rived from chloros, the Greek word
for green.chloroacetic acids See chloro-
ethanoic acids.chlorobenzene A colourless highly
Ûammable liquid, C 6 H 5 Cl; r.d. 1.106;
m.p. –45.43°C; b.p. 131.85°C. It is pre-
pared by the direct chlorination of
benzene using a halogen carrier (see
friedel–crafts reaction), or manu-
factured by the *Raschig process. It
is used mainly as an industrial sol-
vent.2-chlorobuta-1,3-diene (chloro-
prene) A colourless liquid chlori-
nated diene, CH 2 :CClCH:CH 2 ; r.d.
0.96; b.p. 59°C. It is polymerized to
make synthetic rubbers (e.g. neo-
prene).chlorocruorin A greenish iron-con-
taining respiratory pigment that oc-
curs in the blood of polychaete
worms. It closely resembles *haemo-
globin.chloroethane (ethyl chloride)A
colourlessÛammable gas, C 2 H 5 Cl;
m.p. –136.4°C; b.p. 12.3°C. It is made
by reaction of ethene and hydrogen
chloride and used in making lead
tetraethyl for petrol.chloroethanoic acids (chloroacetic
acids)Three acids in which hydro-
gen atoms in the methyl group of
ethanoic acid have been replaced by
chlorine atoms. They are: mono-
chloroethanoic acid (CH 2 ClCOOH);
dichloroethanoic acid (CHCl 2 COOH);
trichloroethanoic acid (CCl 3 COOH).
The presence of chlorine atoms in
the methyl group causes electron
withdrawal from the COOH group
and makes the chloroethanoic acids
stronger acids than ethanoic acid it-
self. The Kavalues (in moles dm–3at
25 °C) are
CH 3 COOH 1.7 × 10 –5
CH 2 ClCOOH 1.3 × 10 –3CHCl 2 COOH 5.0 × 10 –2
CCl 3 COOH 2.3 × 10 –1
chloroethene (vinyl chloride)A
gaseous compound, CH 2 :CHCl; r.d.
0.911; m.p. –153.8°C; b.p. –13.37°C. It
is made by chlorinating ethene to
give dichloroethane, then removing
HCl:
C 2 H 4 + Cl 2 →CH 2 ClCH 2 Cl →
CH 2 CHCl
The compound is used in making
PVC.chloroÛuorocarbon (CFC)A type
of compound in which some or all of
the hydrogen atoms of a hydrocar-
bon (usually an alkane) have been re-
placed by chlorine andÛuorine
atoms. Most chloroÛuorocarbons are
chemically unreactive and are stable
at high temperatures. They are used
as aerosol propellants, refrigerants,
and solvents, and in the manufacture
of rigid packaging foam. A com-
monly encountered commercial
name for these compounds is freon,
e.g. freon 12 is dichlorodiÛuoro-
methane (CCl 2 F 2 ). ChloroÛuoro-
carbons, because of their chemical
inertness, can diffuse unchanged into
the upper atmosphere. Here, photo-
chemical reactions cause them to
break down and react with ozone (see
ozone layer). For this reason, their
use has been discouraged.chloroform See trichloro-
methane.chloromethane (methyl chloride)
A colourlessÛammable gas, CH 3 Cl;
r.d. 0.916; m.p. –97.1°C; b.p. –24.2°C.
It is a *haloalkane, made by direct
chlorination of methane and used as
a local anaesthetic and refrigerant.
chlorophenol Any of the various
compounds produced by chlorinating
a *phenol. Chlorophenols are fairly
acidic and have many uses, including
antiseptics, disinfectants, herbicides,chloroacetic acids 122c