acids and energy-carrying molecules
(e.g. ATP) and also involved in various
metabolic reactions. The element
was discovered by Hennig Brand
(c. 1630–92) in 1669.
A
• Information from the WebElements site
phosphorus(III) bromide (phosphorus tribromide) A colourless fuming liquid, PBr 3 ; r.d. 2.85; m.p. –40°C;
b.p. 173°C. It is prepared by passing
bromine vapour over phosphorus but
avoiding an excess, which would lead
to the phosphorus(V) bromide. Like
the other phosphorus(III) halides,
PBr 3 is pyramidal in the gas phase. In
the liquid phase the P–Br bonds are
labile; for example, PBr 3 will react
with PCl 3 to give a mixture of products in which the halogen atoms
have been redistributed. Phosphorus(III) bromide is rapidly hydrolysed
by water to give phosphonic acid and
hydrogen bromide. It reacts readily
with many organic hydroxyl groups
and is used as a reagent for introducing bromine atoms into organic molecules.
phosphorus(V) bromide (phosphorus pentabromide) A yellow
readily sublimable solid, PBr 5 , which
decomposes below 100°C and is soluble in benzene and carbon tetrachloride (tetrachloromethane). It may be
prepared by the reaction of phosphorus(III) bromide with bromine or the
direct reaction of phosphorus with
excess bromine. It is very readily hydrolysed to give hydrogen bromide
and phosphoric(V) acid. An interesting feature of this material is that in
the solid state it has the structure
[PBr 4 ]
+ Br
– . It is used in organic chemistry as a brominating agent.
phosphorus(III) chloride (phosphorus trichloride) A colourless fuming liquid, PCl 3 ; r.d. 1.57; m.p.
–112°C; b.p. 75.5°C. It is soluble in
ether and in carbon tetrachloride but
reacts with water and with ethanol.
It may be prepared by passing chlorine over excess phosphorus (excess
chlorine contaminates the product
with phosphorus(V) chloride). The
molecule is pyramidal in the gas
phase and possesses weak electronpair donor properties. It is hydrolysed violently by water to
phosphonic acid and hydrogen chloride. Phosphorus(III) chloride is an
important starting point for the synthesis of a variety of inorganic and
organic derivatives of phosphorus.
phosphorus(V) chloride (phosphorus pentachloride) A yellowwhite rhombic solid, PCl 5 , which
fumes in air; r.d. 4.65; m.p. 166.8°C
(under pressure); sublimes at
160–162°C. It is decomposed by
water to give hydrogen chloride and
phosphoric(V) acid. It is soluble in organic solvents. The compound may
be prepared by the reaction of chlorine with phosphorus(III) chloride.
Phosphorus(V) chloride is structurally
interesting in that in the gas phase it
has the expected trigonal bipyramidal form but in the solid phase it consists of the ions [PCl 4 ]
+ [PCl 6 ]
– . The
same ions are detected when phosphorus(V) chloride is dissolved in
polar solvents. It is used in organic
chemisty as a chlorinating agent.
phosphorus(III) chloride oxide
(phosphorus oxychloride; phosphoryl
chloride) A colourless fuming liquid,
POCl 3 ; r.d. 1.67; m.p. 2°C; b.p.
105.3°C. It may be prepared by the
reaction of phosphorus(III) chloride
with oxygen or by the reaction of
phosphorus(V) oxide with phosphorus(V) chloride. Its reactions are very
similar to those of phosphorus(III)
chloride. Hydrolysis with water gives
phosphoric(V) acid. Phosphorus(III)
chloride oxide has a distorted tetrahedral shape and can act as a donor
413
phosphorus(III) chloride oxide
p
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(e.g. ATP) and also involved in various
metabolic reactions. The element
was discovered by Hennig Brand
(c. 1630–92) in 1669.
A
• Information from the WebElements site
phosphorus(III) bromide (phosphorus tribromide) A colourless fuming liquid, PBr 3 ; r.d. 2.85; m.p. –40°C;
b.p. 173°C. It is prepared by passing
bromine vapour over phosphorus but
avoiding an excess, which would lead
to the phosphorus(V) bromide. Like
the other phosphorus(III) halides,
PBr 3 is pyramidal in the gas phase. In
the liquid phase the P–Br bonds are
labile; for example, PBr 3 will react
with PCl 3 to give a mixture of products in which the halogen atoms
have been redistributed. Phosphorus(III) bromide is rapidly hydrolysed
by water to give phosphonic acid and
hydrogen bromide. It reacts readily
with many organic hydroxyl groups
and is used as a reagent for introducing bromine atoms into organic molecules.
phosphorus(V) bromide (phosphorus pentabromide) A yellow
readily sublimable solid, PBr 5 , which
decomposes below 100°C and is soluble in benzene and carbon tetrachloride (tetrachloromethane). It may be
prepared by the reaction of phosphorus(III) bromide with bromine or the
direct reaction of phosphorus with
excess bromine. It is very readily hydrolysed to give hydrogen bromide
and phosphoric(V) acid. An interesting feature of this material is that in
the solid state it has the structure
[PBr 4 ]
+ Br
– . It is used in organic chemistry as a brominating agent.
phosphorus(III) chloride (phosphorus trichloride) A colourless fuming liquid, PCl 3 ; r.d. 1.57; m.p.
–112°C; b.p. 75.5°C. It is soluble in
ether and in carbon tetrachloride but
reacts with water and with ethanol.
It may be prepared by passing chlorine over excess phosphorus (excess
chlorine contaminates the product
with phosphorus(V) chloride). The
molecule is pyramidal in the gas
phase and possesses weak electronpair donor properties. It is hydrolysed violently by water to
phosphonic acid and hydrogen chloride. Phosphorus(III) chloride is an
important starting point for the synthesis of a variety of inorganic and
organic derivatives of phosphorus.
phosphorus(V) chloride (phosphorus pentachloride) A yellowwhite rhombic solid, PCl 5 , which
fumes in air; r.d. 4.65; m.p. 166.8°C
(under pressure); sublimes at
160–162°C. It is decomposed by
water to give hydrogen chloride and
phosphoric(V) acid. It is soluble in organic solvents. The compound may
be prepared by the reaction of chlorine with phosphorus(III) chloride.
Phosphorus(V) chloride is structurally
interesting in that in the gas phase it
has the expected trigonal bipyramidal form but in the solid phase it consists of the ions [PCl 4 ]
+ [PCl 6 ]
– . The
same ions are detected when phosphorus(V) chloride is dissolved in
polar solvents. It is used in organic
chemisty as a chlorinating agent.
phosphorus(III) chloride oxide
(phosphorus oxychloride; phosphoryl
chloride) A colourless fuming liquid,
POCl 3 ; r.d. 1.67; m.p. 2°C; b.p.
105.3°C. It may be prepared by the
reaction of phosphorus(III) chloride
with oxygen or by the reaction of
phosphorus(V) oxide with phosphorus(V) chloride. Its reactions are very
similar to those of phosphorus(III)
chloride. Hydrolysis with water gives
phosphoric(V) acid. Phosphorus(III)
chloride oxide has a distorted tetrahedral shape and can act as a donor
413
phosphorus(III) chloride oxide
p
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