chiralityThe property of existing
in left- and right-handed structural
forms. See optical activity.
chirality elementThe part of a
molecule that makes it exist in left-
and right-handed forms. In most
cases this is a chirality centre (i.e. an
asymmetric atom). In certain cases
the element is a chirality axis. For ex-
ample, in allenenes of the type
R 1 R 2 C=C=CR 3 R 4 the C=C=C chain is a
chirality axis. Certain ring com-
pounds may display chirality as a re-
sult of a chirality plane in the
molecule.chirooptical spectroscopy Spec-
troscopy making use of the proper-
ties of chiral substances when they
interact with polarized light of vari-
ous wavelengths. Optical rotatory
dispersion(the change of optical rota-
tion with wavelength) and *circular
dichroism are old examples of chi-
rooptical spectroscopy. More recent
types of chirooptical spectroscopy are
vibrational optical rotatory disper-
sion, vibrational circular dichroism.
(VCD), and Raman optical activity
(ROA), which are all the result of
the interaction between chiral sub-
stances and polarized infrared
electromagnetic radiation; these
techniques are known as vibrational
optical activity (VOA), as they are as-
sociated with transitions in the vibra-
tional energy levels in the electronic
ground state of a molecule. Chiro-
optical spectroscopy is used in the
analysis of the structure of mol-
ecules.chitinA *polysaccharide compris-
ing chains of N-acetyl-d-glucosamine,
a derivative of glucose. Chitin is
structurally very similar to cellulose
and serves to strengthen the support-
ing structures of various inverte-
brates. It also occurs in fungi.chloralSee trichloroethanal.chloral hydrateSee 2,2,2-
trichloroethanediol.chloratesSalts of the chloric acids;
i.e. salts containing the ions ClO–
(chlorate(I) or hypochlorite), ClO 2 –
(chlorate(III) or chlorite), ClO 3 – (chlo-
rate(V)), or ClO 4 – (chlorate(VII) or per-
chlorate). When used without
speciÜcation of an oxidation state the
term ‘chlorate’ refers to a chlorate(V)
salt.chloric acidAny of the oxoacids of
chlorine: *chloric(I) acid, *chloric(III)
acid, *chloric(V) acid, and
*chloric(VII) acid. The term is com-
monly used without speciÜcation of
the oxidation state of chlorine to
mean chloric(V) acid, HClO 3.chloric(I) acid (hypochlorous acid)
A liquid acid that is stable only in so-
lution, HOCl. It may be prepared by
the reaction of chlorine with an agi-
tated suspension of mercury(II) oxide.
Because the disproportionation of
the ion ClO–is slow at low tempera-
tures chloric(I) acid may be produced,
along with chloride ions by the reac-
tion of chlorine with water at 0°C. At
higher temperatures disproportiona-
tion to the chlorate(V) ion, ClO 3 – ,
takes place. Chloric(I) acid is a very
weak acid but is a mild oxidizing
agent and is widely used as a bleach-
ing agent.chloric(III) acid (chlorous acid) A
pale-yellow acid known only in solu-
tion, HClO 2. It is formed by the reac-
tion of chlorine dioxide and water
and is a weak acid and an oxidizing
agent.chloric(V) acid (chloric acid)A
colourless unstable liquid, HClO 3 ; r.d.
1.2; m.p. <–20°C; decomposes at
40 °C. It is best prepared by the reac-
tion of barium chlorate with sul-
phuric acid although chloric(V) acid
is also formed by the disproportiona-chirality 120c