Dictionary of Chemistry [6th Ed.]

C 6 H 11 NO; r.d. 1.02; m.p. 69–71°C; b.p.

139 °C. It is a *lactam containing the

–NH.CO– group withÜve CH 2 groups

making up the rest of the seven-

membered ring. Caprolactam is used

in making *nylon.

caprylic acidSee octanoic acid.

capture Any of various processes in

which a system of particles absorbs

an extra particle. There are several

examples in atomic and nuclear

physics. For instance, a positive ion

may capture an electron to give a

neutral atom or molecule. Similarly,

a neutral atom or molecule capturing

an electron becomes a negative ion.

An atomic nucleus may capture a

neutron to produce a different (often

unstable) nucleus. Another type of

nuclear capture is the process in

which the nucleus of an atom ab-

sorbs an electron from the innermost

orbit (the K shell) to transform into a

different nucleus. In this process

(called K capture) the atom is left in

an excited state and generally decays

by emission of an X-ray photon.

Radiative capture is any such

process in which the capture results

in an excited state that decays by

emission of photons. A common ex-

ample is neutron capture to yield an

excited nucleus, which decays by

emission of a gamma ray.

carat1.A measure ofÜneness (pu-

rity) of gold. Pure gold is described as

24-carat gold. 14-carat gold contains

14 parts in 24 of gold, the remainder

usually being copper. 2.A unit of

mass equal to 0.200 gram, used to

measure the masses of diamonds and

other gemstones.

carbamideSee urea.

carbanionAn organic ion with a

negative charge on a carbon atom;

i.e. an ion of the type R 3 C–. Carban-

ions are intermediates in certain

types of organic reaction (e.g. the

*aldol reaction).

carbazoleA white crystalline com-

pound found with anthracene,

C 12 H 9 N; m.p. 238°C; b.p. 335°C. It is

used in the manufacture of dyestuffs.

caprylic acid 98

c

N

H

1

2

3

4

5

6

7

8

9

5a 4a

9a 9b

Carbazole

carbeneA species of the type R 2 C:,

in which the carbon atom has two

electrons that do not form bonds.

Methylene, :CH 2 , is the simplest ex-

ample. Carbenes are highly reactive

and exist only as transient intermedi-

ates in certain organic reactions.

They attack double bonds to give cy-

clopropane derivatives. They also

cause insertion reactions, in which

the carbene group is inserted be-

tween the carbon and hydrogen

atoms of a C–H bond:

C–H + :CR 2 →C–CR 2 –H

carbenium ionSee carbocation.

carbideAny of various compounds

of carbon with metals or other more

electropositive elements. True car-

bides contain the ion C4–as in Al 4 C 3.

These are saltlike compounds giving

methane on hydrolysis, and were for-

merly called methanides. Com-

pounds containing the ion C 2 2–are

also saltlike and are known as dicar-

bides. They yield ethyne (acetylene)

on hydrolysis and were formerly

called acetylides. The above types of

compound are ionic but have par-

tially covalent bond character, but

boron and silicon form true covalent

carbides, with giant molecular struc-

tures. In addition, the transition met-

als form a range of interstitial