3. Hydrocarbons are organic compounds that contain
only carbon and hydrogen. They are extremely
important to our society because so many products
are derived from them: fuels, fabrics, plastics,
antifreezes, anaesthetics, insecticides, to name a
few. The major source of aliphatic hydrocarbons is
petroleum, an extremely complex mixture of
compounds. Each of us, on the average, uses several
tons of petroleum each year (directly or indirectly),
mostly for fuel. Aromatic hydrocarbons are mainly
obtained from coal, although small amounts are also
obtained from petroleum.
4. Hydrocarbons may be saturated or unsaturated. A
saturated hydrocarbon is one that is maxed out in terms of
the number of hydrogen that can be present given the
number of carbons in the compound; it is impossible to
add more hydrogen atoms to the compound so it is
saturated with hydrogen. Acyclic alkanes are saturated;
there is no way additional hydrogen can be added while
keeping the same number of carbons and maintaining
normal bonding between the atoms.Alkenes, alkynes,
aromatic compounds, and cyclic alkanes are unsaturated
because hydrogen can be added to them, in theory and
usually in practice, making them into acyclic alkanes.BY :Shubham
5. The hydrocarbon that contain only carbon-carbon single bond is called Saturated
Hydrocarbon. These include open chain hydrocarbon as well as closed
chain hydrocarbons. These compounds are called saturated because
they have maximum number of bonded hydrogen
If different carbon atoms are joined together to form an open
chain of carbon atoms with single bonds, they are called Alkanes.
For example: 2-Methylpropane (Isobutane)
If carbon atoms form a closed chain or ring, they are called Cycloalkanes.
For example: Cyclopentane
7. Alkyl Groups
The removal of one hydrogen from a
molecule of alkane gives the corresponding
alkyl group. For example, if one hydrogen is
removed from methane(CH4), we get an
alkyl group called methyl ( -CH3). Thus alkyl
groups are univalent groups with general
formula CnH2n+1 .
8. Alkenes show following types of structural isomerisms:
The isomers differ with respect to the chain of carbon atoms.
as in alkanes, ethene (C2H4) and propene(C3H6) can have
only one structure but alkenes higher than propene have
For eg: 4 3 2 1 But-1-ene
The isomers differ in the position of the double bonds. For eg:
CH2−CH=CH2−CH3 (But-1-ene) CH3−CH=CH−CH3 (But-2-ene)
9. The hydrocarbons which contain at least one special type of
hexagonal ring of carbon atoms with three double bond in
the alternate positions are called aromatic hydrocarbon. The
ring is called aromatic ring.
For example: i) Toluene ii) o-Xylene
The aromatic compounds may also contain more than one
benzene rings. For example: i) Naphthalene
10. These contain a closed chain or ring in their molecules. They
have the general formula CnH2n.
For example: i) Cyclopropane- or
11. Functional groups
Carbon forms bonds not only with hydrogen but also
with other elements as well such as oxygen, sulphur and
halogens. In a hydrocarbon chain, one or more hydrogen
can be replaced by these elements in such a way that the
tetravalency remains satisfied. Thus, an atom or a group
of atoms which largely determines the chemical
properties of an organic compound is called a functional
These heteroatoms are also present in some groups
and these groups confer characteristic properties of the
compound regardless of the carbon chain.
12. • Halo-groups: This group includes chlorine,
bromine, fluorine and iodine.
• Alcohol: The hydroxyl group attached to a
carbon chain forms alcohol.
General formula: CnH2n+1OH
Suffix used: ol
13. • Aldehyde: Carbon compounds containing -CHO
General formula: RCHO
Suffix used: al
• Ketone: Carbon compounds containing –CO-
General formula: RCOR
Suffix used: one
• Carboxylic Acid: Carbon compounds containing -
General formula: RCOOH
Suffix used: oic acid
14. Homologous series is a family of
structurally similar compounds
containing the same functional group
in which two successive members
differ by –CH2
All members of a homologous
series are called homologues.
The most important homologous
series are as follows:
Alkanes, alkenes, alkynes, alcohols,
aldehydes, ketones, carboxylic acid,
16. Nomenclature Of Alkanes
Nomenclature implies assigning proper name to the basis of certain
standard rules so that the study of these compounds may become
standard. The rules for naming them are as follows:
First of all, select the longest continues chain of carbon atoms in a molecule.
1 2 3 4 5 6 7 8 9
For eg. CH3– CH– CH2– CH2– CH2–CH– CH2– CH2–CH3
In the example ,the longest chain has nine carbons and it is
considered as parent root chain and carbon atoms which are
not included in parent chain are called substituents.BY :Shubham
17. When two or more substituents are present, then end of the parent chain
which gives the lowest set of the locants is preferred for numbering. This
rule is called lowest set of locants.
This means that when two or more different sets of locants are
possible, that set of locants which when compared term with other sets,
each in order of increasing magnitude, has the lowest term at the first
point of difference.
If the same substituent or side chain occurs more than once, the prefix
di(for 2), tri(for 3), tetra(for 4), penta(for 5),hexa(for 6)…etc., are
attached to the names of the substituents. The positions of the
substituents are indicated separately and the numerals representing
their positions are separated by commas.
18. If two or more different substituents or side chains are present in the molecule, they are
named in the alphabetical order along with their appropriate positions. Prefix are
ignored while comparing the substituents.
For eg: 1 2 3 4 5
For eg: CH3CH3
5 4 3 2 1