(p-DMAB) A substituted aldehyde
used in a presumptive test for LSD
and for psilocybin. A 1% solution of pBMAB is used in 10% mineral acid (either sulphuric acid or hydrochloric
acid). This reagent is called Ehrlick’s
reagent or Van Urk’s reagent. LSD is
indicated by a purple colouration;
psilocybin by a red-brown colour.
dimethylbenzenes (xylenes)
Three compounds with the formula
(CH 3 ) 2 C 6 H 4 , each having two methyl
groups substituted on the benzene
ring. 1,2-dimethylbenzene is orthoxylene, etc. A mixture of the isomers
(b.p. 135–145°C) is obtained from petroleum and is used as a clearing
agent in preparing specimens for optical microscopy.
dimethylformamide (DMF) A
colourless liquid compound,
(CH 3 ) 2 NCHO; r.d. 0.944; m.p. –61°C;
b.p. 153°C. The systematic name is
N,N-dimethylmethanamide. It can be
made from methanoic acid (formic
acid) and dimethylamine, and is
widely used as a solvent.
1,3-dimethylxanthine See theophylline.
3,7-dimethylxanthine See theobromine.
dimethylglyoxime (DMG) A
colourless solid, (CH 3 CNOH) 2 , m.p.
234°C. It sublimes at 215°C and
slowly polymerizes if left to stand. It
is used in chemical tests for nickel,
with which it forms a dark-red complex.
dimethyl sulphoxide (DMSO) A
colourless solid, (CH 3 ) 2 SO; m.p. 18°C;
b.p. 189°C. It is used as a solvent and
as a reagent in organic synthesis.
dimorphism See polymorphism.
dinitrogen The normal form of
molecular nitrogen, N 2 used to distinguish it from nitrogen atoms.
dinitrogen oxide (nitrous oxide) A
colourless gas, N 2 O, d. 1.97 g dm
–3
;
m.p. –90.8°C; b.p. –88.5°C. It is soluble in water, ethanol, and sulphuric
acid. It may be prepared by the controlled heating of ammonium nitrate
(chloride free) to 250°C and passing
the gas produced through solutions
of iron(II) sulphate to remove impurities of nitrogen monoxide. It is relatively unreactive, being inert to
halogens, alkali metals, and ozone at
normal temperatures. It is decomposed on heating above 520°C to nitrogen and oxygen and will support
the combustion of many compounds.
Dinitrogen oxide is used as an anaesthetic gas (‘laughing gas’) and as an
aerosol propellant.
dinitrogen tetroxide A colourless
to pale yellow liquid or a brown gas,
N 2 O 4 ; r.d. 1.45 (liquid); m.p. –11.2°C;
b.p. 21.2°C. It dissolves in water with
reaction to give a mixture of nitric
acid and nitrous acid. It may be readily prepared in the laboratory by the
reaction of copper with concentrated
nitric acid; mixed nitrogen oxides
containing dinitrogen oxide may also
be produced by heating metal nitrates. The solid compound is wholly
N 2 O 4 and the liquid is about 99%
N 2 O 4 at the boiling point; N 2 O 4 is diamagnetic. In the gas phase it dissociates to give nitrogen dioxide
N 2 O 4 ˆ 2NO 2
Because of the unpaired electron this
is paramagnetic and brown. Liquid
N 2 O 4 has been widely studied as a
nonaqueous solvent system (selfionizes to NO
+ and NO 3
– ). Dinitrogen
tetroxide, along with other nitrogen
oxides, is a product of combustion
engines and is thought to be involved
in the depletion of stratospheric
ozone.
dinucleotide A compound consisting of two *nucleotides.
dimethylbenzenes
178
d
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used in a presumptive test for LSD
and for psilocybin. A 1% solution of pBMAB is used in 10% mineral acid (either sulphuric acid or hydrochloric
acid). This reagent is called Ehrlick’s
reagent or Van Urk’s reagent. LSD is
indicated by a purple colouration;
psilocybin by a red-brown colour.
dimethylbenzenes (xylenes)
Three compounds with the formula
(CH 3 ) 2 C 6 H 4 , each having two methyl
groups substituted on the benzene
ring. 1,2-dimethylbenzene is orthoxylene, etc. A mixture of the isomers
(b.p. 135–145°C) is obtained from petroleum and is used as a clearing
agent in preparing specimens for optical microscopy.
dimethylformamide (DMF) A
colourless liquid compound,
(CH 3 ) 2 NCHO; r.d. 0.944; m.p. –61°C;
b.p. 153°C. The systematic name is
N,N-dimethylmethanamide. It can be
made from methanoic acid (formic
acid) and dimethylamine, and is
widely used as a solvent.
1,3-dimethylxanthine See theophylline.
3,7-dimethylxanthine See theobromine.
dimethylglyoxime (DMG) A
colourless solid, (CH 3 CNOH) 2 , m.p.
234°C. It sublimes at 215°C and
slowly polymerizes if left to stand. It
is used in chemical tests for nickel,
with which it forms a dark-red complex.
dimethyl sulphoxide (DMSO) A
colourless solid, (CH 3 ) 2 SO; m.p. 18°C;
b.p. 189°C. It is used as a solvent and
as a reagent in organic synthesis.
dimorphism See polymorphism.
dinitrogen The normal form of
molecular nitrogen, N 2 used to distinguish it from nitrogen atoms.
dinitrogen oxide (nitrous oxide) A
colourless gas, N 2 O, d. 1.97 g dm
–3
;
m.p. –90.8°C; b.p. –88.5°C. It is soluble in water, ethanol, and sulphuric
acid. It may be prepared by the controlled heating of ammonium nitrate
(chloride free) to 250°C and passing
the gas produced through solutions
of iron(II) sulphate to remove impurities of nitrogen monoxide. It is relatively unreactive, being inert to
halogens, alkali metals, and ozone at
normal temperatures. It is decomposed on heating above 520°C to nitrogen and oxygen and will support
the combustion of many compounds.
Dinitrogen oxide is used as an anaesthetic gas (‘laughing gas’) and as an
aerosol propellant.
dinitrogen tetroxide A colourless
to pale yellow liquid or a brown gas,
N 2 O 4 ; r.d. 1.45 (liquid); m.p. –11.2°C;
b.p. 21.2°C. It dissolves in water with
reaction to give a mixture of nitric
acid and nitrous acid. It may be readily prepared in the laboratory by the
reaction of copper with concentrated
nitric acid; mixed nitrogen oxides
containing dinitrogen oxide may also
be produced by heating metal nitrates. The solid compound is wholly
N 2 O 4 and the liquid is about 99%
N 2 O 4 at the boiling point; N 2 O 4 is diamagnetic. In the gas phase it dissociates to give nitrogen dioxide
N 2 O 4 ˆ 2NO 2
Because of the unpaired electron this
is paramagnetic and brown. Liquid
N 2 O 4 has been widely studied as a
nonaqueous solvent system (selfionizes to NO
+ and NO 3
– ). Dinitrogen
tetroxide, along with other nitrogen
oxides, is a product of combustion
engines and is thought to be involved
in the depletion of stratospheric
ozone.
dinucleotide A compound consisting of two *nucleotides.
dimethylbenzenes
178
d
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