diol (dihydric alcohol) An *alcohol
containing two hydroxyl groups per
molecule.
dioxan A colourless toxic liquid,
C 4 H 8 O 2 ; r.d. 1.03; m.p. 11°C; b.p.
101.5°C. The molecule has a sixmembered ring containing four CH 2
groups and two oxygen atoms at opposite corners. It can be made from
ethane-1,2-diol and is used as a solvent.
dioxin (2,4,7,8-tetrachlorodibenzop-dioxin) A toxic solid, formed in the
manufacture of the herbicide *2,4,5T and present as an impurity in
Agent Orange. It can cause skin disÜgurement (chloracne) and severe
fetal defects.
dioxonitric(III) acid See nitrous
acid.
dioxygen The normal form of molecular oxygen, O 2 , used to distinguish it from oxygen atoms or from
ozone (O 3 ).
dioxygenyl compounds Compounds containing the positive ion
O 2
+ , as in dioxygenyl hexaÛuoroplatinate O 2 PtF 6 – an orange solid
that sublimes in vacuum at 100°C.
Other ionic compounds of the type
O 2
+ [MF 6 ]
– can be prepared, where M
is P, As, or Sb.
dipeptide A compound consisting
of two amino acid units joined at the
amino (–NH 2 ) end of one and the carboxyl (–COOH) end of the other. This
peptide bond (see peptide) is formed
by a condensation reaction that involves the removal of one molecule
of water.
diphenylamine A colourless crystalline aromatic compound,
(C 6 H 5 ) 2 NH; m.p. 54°C. It is made by
heating phenylamine (aniline) with
phenylamine hydrochloride. It is a
secondary amine and is both slightly
acidic (forming an N-potassium salt)
and slightly basic (forming salts with
mineral acids). Its derivatives are employed as stabilizers for synthetic
rubber and rocket fuels.
diphenylamine test A presumptive test for nitrates. The reagent is a
solution of diphenylamine
((C 6 H 5 )2NH) in sulphuric acid. A positive result is indicated by a blue colour. It was once used in testing for
gunshot residue, but is not particularly reliable.
diphenylmethanone (benzophenone) A colourless solid,
C 6 H 5 COC 6 H 5 , m.p. 49°C. It has a characteristic smell and is used in making
perfumes. It is made from benzene
and benzoyl chloride using the
*Friedel–Crafts reaction with aluminium chloride as catalyst.
diphosgene A colourless liquid,
ClCO.O.CCl 3 , originally used in 1916
by Germany in World War I as a
chemical warfare agent. It is now
used as a reagent in organic synthesis. See also carbonyl chloride.
diphosphane (diphosphine) A yellow liquid, P 2 H 4 , which is spontaneously Ûammable in air. It is
obtained by hydrolysis of calcium
phosphide. Many of the references to
the spontaneous Ûammability of
phosphine (PH 3 ) are in fact due to
traces of P 2 H 4 as impurities.
diphosphine See diphosphane.
diphosphonates See bisphosphonates.
dipolar bond See chemical bond.
dipole A pair of separated opposite
electric charges. The dipole moment
(symbol µ) is the product of the positive charge and the distance between
the charges. Dipole moments are
often stated in *debyes; the SI unit is
the coulomb metre. In a diatomic
molecule, such as HCl, the dipole
179
dipole
d
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containing two hydroxyl groups per
molecule.
dioxan A colourless toxic liquid,
C 4 H 8 O 2 ; r.d. 1.03; m.p. 11°C; b.p.
101.5°C. The molecule has a sixmembered ring containing four CH 2
groups and two oxygen atoms at opposite corners. It can be made from
ethane-1,2-diol and is used as a solvent.
dioxin (2,4,7,8-tetrachlorodibenzop-dioxin) A toxic solid, formed in the
manufacture of the herbicide *2,4,5T and present as an impurity in
Agent Orange. It can cause skin disÜgurement (chloracne) and severe
fetal defects.
dioxonitric(III) acid See nitrous
acid.
dioxygen The normal form of molecular oxygen, O 2 , used to distinguish it from oxygen atoms or from
ozone (O 3 ).
dioxygenyl compounds Compounds containing the positive ion
O 2
+ , as in dioxygenyl hexaÛuoroplatinate O 2 PtF 6 – an orange solid
that sublimes in vacuum at 100°C.
Other ionic compounds of the type
O 2
+ [MF 6 ]
– can be prepared, where M
is P, As, or Sb.
dipeptide A compound consisting
of two amino acid units joined at the
amino (–NH 2 ) end of one and the carboxyl (–COOH) end of the other. This
peptide bond (see peptide) is formed
by a condensation reaction that involves the removal of one molecule
of water.
diphenylamine A colourless crystalline aromatic compound,
(C 6 H 5 ) 2 NH; m.p. 54°C. It is made by
heating phenylamine (aniline) with
phenylamine hydrochloride. It is a
secondary amine and is both slightly
acidic (forming an N-potassium salt)
and slightly basic (forming salts with
mineral acids). Its derivatives are employed as stabilizers for synthetic
rubber and rocket fuels.
diphenylamine test A presumptive test for nitrates. The reagent is a
solution of diphenylamine
((C 6 H 5 )2NH) in sulphuric acid. A positive result is indicated by a blue colour. It was once used in testing for
gunshot residue, but is not particularly reliable.
diphenylmethanone (benzophenone) A colourless solid,
C 6 H 5 COC 6 H 5 , m.p. 49°C. It has a characteristic smell and is used in making
perfumes. It is made from benzene
and benzoyl chloride using the
*Friedel–Crafts reaction with aluminium chloride as catalyst.
diphosgene A colourless liquid,
ClCO.O.CCl 3 , originally used in 1916
by Germany in World War I as a
chemical warfare agent. It is now
used as a reagent in organic synthesis. See also carbonyl chloride.
diphosphane (diphosphine) A yellow liquid, P 2 H 4 , which is spontaneously Ûammable in air. It is
obtained by hydrolysis of calcium
phosphide. Many of the references to
the spontaneous Ûammability of
phosphine (PH 3 ) are in fact due to
traces of P 2 H 4 as impurities.
diphosphine See diphosphane.
diphosphonates See bisphosphonates.
dipolar bond See chemical bond.
dipole A pair of separated opposite
electric charges. The dipole moment
(symbol µ) is the product of the positive charge and the distance between
the charges. Dipole moments are
often stated in *debyes; the SI unit is
the coulomb metre. In a diatomic
molecule, such as HCl, the dipole
179
dipole
d
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