Boron trichloride
Encyclopedia : B : BO : BOR : Boron trichloride
| Boron trichloride | |
|---|---|
| |
| General | |
| Systematic name | Boron trichloride |
| Other names | Boron(III) chloride |
| Molecular formula | BCl3 |
| Molar mass | 117.17 g/mol |
| Appearance | Colorless gas, fumes in air |
| CAS number | [10294-34-5] |
| Properties | |
| Density and phase | 1.43 g/ml (O °C) |
| Solubility in water | decomp. |
| Melting point | −107.3 °C |
| Boiling point | 12.5 °C |
| Structure | |
| Molecular shape | Trigonal planar (D3h) |
| Bond length | 173 pm (B–Cl) |
| Dipole moment | zero |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Very toxic (T+) |
| NFPA 704 | |
| R-phrases | R14, R26/28, R34 |
| S-phrases | SS1/2, S9, S26, S28, S36/37/39, S45 |
| Flash point | Non-flammable |
| RTECS number | ED1925000 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | Boron trifluoride Boron tribromide Boron triiodide |
| Other cations | Aluminium chloride Gallium chloride |
| Related compounds | Boron oxide Carbon tetrachloride |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) [Chemical infoboxInfobox disclaimer and references] | |
Boron trichloride (BCl3) is a colorless, toxic and corrosive, nonflammable, liquified gas. It can be broken down by water to hydrogen chloride and boric acid. It forms a white smoke in humid air. It is shipped as a liquid under its own vapor pressure (1.5 bar at room temperature).
Production
Boron trichloride is produced by direct chlorination of boron oxide and coal at 500°C with chlorine.
- B2O3 + 3 C + Cl2 → 2 BCl3 + 3 CO
Uses
Boron trichloride is a starting material for the production of elemental boron. It is also used in the refining of aluminium, magnesium, zinc, and copper alloys to remove nitrides, carbides, and oxides from molten metal. It has been used successfully as a soldering flux for alloys of aluminum, iron, zinc, tungsten, and monel. Aluminum castings can be improved by treating the melt with boron trichloride vapors. In the manufacture of electrical resistors, a uniform and lasting adhesive carbon film can be put over a ceramic base by a process that has been developed, using the addition of BCl3 to benzene at high temperature. It has been used in the field of high energy fuels and rocket propellants as a source of boron to raise BTU value.Chemistry
Boron reacts with all the halogens to give monomeric, highly reactive trihalides (like boron tribromide and boron trichloride). BCl3 readily form complexes with amines, phosphines, ethers, and halide ions. Examples include complex formation between boron trichloride and trimethylamine, as well as between boron trifluoride and fluoride ion. When boron trichloride is passed at low pressure through devices delivering an electric discharge, diboron tetrachloride, the formula written as Cl2B-BCl2, and tetraboron tetrachloride, formula B4Cl4, are formed. Diboron tetrachloride decomposes at room temperatures to give a series of monochlorides having the general formula (BCl)n, in which n may be 8, 9, 10, or 11; the compounds with formulas B8Cl8 and B9Cl9 are known to contain closed cages of boron atoms.NMR
Boron naturally occurs as two isotopes: one of atomic mass 10 (18.8 percent) and one of atomic mass 11 (81.2 percent). Both nuclei possess nuclear spin (rotation of the atomic nuclei); that of boron-10 has a value of 3 and that of boron-11, 3/2, the values being dictated by quantum factors. These isotopes are, therefore, of use in nuclear magnetic resonance spectroscopy; and spectrometers specially adapted to detecting the boron-11 nucleus are available commercially. The boron-10 and boron-11 nuclei also cause splitting in the resonances (that is, the appearance of new bands in the resonance spectra) of other nuclei (e.g., those of hydrogen atoms bonded to boron). The boron-10 isotope is unique in that it possesses an extremely large capture cross section for thermal neutrons (i.e., it readily absorbs neutrons of low energy). The capture of a neutron by a nucleus of this isotope results in the expulsion of an alpha particle.External links
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
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