Potassium compounds with oxygen

Potassium foms two compounds with oxygen, a protoxide KO, and a peroxide KO,. 

The principal product of the reaction of the alkali metals with oxygen varies systematically down the group (Fig. 14.15). Ionic compounds formed from cations and anions of similar radius are commonly found to he more stable than those formed from ions with markedly different radii. Such is the case here. Lithium forms mainly the oxide, Li20. Sodium, which has a larger cation, forms predominantly the very pale yellow sodium peroxide, Na202. Potassium, with an even bigger cation, forms mainly the superoxide, K02, which contains the superoxide ion, O,. ... 

Silicon w is first isolated and described as an element in 1824 by Jdns Jacob Berzelius, a Swedish chemist. Silicon does not occur uncombined in nature, i.e.- as an element. It is found in practically aU rocks as well as in sand, clays, and soils, combined either with oxygen as silica (Si02= silicon dioxide) or with oxygen plus other elements (e.g., aliuninum, mcignesium, calcium, sodium, potassium, or iron) as silicates. Its compounds also occur in all natural waters, in the atmosphere (as siliceous dust), in many plants, and in the skeletons, tissues, and body fluids of some animals. 

Zirconium reduces almost all oxygen-containing salts. This is the case for alkali hydroxides (accidents with the lithium, sodium and potassium compounds) and zirconium hydroxide, lithium, sodium and potassium carbonates, alkaline sulphates sodium tetraborate and copper (II) oxide. This is true especially for oxidising salts such as alkaline chromates and dichromates, chlorates (accident with potassium salt) and nitrates (accident with potassium salt). 

Certain Schiff bases, i.e. 122, were synthesized as model compounds for Latia luciferin. This compound exhibits strong blue chemiluminescence ( max 385 nm) on oxidation with oxygen in DMSO/potassium t.-butylate, the main products being acetone and 2-formamido pyridine 124. The mechanism suggested by Me Capra and Wrigglesworth includes the concerted bond cleavage of a dioxetane derivative 123. 

The strong preference for oxygen over carbon as a donor atom is shown by the rapid decomposition in water of most compounds with a covalent M—C bond or an ionic M+. .. C- interaction. The effect of the differences in electronegativity is shown in the structures of methyl lithium and methyl potassium. The methyl lithium tetramer, (39), has a cubane ... 

Hexacyanoferric(II) acid, ferrocyanic acid or tetrahydrogen hexakis(cyanate-(4-)) [17126-47-5] is used to prepare many adducts with oxygen-containing organics. Also addition compounds with inorganic salts are known. This acid may be obtained as a white precipitate upon addition of potassium ferrocyanide to concentrated hydrochloric acid ... 

A compound with half of the u.3-Se replaced by fi3- has been obtained in the preceding reaction as another product (121). This is formulated as K2Mo3Se12 5O0 5 and is the first example of the Mo3 cluster compound with a /li3- ligand. The cluster is more closely packed than the ammonium salt because of the smaller size of potassium ion and the replacement of half the /n3-Se atoms by smaller oxygen atoms. 

As noted earlier, the similarities between H+ and alkali metal cations have led to the use of the former as a probe in biological studies, including studies with various macrocydic ligands, especially those with oxygen donor atoms. The thallium(I) cryptates behave kinetically like the potassium compounds, and the binding constants to 18-crown-6 have been measured by 205T1 NMR methods.347 Several Tl1 compounds with crown ethers (L) have been prepared in... 

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