The special compounds They are all those made up of the covalent hydrides of the carbonoids and nitrogenoids. These are compounds with the formula EH4, for carbonids or group 14 elements, or formula EH3 for nitrogenoids or elements of group 15.
The reason why some chemists refer to these hydrides as special compounds is not very clear; this name can be relative although, ignoring that among them is not the HtwoOr, some are very unstable and rare, so they might be worthy of such a qualifier..
Two molecules of EH hydrides are shown in the upper image.4 (left) and EH3 (right) with a model of spheres and bars. Note that the hydrides EH4 are tetrahedral, while EH3 have trigonal pyramid geometry, with a pair of electrons above the central atom E.
As you go down groups 14 and 15, the central atom grows and the molecule becomes heavier and more unstable; since the E-H bonds are weakened by the poor overlap of their orbitals. The heavier hydrides are perhaps the true special compounds, while CH4, for example, it is quite abundant in nature.
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By dividing the special compounds into two defined groups of covalent hydrides, a brief description of their characteristics will be given separately..
As mentioned at the beginning, your formulas are EH4 and consist of tetrahedral molecules. The simplest of these hydrides is CH4, which ironically is also classified as a hydrocarbon. The most important thing about this molecule is the relative stability of its C-H bonds..
Also, the C-C bonds are very strong, causing the CH4 can be concatenated to originate the family of hydrocarbons. In this way, C-C chains of great lengths and with many C-H bonds arise..
Not the same with its heavier counterparts. The SiH4, for example, it has very unstable Si-H bonds, which makes this gas a more reactive compound than hydrogen itself. In addition, their concatenations are not very efficient or stable, originating Si-Si chains of only ten atoms at most..
Such concatenation products include hexahydrides, EtwoH6: CtwoH6 (ethane), YestwoH6 (disilane), GetwoH6 (digestive), and SntwoH6 (diestannan).
The other hydrides: GeH4, SnH4 and PbH4 They are even more unstable and explosive gases, of which their reducing action is taken advantage of. Al PbH4 it is considered as a theoretical compound, since it is so reactive that it has not been able to be obtained properly.
On the side of nitrogen hydrides or group 15, we find the trigonal pyramid molecules EH3. These compounds are also gaseous, unstable, colorless, and toxic; but more versatile and useful than HD4.
For example, NH3, The simplest of them is one of the most industrially produced chemical compounds, and its unpleasant smell characterizes it very well. The PH3 meanwhile it smells of garlic and fish, and the AsH3 smells like rotten eggs.
All EH molecules3 they are basic; but the NH3 is crowned in this characteristic, being the strongest base due to the higher electronegativity and electron density of nitrogen.
NH3 can also be concatenated, like CH4, only to a much lesser degree; hydrazine, NtwoH4 (HtwoN-NHtwo), and the triazane, N3H5 (HtwoN-NH-NHtwo), are examples of compounds caused by the concatenation of nitrogen.
Similarly the hydrides PH3 and AsH3 are concatenated to originate PtwoH4 (HtwoP-PHtwo), and AstwoH4 (HtwoAs-AsHtwo), respectively.
To name these special compounds, two nomenclatures are used most of the time: the traditional and the IUPAC. The hydrides EH will be broken down below4 and eh3 with their respective formulas and names.
- CH4: methane.
- Yes H4: silane.
- GeH4: German.
- SnH4: stannan.
- PbH4: plumbano.
- NH3: ammonia (traditional), azano (IUPAC).
- PH3: phosphine, phosphane.
- AsH3: arsine, arsano.
- SbH3: stibnite, stiban.
- BiH3: bismutin, bismutane.
Of course, the systematic and stock nomenclatures can also be used. In the first, the number of hydrogen atoms is specified with the Greek prefixes di, tri, tetra, etc. The CH4 It would come to be called according to this nomenclature carbon tetrahydride. While according to the stock nomenclature, the CH4 would be called carbon (IV) hydride.
Each of these special compounds presents multiple methods of preparation, either on industrial scales, laboratory, and even in biological processes..
Methane is formed by various biological phenomena where high pressures and temperatures fragment hydrocarbons of higher molecular masses..
It accumulates in huge pockets of gases in equilibrium with oil. Also, deep in the Arctic it remains encased in ice crystals called clathrates..
Silane is less abundant, and one of the many methods by which it is produced is represented by the following chemical equation:
6Htwo(g) + 3SiOtwo(g) + 4Al (s) → 3SiH4(g) + 2AltwoOR3(s)
Regarding GeH4, It is synthesized at the laboratory level according to the following chemical equations:
NatwoGeo3 + NaBH4 + HtwoO → GeH4 + 2 NaOH + NaBOtwo
And the SnH4 forms when reacts with KAlH4 in a tetrahydrofuran (THF) medium.
Ammonia, like CH4, it can form in nature, especially in outer space in the form of crystals. The main process by which NH is obtained3 is by means of the Haber-Bosch, represented by the following chemical equation:
3 Htwo(g) + Ntwo(g) → 2 NH3(g)
The process involves the use of high temperatures and pressures, as well as catalysts to promote the formation of NH3.
Phosphine is formed when white phosphorus is treated with potassium hydroxide:
3 KOH + P4 + 3 HtwoO → 3 KHtwoPOtwo + PH3
Arsine is formed when its metal arsenides react with acids, or when an arsenic salt is treated with sodium borohydride:
Na3As + 3 HBr → AsH3 + 3 NaBr
4 AsCl3 + 3 NaBH4 → 4 AsH3 + 3 NaCl + 3 BCl3
And bismuthin when methylbismuthin is disproportionate:
3 BiHtwoCH3 → 2 BiH3 + Bi (CH3)3
Finally, some of the many uses of these special compounds are mentioned:
- Methane is a fossil fuel used as cooking gas.
- Silane is used in organic synthesis of organosilicon compounds by adding to the double bonds of alkenes and / or alkynes. Likewise, silicon can be deposited from it during the manufacture of semiconductors..
- Like the SiH4, Germanic is also used to add Ge atoms as films in semiconductors. The same applies for stibnite, adding Sb atoms on silicon surfaces by electrodeposition of its vapors..
- Hydrazine has been used as rocket fuel and to extract precious metals.
- Ammonia is destined for the fertilizer and pharmaceutical industry. It is practically a reactive source of nitrogen, allowing the addition of N atoms to an infinity of compounds (amination).
- Arsine came to be considered a chemical weapon during World War II, leaving the infamous phosgene gas, COCl, in its place.two.
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