Carboxyl groups formation

Pelizzetti et al, 1992) (Figure 23.4). Reaction of the TV-ethyl group similarly leads to the formation of acetamido and formylamino products (Pelizzetti et al., 1992) (Figure 23.5, Table 23.2). Further oxidation results in carboxyl group formation, with subsequent photocatalytic decarboxylation leading to the corresponding dealkylated products. 

Carbon monoxide, evolution from cellulose on beating, 428, 429 Carbonylation, of alkyl balides, 61 Carbonyl groups, formation from cellulose on heating, 426, 428, 435 Carboxyl groups, formation from cellulose on beating, 426, 427, 435 Cardenolides, synthesis of 1,2-cis-, 267 Cellobiose, /8-, mutarotation of, 23 Cellulase, 376 Cellulose... 

Water, appearing in the system during forming polyene structures from the product of PETP thermal destruction - acetaldehyde, causes hydrolysis of ester bonds, increasing the rate of carboxyl groups formation. Besides, there takes place decrease of polymer relative viscosity [202]. 

Such a reaction has been shown to give 1-butene and carboxyl groups in equivalent yields (about 2 x 10-2) in the liquid-phase photolysis of undiluted di-n-butylterephthalate [116]. From Table 4 it can be seen that the quantum yields of chain scission and of carboxyl group formation are almost identical this suggests that reaction (22) is the main cause of chain scission in the photolysis of polyethylene terephthalate. It must also be pointed out that reactions (19) and (21) do not necessarily yield chain scission, since the probability of the macro-radicals escaping the cage is rather low in a rigid matrix. Indeed, the appearance of an absorption maximum near 775 cm-1 in the infrared spectrum of polyethylene terephthalate irradiated at 313 nm has been ascribed to... 

Transformation of carboxylic acids into more reactive derivatives, particularly halides and anhydrides, is an activation of the carboxylic group. Formation of more reactive carboxylic acid derivatives may be described as moving the carboxylic group energetically uphill, from where it can be favorably transformed downhill into a less reactive congener. Activated carboxylic acid derivatives characterize the localized partial positive charge on the carbonyl C atom and reactivity against weak nucleophiles such as water, alcohols, ammonia or amines. 

Initially, the rate of carboxyl group formation is somewhat higher than observed during the later part of degradation which possibly reflects the presence of a small percentage of hydrolytically more labile linkages. 

Aryl- or alkenylpalladium comple.xcs can be generated in situ by the trans-metallation of the aryl- or alkenylmercury compounds 386 or 389 with Pd(Il) (see Section 6). These species react with 1,3-cydohexadiene via the formation of the TT-allylpalladium intermediate 387, which is attacked intramolecularlv by the amide or carboxylate group, and the 1,2-difunctionalization takes place to give 388 and 390[322]. Similarly, the ort/trt-thallation of benzoic acid followed by transmetallation with Pd(II) forms the arylpalladium complex, which reacts with butadiene to afford the isocoumarin 391, achieving the 1,2-difunctionalization of butadiene[323]. 

On the other hand, with 4,5-thiazoledicarboxylic acid the 5-carboxyl group is the more labile (3, 5, 51) contrary to results found by other workers (52). For example. Huntress et al. (5) have shown that pyrolysis of 2-phenyl-4,5-thiazoledicarboxylic acid (7) gives evolution of carbon dioxide and the formation of 2-phenyl-4-thiazolecarboxylic acid (8i (Scheme 5). 

Ester formation is a typical reaction of the carboxyl group... 

To direct the synthesis so that only Phe Gly is formed the ammo group of phe nylalanme and the carboxyl group of glycine must be protected so that they cannot react under the conditions of peptide bond formation We can represent the peptide bond for matron step by the following equation where X and Y are amine and carboxyl protecting groups respectively... 

Section 27 5 Ammo acids undergo reactions characteristic of the ammo group (e g amide formation) and the carboxyl group (e g esterification) Ammo acid side chains undergo reactions characteristic of the functional groups they contain... 

Section 27 17 Peptide bond formation between a protected ammo acid having a free carboxyl group and a protected ammo acid having a free ammo group can be accomplished with the aid of N N dicyclohexylcarbodiimide (DCCI)... 

These association reactions can be controlled. Acetone or acetonylacetone added to the solution of the polymeric electron acceptor prevents insolubilization, which takes place immediately upon the removal of the ketone. A second method of insolubiUzation control consists of blocking the carboxyl groups with inorganic cations, ie, the formation of the sodium or ammonium salt of poly(acryhc acid). Mixtures of poly(ethylene oxide) solutions with solutions of such salts can be precipitated by acidification. 

Acylation. A/-Acylation and related reactions ate brought about in straightforward ways with acyl chloride or acid anhydride, although the proximity of the carboxyl group may produce other reactions, eg, oxa2olinone formation, under some conditions. 

Esterification, Amidation, and Acid Chloride Formation. Amino acids undergo these common reactions of the carboxyl group with due regard for the need for A/-protection. 

Anhydride Formation. The carboxyl group ia A/-protected amino acids is converted iato the symmetrical anhydride on treatment with the carbodiimide (84). 

Carboxylic Acid Group. Reactions of the carboxyl group include decarboxylation, reduction to alcohols, and the formation of salts, acyl hahdes, amides, and esters. 

Generally, the carboxyl group is not readily reduced. Lithium aluminum hydride is one of the few reagents that can reduce these organic acids to alcohols. The scheme involves the formation of an alkoxide, which is hydroly2ed to the alcohol. Commercially, the alternative to direct reduction involves esterification of the acid followed by the reduction of the ester. 

During certain substitution reactions, the carboxyl group is often replaced by the entering group. An example is fuming nitric acid, which results in the formation of trinitrophenol. Another is the bromination of saUcyhc acid in aqueous solution to yield 2,4,6-tribromophenol [25376-38-9] (eq. 6). 

Reactions of the carboxyl group include salt and acid chloride formation, esterification, pyrolysis, reduction, and amide, nitrile, and amine formation. Salt formation occurs when the carboxyUc acid reacts with an alkaline substance (22)... 

Ring closure resulting from attack of a heteroatom on a carboxyl group or its equivalent is merely a case of intramolecular esterification or amide formation. The y-butyrolactones or pyrrolidones obtained from such reactions are usually regarded as the province of aliphatic chemistry, so only a few examples are offered by way of illustration in Scheme 15. 

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