Selenium IV Oxychloride

SeOj + 2HCl- Se02 2HCl SeOs 2HC1 + H2SO4 SeOClj + HjSOvHjO 

Submitted by G. B. L. Smith and Julius Jackson Checked by J. J. Pitha and Va Blanchard  

Selenium(IV) oxychloride was syntheazed first by Weber in 1859 by heating together the vapors of selenium(IV) oxide and selenium (IV) chloride. It was later prepared by Michaelis by the interaction of selenium(IV) oxide and phosphorus(V) chloride. Cameron and Macallam allowed a mixture of selenium(IV) oxide and sodium chloride to interact and obtained sodium selenite and selenium(IV) oxychloride. 

The classical researches of Victor Lenher on selenium(IV) oxychloride (reviewed by Smith ) were begun about 1919 at the University of Wisconsin. Lenher suggested the following practical laboratory methods for the preparation of selenium(IV) oxychloride (1) union of selenium(IV) oxide and selenium(IV) chloride (2) partial hydrolysis of sele-nium(IV) chloride, and (3) dehydration of Se02 2HCl (dichloroselenious acid, H2Se02Cl2).  

I Kedrie Chemical Laboratories, Michigan State College, East Lansing, Mich. 

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Selenium(IV) oxychloride, 3 130 Selenium (II) xanthates, 4 91 Selenocyanates, metal, 2 186, 188 Shaking apparatus, for keeping... 

ROH -> RCl. Chlorotrimethylsilane itself does not convert alcohols into alkyl chlorides, but this conversion proceeds readily in the presence of Se02. The actual reagent is believed to be selenium(IV) oxychloride, SeOCl2, which can be isolated in 74% yield from the reaction of SeO, with ClSi(CH,),. 

Transfer of Selenium(IV) Oxychloride. Since the pure substance is very hygroscopic, special precautions must be... 

Pure selenium(IV) oxychloride melts at 10.9 to 11° and boils at 177.2° (744 mm.). It has a high dielectric constant (about 55 at 25°)and is therefore an interesting nonprotonic solvent in which a wide variety of reactions may be caused to take place. The specific conductance of selenium(IV) oxychloride is also high (2.0 X lO" mho at 25°), in which respect it is similar to sulfuric acid, and this property is probably related to the fact that these solvents are powerful solvolyzing agents. It presumably undergoes autoionization in accordance with the equation ... 

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