Methane, silane, and germane, three simple group 14 hydrides
Group 14 hydrides are chemical compounds composed of hydrogen atoms and group 14 atoms (the elements of group 14 are carbon, silicon, germanium, tin, lead and flerovium).
Group 14 hydrides are chemical compounds composed of hydrogen atoms and group 14 atoms (the elements of group 14 are carbon, silicon, germanium, tin, lead and flerovium).
The tetrahydride series has the chemical formula XH4, with X representing any of the carbon family. Methane is commonly the result of the decomposition of organic matter and is a greenhouse gas. The other hydrides are generally unstable, poisonous metal hydrides.
They take on a pyramidal structure, and as such are not polar molecules like the other p-block hydrides.
Unlike other light hydrides such as ammonia, water and hydrogen fluoride, methane does not exhibit any anomalous effects attributed to hydrogen bonding, and so its properties conform well to the prevailing trend of heavier group 14 hydrides.
| Compound | Chemical formula | Molecular geometry | Space-filling model |
|---|---|---|---|
| carbon tetrahydride hydrogen carbide methane (carbane) | CH4 |  |  |
| silicon tetrahydride hydrogen silicide (silane) | SiH4 |  |  |
| germanium tetrahydride hydrogen germanide (germane) | GeH4 |  |  |
| tin tetrahydride hydrogen stannide (stannane) | SnH4 |  |  |
| lead tetrahydride hydrogen plumbide (plumbane) | PbH4 |  |  |
| flerovium tetrahydride hydrogen flerovide (flerovane) | FlH4 |
This series has the chemical formula X2H6. Ethane is commonly found alongside methane in natural gas. The other hydrides of the chemical formula X2H6 are less stable than the corresponding tetrahydrides XH4, and they are more and more less stable as X goes from carbon (ethane C2H6 is stable) down to lead (or flerovium) in the periodic table (diplumbane Pb2H6 is unknown [1] ).
| Compound | Chemical formula | Molecular geometry | Space-filling model |
|---|---|---|---|
| Ethane (dicarbon hexahydride) (dicarbane) | C2H6 |  |  |
| Disilane (disilicon hexahydride) | Si2H6 |  |  |
| Digermane (digermanium hexahydride) | Ge2H6 |  |  |
| Distannane (ditin hexahydride) | Sn2H6 |  |  |
| Diplumbane (dilead hexahydride) | Pb2H6 |  |  |
| Diflerovane (diflerovium hexahydride) | Fl2H6 |
All straight-chain saturated group 14 hydrides follow the formula XnH2n+2, the same formula for the alkanes.
Many other group 14 hydrides are known. Carbon forms a huge variety of hydrocarbons (among the simplest alkanes are methane CH4, ethane C2H6, propane C3H8, butane C4H10, pentane C5H12 and hexane C6H14, with a wide range of uses. There is also polyethylene (CH2)n, where n is very large, a stable hydrocarbon polymer, the most commonly produced plastic. [2] Hydrocarbons also include alkenes, which contain a double bond between carbon atoms (e.g. ethylene H2C=CH2), alkynes, which contain a triple bond between carbon atoms (e.g. acetylene H−C≡C−H), cyclic and branched hydrocarbons (e.g. cyclohexane C6H12, limonene C10H16, which is a cyclic hydrocarbon with double bonds between carbon atoms, and neopentane C(CH3)4, which is a branched hydrocarbon), as well as aromatic hydrocarbons such as benzene C6H6 and toluene C6H5−CH3), whose study forms the core of organic chemistry. [3]
Alongside hydrogen, carbon can form compounds with the chemically similar halogens, forming haloalkanes. The simplest of this series, the halomethanes, contain compounds such as dichloromethane CH2Cl2, chloroform CHCl3 and iodoform CHI3. Other such important chemicals include vinyl chloride H2C=CHCl, which is used in the production of PVC.
The other group 14 elements have a lower tendency to catenate. Hydrosilicons (binary silicon-hydrogen compounds), a silicon analogs of hydrocarbons, such as silanes SinH2n+2 are known for n = 1–8, in which thermal stability decreasing as n increases (e.g. silane SiH4 and disilane Si2H6), as are cyclosilanes (e.g. cyclopentasilane Si5H10 and cyclohexasilane Si6H12). They are very reactive, pyrophoric colourless gases or volatile liquids. Their volatility is intermediate between the alkanes and the germanes. [4] Unsaturated silanes, the silenes and silynes, have been characterized spectroscopically. The first members of each respectively are disilene H2Si=SiH2 and disilyne H−Si≡Si−H, the silicon analogues of ethylene and acetylene respectively.
The first five hydrogermaniums GenH2n+2 are known and are fairly similar to the hydrosilicones, [5] e.g. germane GeH4 and digermane Ge2H6. They are germanium analogues of alkanes.
Stannane SnH4, a strong reducing agent slowly decomposes at room temperature to tin and hydrogen gas, and is decomposed by concentrated aqueous acids or alkalis; distannane, Sn2H6 is still more unstable, and longer hydrostannums (hydrotins) are unknown. Stannane and distannane are tin analogues of methane and ethane respectively.
Plumbane PbH4 is very poorly characterised and is only known in trace amounts: even at low temperatures, synthesis methods that yield the other MH4 compounds fail to give PbH4. No other hydroplumbums (hydroleads) are known. [1] However, some substituted diplumbanes, with a general chemical formula R3Pb−PbR3 are more stable, where the R groups are organyl.
Compounds containing hydrogen and multiple group 14 elements are known, one of the most famous of these being tetraethyllead Pb(CH2CH3)4 which contains carbon and lead. The other examples are methylsilane H3C−SiH3 which contains carbon and silicon, tris(trimethylsilyl)germanium hydride ((CH3)3Si)3GeH which contain carbon, silicon and germanium, silylgermane or germylsilane H3Si−GeH3 which contains silicon and germanium, and hexaphenyldiplumbane (C6H5)3Pb−Pb(C6H5)3 which contains carbon and lead. [6]
In organic chemistry, an alkane, or paraffin, is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carbon–carbon bonds are single. Alkanes have the general chemical formula CnH2n+2. The alkanes range in complexity from the simplest case of methane, where n = 1, to arbitrarily large and complex molecules, like pentacontane or 6-ethyl-2-methyl-5-(1-methylethyl) octane, an isomer of tetradecane.
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may be similar to that of gasoline or lighter fluid. They occur in a diverse range of molecular structures and phases: they can be gases, liquids, low melting solids or polymers.
In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen atom with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and more frequently in the past) been applied to all compounds containing covalently bound H atoms. In this broad and potentially archaic sense, water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. In covalent compounds, it implies hydrogen is attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.
Silane (Silicane) is an inorganic compound with chemical formula SiH4. It is a colorless, pyrophoric, toxic gas with a sharp, repulsive, pungent smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Silane with alkyl groups are effective water repellents for mineral surfaces such as concrete and masonry. Silanes with both organic and inorganic attachments are used as coupling agents. They are commonly used to apply coatings to surfaces or as an adhesion promoter.
In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term alkyl is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of −CnH2n+1. A cycloalkyl group is derived from a cycloalkane by removal of a hydrogen atom from a ring and has the general formula −CnH2n−1. Typically an alkyl is a part of a larger molecule. In structural formulae, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is methyl, with the formula −CH3.
In chemical nomenclature, the IUPAC nomenclature of organic chemistry is a method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). It is published in the Nomenclature of Organic Chemistry. Ideally, every possible organic compound should have a name from which an unambiguous structural formula can be created. There is also an IUPAC nomenclature of inorganic chemistry.
In chemistry, catenation is the bonding of atoms of the same element into a series, called a chain. A chain or a ring may be open if its ends are not bonded to each other, or closed if they are bonded in a ring. The words to catenate and catenation reflect the Latin root catena, "chain".
In chemistry, halogenation is a chemical reaction which introduces one or more halogens into a chemical compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens. Halides are also commonly introduced using salts of the halides and halogen acids. Many specialized reagents exist for and introducing halogens into diverse substrates, e.g. thionyl chloride.
In organic chemistry, a substituent is one or a group of atoms that replaces atoms, thereby becoming a moiety in the resultant (new) molecule.
In organic chemistry, a homologous series is a sequence of compounds with the same functional group and similar chemical properties in which the members of the series differ by the number of repeating units they contain. This can be the length of a carbon chain, for example in the straight-chained alkanes (paraffins), or it could be the number of monomers in a homopolymer such as amylose. A homologue is a compound belonging to a homologous series.
Organotin chemistry is the scientific study of the synthesis and properties of organotin compounds or stannanes, which are organometallic compounds containing tin–carbon bonds. The first organotin compound was diethyltin diiodide, discovered by Edward Frankland in 1849. The area grew rapidly in the 1900s, especially after the discovery of the Grignard reagents, which are useful for producing Sn–C bonds. The area remains rich with many applications in industry and continuing activity in the research laboratory.
Germane is the chemical compound with the formula GeH4, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is tetrahedral. It burns in air to produce GeO2 and water. Germane is a group 14 hydride.
Silanes are saturated chemical compounds with the empirical formula SixHy. They are hydrosilanes, a class of compounds that includes compounds with Si−H and other Si−X bonds. All contain tetrahedral silicon and terminal hydrides. They only have Si−H and Si−Si single bonds. The bond lengths are 146.0 pm for a Si−H bond and 233 pm for a Si−Si bond. The structures of the silanes are analogues of the alkanes, starting with silane, SiH4, the analogue of methane, continuing with disilane Si2H6, the analogue of ethane, etc. They are mainly of theoretical or academic interest.
Silicon compounds are compounds containing the element silicon (Si). As a carbon group element, silicon often forms compounds in the +4 oxidation state, though many unusual compounds have been discovered that differ from expectations based on its valence electrons, including the silicides and some silanes. Metal silicides, silicon halides, and similar inorganic compounds can be prepared by directly reacting elemental silicon or silicon dioxide with stable metals or with halogens. Silanes, compounds of silicon and hydrogen, are often used as strong reducing agents, and can be prepared from aluminum–silicon alloys and hydrochloric acid.
In chemistry, an onium ion is a cation formally obtained by the protonation of mononuclear parent hydride of a pnictogen, chalcogen, or halogen. The oldest-known onium ion, and the namesake for the class, is ammonium, NH+4, the protonated derivative of ammonia, NH3.
In organic chemistry, the suffix -ane forms the names of organic compounds where the −C−C− group has been attributed the highest priority according to the rules of organic nomenclature. Such organic compounds are called alkanes. They are saturated hydrocarbons.
Plumbane is an inorganic chemical compound with the chemical formula PbH4. It is a colorless gas. It is a metal hydride and group 14 hydride composed of lead and hydrogen. Plumbane is not well characterized or well known, and it is thermodynamically unstable with respect to the loss of a hydrogen atom. Derivatives of plumbane include lead tetrafluoride, PbF4, and tetraethyllead, (CH3CH2)4Pb.
Polysilicon hydrides are polymers containing only silicon and hydrogen. They have the formula where 0.2 ≤ n ≤ 2.5 and x is the number of monomer units. The polysilicon hydrides are generally colorless or pale-yellow/ocher powders that are easily hydrolyzed and ignite readily in air. The surfaces of silicon prepared by MOCVD using silane (SiH4) consist of a polysilicon hydride.
Digermane is an inorganic compound with the chemical formula Ge2H6. One of the few hydrides of germanium, it is a colourless liquid. Its molecular geometry is similar to ethane.
Silylgermane is an inorganic compound with the chemical formula H3Si−GeH3. It is a colorless gas with an unpleasant odor. It is unstable in air. It is very flammable, very toxic and corrosive. It reacts with alkali liberating hydrogen.