Oxoacid salts and other compounds

Jacobs and U. Metzner, Z anorg. allg. Chcm. S97, 97-J06 (1991). D. Mootz and H. Rutter, Z anorg. allg. Chetn, 608. 123-30(1992). 

The alkali metal hydroxides are also readily absorb CO2 and H2S to form carbonates (or hydrogencarbonates) and sulfides (or hydrogen-sulfides), and are extensively used to remove mercaptans from petroleum products. Amphoteric oxides such as those of Al, Zn, Sn and Pb react with MOH to form aluminates, zincates, stannates and plumbates, and even SiC 2 (and silicate glasses) are attacked. 

Production and uses of LiOH have already been discussed (p. 70). Huge tonnages of NaOH and KOH are produced by electrolysis of brine (pp. 71, 73) and the enormous industrial importance of these chemicals has already been alluded to. 

Many binary and pseudo-binary compounds of the alkali metals are more conveniently treated within the context of the chemistry of the other element and for this reason discussion Is deferred to later chapters, e.g. borides (p. 145), 

Lithium, Sodium, Potassium, Rubidium, Caesium and Francium 

25 and 7) but little detailed structural information is available. The anhydrous compounds all show the influence of oriented OH groups on the structure, and there is evidence of weak O—H - O bonding for KOH and RbOH. Melting points are substantially lower than those of the halides, decreasing from 47 TC for LiOH to 272° for CsOH, and the mp of the hydrates is even lower, e.g. 2.5°C (incongr.) for CSOH.2H2O and -5.5°C for the trihydrate. 

The alkali metal hydroxides are the most basic of all hydroxides. They react with acids to form salts and with alcohols to form alkoxides. The alkoxides are oligomeric and the degree of polymerization can vary depending on the particular metal and the state of aggregation. The ferr-butoxides, MOBu, (Bu = OCMej) can be considered as an example. Crystalline (KOBu )4 has a cubane-like structure and the tetramer persists in tetrahydrofuran solution and in the gas phase. - By contrast, (NaOBu )4 is exclusively tetrameric in thf, but is a mixture of hexamers and nonamers 

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Other oxoacid salts and binary compounds are more conveniently discussed under the chemistry of the appropriate non-metals in later chapters. 

Compounds of Tl have many similarities to those of the alkali metals TIOH is very soluble and is a strong base TI2CO3 is also soluble and resembles the corresponding Na and K compounds Tl forms colourless, well-crystallized salts of many oxoacids, and these tend to be anhydrous like those of the similarly sized Rb and Cs Tl salts of weak acids have a basic reaction in aqueous solution as a result of hydrolysis Tl forms polysulfldes (e.g. TI2S3) and polyiodides, etc. In other respects Tl resembles the more highly polarizing ion Ag+, e.g. in the colour and insolubility of its chromate, sulfide, arsenate and halides (except F), though it does not form ammine complexes in aqueous solution and its azide is not explosive. 

The oxide (p. 1209), chalcogenides (p. 1210) and halides (p. 1211) have already been described. Of them, the only ionic compound is HgF2 but other compounds in which there is appreciable charge separation are the hydrated salts of strong oxoacids, e.g. the nitrate, perchlorate, and sulfate. In aqueous solution such salts are extensively hydrolysed (HgO is only very weakly basic) and they require acidification to prevent the formation of polynuclear hydroxo-bridged species or the precipitation of basic salts such as Hg(OH)(N03) which contains infinite zigzag chains ... 

Oxygen has major uses in the chemical industry too. It is used to oxidize methane, ethylene, and other hydrocarbons. Oxidation of methane produces synthesis gas. Ethylene oxidation yields products such as ethylene oxide, acetaldehyde, and acetic acid. Oxygen also is used in making many commercial inorganic compounds including various metal oxides, oxoacids, and 0x0-salts. 

A process for the coproduction of acetic anhydride and acetic acid, which has been operated by BP Chemicals since 1988, uses a quaternary ammonium iodide salt in a role similar to that of Lil [8]. Beneficial effects on rhodium-complex-catalyzed methanol carbonylation have also been found for other additives. For example, phosphine oxides such as Ph3PO enable high catalyst rates at low water concentrations without compromising catalyst stability [40—42]. Similarly, iodocarbonyl complexes of ruthenium and osmium (as used to promote iridium systems, Section 3) are found to enhance the activity of a rhodium catalyst at low water concentrations [43,44]. Other compounds reported to have beneficial effects include phosphate salts [45], transition metal halide salts [46], and oxoacids and heteropolyacids and their salts [47]. 

The oxoacids of P are more numerous than those of any other element, and the number of oxoanions and oxo-salts is probably exceeded only by those of Si. Many are of great importance technologically and their derivatives are vitally involved in many biological processes (p. 528). Fortunately, the structural principles covering this extensive array of compounds are very simple and can be stated as follows ... 

A ternary compound consists of three elements. Ternary acids (oxoacids) are compounds of hydrogen, oxygen, and (usually) a nonmetal. Nonmetals that exhibit more than one oxidation state form more than one ternary acid. These ternary acids differ in the number of oxygen atoms they contain. The suffixes -ous and -ic following the stem name of the central element indicate lower and higher oxidation states, respectively. One common ternary acid of each nonmetal is (somewhat arbitrarily) designated as the -ic acid. That is, it is named by putting the element stem before the -ic suffix. The common ternary -ic acids are shown in Table 4-16. It is important to learn the names and formulas of these acids, because the names of all other ternary acids and salts are derived from them. There are no common -ic ternary acids for the omitted nonmetals. 

The majority of acids are ternary compounds. They contain three different elements—hydrogen and two other nonmetals. If one of the nonmetals is oxygen, the acid is called an oxoacid. Think of oxoacids as combinations of hydrogen ions (H ) and oxoanions. The scheme for naming oxoacids is similar to that outlined for oxoanions, except that the ending -ous is used instead of -ite and -ic instead of -ate. Several oxoacids are listed in Table 3.6. Also listed are the names and formulas of compounds in which the hydrogen of the oxoacid has been replaced by a metal, such as sodium. These compounds are called salts we will say much more about them in later chapters, beginning in Chapter 5. Acids are molecular compounds, and salts are ionic compoimds. 

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