of Organic Chemistry
chemistry is the study of compounds of carbon. Carbon has a tendency to form
more compounds with itself and other atoms (H, O, N, S and halogens) than any
other elements. The tendency of an atom to form a chain of bonds with the atoms
of the same element is called catenation. The high strength of C-C bond is
responsible for its catenation property.
word 'organic' means 'derived from living organisms'. Organic compounds were
thought to be found only in living things. Cell the basic unit of living
things, consumes, creates and consists of mainly organic compounds. DNA, the
genetic material, the lipids, that forms our cell membrane and the glycogen the
energy reserve stored in our liver are all organic compounds. Except few
inorganic compounds like salt, water etc... all others such as food, medicine,
clothing, cosmetics, fuel etc... are compounds of carbon. All the essential
biochemical reactions are also organic in nature leading to the fomation
various essential bioorganic molecules such as lipoproteins, phospolipids,
of acetic acid by kolbe and methane by Berthlot, confirmed that organic
compounds can be synthesized in laboratory. Since then, millions of organic
compounds were synthesised and characterised. The field of organic chemistry is
very vast and its principles find applications in many industries including
food, textile, pertrochemical, pharmaceutical, dye, polymers, fetiliser,
cosmetics etc... Discussing the importance of organic chemistry is just like
describing a drop of water in a mighty ocean.
knowledge of chemical bonding and molecular structure will help in
understanding the properties of organic compounds. We know that, the carbon has
four valance electrons and its ground state electronic configuration is 1s2
2s2 2p2. An atom can attain noble gas electronic
configuration either by transferring or sharing of electrons. It is not
possible for the carbon to form either C4+ or C4- ions to
attain the nearest noble gas configuration, as it requires large amount of
energy. This implies that carbon cannot form ionic bond. Almost in all
compounds of carbon, it forms four covalent bonds.
formation of four covalent bonds can be explained as below. During bond
formation, one of the electrons from 2s orbital is promoted to 2pz
orbital. The formation of four sigma bonds by carbon can be explained on the
basis of sp3 hybridisation of carbon. Carbon forms multiple (double and triple)
bonds in certain compounds. These can be explained by sp2 and sp
hybridisation of carbon. The carbon forms relatively short bonds which enable
the lateral overlap of unhybridised 2p orbitals of sp2 and sp
hybridised carbon to form one and two pi bonds respectively.
Molecular stucture can be derived from the type of
hybridisation. An sp3 hybridised carbon will have a tetrahedral
geometry, a sp2 hybridised carbon will have trigonal planar
geometry. and sp hybridised carbon will have a linear geometry.
organic compounds have the following characteristic properties.
They are covalent compounds of carbon and generally insoluble in water and
readily soluble in organic solvent such as benzene, toluene, ether, chloroform
Many of the organic compounds are inflammable (except CCl4).They
possess low boiling and melting points due to their covalent nature
Organic compounds are characterised by functional groups. A functional group is
an atom or a specific combination of bonded atoms that react in a characteristic
way, irrespective of the organic molecule in which it is present. In almost all
the cases, the reaction of an organic compound takes place at the functional
group. They exhibit isomerism which is a unique phenomenon.
4. Homologous series: A series of organic compounds each
containing a characteric functional
group and the successive members differ from each other in molecular formula by
a CH2 group is called homologous series. Eg.
Alkanes: Methane (CH4), Ethane (C2H6),
Propane (C3H8) etc..
Alcohols: Methanol (CH3OH), Ethanol
(C2H5OH) Propanol (C3H7OH) etc..)
of the homologous series are represented by a general formula Alkanes CnH2n+2,
Alkenes CnH2n, Alkynes CnH2n-2 and
can be prepared by general methods. They show regular gradation in physical
properties but have almost similar chemical property.