Fluorine selenium

CHEMICAL PROPERTIES incompatible with strong acids, sulfur, Ni(NOj)2, wood and other combustibles reacts violently with titanium, ammonium nitrate, potassium perchlorate, potassium, performic acid, fluorine, selenium, sulfur, and sulfur compounds, hydrazine, ammonia, and hydrazoic acid... 

Physiological roles have also been demonstrated for a number of other trace elements, such as silicon, fluorine, selenium, chromium, nickel, tin and vanadium. The element, silicon, appears to have a structural function in some plants, notably in rice [70] and there is some evidence that it is... 

Both selenium hexafluoride and tellurium hexafluoride are more reactive than sulphur hexafluoride. Tellurium hexafluoride is slowly hydrolysed by water to telluric) VI) acid and on heating it decomposes to fluorine and the tetrafluoride. 

We also developed a number of other useful new fluorinating reagents. They ineluded a convenient in situ form of sulfur tetrafluoride in pyridinium polyhydrogen fluoride, selenium tetrafluoride, and ey-anurie fluoride. We introdueed uranium hexafluoride (UFg), depleted from the U-235 isotope, which is an abundant by-product of enrichment plants, as an effective fluorinating agent. 

Sihcon and boron bum ia fluorine forming siUcon tetrafluoride [7783-61-17, SiF, and boron trifluoride [7637-07-2] respectively. Selenium and tellurium form hexafluorides, whereas phosphoms forms tri- or pentafluorides. Fluorine reacts with the other halogens to form eight interhalogen compounds (see Fluorine compounds, inorganic-halogens). 

Under unusual circumstances, toxicity may arise from ingestion of excess amounts of minerals. This is uncommon except in the cases of fluorine, molybdenum, selenium, copper, iron, vanadium, and arsenic. Toxicosis may also result from exposure to industrial compounds containing various chemical forms of some of the minerals. Aspects of toxicity of essential elements have been pubhshed (161). 

Nitrogen and sodium do not react at any temperature under ordinary circumstances, but are reported to form the nitride or azide under the influence of an electric discharge (14,35). Sodium siHcide, NaSi, has been synthesized from the elements (36,37). When heated together, sodium and phosphoms form sodium phosphide, but in the presence of air with ignition sodium phosphate is formed. Sulfur, selenium, and tellurium form the sulfide, selenide, and teUuride, respectively. In vapor phase, sodium forms haHdes with all halogens (14). At room temperature, chlorine and bromine react rapidly with thin films of sodium (38), whereas fluorine and sodium ignite. Molten sodium ignites in chlorine and bums to sodium chloride (see Sodium COMPOUNDS, SODIUM HALIDES). 

Fluorine and selenium, in the form of a phenylselenenyl group, add to nucleophilic olefins with Markovnikov regioselectivity and anti stereoselectivity on reaction with several reagents that may form phenylselenenyl fluoride in situ [792, 193, 194] (equation 30)... 

Abundances of lUPAC (the International Union of Pure and Applied Chemistry). Their most recent recommendations are tabulated on the inside front fly sheet. From this it is clear that there is still a wide variation in the reliability of the data. The most accurately quoted value is that for fluorine which is known to better than I part in 38 million the least accurate is for boron (1 part in 1500, i.e. 7 parts in [O ). Apart from boron all values are reliable to better than 5 parts in [O and the majority arc reliable to better than I part in 10. For some elements (such as boron) the rather large uncertainty arises not because of experimental error, since the use of mass-spcctrometric measurements has yielded results of very high precision, but because the natural variation in the relative abundance of the 2 isotopes °B and "B results in a range of values of at least 0.003 about the quoted value of 10.811. By contrast, there is no known variation in isotopic abundances for elements such as selenium and osmium, but calibrated mass-spcctrometric data are not available, and the existence of 6 and 7 stable isotopes respectively for these elements makes high precision difficult to obtain they are thus prime candidates for improvement. 

The magnetic criterion is particularly valuable because it provides a basis for differentiating sharply between essentially ionic and essentially electron-pair bonds Experimental data have as yet been obtained for only a few of the interesting compounds, but these indicate that oxides and fluorides of most metals are ionic. Electron-pair bonds are formed by most of the transition elements with sulfur, selenium, tellurium, phosphorus, arsenic and antimony, as in the sulfide minerals (pyrite, molybdenite, skutterudite, etc.). The halogens other than fluorine form electron-pair bonds with metals of the palladium and platinum groups and sometimes, but not always, with iron-group metals. 

A selenium/phosphorus mixture incandesces, whereas fluorine causes selenium to combust at ambient temperature. 

Chromium trioxide Selenium Fluorine Non-metals Potassium bromate Non-metals Silver(I) oxide Non-metals Sodium peroxide Non-metals... 

Methylated organo-selenium has been determined by GC/MS or fluorine-induced chemiluminescence to determine DMSe, DMDSe, and DMSeS. This last compound, dimethyl selenenyl sulfide, was mistakenly identified as dimethyl selenone (CH3Se02CH3) in earlier work with bacteria.181,182 However, much recent work with many microorganisms have shown ample evidence of DMSeS production from Gram-negative bacteria,181,183 phototrophic bacteria,167,184 phytoplankton185 and in B. juncea detailed above. SPME with microwave-induce plasma atomic emission spectrometry was recently used to... 

As mentioned in the introduction, partially fluorinated compounds are highly useful, however methods for their synthesis are strictly limited in many cases. For example, nucleophilic substitution occurs with difficulty at the position a to a trifluoromethyl group due to its strong electron-withdrawing effect, although sulfur and selenium nucleophiles undergo such a substitution rather efficiently (Scheme 6.1). 

This review is conceived as a progress report. It includes only compounds of selenium and tellurium with the element directly bonded to fluorine. The chemical literature of the last 10 years, including 1979, has been searched thoroughly, and emphasis has been placed on facts rather than on interpretation. There are some earlier reviews covering the same area "Fluorine Compounds of Selenium and Tellurium 1970 (40), "Inorganic Selenium Chemistry 1975 (48), and "Inorganic Chemistry of Tellurium 1975 (53). 

Bis(pentafluoroselenium) oxide, F5SeOSeF5 (mp -82.1°C, bp 55.2°C), is produced besides F5SeOOSeF5 by the reaction of fluorine with selenium dioxide (141, 182). Bis(pentafluorotellurium) oxide, F5TeOTeF5 (mp - 36.6°C, bp 59.8°C) is prepared by the method shown in Eq. (22) (58). This compound has been obtained several times since 1933, but was always mistakenly characterized as Te2F10. The proposed existence of Te2F10, which in fact has not been prepared to date,... 

The essential microelements are only required in trace amounts (see also p.2). This group includes iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), cobalt (Co), chromium (Cr), selenium (Se), and molybdenum (Mo). Fluorine (F) is not essential for life, but does promote healthy bones and teeth. It is still a matter of controversy whether vanadium, nickel, tin, boron, and silicon also belong to the essential trace elements. 

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