calculation of no of optical isomers.....
Type 1 : when molecule is not divisible into two equal halves and contains 'n'
asymmaetric carbon atoms, then
no of optically active isomers (a) = 2^n
no of meso forms, (m) = 0
no of racemice mixture (r) = a/2
Note : racemice forms will never be included in total no of optical isomers
Total no of optical isomers =a + m
e.g no of optical active isomers of glucose
= total no of isomers of glucose
= 2^ 4 =16
Type 2: When molecule is divisble in two equal halves,
case (i) if n is even,
then a= 2^(n-1)
r= a/2
m= 2^{(n/2)-1}
total no of isomers =a +m
Case (ii) if n is odd, a= [{2 ^(n-1)} - {2 ^ (n-1)/2}]
r= a/2
m=2^ (n-1)/2
total no of isomers =a +m
e.g for tartaric acid,
n=2
a= 2^ (2-1) = 2
m = 1
thrfore total no of optical isomers = 3
20 Nickels awarded!
702
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