The hydrogen selenium or hydrogen selenide is an inorganic compound whose chemical formula is HtwoI know. It is covalent in nature, and under ordinary conditions of temperature and pressure it is a colorless gas; but with a strong smell recognizable at its slightest presence. Chemically, it is a chalcogenide, so selenium has a valence of -2 (Setwo-).
Of all the selenides, the HtwoIt is the most toxic because its molecule is small and its selenium atom has less steric hindrance when reacting. On the other hand, its odor allows those who work with it to detect it on the spot in the event of a leak outside the laboratory hood..
Hydrogen selenide can be synthesized by the direct combination of its two elements: molecular hydrogen, Htwo, and metallic selenium. It can also be obtained by dissolving selenium-rich compounds, such as iron (II) selenide, FeSe, in hydrochloric acid..
On the other hand, hydrogen selenide is prepared by dissolving hydrogen selenide in water; that is, the first is dissolved in water, while the second consists of gaseous molecules.
Its main use is to be a source of selenium in organic and inorganic synthesis.
Article index
In the upper image it is observed that the molecule of HtwoIt is of angular geometry, although its angle of 91 ° makes it look more like an L than a V. In this model of spheres and rods, the hydrogen and selenium atoms are the white and yellow spheres. respectively.
This molecule, as shown, is the one in the gas phase; that is, for hydrogen selenide. When dissolved in water, it releases a proton and in solution we have the pair HSe- H3OR+; this pair of ions comes to hydrogen selenide, denoted as HtwoSe (ac) to differentiate it from hydrogen selenide, HtwoSe (g).
Therefore, the structures between the HtwoSe (ac) and HtwoSe (g) are very different; the first is surrounded by an aqueous sphere and has ionic charges, and the second consists of an agglomerate of molecules in the gas phase.
Molecules of HtwoThey can barely interact with each other by very weak dipole-dipole forces. Selenium, although it is less electronegative than sulfur, concentrates a higher electron density by "taking it away" from the hydrogen atoms..
If the molecules of HtwoThey are subjected to extraordinary pressure (hundreds of GPa), theoretically they are forced to solidify through the formation of Se-H-Se bonds; These are bonds of three centers and two electrons (3c-2e) where hydrogen participates. Therefore, the molecules begin to form polymeric structures that define a solid..
Under these conditions, the solid can be enriched with more hydrogen, which completely modifies the resulting structures. In addition, the composition becomes type HnSe, where n varies from 3 to 6. Thus, selenium hydrides compressed by these pressures, and in the presence of hydrogen, have chemical formulas H3Se to H6I know.
These hydrogen-enriched selenium hydrides are estimated to have superconducting properties.
Colorless gas that at low temperatures smells like rotten radish and rotten eggs if its concentration increases. Its smell is worse and more intense than that of hydrogen sulfide (which is already quite unpleasant). However, this is a good thing, as it helps its easy detection and reduces the risks of prolonged contact or inhalation..
When it burns, it gives off a bluish flame as a result of the electronic interactions in the selenium atoms..
80.98 g / mol.
-41 ° C.
-66 ° C.
9.5 atm at 21 ° C.
3,553 g / L.
3.89.
0.70 g / 100 mL. This corroborates the fact that the selenium atom of HtwoCannot form appreciable hydrogen bonds with water molecules.
-Soluble in CStwo, which is not surprising because of the chemical analogy between selenium and sulfur.
-Soluble in phosgene (at low temperatures, as it boils at 8 ° C).
As already explained in previous sections, the name of this compound varies depending on whether HtwoIt is in the gaseous phase or dissolved in water. When it is in water, it speaks of selenhydric acid, which is nothing more than a hydracid in inorganic terms. Unlike gaseous molecules, its acid character is greater.
However, whether as a gas or dissolved in water, the selenium atom maintains the same electronic characteristics; for example, its valence is -2, unless it undergoes an oxidation reaction. This valence of -2 is the reason why it is called seleniaurochs hydrogen, since the selenide anion is Setwo-; which is more reactive and reducing than Stwo-, sulfide.
If systematic nomenclature is used, the number of hydrogen atoms in the compound has to be specified. Thus, the HtwoIt's called: selenide gavehydrogen.
Some sources refer to it as a hydride. If it really were, selenium would have a positive charge of +2, and hydrogen would have a negative charge of -1: SeHtwo (I knowtwo+, H-). Selenium is a more electronegative atom than hydrogen, and therefore ends up “hoarding” the highest electron density in the H moleculetwoI know.
However, as such the existence of selenium hydride cannot be theoretically ruled out. In fact, with the presence of the anions H- It would facilitate the Se-H-Se bonds, responsible for the solid structures formed at enormous pressures according to computational studies.
Although it seems contradictory, despite the great toxicity of HtwoIt is produced in the body in the metabolic pathway of selenium. However, as soon as it is produced, cells use it as an intermediate in the synthesis of selenoproteins, or it ends up being methylated and excreted; one of the symptoms of this is the taste of garlic in the mouth.
The HtwoIt is used mainly to add selenium atoms to solid structures, such as semiconductor materials; to organic molecules, such as alkenes and nitriles for the synthesis of organic selenides; or to a solution to precipitate metal selenides.
Yet No Comments