Dictionary of Chemistry [6th Ed.]

C 6 H 12 N 4 , which is obtained from am-
monia and methanal. Cyclonite is a
very powerful explosive used mainly
for military purposes. It is also called
RDX. The abbreviation is for ‘Re-
search Department composition X’,
used at the Chemical Research and
Development Department, Wool-
wich.

cyclo-octatetraene(COT)A yellow
liquid cyclic compound, C 8 H 8 , with
eight carbon atoms and four double
bonds in its ring; b.p. 142°C. It is
made by polymerizing ethyne (acety-
lene) in the presence of nickel salts.
It forms addition compounds and cer-
tain metal complexes, such as ura-
nocene, (C 8 H 8 ) 2 U.

cyclopentadiene A colourless liq-
uid cyclic alkene, C 5 H 6 ; r.d. 0.8021;
m.p. –97.2°C; b.p. 40.0°C. It is pre-
pared as a by-product during the frac-
tional distillation of crude benzene
from coal tar. It undergoes condensa-
tion reactions with ketones to give
highly coloured compounds (ful-
venes) and readily undergoes poly-
merization at room temperature to
give the dimer, dicyclopentadiene.
Cyclopentadiene itself is not an aro-
matic compound because it does not
have the required number of pi elec-
trons. However, removal of a hydro-
gen atom produces the stable
cyclopentadienyl ion, C 5 H 5 – , which
does have aromatic properties. In
particular, the ring can coordinate to
positive ions in such compounds as
ferrocene.

159 cystine

c

C

H 2

CH

C

H

C

H

CH

Cyclopentadiene

Cyclophane

cyclopentadienyl ionSee cy-

clopentadiene.

cyclophaneA compound consist-

ing of one or more aromatic rings

forming part of a larger ring system

in which aliphatic chains of the CH 2

groups link the aromatic rings. Com-

pounds of this type have the sufÜx

phanein their names. Depending on

the sizes of the (CH 2 )nchains, the aro-

matic rings may not be planar.

A

• Information about IUPAC nomenclature

cyclopropane A colourless gas,

C 3 H 6 , b.p. –34.5°C, whose molecules

contain a triangular ring of carbon

atoms. It is made by treating 1,3-di-

bromopropane with zinc metal, and

is used as a general anaesthetic.

cyclosarinA highly toxic colourless

liquid, C 7 H 14 FO 2 P; r.d. 1.13; m.p.

–30°C; b.p. 239°C. it is aÛuorinated

organophosphorus compound,

(Ûuoromethylphosphoryl)oxycyclo-

hexane. Cyclosarin was discovered in

1949 and belongs to the G-series of

*nerve agents (GF).

cyclotetramethylenetetran-

itramineSee hmx.

cylinder gasSee bottled gas.

cysteineSee amino acid.

cystineA molecule resulting from

the oxidation reaction between the

sulphydryl (–SH) groups of two cys-