which rapidly darkens on standing in
air. It is made by the reduction of 1,4-
nitrophenylamine and is used as a
photographic develop and hair dye.
1,2-diaminoethane(ethylenedi-
amine)A colourless fuming liquid
that smells of ammonia,
H 2 NCH 2 CH 2 NH 2 ; b.p. 116°C. It is
made from ammonia and 1,2-
dichloroethane, which are heated
under pressure with a copper(I) chlo-
ride catalyst. In air it absorbs water
and carbon dioxide to form di-
aminoethane carbamate. With fatty
acids diaminoethane produces soaps,
employed as emulsifying agents and
detergents. It is also used as a solvent
(for resins) and in making coatings,
paper and textiles. Crystals of its tar-
trate derivative are employed in
piezoelectric devices. It is a bidentate
ligand, given the symbol en in formu-
lae.
1,6-diaminohexane(hexamethyl-
enediamine)A solid colourless
amine, H 2 N(CH 2 ) 6 NH 2 ; m.p. 41°C; b.p.
204 °C. It is made by oxidizing cyclo-
hexane to hexanedioic acid, reacting
this with ammonia to give the am-
monium salt, and dehydrating the
salt to give hexanedionitrile
(NC(CH 2 ) 6 CN). This is reduced with
hydrogen to the diamine. The com-
pound is used, with hexanedioic acid,
for producing *nylon 6,6.
diamond The hardest known min-
eral (with a hardness of 10 on Mohs’
scale). It is an allotropic form of pure
*carbon that has crystallized in the
cubic system, usually as octahedra or
cubes, under great pressure. Dia-
mond crystals may be colourless and
transparent or yellow, brown, or
black. They are highly prized as gem-
stones but also have extensive uses
in industry, mainly for cutting and
grinding tools. Diamonds occur in an-
cient volcanic pipes of kimberlite;
the most important deposits are in
South Africa but others are found in
Tanzania, the USA, Russia, and Aus-
tralia. Diamonds also occur in river
deposits that have been derived from
weathered kimberlite, notably in
Brazil, Zaïre, Sierra Leone, and India.
Industrial diamonds are increasingly
being produced synthetically.173 diastereoisomers
d
Diamonddiamond-anvil cellA device for
producing very high pressures. A
sample of material to be subject to
the high pressure is placed in a cav-
ity between two high-quality dia-
monds. The diamond-anvil cell
operates like a nutcracker, with pres-
sures up to 1 megabar (10^11 Pa) being
exerted by turning a screw. The pres-
sure exerted can be determined by
spectroscopy for small samples of
ruby in the material being com-
pressed, while the sample itself is ob-
served optically. A use of the
diamond-anvil cell is to study the in-
sulator–metal transition in such sub-
stances as iodine as the pressure is
increased. This type of study is the
nearest laboratory approach to the
structure of matter in the conditions
obtaining in the interior of the earth.diaspore A mineral form of a
mixed aluminium oxide and hydrox-
ide, AlO.OH. See aluminium hydrox-
ide.diastaseSee amylase.
diastereoisomers Stereoisomers
that are not identical and yet not
mirror images. For instance, the d-
form of tartaric acid and the meso