Hydrocarbons are organic compounds made of only carbon and hydrogen. They are divided into two categories: aliphatic and aromatic. Aliphatic hydrocarbons include open-chain and cyclic compounds resembling open chains. Carbon atoms in aliphatic hydrocarbons are linked in chains that can be straight or branched. Aromatic hydrocarbons form ring structures with at least one carbon atom bonded to three or four other carbons. Examples are benzene and other compounds with similar properties. Hydrocarbons are named using IUPAC or common systems, which specify prefixes to indicate structure, substituents, and their positions.

2. Hydrocarbon are organic compound which
contain carbon and hydrogen only. For example
(methane) CH4
Benzene (C6H6) etc.
Hydrocarbon are divided into two major
categories i.e (A) Aliphatic hydrocarbon (B)
Aromatic hydrocarbon.
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3. These include the open chain (acyclic)
compound and
Those cyclic compounds which resemble the
open chain
Compound in their chemical properties e.g.
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4. IN these hydrocarbon, the carbon atoms are
linked
Together in the form of chains which may
either be;
In this case no carbon atom is linked
directly to more than two carbon
atoms.
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5. In this Case, at least one carbon atom is
linked directly to three or four carbon
atoms. E.g
CH3
CH3- CH- CH3
Iso-butane
↓
Both straight and branched
hydrocarbon may be:
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8. In these hydrocarbon the carbon atoms are
bonded together in such a way that they form a
ring or cyclic structure. Like open chain
hydrocarbon, they may also be classified as
i. Saturated
ii. Un saturated for example

9. Benzene (C6H6) is the parent member of this class
and hence aromatic is the term used for benzene
and all those compound that resemble benzene in
their chemical properties e.g.
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10. Alkane are named by the following
two system.
(A) Common System (B) IUPAC
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12. i.The prefix n- is used for those alkanes in which all the carbon
Atom are in one continuous chain (straight chain or normal
alkanes)
CH3-CH2-CH2-CH3 CH3-CH2-CH2-CH2-CH3
n-butane n-pentane
ii.The prefix iso-is used for those alkanes which have a methyl
Group(-ch3)attached to the second last carbon atom of the
continuous chain.
CH3
CH3-CH-CH2-CH3
iii. The prefix neo is used for those alkanes which have two methyl
group attached to the second last carbon atom of the continuous
chain.
CH3
CH3-C-CH3
CH3 By jawher Ali

13. 1.Select the longest continuous chain of carbon atoms and
consider it as a parent compound.
c-c-c-c-c-
2. Number the longest chain from one end or the other so as to
give the carbon carrying the substituent (alkyl group), the
lowest possible number.
ch3-ch-ch2-ch2-ch3
ch3
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14. 3.Name the substituent along with its position by indicating the
number of the carbon atom to which it is attached, before the
parent name.
CH3-CH-CH2-CH2-CH3
CH3
1 2 3 4
5
4. When two or more different substituents are attached,
they are named in alphabetical order along with their position
before the parent name.
C2H5 CH3
CH3 - CH2 -CH- CH-CH3
5 4 3 2
1
3-Ethyl -2-methyl
pentane
2-Methylpentane
5. When the same substituent is present more than once, a prefix di,
tri, tetra etc is used before the substituent name and position of each
substituent is indicated by a separate number.
CH3
CH3 – CH2 – CH – CH – CH3
CH3
5 4 3 2
1
2-3 Dimetyl
pentane

15. 6.When two substituent (same or different) are atttached to the
same carbon atom, the number of that carbon atom is repeated.
CH3
CH3 – CH2 – C – CH2 – CH3
CH3
1 2 3 4
5
3,3-Dimetyl pentane
7. When there are more than one longest chains, select the
chain which carries more substituent.
CH3 – CH2 – CH – CH2 – CH2 – CH3
CH3 – CH – CH3
3 4 5
6
2
1
3-Ethyl -2-methyl hexane
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16. Cycloalkane are named by placing the prefix “cyclo-”
To the name of alkane having the same number of
Carbon atoms as in the ring.
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17. For convenience, cycloalkane are represented by
geometric figures. Each corner represent a-CH2
group.
Cyclopropane is represented by triangle
Cyclopentane is represented by pentagon
Cyclohexane is represented by hexagon.
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