unpleasant odour; r.d. 1.114 (liquid at
0°C); m.p. –111.3°C; b.p. 7°C. It is the
acid anhydride of malonic acid, from
which it can be prepared by dehydration using phosphorus(V) oxide. The
molecule is linear (O:C:C:C:O).
tricarboxylic acid cycle See krebs
cycle.
trichloroethanal (chloral) A liquid
aldehyde, CCl 3 CHO; r.d. 1.51; m.p.
–57.5°C; b.p. 97.8°C. It is made by
chlorinating ethanal and used in
making DDT. See also 2,2,2trichloroethanediol.
2,2,2-trichloroethanediol (chloral
hydrate) A colourless crystalline
solid, CCl 3 CH(OH) 2 ; r.d. 1.91; m.p.
57°C; b.p. 96.3°C. It is made by the
hydrolysis of trichloroethanal and is
unusual in having two –OH groups
on the same carbon atom. Gem diols
of this type are usually unstable; in
this case the compound is stabilized
by the presence of the three Cl
atoms. It is used as a sedative.
trichloroethene (trichlorethylene)
A colourless liquid, CCl 2 =CHCl, b.p.
87°C. It is toxic and nonÛammable,
with a smell resembling that of chloroform (trichloromethane). It is
widely used as a solvent in dry cleaning and degreasing. It is also used to
extract oils from nuts and fruit, as
an anaesthetic, and as a Üre extinguisher.
trichloromethane (chloroform) A
colourless volatile sweet-smelling liquid *haloform, CHCl 3 ; r.d. 1.48; m.p.
–63.5°C; b.p. 61.7°C. It can be made
by chlorination of methane (followed
by separation of the mixture of products) or by the haloform reaction. It
is an effective anaesthetic but can
cause liver damage and it has now
been replaced by other halogenated
hydrocarbons. Chloroform is used as
a solvent and raw material for making other compounds.
triclinic See crystal system.
tridymite A mineral form of *silicon(IV) oxide, SiO 2 .
triethanolamine See ethanolamine.
triglyceride (triacylglycerol) An
ester of glycerol (propane-1,2,3-triol)
in which all three hydroxyl groups
are esteriÜed with a fatty acid.
Triglycerides are the major constituent of fats and oils and provide a
concentrated food energy store in living organisms as well as cooking fats
and oils, margarines, etc. Their physical and chemical properties depend
on the nature of their constituent
fatty acids. In simple triglycerides all
three fatty acids are identical; in
mixed triglycerides two or three different fatty acids are present.
trigonal bipyramid See illustration at complex.
trihydrate A crystalline hydrate
that contains three moles of water
per mole of compound.
trihydric alcohol See triol.
3,4,5-trihydroxybenzoic acid See
gallic acid.
triiodomethane (iodoform) A yellow volatile solid sweet-smelling
*haloform, CHI 3 ; r.d. 4.1; m.p. 115°C.
It is made by the haloform reaction.
triiron tetroxide (ferrosoferric
oxide) A black magnetic oxide,
Fe 3 O 4 ; r.d. 5.2. It is formed when iron
is heated in steam and also occurs
naturally as the mineral *magnetite.
The oxide dissolves in acids to give a
mixture of iron(II) and iron(III) salts.
trimethylaluminium (aluminium
trimethyl) A colourless liquid,
Al(CH 3 ) 3 , which ignites in air and reacts with water to give aluminium
hydroxide and methane, usually with
extreme vigour; r.d. 0.752; m.p. 0°C;
535
trimethylaluminium
t
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0°C); m.p. –111.3°C; b.p. 7°C. It is the
acid anhydride of malonic acid, from
which it can be prepared by dehydration using phosphorus(V) oxide. The
molecule is linear (O:C:C:C:O).
tricarboxylic acid cycle See krebs
cycle.
trichloroethanal (chloral) A liquid
aldehyde, CCl 3 CHO; r.d. 1.51; m.p.
–57.5°C; b.p. 97.8°C. It is made by
chlorinating ethanal and used in
making DDT. See also 2,2,2trichloroethanediol.
2,2,2-trichloroethanediol (chloral
hydrate) A colourless crystalline
solid, CCl 3 CH(OH) 2 ; r.d. 1.91; m.p.
57°C; b.p. 96.3°C. It is made by the
hydrolysis of trichloroethanal and is
unusual in having two –OH groups
on the same carbon atom. Gem diols
of this type are usually unstable; in
this case the compound is stabilized
by the presence of the three Cl
atoms. It is used as a sedative.
trichloroethene (trichlorethylene)
A colourless liquid, CCl 2 =CHCl, b.p.
87°C. It is toxic and nonÛammable,
with a smell resembling that of chloroform (trichloromethane). It is
widely used as a solvent in dry cleaning and degreasing. It is also used to
extract oils from nuts and fruit, as
an anaesthetic, and as a Üre extinguisher.
trichloromethane (chloroform) A
colourless volatile sweet-smelling liquid *haloform, CHCl 3 ; r.d. 1.48; m.p.
–63.5°C; b.p. 61.7°C. It can be made
by chlorination of methane (followed
by separation of the mixture of products) or by the haloform reaction. It
is an effective anaesthetic but can
cause liver damage and it has now
been replaced by other halogenated
hydrocarbons. Chloroform is used as
a solvent and raw material for making other compounds.
triclinic See crystal system.
tridymite A mineral form of *silicon(IV) oxide, SiO 2 .
triethanolamine See ethanolamine.
triglyceride (triacylglycerol) An
ester of glycerol (propane-1,2,3-triol)
in which all three hydroxyl groups
are esteriÜed with a fatty acid.
Triglycerides are the major constituent of fats and oils and provide a
concentrated food energy store in living organisms as well as cooking fats
and oils, margarines, etc. Their physical and chemical properties depend
on the nature of their constituent
fatty acids. In simple triglycerides all
three fatty acids are identical; in
mixed triglycerides two or three different fatty acids are present.
trigonal bipyramid See illustration at complex.
trihydrate A crystalline hydrate
that contains three moles of water
per mole of compound.
trihydric alcohol See triol.
3,4,5-trihydroxybenzoic acid See
gallic acid.
triiodomethane (iodoform) A yellow volatile solid sweet-smelling
*haloform, CHI 3 ; r.d. 4.1; m.p. 115°C.
It is made by the haloform reaction.
triiron tetroxide (ferrosoferric
oxide) A black magnetic oxide,
Fe 3 O 4 ; r.d. 5.2. It is formed when iron
is heated in steam and also occurs
naturally as the mineral *magnetite.
The oxide dissolves in acids to give a
mixture of iron(II) and iron(III) salts.
trimethylaluminium (aluminium
trimethyl) A colourless liquid,
Al(CH 3 ) 3 , which ignites in air and reacts with water to give aluminium
hydroxide and methane, usually with
extreme vigour; r.d. 0.752; m.p. 0°C;
535
trimethylaluminium
t
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