4 .) The lower number is given to the first in alphabetical order . 5 .) The carbon atom of the branch that attaches to the root alkane is numbered 1 .
Organic compounds having Functional Groups :
The longest chain of carbon atoms containing the functional groups is numbered in such a way that the functional group attached to the carbon atom gets the lowest possible number in the chain .
When there are more functional groups then a priority order is followed as :
-COOH , -SO3H , -COOR , COCl , -CONH2 , -CN , -HC = O , = C = O , -OH , -NH2 , = C = C =, -CΞ C- .
ISOMERISM
Two or more compounds having the same molecular formula but different physical and chemical properties are called isomers and this phenomenon is called isomerism .
Chain isomerism : When two or more compounds having same molecular formula but different carbon skeletons are referred to as chain isomers .
Position Isomerism : Compounds which have the same structure of carbon chain but differ in position of double or triple bonds or functional group are called position isomers and this phenomenon is called Position Isomerism . e g