Tellurium Dioxide TeO

The pure form of tellurium burns with a blue flame and forms tellurium dioxide (TeO ). It is brittle and is a poor conductor of electricity. It reacts with the halogens of group 17, but not with many metals. When it reacts with gold, it forms gold telluride. Tellurium is insoluble in water but readily reacts with nitric acid to produce tellurous acid. If inhaled, it produces a garlic-like odor on one s breath. 

Tellurium dioxide (TeO ) is a whitish crystalline powder that is slightly soluble in water. It is also toxic when inhaled. 

Figure 2.4 An acousto-optic tunable filter (a) tellurium dioxide (TeO,) crystal, (b) incident or input beam, (c) acoustic transducer, (d) rf input, (e) monochromatic light (ordinary beam), (f) nonscattered light beam, (g) monochromatic light (extraordinary beam), and (h) acoustic wave absorber.

Tellurium. Dioxide as a Base.—Tellurium dioxide possesses definite basic tendencies, the tellurium being capable of acting as a quadrivalent atom and the group TeO, tclluryl, as a bivalent basic radical. 

TeOs, tellurium dioxide TeCl4, tellurium tetrachloride... 

The additions of tellurium tetrahalides to olefins in the presence of alcohols proceed equally well when the tetrahalides are generated in the reaction mixture from tellurium dioxide and chlorotrimethylsilane in methanoP or concentrated hydrochloric acid/methanol. trans-2-Methoxycyclohexyl tellurium trichloride was obtained in this manner in quantitative yield . In the reactions of terminal alkenes, the TeCl3 group (from TeO and concentrated hydrochloric acid) added according to the Markovnikov rule producing 2-alkoxy-1 -alkyl tellurium trichlorides. The trichlorides were not isolated but were reduced with disodium disulfite to the ditellurium compounds, which, in turn, were converted to the tellurium trichlorides by treatment with sulfuryl chlorides. For data on these tellurium trichlorides see p. 316. The overall yields range from 15 to 70%. 

Tellurium monoxide, TeO, is obtained by heating TeSOj in a vacuum to 230°, sulfur dioxide being evolved. It is amorphous, brown to black in color, and is easily oxidized. 

Tellurium trioxide, TeOs, is made by carefully heating H2TeO< to a red heat. It is an orange-yellow crystalline substance, sparingly soluble in water, and easily decomposed by heat, forming the dioxide and oxygen. 

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. 

Tellurium is converted into the dioxide, Te02, by nitric acid. Like sulphur and selenium, it forms two anions, the tellurite, TeOf, and the tellurate, TeO -. 

Oxygen forms three oxides, TeO, Te02, and TeOj. The first two are somewhat basic in nature and are represented by numerous salts in which tellurium is bivalent or quadrivalent, respectively. The dioxide and the trioxide are both mainly acidic in character, although a few hexavalent salts of tellurium are known. 

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