petroleum. Its main use is as bottled
gas for fuel.
propanedioic acid (malonic acid)
A white crystalline dicarboxylic acid,
HOOCCH 2 COOH; m.p. 132°C. It de-
composes above its melting point to
ethanoic acid. Propanedioic acid is
used in the synthesis of other dicar-
boxylic acids.propanoic acid (propionic acid) A
colourless liquid *carboxylic acid,
CH 3 CH 2 COOH; r.d. 0.99; m.p.
–20.8°C; b.p. 141°C. It is used to
make calcium propanate – an addi-
tive in bread.
propanol Either of two *alcohols
with the formula C 3 H 7 OH. Propan-1-
ol is CH 3 CH 2 CH 2 OH and propan-2-ol
is CH 3 CH(OH)CH 3. Both are colour-
less volatile liquids. Propan-2-ol is
used in making propanone (acetone).
propanone (acetone)A colourless
Ûammable volatile compound,
CH 3 COCH 3 ; r.d. 0.79; m.p. –95.4°C;
b.p. 56.2°C. The simplest *ketone,
propanone is miscible with water. It
is made by oxidation of propan-2-ol
(see propanol) or is obtained as a by-
product in the manufacture of phe-
nol from cumene; it is used as a
solvent and as a raw material for
making plastics.propellant 1.A substance that
burns rapidly in a controlled way,
used to propel a projectile (e.g. from
a gun). InÜrearms, gunpowder and
cordite are common examples. 2.A
fuel used in a rocket engine. Usually
the propellant is a fuel and an oxi-
dizer; for example kerosene or liquid
hydrogen with a liquid oxygen pro-
pellant. 3.A substance used to pro-
duce the spray in an aerosol can.
Aerosol propellants are volatile sub-
stances that can be liqueÜed under
pressure and are able to dissolve the
working substance. When the pres-
sure is released, the liquid vaporizesproducing the spray. Formerly
chloroÛuorocarbons were used but
their use has been discontinued be-
cause of their effect on the ozone
layer. Most aerosol cans use liquid
hydrocarbon mixtures as the propel-
lant.propenal (acrolein) A colourless
pungent liquid unsaturated aldehyde,
CH 2 :CHCHO; r.d. 0.84; m.p. –87°C;
b.p. 53°C. It is made from propene
and is used in producing polyester
and polyurethane resins.propene (propylene) A colourless
gaseous hydrocarbon, CH 3 CH:CH 2 ;
m.p. –185.25°C; b.p. –47.4°C. It is an
*alkene obtained from petroleum by
cracking alkanes. Its main use is in
the manufacture of polypropene.propenoate (acrylate)A salt or
ester of *propenoic acid.propenoic acid (acrylic acid)An
unsaturated liquid *carboxylic acid,
CH 2 :CHCOOH; m.p. 13°C; b.p.
141.6°C. It readily polymerizes and it
is used in the manufacture of
*acrylic resins.
propenol (allyl alcohol)A pungent-
smelling colourless unsaturated liq-
uid alcohol, CH 2 =CHCH 2 OH; b.p.
97 °C. It is found in wood alcohol and
can be prepared in the laboratory by
reducing propenal or by heating glyc-
erol with oxalic acid. Industrially, it
is made by the high-temperature cat-
alytic reaction between propenal and
2-propanol or by the hydrolysis of 2-
chloropropene, which is made by
chlorinating propene. Potassium per-
manganate oxidizes propenol to glyc-
erol and silver oxide converts it to a
mixture of propenoic acid and prope-
nal.propenonitrile (acrylonitrile; vinyl
cyanide)A colourless liquid,
H 2 C:CHCN; r.d. 0.81; m.p. –83.5°C. It
is an unsaturated nitrile, made frompropanedioic acid 440p