Chemical elements
  Silicon
    Isotopes
    Energy
    Physical Properties
    Chemical Properties
      Silicon Tetrahydride
      Silicomethane
      Silicane
      Silico-ethane
      Silico-acetylene
      Bromosilicane
      Silicofluoroform
      Trifluorosilicane
      Silicochloroform
      Trichlorosilicane
      Silicobromoform
      Tribromosilicane
      Silico-iodoform
      Tri-iodosilicane
      Silicon Tetrafluoride
      Hydrofluosilicic Acid
      Silicon Subfluoride
      Silicon Tetrachloride
      Tetrachlorosilicane
      Silicon Tetrabromide
      Tetrabromosilicane
      Silicon Tetra-iodide
      Tetra-iodosilicane
      Mixed Halides of Silicon
      Halogen Derivatives of Silico-ethane
      Halogen Derivatives of Silicopropane
      Halogen Derivatives of Silicobutane
      Halogen Derivatives of Silicopentane and Silicohexane
      Silicon Oxychlorides
      Silica
      Silicon Dioxide
      Silicates
      Silicoformic Anhydride
      Silico-oxalic Acid
      Silicomes-oxalic Acid
      Silicon Disulphide
      Silicon Monosulphide
      Silicon Oxysulphide
      Silicon Thiochloride
      Silicon Thiobromide
      Silicon Chloroitydrosulphide
      Silicothio-urea
      Silicon Selenide
      Silicon Tetramide
      Silicon Di-imide
      Silicon Nitrimide
      Silicam
      Siliconitrogen Hydride
      Silicon Nitrides
      Crystalline Silicon Monocarbide
      Carborundum
      Silicon Dicarbide
      Silicon Carboxide
      Borides of Silicon
    PDB 1fuq-4ehr

Silicon Tetrabromide, SiBr4






Silicon Tetrabromide (Tetrabromosilicane), SiBr4, first obtained by Serullas, is prepared similarly to silicon tetrachloride by passing bromine vapour over an intimate mixture of silica and carbon or the crude silicon of Gattermann; hydrogen bromide may be substituted for bromine, when silicobromoform accompanies the tetrabromide. An alternative method consists in causing silicon tetrachloride to react with carbon tetrabromide, when exchange of halogen takes place.


Properties of Silicon Tetrabromide

Silicon tetrabromide is a heavy, colourless liquid which evolves dense white fumes in moist air; its density at 0° C. is 2.8128 (Pierre) or 2.82 (Reynolds); its boiling-point has been found by different observers to lie between 148° C. and 154° C. The most recent, and probably the most accurate, determination is that of Blix, who found 150.8° C. at 751.4 mm. pressure. Solid silicon tetrabromide is a pearly crystalline mass which according to Blix melts at 5° C., but according to other observers between -12° C. and -15° C. The solid is heavier than the liquid.

The heats of formation are as follow:

Si (cryst.) + 4Br (liq.) = SiBr4 (liq.) + 71,000 calories.
Si (cryst.) + 4Br (vap.) = SiBr4 (vap.) + 85,800

Water reacts vigorously with silicon tetrabromide, hydrolysing it with the formation of silicic and hydrobromic acids; litharge produces some lead bromide and lead silicate; ammonia forms the white, amorphous, additive compound SiBr4.7NH3, which is decomposed by water; phosphine, organic bases, and thio- and alkylated ureas also form additive compounds with silicon tetrabromide.
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