CHEMISTRY

NAME- ABHINAB

BORUAH

CLASS-10 ROLL NO-

12

SEC-A

TOPIC- ISOMERS

ISOMERS

In inorganic chemistry, a given molecular formula represents only one

compound. For example H2SO4 represents only one compound,sulphuric

acid. A given molecular formula can be represent two or more different

compounds. This is because in organic compounds, the same carbon

atoms can be arranged in several ways to give different structures and

hence different compounds. For example, in organic chemistry, the same

molecular formula C4H10 represents two compounds: normal butane and

iso-butane. The organic compounds having the same molecular formula

but different structures are known as isomers.

What is isomerism ?

The existence of two or more different organic compounds having the same molecular formula but different structures is called isomerism. Isomerism is possible only with hydrocarbons having 4 or more carbon atoms, because only then we can have two or more different arrangements of carbon atoms. No isomerism is possible in hydrocarbons containing 1,2,or 3 carbon atoms per molecule because then only one arrangement of carbon atoms is possible. For example, no isomerism is possible in methane,ethane,and propane because they contain one, two or three carbon atoms respectively. Two isomers of the compound butane possible. Three isomers of the compound pentane are possible. And five isomers of the compound hexane are possible. As the number of carbon atoms in an alkane molecules increases, the number of possible isomers increases rapidly.

How to draw the structural formulae of all the isomers of an alkane?

In order to draw the structural formulae of all the isomers of an alkane, we should take first all the carbon atoms present in alkane molecule in a straight chain and attach hydrogen atoms to all the free valencies of carbon atoms. This will give us the first isomer which is said to be normal- alkane .After this we have to work out as many branched chain isomers of alkane as possible by drawing different arrangements of its carbon atoms.

END OF PRESENTATION

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