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Silanes

 

Silanes are binary compounds of silicon and hydrogen with the general formula of SinH2n+2. They have only single SiSi and SiH covalent bonds (The simplest one, SiH4 has only four SiH bonds). Each silicon atom in silanes bonds to four other atoms (either hydrogen or silicon) of which at least one is another silicon atom except in the case of SiH4 in which all four atoms are hydrogen atoms. In this way, silanes are analogues of the alkanes (hydrocarbons with the general formula CnH2n+2) where silanes instead of carbon atoms have silicon atoms. Such analogues arent unexpected in chemistry since carbon and silicon belong to a same group (the group 14) and therefore they are expected to have similarities in their compounds. Both alkanes and silanes lack any multiple covalent bonds and are considered as saturated compounds. Both silanes and alkanes also lack any cyclic pattern so they are acyclic. It is possible to have cyclic analogues of them where saturated monocyclic silicon hydrides (saturated monocyclic hydrosilicons) are called cyclosilanes and saturated monocyclic hydrocarbons are called cycloalkanes.

 

Silicon atoms are no match to carbon atoms in catenation (bonding together to form lengthy chains). While there is no limit for the number of carbon atoms in alkanes, it is hard to synthesize silanes with more than eight silicon atoms due to stability issues. In other words, in contrast to alkanes, silanes are extremely reactive and their thermal stability decreases as chain length increases. As a result, silanes with eight or less silicon atoms are the only well-known silanes. However, other similar compounds of silicon may have greater catenation, for example, SinF2n+2 (silicon fluorides) with n up to 14 are known and also in combination with oxygen, silicon can form unlimited structures like (SiO32-)n which are polymeric anions in the form (Si(O)2O)n.

 

 

 

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