Selenous add

Xenon (II) Pentafluoroorthoselenate. Xe[Fj SeO] 2 mw 512.20 bright yel cryst mp 130° (decompn). Sol in acetonitrile and C tetrachloride. Prepn is by treating Xe difluoride with 2 moles of anhydr selenic add. The compd reacts explosively with oxidizeable substances Ref K. Seppert, Ang Chem (Intml Edn Engl) 11, 7234 (1972)... 

Vanadium pentoxide and selenous add condense together to form a large number of complex vanadoselenites which are described on p. 89. 

The reaction requires dissolution of Au metal, because no readion occurs in the absence of selenic add when the readion is conduded with colloidal Au metal in concentrated sulfuric add as solvent. Consistently, control readions show that Au metal is readily dissolved by 3 M selenic add in 96 % sulfuric add as solvent at temperatures below 180 °C. 

Hydrogen sulphide no precipitation occurs. If the solution is boiled with concentrated hydrochloric acid, the selenic add is reduced to selenious acid hydrogen sulphide then precipitates a mixture of selenium and sulphur. 

Using Procedure I, 1 y Te may be detected in the presence of 500 times the amount of selenium (as selenic acid). Selenious acid interferes with the tellurium test, so that any selenite present must be oxidized to selenate (by bromine) before the reaction. Using Procedure II, 2.5 y Te may be detected in the presence of 20,000 times the amoxmt of Se (as selenic add). 

On the basis of the discussion of the relative strengths of the oxoadds given in Chapter 11, would you expect sulfurous or selenous add to be the stronger acid Briefly rationalize your answer. 

The ease with which the dipolarophile interacts with vinylacetylenes depends mainly on a spatial factor. The study of the reactions of alkylthiobuten-3-ynones-l and their selenic and telluric analogs with DPNT shows that, in this case, nitrilimine also acts as a nucleophilic agent with a nucleophilic center on the carbon atom of the 1,3-dipole and always adds to the terminal carbon of the enyne system to form l,3-diphenyl-5-/ -2-pyrazolenines. The oxidation of the latter with chloranil leads to alkynylpyrazoles (65ZOR51). 

Let us add here that despite the general similarities of selenium and sulfur in their chemical properties, the chemistry of selenium differs from that of sulfur in two important aspects their oxoanions are not similarly reduced, and their hydrides have different acid strengths. For example, Se(-HlV) tends to undergo reduction to Se(-II), whereas S(-hIV) tends to undergo oxidation. This difference is evidenced by the ability of selenous acid to oxidize sulftirous acid ... 

Add potassium permanganate and dichromate solutions respectively to two test tubes containing selenous acid solutions acidified with sulphuric acid. Heat the contents of the test tubes. What do you observe Write the equations of the reactions. What properties does selenous acid exhibit in this case ... 

Zinc forms a wide variety of other salts, many by reaction with the adds, though some can only be obtained by fusing the oxides together. The salts include arsenates (ortho, pyro, and meta), the borate, bromate, chlorate, chlorite, various chromates, cyanide, iodate. various periodates, permanganate, phosphates (ortho, pyro, meta, various double phosphates 1. die selenate, selenites, various silicates, fluosilicate. sulfate, sulfite, and duocyanate. 

Homopropargylic alcohols are readily available substrates that can be used for the synthesis of 7-lactones. Cul-catalyzed selenation with PhSeBr at the alkyne terminus affords alkynyl aryl selenides. These react with an excess of /i-toluenesulfonic acid monohydrate, in dichloromethane at 60°C, to form a selenium-stabilized vinyl cation intermediate. The cation is then intramolecularly trapped by the tethered hydroxyl group to afford a cyclic selenoketene acetal, which readily adds a molecule of water to give the 7-lactone products (Scheme 55) <2006SL587>. 

This limitation can be overcome using the anion of alkyl phenyl selenoxides which add to ketones and rearrange in situ (equation 34).The amalgam reduction is required to remove the small amount of a-phenyl selenated ketones formed in the reaction. 

The correlation of the shape of uptake curves with pK i (sigmoidal uptake curves for relatively strong acids, uptake curves with a maximum for very weak acids) is limited, e.g. selenic IV acid (sigmoidal curves with a few exceptions) is weaker than arsenic V or phosphoric add (for which adsorption maxima are often observed). The discrepancies in sorption behavior of anions can be due to dissolution of the adsorbents. 

Selenic aeid, H2ScO<, is formed by the oxidation of selenious acid by such reagents as potassium permanganate, chlorine, or bromine. The best method of preparing pure selenic acid is to add pure bromine to Ag2Se02, filter off AgBr, and warm to remove bromine and water. Add H2S to remove H2SeO and filter off the precipitated S and Se. The water solution of selenic acid can be concentrated somewhat at ordinary pressures,... 

Since the original description of Detrisac et al. [46] a 1 1 mixture of DMEM and HAMF12, supplemented with hydrocortisone, triiodothyronine, insulin, transferrin and selenate (currently known as K1 medium) [51], has been the most widely used medium in human (proximal) tubular epithelial cell culture. Several authors add serum because of its growth promoting effect. 

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