Heterocyclic compound
Heterocyclic compounds are organic compounds with a ring structure that contains
in the cycle carbon atoms and at least one other element, such as N, O, or S.
Heterocyclic compounds include many of the biochemical material essential to life.
For example, nucleic acids, the chemical substances that carry the genetic
information controlling inheritance, consist of long chains of heterocyclic units held
together by other types of materials. Many naturally occurring pigments, vitamins,
and antibiotics are heterocyclic compounds, as are most hallucinogens. Modern
society is dependent on synthetic heterocycles for use as drugs, pesticides, dyes,
and plastics.
Pyridine
General Aspects of Heterocyclic Compounds
The most common heterocycles are those having five- or six-membered rings and
containing heteroatoms of nitrogen (N), oxygen (O), or sulfur (S). The best known
of the simple heterocyclic compounds are pyridine, pyrrole, furan, and thiophene. A
molecule of pyridine contains a ring of six atoms—five carbon atoms and one
nitrogen atom. Pyrrole, furan, and thiophene molecules each contain five-membered
rings, composed of four atoms of carbon and one atom of nitrogen, oxygen, or sulfur,
respectively.
Pyridine
Pyridine is a colorless liquid. It boils at 115 degrees Celsius (239 F) and freezes at 42 degrees Celsius (-43.6 F). Its density is very close to that of water, at 0.982 g/cm3
(water's density is 1). It is able to mix easily with water and most other organic
solvents.
Pyridine and pyrrole are both nitrogen heterocycles—their molecules contain
nitrogen atoms along with carbon atoms in the rings. The molecules of many
biological materials consist in part of pyridine and pyrrole rings, and such materials
yield small amounts of pyridine and pyrrole upon strong heating. In fact, both of
these substances were discovered in the 1850s in an oily mixture formed by strong
heating of bones. Today, pyridine and pyrrole are prepared by synthetic reactions.
Their chief commercial interest lies in their conversion to other substances, chiefly
dyestuffs and drugs. Pyridine is used also as a solvent, a waterproofing agent,
a rubber additive, an alcohol denaturant, and a dyeing adjunct.
Pyrrole
characterized by a ring structure composed of four carbon atoms and
one nitrogen atom. The simplest member of the pyrrole family is pyrrole itself,
a compound with molecular formula C4H5N. The pyrrole ring system is present in
the amino acids proline and hydroxyproline; and in coloured natural products, such
as chlorophyll, heme (a part of hemoglobin), and the bile pigments. Pyrrole
compounds also are found among the alkaloids, a large class of alkaline organic
nitrogen compounds produced by plants.
Uses of pyrrole
Pyrrole is a precursor to the drug tolmetin. Polypyrrole is of some commercial
value. N-Methylpyrrole is a precursor to N-methylpyrrolecarboxylic acid, a
building-block in pharmaceutical chemistry. Pyrroles are also found in several
drugs, including atorvastatin, ketorolac etc. Pyrroles are used as lightfast red, scarlet,
and carmine pigments.[
Indole
a colorless to yellowish solid, C8H7N, having a low melting point and a fecal odor,
found in the oil of jasmine and clove and as a putrefaction product from animals'
intestines: used in perfumery and as a reagent.
Uses
Indole-3-carbinol is a substance found in vegetables such as broccoli, Brussels
sprouts, cabbage, collards, cauliflower, kale, mustard greens, turnips, and rutabagas.
It can also be produced in the laboratory.
Indole-3-carbinol is used for prevention of breast cancer, colon cancer, and other
types of cancer. The National Institutes of Health (NIH) has reviewed indole-3carbinol as a possible cancer preventive agent and is now
sponsoring clinical research for breast cancer prevention.
Structure of Indole
Quinoline
Quinoline, any of a class of organic compounds of the aromatic heterocyclic series
characterized by a double-ring structure composed of a benzene and a pyridine ring
fused at two adjacent carbon atoms. The benzene ring contains six carbon atoms,
while the pyridine ring contains five carbon atoms and a nitrogen atom. The simplest
member of the quinoline family is quinoline itself, a compound with molecular
structure C9H7N.
Uses of Quinoline
Quinoline is used principally for the manufacture of nicotinic acid, which
prevents pellagra in humans, and other chemicals. Several methods are known for
its preparation, and production of synthetic quinoline exceeds that from coal tar.
Several alkaloids (alkaline organic compounds produced in plants) are members of
the quinoline family; these include quinine and other derivatives from the cinchona
tree. The antimalarial drugs chloroquine, mefloquine, and amodiaquin are synthetic
quinoline compounds, as are dibucaine hydrochloride, a long-acting
local anesthetic that is commonly used as a topical agent to relieve pain from minor
cuts and insect bites and stings, and cyanine, the oldest of an important class of dyes.
Structure of Quinoline