calculate total no of isomers of a compound

Cool goIITian

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25 Apr 2009 13:18:26 IST
Posts: 34
25 Apr 2009 13:18:26 IST
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calculate total no of isomers of a compound
DOUBLE BOND EQUIVALENTS or INDEX NUMBER:
It is a numerical value on the basis of which we can have an idea about the different type of equivalent structures we can have for a given formula.
 
Knowing the DBE the problems on structural isomerism can be more easily solved.
 
Mathematically,  
DBE= {( n(v-2))/2}+1
where n is the number of atoms
v is the valency of the atom.
Eg 1):
Consider C4H6
DBE={4(4-2)/2+6(1-2)/2}+1
={(8-6)/2}+1
=2
This implies that the molecule may contain,
1)two double bonds or one triple bond.
2)one ring and one double bond.
3)two rings.
 
Thus by knowing the DBE total number of structural isomers can be formulated.
 
Eg 2):
Consider C3H6O
DBE={3(4-2)/2+6(1-2)/2+1(2-2)/2}+1
=1
So the isomers may contain either a double bond or a ring.
 
I hope this is helpful!
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Comments (2)


Blazing goIITian

Joined: 12 Jan 2008 13:19:35 IST
Posts: 321
25 Apr 2009 14:35:02 IST
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yes it definitely was helpful..thanks a lot..

New kid on the Block

Joined: 23 Jan 2012 08:59:48 IST
Posts: 2
23 Jan 2012 08:59:49 IST
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That's cool !



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