known as hashish. The normal
method of using cannabis is to
smoke it, although it can also be
taken in certain foods. Cannabis is a
class C controlled substance in the
UK. It contains a large number of re-
lated compounds known as herbal
cannabinoids. The main active com-
ponent is tetrahydrocannabinol
(THC).
Cannizzaro, Stanislao
(1826–1910) Italian chemist. He dis-
covered the *Cannizzaro reaction in
- His main contribution to chem-
istry was his recognition of the valid-
ity of *Avogadro’s law and his
deduction that common gases such
as H 2 and O 2 are diatomic molecules.
This led to the establishment of a re-
liable system of atomic and molecu-
lar weights.
Cannizzaro reaction A reaction of
aldehydes to give carboxylic acids
and alcohols. It occurs in the pres-
ence of strong bases with aldehydes
that do not have alpha hydrogen
atoms. For example, benzenecar-
baldehyde gives benzenecarboxylic
acid and benzyl alcohol:
2C 6 H 5 CHO →C 6 H 5 COOH +
C 6 H 5 CH 2 OHAldehydes that have alpha hydrogen
atoms undergo the aldol reaction in-
stead. The Cannizzaro reaction is an
example of a disproportionation. It
was discovered by Stanislao *Canniz-
zaro.
canonical formOne of the possi-
ble structures of a molecule that to-
gether form a *resonance hybrid.
capillaryA tube of small diameter.
capillary electrophoresis (CE)A
technique for investigating mixtures
of charged species. In capilliary zone
electrophoresis (CZE), the sample is
introduced into aÜne capillary tube,
with each end of the capillary placed
in a reservoir containing an elec-
trolyte (e.g. a buffer solution). The
source reservoir contains a positive
electrode and the destination reser-
voir contains a negative electrode. A
high potential difference is main-
tained between the electrodes. Com-
ponents of the sampleÛow through
the buffer solution in the capillary
under the inÛuence of the electric
Üeld. Their mobility depends on their
charge, size, and shape, and the com-
ponents separate as they move
through the tube. They are detected
close to the end of the capillary, usu-
ally by ultraviolet absorption. Capil-
liary gel electrophoresis (CGE) is used
for separating large charged species,
such as DNA fragments. The capil-
liary isÜlled with a gel and separa-
tion depends on the size of the
species. In CE, a graph of detector
output against time is known as an
electropherogram. Individual compo-
nents can be identiÜed by their reten-
tion times in the capillary. The
technique can be highly sensitive
and is widely used in forensic labora-
tories.
capillary gel electrophoresis
(CGE)See capillary electro-
phoresis.capillary zone electrophoresis
(CZE)See capillary electro-
phoresis.capric acidSee decanoic acid.caproic acid See hexanoic acid.
caprolactam (6-hexanelactam)A
white crystalline substance,97 caprolactam
c
Caprolactam