) or at the hydroxyl oxygen (O acylation)... 

The O acylation of phenols with carboxylic acid anhydrides can be conveniently catalyzed m either of two ways One method involves converting the acid anhydride to a more powerful acylatmg agent by protonation of one of its carbonyl oxygens Addi tion of a few drops of sulfuric acid is usually sufficient... 

The alcohol groups of carbohydrates undergo chemical reactions typical of hydroxyl functions They are converted to esters by reaction with acyl chlorides and carboxylic acid anhydrides... 

Step 2 Structurally O acylisoureas resemble carboxylic acid anhydrides and are powerful acylatmg agents In the reaction s second stage the amine adds to the carbonyl group of the O acylisourea to give a tetrahedral intermediate... 

Friedel-Crafts acylation (Section 12 7) An electrophilic aro matic substitution in which an aromatic compound reacts with an acyl chloride or a carboxylic acid anhydride in the presence of aluminum chlonde An acyl group becomes bonded to the nng... 

Ethers of benzenepentol have been obtained by Dakin oxidation of the appropriately substituted acetophenone. Thus, the oxidation of 2-hydroxy-3,4,6-ttimethoxyacetophenone and 2-hydroxy-3,4,5-ttimethoxyacetophenone with hydrogen peroxide ia the presence of alkali gives l,2-dihydroxy-3,4,6-ttimethoxybenzene and l,2-dihydroxy-3,4,5-ttimethoxybenzene, respectively further methylation of these ethers yields the pentamethyl ether of benzenepentol (mp 58—59 degC) (253). The one-step aromatization of myoinositol to produce esters of pentahydroxybenzene is achieved by treatment with carboxylic acid anhydrides ia DMSO and ia the presence of pyridine (254) (see Vitamins). 6-Alkyl- or... 

By virtue of their fused /3-lactam-thiazolidine ring structure, the penicillins behave as acylating agents of a reactivity comparable to carboxylic acid anhydrides (see Section 5.11.2.1). This reactivity is responsible for many of the properties of the penicillins, e.g. difficult isolation due to hydrolytic instability (B-49MI51102), antibacterial activity due to irreversible transpeptidase inhibition (Section 5.11.5.1), and antigen formation via reaction with protein molecules. 

Esterification with carboxylic acid anhydrides (Section 15.8) Carboxylic acid anhydrides react with alcohols to form esters in the same way that acyl chlorides do. 

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