Of oxyacids

The kinetic behaviour of metal salts of oxyacids may be influenced by water of crystallization. Where complete-dehydration precedes decomposition, the anhydrous material is the product of a previous rate process and may have undergone recrystallization. If water is not effectively removed, there may at higher temperature be the transient formation of a melt prior to decomposition. The usual problems attend the identification of partial or transient liquefaction of the reactant in the mechanistic interpretation of kinetic data. 

Lipase-catalyzed polymerizahon of oxyacid esters was reported. PPL catalyzed the polymerizahon of methyl 6-hydroxyhexanoate. ° The polymer with DP up to 100 was synthesized by polymerization in hexane at 69°C for more than 50 days. The PPL-catalyzed polymerization of methyl 5-hydroxypentanoate for 60 days produced the polymer with DP of 29. Solvent effects were... 

Lipase-Catalyzed Polycondensation of Oxyacids and their Esters 243... 

To keep this review to a reasonable length we had to limit our discussions to reactions of only sulfur oxyacids and their anhydrides. While we have introduced, where pertinent to the topic under discussion, results from a number of studies involving other derivatives of oxyacids of sulfur, there has been extensive work on mechanism and reactivity in reactions of some sulfur oxyacid derivatives that we have not been able to include, but of which we feel the reader should at least be aware. We will therefore indicate briefly what some of these areas are and given some leading references, so that persons wishing to do so may explore these topics on their own. 

Chlorine forms a number of oxyacids. Which of the following is the correct order of increasing acid strength ... 

Au salts of oxyacids are rare, and when they do exist, they readily decompose. AuCN is stable and insoluble in HOH, but Au(CN)3 is unknown even though the complex Au(CN)4 can be prepared. 

More important for inorganic oxyacids is the number of oxygen atoms surrounding the central atom. Thus in the series of chlorine oxyacids. acid strength increases in the order HOCI < HOClO < H0C102 <- HOClOj. The trends in acidity of oxyacids, and even reasonably accurate predictions of their pKu values, can be obtained from 19... 

The literature on metal complexes of carbohydrates through 1965 has been fully reviewed by Rendleman (I), and we shall therefore only discuss recent work. We shall not discuss the complexes formed with strong bases, such as calcium and barium oxide these are salts in which the sugar acts as a weak acid, losing one or several protons. Nor shall we discuss the complexes formed with anions of oxyacids—e.g., borate, stannate, periodate, etc. ions all these are compounds formed by covalent bonds in alkaline solution. We are concerned only with complexes formed with cations in neutral aqueous solution there is no evidence for the formation of complexes between sugars and simple anions in neutral aqueous solution. (For an example of complex formation between a sugar derivative and chloride ion in chloroform solution, see Reference 3.)... 

It is generally true that for a series of oxyacids of the same element (e.g., HCIO4, HCIO3, HC102, and HOC1), the acid containing the element in the highest oxidation state will be the... 

Sulfur, selenium, and tellurium form a variety of oxyacids. Certain of these compounds and their derivatives are of great importance, with the most important of all these compounds being sulfuric acid. Because of the extraordinary significance of that compound, it will be described in more detail in a separate section. The major oxyacids of sulfur are shown in Table 15.6. Differences between the sulfur oxyacids and those of selenium and tellurium will be discussed later. 

A relatively large number of oxyacids of the halogens exist. Because of the extensive redox chemistry of these compounds, there is an enormous number of reactions involving them. We will give only an overview in keeping with the spirit and space requirements of this survey. 

Platinum and gold are regarded as unattackable metals because they are nearly always in the passive state. A gold anode dissolves in neutral or acid chloride solutions at very low c.d. s to form Au " + ions at a potential of about + 1.2 volts as the current is increased, however, the potential rises rapidly to + 1.7 volts, the electrode ceases to dissolve and chlorine is evolved instead. Platinum is actually less noble than gold, but it is rendered passive much more easily, especially in solutions of oxyacids if the electrolyte contains ammonia or hydrochloric acid, however, platinum suffers appreciable anodic attack, particularly if the metal is in a finely-divided form. 

A wide range of oxyacids is possible with more than one sulfur atom. Although the acids are not always very stable, the oxyanions are often more easily prepared. Many of these are likely intermediates in the oxidation of aqueous sulfites and occur at low concentration in water droplets in the atmosphere. Higher concentrations of sulfur oxyanions such as 8406, SsO , and S Ol can be found in mineralized acid-sulfate waters of volcanic crater lakes (e.g., Sriwana et al, 2000). 

In the series of oxyacids of chlorine, the acid strength in aqueous solution is in the order HCIO4 > HCIO3 > HCIO2 > HOCl... 

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