Chemistry 11 Notes for Chemistry Notes

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IUPAC Name Format

Cyclic compound:
S. prefix + P. prefix + word root + P. suffix + S. suffix
Acyclic Compound:
Prefix + word root + P. suffix + S. suffix

1. Rules for selection of Carbon chain (parent chain)

Longest chain rule: select longest continuous chain of carbon atom

Larger number of side chain:

If two c-chain have equal length (i.e having same number of c-atom), select c-chain which has greater number of side chains.


2. Rules for numbering C-atom in parent chain

If only one side chain or substituent is present, the numbering of carbon atom is carried out in such a way that the carbon atom which carries substituent on side chain gets the lowest possible number.


If more than one side chain or substituent is present then the numbering of c-atom is carried in such a way that the sum of locant should be lowest. This rule is also known as lowest sum rule.

Note: Locant is the position or location number of side chain or substituent in parent chain.

If two different substituent are present at equal position from two ends then the substituent which comes first in alphabetical order gets the lowest position number.


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