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Silicon hydride
Since the atomic radius of Si is larger than that of C, silicon atoms are formed between them
.
The degree of overlap of atomic orbitals when bonding is small, and the degree of overlap when forming a π bond is even smaller.
1.
Preparation of Silane
High purity SiH 4 can be obtained by reducing SiCl 4 with LiAlH 4 in the medium of ether .
SiCl 4 +LiAlH 4 =SiH 4 +LiCl+AICl 3
Mg 2 Si reacts with hydrochloric acid to obtain SiH 4 containing impurities such as disilane
.
Mg 2 Si+4HC1=SiH 4 + 2MgCl 2
The raw material Mg 2 Si can be obtained by reducing SiO 2 with metal Mg at a high temperature
.
SiO 2 +4Mg=Mg 2 Si+2MgO
2.
The nature of alkylene
The most typical and stable silane is SiH 4 , which is a colorless and odorless gas
.
SiH 4 is stable at room temperature.
SiH 4 is unstable and decomposes when heated to 500°C (while CH 4 decomposes above 1000°C)
.
SiH 4 =Si+2H 2
SiH 4 has strong reducibility and spontaneously ignites in the air
.
SiH 4 is easily hydrolyzed, and substantially undergoes an oxidation-reduction reaction with water, and the oxidation number of Si remains unchanged
.
SiH 4 +(n+2)H 2 O=SiO 2 ·nH 2 O+4H 2
13.
2.
SiF 4 is a colorless gas at room temperature , SiCl 4 and SiBr 4 are colorless liquids, and Sil 4 is a white solid
.
The melting point and boiling point increase sequentially, and the radii of the molecules increase sequentially to increase the dispersion force between the molecules
The HF generated by the hydrolysis reaction of SiF 4 can further react with SiF 4 to generate H 2 SiF 6
.
Of SiCl .
4 is a silicon halide the most important, the HCI can be used to prepare high-purity silicon, highly humid air encountered hydrolysis take the fog, not generated and further of SiCl .
SiCl 4 +4H 2 O=H 4 SiO 4 +4HCl
H 2 SiF 6 is a strong acid, which is equivalent to the acidity of H 2 SO 4
.
The salt formed by H 2 SiF 6 and soft base is easy to dissolve, such as PbSiF 6 ; but the salt formed with hard base with a large radius is hard to dissolve, such as K 2 SiF 6 has very low solubility
.
Related Links: The properties and preparation methods of elemental silicon
