Boron trichloride

Boron trichloride
Boron trichloride
Are common
Systematic ; name	boron (III) chloride
Abbreviations	trichloroboron
Traditional names	boron trichloride, boron chloride
Chem. formula	Bcl 3
Rat formula	Bcl 3
Physical properties
condition	colorless gas smoking in the air
Molar mass	(at 9.23% and Cl 90.77% by weight) 117.17 g / mol
Density	(at 0 ° C) 1.326 g / cm³
Thermal properties
T. melt.	-107.3 ° C
T. bale.	12.6 ° C
T. aux.	-17 ° C
Cr. point	temperature: 178.8 ° C pressure: 3.87 MPadensity: 0.7 g / cm³
Like heat resistant.	107 J / (mol · K)
Enthalpy of Education	-427 kJ / mol
Steam pressure	(at −92 ° C) 1 mmHg (at −68 ° C) 10 mmHg (at −33.5 ° C) 100 mmHg(at 20 ° C) 150 kPa
Chemical properties
Solubility in water	decays
Solubility in other substances	decomposes in ethanol , soluble in carbon tetrachloride
Optical properties
Refractive index	1.00139
Structure
Coordination geometry	trigonal, flat
Dipole moment	0 D
Classification
Reg. CAS number	10294-34-5
PubChem
Reg. EINECS number
Smiles
Inchi
Reg. EC number	233-658-4
RTECS	ED1925000
UN number
ChemSpider
Security
Toxicity	0 four 2

Boron trichloride is a binary inorganic compound of boron and chlorine with the formula BCl ₃ . It is a colorless gas.

Physical Properties

Under standard conditions , boron trichloride is a heavy, colorless gas, which, due to interaction with water vapor, smokes in moist air.

Under normal conditions , it is a liquid whose vapor pressure is described by the equation:

p_{\mathsf {(mmHg)}}=2115~T^{-1}-7.04\lg T+27.56

{\ displaystyle p _ {\ mathsf {(mmHg)}} = 2115 ~ T ^ {- 1} -7.04 \ lg T + 27.56}

p_{\mathsf {(mmHg)}}=2115~T^{-1}-7.04\lg T+27.56

In the Solid state, boron trichloride forms crystals of hexagonal syngony , space group P6 ₃ , a = 0.6140 nm, c = 0.6603 nm, Z = 9.

The boron trichloride molecule is a regular triangle (like other boron trihalides ) with a B – Cl bond length of 0.175 nm. Due to trigonal symmetry, the molecule has a zero dipole moment.

Boron trichloride does not form dimers , although there is indirect evidence that it can form dimers at very low temperatures (20 K ).

Getting

Boron trichloride can be synthesized from elements:

{\mathsf {2B+3Cl_{2}{\xrightarrow {>400^{o}C}}2BCl_{3}}}

{\ displaystyle {\ mathsf {2B + 3Cl_ {2} {\ xrightarrow {> 400 ^ {o} C}} 2BCl_ {3}}}}

{\mathsf {2B+3Cl_{2}{\xrightarrow {>400^{o}C}}2BCl_{3}}}

In industry, instead of pure boron, its alloys, for example, ferroboron, are used .

Also, the industry uses the chlorination method at a temperature of ~ 1000 ° C of a mixture of boron oxide and coke :

{\mathsf {B_{2}O_{3}+3C+3Cl_{2}{\xrightarrow {1000^{o}C}}2BCl_{3}+3CO}}

{\ displaystyle {\ mathsf {B_ {2} O_ {3} + 3C + 3Cl_ {2} {\ xrightarrow {1000 ^ {o} C}} 2BCl_ {3} + 3CO}}}

In Russia, the industrial method of chlorination of boron carbide is used at a temperature of 900-1000 ° C:

{\mathsf {B_{4}C+6Cl_{2}{\xrightarrow {1000^{o}C}}4BCl_{3}+C}}

{\ displaystyle {\ mathsf {B_ {4} C + 6Cl_ {2} {\ xrightarrow {1000 ^ {o} C}} 4BCl_ {3} + C}}}

Aluminum trichloride and boron trifluoride can exchange halogens:

{\mathsf {AlCl_{3}+BF_{3}{\xrightarrow {~T~}}BCl_{3}+AlF_{3}}}

{\ displaystyle {\ mathsf {AlCl_ {3} + BF_ {3} {\ xrightarrow {~ T ~}} BCl_ {3} + AlF_ {3}}}}

In laboratory practice, boron trichloride is obtained by the decomposition of its adducts, for example, BCl ₃ S (CH ₃ ) ₂ , which are convenient in use, since they are solid substances:

{\mathsf {(CH_{3})_{2}SBCl_{3}\rightleftarrows (CH_{3})_{2}S+BCl_{3}}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {2} SBCl_ {3} \ rightleftarrows (CH_ {3}) _ {2} S + BCl_ {3}}}}

Chemical Properties

It is completely hydrolyzed with water with the release of a large amount of heat:

{\mathsf {BCl_{3}+3H_{2}O\rightarrow B(OH)_{3}\downarrow +3HCl}}

{\ displaystyle {\ mathsf {BCl_ {3} + 3H_ {2} O \ rightarrow B (OH) _ {3} \ downarrow + 3HCl}}}

Reacts with diluted and concentrated alkalis:

{\mathsf {4BCl_{3}+14NaOH\rightarrow Na_{2}B_{4}O_{7}+12NaCl+7H_{2}O}}

{\ displaystyle {\ mathsf {4BCl_ {3} + 14NaOH \ rightarrow Na_ {2} B_ {4} O_ {7} + 12NaCl + 7H_ {2} O}}}

{\mathsf {BCl_{3}+4NaOH\rightarrow Na[B(OH)_{4}]+3NaCl}}

{\ displaystyle {\ mathsf {BCl_ {3} + 4NaOH \ rightarrow Na [B (OH) _ {4}] + 3NaCl}}}

Hydrogen reduced to boron or borane :

{\mathsf {2BCl_{3}+3H_{2}{\xrightarrow {800-1200^{o}C}}2B+6HCl}}

{\ displaystyle {\ mathsf {2BCl_ {3} + 3H_ {2} {\ xrightarrow {800-1200 ^ {o} C}} 2B + 6HCl}}}

{\mathsf {2BCl_{3}+6H_{2}{\xrightarrow {450^{o}C,Cu,Al}}B_{2}H_{6}+6HCl}}

{\ displaystyle {\ mathsf {2BCl_ {3} + 6H_ {2} {\ xrightarrow {450 ^ {o} C, Cu, Al}} B_ {2} H_ {6} + 6HCl}}}

Burns in oxygen (in air at a temperature> 400 ° C):

{\mathsf {4BCl_{3}+3O_{2}{\xrightarrow {}}2B_{2}O_{3}+6Cl_{2}}}

{\ displaystyle {\ mathsf {4BCl_ {3} + 3O_ {2} {\ xrightarrow {}} 2B_ {2} O_ {3} + 6Cl_ {2}}}}

Fluorine displaces chlorine from the compound:

{\mathsf {2BCl_{3}+3F_{2}{\xrightarrow {}}2BF_{3}+3Cl_{2}}}

{\ displaystyle {\ mathsf {2BCl_ {3} + 3F_ {2} {\ xrightarrow {}} 2BF_ {3} + 3Cl_ {2}}}}

Boron trichloride is a Lewis acid that forms adducts with tertiary amines , phosphines , esters , thioethers and halide ions :

{\mathsf {BCl_{3}+PH_{3}\rightleftarrows BCl_{3}\cdot PH_{3}}}

{\ displaystyle {\ mathsf {BCl_ {3} + PH_ {3} \ rightleftarrows BCl_ {3} \ cdot PH_ {3}}}}

Reacts with organotin compounds:

{\mathsf {2BCl_{3}+R_{4}Sn\longrightarrow 2RBCl_{2}+R_{2}SnCl_{2}}}

{\ displaystyle {\ mathsf {2BCl_ {3} + R_ {4} Sn \ longrightarrow 2RBCl_ {2} + R_ {2} SnCl_ {2}}}}

When passing an electric spark through boron trichloride, lower boron chlorides B ₂ Cl ₆ , B ₄ Cl ₄ , B ₈ Cl ₈ are obtained:

{\mathsf {2BCl_{3}{\xrightarrow {}}B_{2}Cl_{4}+Cl_{2}}}

{\ displaystyle {\ mathsf {2BCl_ {3} {\ xrightarrow {}} B_ {2} Cl_ {4} + Cl_ {2}}}}

Reacts with alcohols to produce borate esters:

{\mathsf {BCl_{3}+R{\text{-}}OH{\xrightarrow {}}B(OR)_{3}+3HCl}}

{\ displaystyle {\ mathsf {BCl_ {3} + R {\ text {-}} OH {\ xrightarrow {}} B (OR) _ {3} + 3HCl}}}

When heated, reacts with boric anhydride to produce boron oxychloride:

{\mathsf {BCl_{3}+B_{2}O_{3}{\xrightarrow {200^{o}C}}3BOCl}}

{\ displaystyle {\ mathsf {BCl_ {3} + B_ {2} O_ {3} {\ xrightarrow {200 ^ {o} C}} 3BOCl}}}

Metals can reduce boron trichloride to boron or form borides:

{\mathsf {BCl_{3}+3Na{\xrightarrow {150^{o}C}}B+3NaCl}}

{\ displaystyle {\ mathsf {BCl_ {3} + 3Na {\ xrightarrow {150 ^ {o} C}} B + 3NaCl}}}

{\mathsf {2BCl_{3}+6Mg{\xrightarrow {}}Mg_{3}B_{2}+3MgCl_{2}}}

{\ displaystyle {\ mathsf {2BCl_ {3} + 6Mg {\ xrightarrow {}} Mg_ {3} B_ {2} + 3MgCl_ {2}}}}

Application

Boron trichloride is the starting material for the production of pure boron .
It is also used in the processing of aluminum , magnesium , zinc and copper alloys to remove nitrides , carbides and oxides from molten metal .
Boron trichloride was used as a flux for brazing alloys of aluminum , iron , zinc , tungsten and a copper-nickel alloy .
Processing liquid aluminum with boron trichloride vapors improves the quality of the castings.
It is used in the manufacture of electrical resistances for bonding a carbon film to a ceramic base.
Used in plasma etching in the production of microelectronics
Used as a reagent in organic synthesis.

Security

Boron trichloride is an aggressive reagent .