Oxoacids anions

X-Ray diffraction studies of the oxoacid anions indicate the following probable arrangements for the acids ... 

The oxidative cleavage of an a-oxoacid is a major step in the metabolism of carbohydrates and of amino acids and is also a step in the citric acid cycle. In many bacteria and in eukaryotes the process depends upon both thiamin diphosphate and lipoic acid. The oxoacid anion is cleaved to form C02 and the remaining acyl group is combined with coenzyme A (Eq. 15-33). 

Sulfur forms many oxoacids, though few of them can be isolated in pure form. Most are prepared in aqueous solution or as crystalline salts of the corresponding oxoacid anions. Table 16.6.1 lists the common oxoacids of sulfur. 

Oxoacid anions. Although it is quite practical to treat oxygen in the same manner as ordinary ligands and use it in the naming of anions by coordination nomenclature, some names having the suffix -ite (indicating a lower-than-maximum oxidation state) are useful and therefore are still permitted. 

The names of oxoacids are simply related to those of the corresponding oxoanions. The -ate suffix of the anion is replaced by -ic in the acid. In a similar way, the suffix -ite is replaced by the suffix -ous. The prefixes per- and hypo- found in the name of the anion are retained in... 

An oxidizing acid is an oxoacid in which the anion is an oxidizing agent examples are HNOj and HCIO,. 

In solution this reaction is rather rapid but in the solid state autoxidation takes place much slower. Nevertheless, commercial sulfides and polysulfides of the alkali and alkali earth metals usually contain thiosulfate (and anions of other sulfur oxoacids) as impurities [6]. For all these reasons the chemistry of polysulfides is rather complex, and some of the earlier studies on polysulfides (prior to ca. 1960) are not very rehable experimentally and/or describe erroneous interpretations of the experimental results. 

The name of each oxoacid is based on the name of the polyatomic anion from which it forms, followed by the word acid. Review Table for the names of common polyatomic anions. 

An oxoacid that forms from a polyatomic anion whose name ends in -ate has a name ending in -ic. For example, HNO3 forms by adding a proton to the nitrate polyatomic anion, so HNO3 is nitric acid. Likewise, HCIO4 is perchloric acid from the perchlorate anion. 

Water is a proton donor and a proton acceptor. The sodium ion is neither an acid nor a base, so it is a spectator ion in this solution. Hypochlorite is the conjugate base of the weak oxoacid, HOCl. The OCr anion accepts a proton from a water molecule ... 

Pol /protic acids also show clearly the effect of charge on acidity. As mentioned earlier, the successive Za values for a pol /protic oxoacid decrease by approximately five orders of magnitude. The neutral parent acid always is a stronger acid than is the anion produced by removing one proton. 

The reduction of 2-oxoacids bound to different chiral auxiliaries gave the 2-hydroxyacid derivatives in a 64 to 76% yield and 42 to 86% de depending on solvent, proton donor, supporting electrolyte, temperature, and substituent R in the oxoacid. The results are in accordance with an ECE reduction of the 2-oxoamide to an enolate anion, which subsequently undergoes a face-selective protonation to the hydroxy acid [346, 347]. 

This system is additive and was developed originally to name coordination compounds, although it can be used in other circumstances when appropriate. For a discussion, see the Nomenclature of Inorganic Chemistry, Chapter 10. The compound to be named is considered as a central atom together with its ligands, and the name is developed by assembling the individual names of the constituents. This system has also been applied to name oxoacids and the related anions. Coordination names for oxoanions are cited in the examples throughout the text, and they are presented in detail in Section 4.4.5 (p. 69). 

The names of heteroatomic electronegative constituents generally take the anion ending -ate, which is also characteristic of the names of anions of oxoacids (sulfate, phosphate, nitrate, etc.). Many such anions are coordination compounds, and these names are assembled using the rules of coordination nomenclature (see Section 4.4, p. 51). 

A full list of permitted alternative names for oxoacids and derived anions can be found in [Table 1-4). 

The addition of an enolate anion to C02 to form a (3-oxoacid represents one of the commonest means of incorporation of C02 into organic compounds. The reverse reaction of decarboxylation is a major mechanism of biochemical formation of C02. The equilibrium constants usually favor decarboxylation but the cleavage of ATP can be coupled to drive carboxylation when it is needed, e.g., in photosynthesis. 

Decarboxylation of p-oxoacids. Beta-oxoacids such as oxaloacetic acid and acetoacetic acid are unstable, their decarboxylation being catalyzed by amines, metal ions, and other substances. Catalysis by amines depends upon Schiff base formation,232 while metal ions form chelates in which the metal assists in electron withdrawal to form an enolate anion.233 235... 

Names of monatomic anions end in -ide oxoanions are anions that contain oxygen. Oxoacids are molecular acids that contain oxygen. Within a series, the suffixes -ate and -ic acid indicate a greater number of oxygen atoms than the suffixes -ite and -ous acid. 

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