NEET General Organic Chemistry Naming Of Organic Compounds Containing A Functional Group Notes

Naming Of Organic Compounds Containing A Functional Group

Prefix and suffix names of a few common functional groups and their decreasing order of priority are given in the table.

It may be noted that the groups -R, -OR, -NO₂, -X, etc. are considered as substituents and are indicated as prefixes.

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1. Longest chain– The parent chain is the one which has a functional group directly attached to it, even if it violates the longest chain rule.
2. Numbering of parent chain-The numbering should be done in such a way that the carbon linking to the functional group gets the lowest number even if it violates the lowest sum rule or locant rule. When the functional group itself contains carbon atom, then that carbon atom is assigned as number 1.
3. Naming of compounds with polyfunctional group- If there is more than one functional group present in a compound, then one of the functional group is chosen as the principal functional group (secondary suffix) and the remaining functional groups are treated as (substituents) subordinate functional groups.

The functional group with higher priority in the sequence given below is termed as principal functional group.

Nomenclature Of Substituted Benzene Compounds

Benzene is a six-membered cyclic compound with alternate single and double bonds. It is represented in any one of the following ways:

1. Naming of monosubstituted benzene

It is derived by adding the name of the substituent with the word benzene. Substituent + benzene 23/11 substituted benzene

Naming of monosubstituted benzene Example:

Special names of some monosubstituted benzene compounds

If the functional group is attached to the carbon chain connected to benzene ring, then benzene ring is considered as a substituent and is prefixed before the root word as phenyl.

2. Naming of disubstituted benzene

If the substituents are the same: In such case, the relative position of the substituents must be indicated by adding the symbols o – (1, 2); m – (1, 3) ; p – (1, 4).

Naming of disubstituted benzene Example:

If the two substituents are different: The substituents are named in alphabetical order.

If there are more than two substituents: The numbering is done in such a way that it satisfies the lowest sum rule.

Nomenclature Of Bicyclo Compounds

Bicyclo compounds contain two fused rings with the help of a bridge. We use the name of the alkane corresponding to the total number of carbon atoms as the base name.

1. The carbon atoms common to both the rings are called bridgeheads, and each bond or chain of atoms connecting the bridgehead atoms is called a bridge.
2. While naming the bi-cycloalkane we write an expression between the word bicyclo and alkane (in square bracket), that denotes the number of carbon atoms in each bridge. The numerals are written in descending order and the numbers are separated by a point.
3. If substituents are present, we number the bridged ring system beginning at one bridgehead, proceeding first along the longest bridge to the other bridge head, then along the second next longest bridge back to the first bridge head. The shortest bridge is numbered in the last.

Nomenclature of Bicyclo compounds Example: