Orthotelluric acid

In the -1-6 oxidation state the oxoacids of 8e and Te show little resemblance to each other. H28e04 resembles H28O4 (p. 710) whereas orthotelluric acid Te(OH)g and polymetatelluric acid (H2Te04) are quite different. 

Te (tellurium, brown black, amorphous), Te02 (tellurous anhydride, white), Te02 hydr. (tellurous acid, H2Te03 or Te02-H20, white, amorphous), TeOs hydr. (orthotelluric acid, H6Te06 or Te03 3H20, colorless, cubic or monoclinic). 

Synonyms orthotelluric acid telluric (VI) acid hydrogen tellurate... 

Tellurium burns in air with a greenish-blue flame. The combustion product is dioxide, Te02, the most stable oxide of the metal. Tellurium also forms other oxides the monoxide, TeO, the trioxide, TeOs, and the pentoxide, Te205. Monoxide has not yet been obtained in solid form. Like sulfur and selenium, tellurium forms oxyacids. Such oxyacids include orthotelluric acid, HeTeOe and tellurous acid, H2Te03, in which the metal is in +6 and +4 valence states respectively. 

The higher sulfides of tellurium such as TeS2 and TeSs, are obtained from tellurite solutions by precipitation with hydrogen sulfide or sodium sulfide. Tellurium reacts with concentrated sulfuric acid to form red oxysulfide of the composition, TeSOs. With nitric acid, the metal is oxidized to dioxide, Te02. Oxidation of tellurium with chromic acid or potassium permanganate in nitric acid yields orthotelluric acid (HeTeOe). 

Tellurium Hexafluoride. Tellurium hexafluoride, TeF6 melts at —38° C and sublimes at —39° C, forming a colorless gas. It hydrolyzes slowly to orthotelluric acid and is reduced by tellurium to TeF4. 

The fact that the dihydrate in aqueous solution is a much weaker acid than sulphuric acid (see p. 385) may be cited as evidence that the two acids are materially different in nature, and this supports the view that the dihydrate in solution is actually orthotelluric acid. 

Orthotelluric acid, 3 145,147 Osmium compounds, nitrido, 6 204 Osmium (IV) oxide, formation of black, by ammonium hexa-bromoosmate(IV), 5 206 Osmium(VIII) oxide, precautions in using, 5 205... 

Tellurium compounds that do not have a tellurium-carbon bond but contain at least one carbon atom in the molecule, in which the tellurium atom is divalent, tetravalent, or hexavalent, have been prepared. The tellurium atom in these compounds is linked to carbon atoms via one or more heteroatoms such as B, Al, Si, Ge, Sn, Pb, P, As, S, Se, and Hg. The derivatives of divalent tellurium can be considered to be derived from the unknown telluroxylic acid (H2Te02), those of tetravalent tellurium from the unknown orthotellurous acid (H4Te04), and those of hexavalent tellurium from the well known orthotelluric acid (H6Te06). 

Compounds containing tetra valent tellurium in which the tellurium atom is bonded via one or more heteroatoms to at least one carbon atom, can formally be considered as condensation products formed from orthotellurous acid and compounds with one or two active hydrogen atoms in the molecule. 

The free orthotellurous acid is unknown. However, orthotellurous halides (tellurium tetrahalides), the mixed anhydrides derived from orthotellurous acid and hydrogen halides, are well known. 

This section presents the methods for the preparation of tetravalent tellurium compounds that fulfill the following conditions the tellurium atom is not directly bonded to a carbon atom and the molecule contains at least one carbon atom. These orthotellurous acid derivatives are arranged according to the groups in the periodic table to which the atom... 

Orthotelluric acid is a crystalline, well-characterized compound. All the hexavalent tellurium compounds discussed in this chapter are derivatives of orthotelluric acid. Telluric acid (H2Tc04), corresponding to sulfuric acid, is not known. Organic derivatives of such a telluric acid similar, for instance, to dimethyl sulfate, are also unknown. 

Hexamethoxy tellurium was prepared by the addition of orthotelluric acid to a solution of diazomethane in diethyl ether1,2. 

Orthotelluric acid, l,3-dihydrobenzo[c]tellurophene 1,1-diiodide, potassium O,O-dialkyl dithiophosphate, and triethylamine in dichloromethane were stirred for two hours. The resulting solution was poured into water to precipitate a white solid that was proven by X-ray crystallographic analysis to be an orthotellluric acid derivative4. 

SYNS ORTHOTELLURIC ACID TELLURATE TELLURIC(VI) ACID TELLURIUM HYDROXIDE... 

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