When was silane discovered?

Chemical compound (SiH4)

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This article is about the compound with chemical formula SiH4, which belongs to a broader class of compounds known as silanes.

Silane (Silicane) is an inorganic compound represented by the chemical formula SiH4. It appears as a colorless, pyrophoric, and toxic gas possessing a sharp, pungent odor, reminiscent of acetic acid. Silane is significant in the production of elemental silicon, with silane chains featuring alkyl groups being utilized as effective water repellents for mineral surfaces, including concrete and masonry. Additionally, silanes with a mix of organic and inorganic groups serve as coupling agents, frequently applied for surface coatings or as adhesion promoters.

Laboratory-scale routes

In the 19th century, silane was first identified by the German chemists Heinrich Buff and Friedrich Woehler. They discovered it while conducting experiments that involved the reaction of hydrochloric acid with aluminum silicide, a compound they had earlier synthesized. Buff and Woehler referred to it as siliciuretted hydrogen.

For educational demonstrations, silane can be generated by heating magnesium powder with sand to form magnesium silicide (Mg2Si), followed by treating this mixture with hydrochloric acid. In this reaction, the magnesium silicide interacts with the acid, generating silane gas, which ignites spontaneously upon contact with air, leading to small explosions. This process can be classified as a heterogeneous acid-base reaction, where the isolated Si4- ions in Mg2Si behave as Brønsted-Lowry bases capable of accepting protons. This is represented by the equation:

4 HCl + Mg2Si ' SiH4 + 2 MgCl2

Typically, alkaline-earth metals create silicides with defined stoichiometries, which can react with Brønsted-Lowry acids to form various silicon hydrides depending on the Si anion structure present in the silicide. The products may include SiH4 and/or larger molecules from the homologous series SinH2n+2, or even silicic acid. For example, the structure of the silicide with zigzag chains of Si2- anions (where each Si atom holds two lone pairs able to accept protons) can lead to the formation of a polymeric hydride (SiH2)x.

Another method for producing silane in laboratory conditions involves the application of sodium amalgam to dichlorosilane (SiH2Cl2), resulting in the formation of monosilane alongside some yellow polymerized silicon hydride (SiH)x.

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