Reaction with carboxylate ions

Figure 2 Basal spacings of basic copper acetate after reaction with carboxylate ions with different niunber of carbon atoms (n) in the alkyl chains . (Reproduced with permission of Elsevier Science Publishers, B. V.)...

Reaction of carboxylate ion with nitrophenyl sulfites gives the carboxylate -nitrophenyl esters. If the -nitrophenyl sulfite is unsymmethcal (02NCgH40S(0)0R, where R is ethyl or phenyl), carboxylate attacks the -nitrophenyl side (69). Some amino acids react with methyl and benzyl sulfites in the presence of -toluenesulfonic acid to give methyl and benzyl esters of the amino acids as -toluenesulfonate salts (70). With alcohols, the conversion of henzil to a monoacetal upon addition of sulfuric acid to the henzil in methanol and dimethyl sulfite proceeds in high yield (71). 

The haloalkane dehydrogenase is believed to act by using one of its side-chain carboxylates to displace chloride by an Sn2 mechanism. (Recall the reaction of carboxylate ions with alkyl halides from Table 8.1.)... 

B Castro, J-R Dormoy, G Evin, C Selve. Peptide coupling reagents. Part VII. Mechanism of the formation of active esters of hydroxybenzotriazole in the reaction of carboxylate ions on the BOP reagent for peptide coupling. A comparison with Itoh s reagent. J Chem Res (S) 82, 1977. 

The value of = 1 X 10 s for the first-order rate constant for collapse of an ion pair between Me-4 and pentaflourobenzoate ion is larger than the second-order rate constant rcoo = 5x10 M s reported for the bimolecular addition of alkane carboxylates to Me-4. This second-order rate constant is limited by the rate constant for formation of an ion pair between Me-4 and a carboxylate ion. The larger barrier to encounter-limited reactions of carboxylate ions compared with the diffusion-limited reactions of anions such as azide ion, = 5 X 10 represents the barrier to desolvation of nucleophile that must precede formation of an ion pair between Me-4 and a carboxylate ion (Scheme 13). ... 

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. 

Kinetic data show that in seawater medium S42 reacts about 20-30 times faster than HS with acrylic acid, whereas the reaction of S42 with acrylonitrile is only about 4-6 times higher than with HS. However, in any environment, the importance of polysulfide versus bisulfide reactions is also dependent on their relative concentrations. In a situation where polysulfide and bisulfide ions are present in similar concentrations, our results imply that polysulfide ions, rather than bisulfide, are the important sulfur nucleophiles for reactions with activated unsaturated molecules having a terminal carboxyl group (e.g. acrylic acid, cinnamic acid). However, for neutral molecules such as fucoxanthin, in addition to polysulfide ions, reactions with bisulfide ions will also be of importance. 

The establishment of the main features of the reactions of carboxylate ions with 3-unsubstituted isoxazolium salts is fully described in the classic paper by Woodward and Olofson.165 A generalized reaction scheme is shown as Scheme 10. Deprotonation at the 3-position is rapidly followed (or more probably accompanied) by ring opening to give the ketoketenimine (54). Ketoketenimines have been detected spectroscopically and are sufficiently stable for isolation in some cases.166,167 Reaction of carboxylic acid... 

Oxidation of C—bonds by copper ion catalyzed reaction with an organic peroxy ester (the Kha-rasch-Sosnovsky reaction) was at one time very popular for allylic oxidation and has been thoroughly reviewed. The reaction is usually carried out by dropwise addition of peroxy ester (conunonly r-butyl peracetate or r-butyl perbenzoate) to a stirred mixture of substrate and copper salt (0.1 mol % commonly copper(I) chloride or bromide) in an inert solvent at mildly elevated temperature (60-120 C). The mechanism involves three steps (i) generation of an alkoxy radical (ii) hyttogen atom abstractitm and (iii) radical oxidation and reaction with carboxylate anion (Scheme 11). 

It is also discussed in the literature that, under moist conditions, basic complexes can be formed by reaction of zinc phosphate with inorganic ions or with carboxylic groups of the resin used, which lead, by reaction with metal ions, to so-called adhesion, cross-linking and inhibitor complexes [5.67-5.69]. Under the assumption, that the hydrolyzation process is the prerequisite for the effectiveness of zinc phosphates, this means that such pigments need a certain time before becoming active [5.69]. 

The Bronsted relation is accurately obeyed for the individual ketones in Table 2 with carboxylate ions as catalysts. However, the trend of j3 with reactivity implies that if one ketone could be studied over a wide range of catalyst strength, the Bronsted plot would be curved and the Bronsted exponent would vary. Proton transfer from acetylacetone [17] has been studied with bases covering a pK range of ca. 15 units using the temperature-jump method. The values of fef and kr for reaction between acetylacetone and carboxylate ions, phenolate ions, hydroxide ion, and water are shown in Fig. 3. The data refer to reaction (72)... 

Although the hydrolysis of alkyl halides to alcohols has been extensively investigated, an alternative two-step sequence involving substitution with carboxylate ion is more practical for the preparation of alcohols. Activation of the carboxylate anion prepared by the reaction of the acid with a base can be achieved (i) by use of a polar aprotic solvent and (ii) by use of aprotic apolar solvents under phase transfer catalysis, polymer conditions, or with crown ethers. 

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