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Ketones with two available α-methylene positions react more quickly at the least hindered position.: [1] Allylic oxidation can be predicted by the substitution pattern on the olefin. In the case of 1,2-disubstituted olefins, reaction rates follow CH > CH 2 > CH 3: Geminally-substituted olefins react in the same order of reaction rates as above ...
Some selenium-containing heterocycles exhibit antiinflammatory and antitumor activity, among other medicinal uses. Using selenourea as a precursor is considered to be the most efficient means of selenium-containing heterocyclic synthesis. [9] Another class of reactions is the complexation of selenourea with transition metals and metalloids.
Selenium is found in metal sulfide ores, where it substitutes for sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores. Minerals that are pure selenide or selenate compounds are rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells.
Selenium, like manganese, can be used in small concentrations to decolorize glass, or in higher concentrations to impart a reddish color, caused by selenium nanoparticles dispersed in glass. It is a very important agent to make pink and red glass. When used together with cadmium sulfide, [9] it yields a brilliant red color known as "Selenium Ruby".
Selenium compounds are compounds containing the element selenium (Se). Among these compounds, selenium has various oxidation states , the most common ones being −2, +4, and +6. Selenium compounds exist in nature in the form of various minerals, such as clausthalite , guanajuatite , tiemannite , crookesite etc., and can also coexist with ...
Selenium is toxic in high concentrations. As sodium selenite, the chronic toxic dose for human beings was described as about 2.4 to 3 milligrams of selenium per day. [7] In 2000, the US Institute of Medicine set the adult Tolerable upper intake levels (UL) for selenium from all sources - food, drinking water and dietary supplements - at 400 μg/day. [8]
Gpx1, Gpx2, Gpx3, and Gpx4 have been shown to be selenium-containing enzymes, whereas Gpx6 is a selenoprotein in humans with cysteine-containing homologues in rodents. Amyloid beta, when bound to heme, has been shown to have peroxidase activity. [2] A typical group of peroxidases are the haloperoxidases. This group is able to form reactive ...
Hydroxy, thiol, carboxylic acid, primary and secondary amine functional groups cannot be used with phosphonites in the reaction as they all react with the phosphonite. [5] Phosphinites are the most reactive class of reagents used in this reaction. They react to produce phosphine oxides.