๐๐ญ๐ซ๐๐ข๐ ๐ก๐ญ ๐๐ก๐๐ข๐ง ๐ก๐ฒ๐๐ซ๐จ๐๐๐ซ๐๐จ๐ง๐ฌ: The names of such compounds are based on their chain structure, and end with suffix โ-aneโ and carry a prefix indicating the number of carbon atoms present in the chain (except from `color{red}(CH_4)` to `color{red}(C_4H_(10))`, where the prefixes are derived from trivial names).
๐๐ซ๐๐ง๐๐ก๐๐ ๐๐ก๐๐ข๐ง ๐ก๐ฒ๐๐ซ๐จ๐๐๐ซ๐๐จ๐ง๐ฌ: In a branched chain compound small chains of carbon atoms are attached at one or more carbon atoms of the parent chain. The small carbon chains (branches) are called alkyl groups.
In order to name such compounds, the names of alkyl groups are prefixed to the name of parent alkane. An alkyl group is derived from a saturated hydrocarbon by removing a hydrogen atom from carbon. An alkyl group is named by substituting `color{brown}("โ๐ฆ๐โ")` for `color{brown}("โ๐๐๐โ")` in the corresponding alkane.
Abbreviations are used for some alkyl groups. For example, methyl is abbreviated as `color{red}("Me")`, ethyl as `color{red}("Et")`, propyl as `color{red}("Pr")` and butyl as `color{red}("Bu")`. The alkyl groups can be branched also.
Common branched groups have specific trivial names. For example, the propyl groups can either be n-propyl group or isopropyl group. The branched butyl groups are called sec-butyl, isobutyl and tert-butyl group. We also encounter the structural unit, `color{red}(โCH_2C(CH_3)_3),` which is called neopentyl group.
`star` `color{red}("Nomenclature of branched chain alkanes:")`
We encounter a number of branched chain alkanes. The rules for naming them are given below.
1. First of all, the ๐ฅ๐จ๐ง๐ ๐๐ฌ๐ญ ๐๐๐ซ๐๐จ๐ง ๐๐ก๐๐ข๐ง ๐ข๐ง ๐ญ๐ก๐ ๐ฆ๐จ๐ฅ๐๐๐ฎ๐ฅ๐ ๐ข๐ฌ ๐ข๐๐๐ง๐ญ๐ข๐๐ข๐๐. In the example (I) given below, the longest chain has nine carbons and it is considered as the parent or root chain. Selection of parent chain as shown in (II) is not correct because it has only eight carbons.
2.The carbon atoms of the parent chain are numbered to identify the parent alkane and to locate the positions of the carbon atoms at which branching takes place due to the substitution of alkyl group in place of hydrogen atoms. ๐๐ก๐ ๐ง๐ฎ๐ฆ๐๐๐ซ๐ข๐ง๐ ๐ข๐ฌ ๐๐จ๐ง๐ ๐ข๐ง ๐ฌ๐ฎ๐๐ก ๐ ๐ฐ๐๐ฒ ๐ญ๐ก๐๐ญ ๐ญ๐ก๐ ๐๐ซ๐๐ง๐๐ก๐๐ ๐๐๐ซ๐๐จ๐ง ๐๐ญ๐จ๐ฆ๐ฌ ๐ ๐๐ญ ๐ญ๐ก๐ ๐ฅ๐จ๐ฐ๐๐ฌ๐ญ ๐ฉ๐จ๐ฌ๐ฌ๐ข๐๐ฅ๐ ๐ง๐ฎ๐ฆ๐๐๐ซ๐ฌ. Thus, the numbering in the above example should be from left to right (branching at carbon atoms 2 and 6) and not from right to left (giving numbers 4 and 8 to the carbon atoms at which branches are attached).
3.The names of alkyl groups attached as a branch are then prefixed to the name of the parent alkane and position of the substituents is indicated by the appropriate numbers. If different alkyl groups are present, they are listed in alphabetical order. Thus, name for the compound shown above is: 6-ethyl-2- methylnonane. [Note: the numbers are separated from the groups by hyphens and there is no break between methyl and nonane.]
4. If two or more identical substituent groups are present then the numbers are separated by commas. The names of identical substituents are not repeated, instead prefixes such as di (for 2), tri (for 3), tetra (for 4), penta (for 5), hexa (for 6) etc. are used. While writing the name of the substituents in alphabetical order, these prefixes, however, are not considered. Thus, the following compounds are named as:
5. If the two substituents are found in equivalent positions, the ๐ฅ๐จ๐ฐ๐๐ซ ๐ง๐ฎ๐ฆ๐๐๐ซ ๐ข๐ฌ ๐ ๐ข๐ฏ๐๐ง ๐ญ๐จ ๐ญ๐ก๐ ๐จ๐ง๐ ๐๐จ๐ฆ๐ข๐ง๐ ๐๐ข๐ซ๐ฌ๐ญ ๐ข๐ง ๐ญ๐ก๐ ๐๐ฅ๐ฉ๐ก๐๐๐๐ญ๐ข๐๐๐ฅ ๐ฅ๐ข๐ฌ๐ญ๐ข๐ง๐ . Thus, the following compound is 3-ethyl-6-methyloctane and not 6-ethyl-3-methyloctane.
6. The branched alkyl groups can be named by following the above mentioned procedures. However, the ๐๐๐ซ๐๐จ๐ง ๐๐ญ๐จ๐ฆ ๐จ๐ ๐ญ๐ก๐ ๐๐ซ๐๐ง๐๐ก ๐ญ๐ก๐๐ญ ๐๐ญ๐ญ๐๐๐ก๐๐ฌ ๐ญ๐จ ๐ญ๐ก๐ ๐ซ๐จ๐จ๐ญ ๐๐ฅ๐ค๐๐ง๐ is numbered 1 as exemplified below.
The name of such branched chain alkyl group is placed in parenthesis while naming the compound. While writing the trivial names of substituentsโ ๐ข๐ง ๐๐ฅ๐ฉ๐ก๐๐๐๐ญ๐ข๐๐๐ฅ ๐จ๐ซ๐๐๐ซ, ๐ญ๐ก๐ ๐ฉ๐ซ๐๐๐ข๐ฑ๐๐ฌ ๐ข๐ฌ๐จ- ๐๐ง๐ ๐ง๐๐จ- ๐๐ซ๐ ๐๐จ๐ง๐ฌ๐ข๐๐๐ซ๐๐ ๐ญ๐จ ๐๐ ๐ญ๐ก๐ ๐ฉ๐๐ซ๐ญ ๐จ๐ ๐ญ๐ก๐ ๐๐ฎ๐ง๐๐๐ฆ๐๐ง๐ญ๐๐ฅ ๐ง๐๐ฆ๐ ๐จ๐ ๐๐ฅ๐ค๐ฒ๐ฅ ๐ ๐ซ๐จ๐ฎ๐ฉ. ๐๐ก๐ ๐ฉ๐ซ๐๐๐ข๐ฑ๐๐ฌ ๐ฌ๐๐- ๐๐ง๐ ๐ญ๐๐ซ๐ญ- ๐๐ซ๐ ๐ง๐จ๐ญ considered to be the part of the fundamental name. The use of `color{brown}("๐๐ ๐")` and related common prefixes for naming alkyl groups is also allowed by the IUPAC nomenclature as long as these are not further substituted.
In multisubstituted compounds, the following rules may aso be remembered:
โข If there happens to be two chains of equal size, then that chain is to be selected which contains more number of side chains.
โข After selection of the chain, numbering is to be done from the end closer to the substituent.
๐๐ฒ๐๐ฅ๐ข๐ ๐๐จ๐ฆ๐ฉ๐จ๐ฎ๐ง๐๐ฌ: A saturated monocyclic compound is named by prefixing โcycloโ to the corresponding straight chain alkane. If side chains are present, then the rules given above are applied. Names of some cyclic compounds are given below
๐๐ญ๐ซ๐๐ข๐ ๐ก๐ญ ๐๐ก๐๐ข๐ง ๐ก๐ฒ๐๐ซ๐จ๐๐๐ซ๐๐จ๐ง๐ฌ: The names of such compounds are based on their chain structure, and end with suffix โ-aneโ and carry a prefix indicating the number of carbon atoms present in the chain (except from `color{red}(CH_4)` to `color{red}(C_4H_(10))`, where the prefixes are derived from trivial names).
๐๐ซ๐๐ง๐๐ก๐๐ ๐๐ก๐๐ข๐ง ๐ก๐ฒ๐๐ซ๐จ๐๐๐ซ๐๐จ๐ง๐ฌ: In a branched chain compound small chains of carbon atoms are attached at one or more carbon atoms of the parent chain. The small carbon chains (branches) are called alkyl groups.
In order to name such compounds, the names of alkyl groups are prefixed to the name of parent alkane. An alkyl group is derived from a saturated hydrocarbon by removing a hydrogen atom from carbon. An alkyl group is named by substituting `color{brown}("โ๐ฆ๐โ")` for `color{brown}("โ๐๐๐โ")` in the corresponding alkane.
Abbreviations are used for some alkyl groups. For example, methyl is abbreviated as `color{red}("Me")`, ethyl as `color{red}("Et")`, propyl as `color{red}("Pr")` and butyl as `color{red}("Bu")`. The alkyl groups can be branched also.
Common branched groups have specific trivial names. For example, the propyl groups can either be n-propyl group or isopropyl group. The branched butyl groups are called sec-butyl, isobutyl and tert-butyl group. We also encounter the structural unit, `color{red}(โCH_2C(CH_3)_3),` which is called neopentyl group.
`star` `color{red}("Nomenclature of branched chain alkanes:")`
We encounter a number of branched chain alkanes. The rules for naming them are given below.
1. First of all, the ๐ฅ๐จ๐ง๐ ๐๐ฌ๐ญ ๐๐๐ซ๐๐จ๐ง ๐๐ก๐๐ข๐ง ๐ข๐ง ๐ญ๐ก๐ ๐ฆ๐จ๐ฅ๐๐๐ฎ๐ฅ๐ ๐ข๐ฌ ๐ข๐๐๐ง๐ญ๐ข๐๐ข๐๐. In the example (I) given below, the longest chain has nine carbons and it is considered as the parent or root chain. Selection of parent chain as shown in (II) is not correct because it has only eight carbons.
2.The carbon atoms of the parent chain are numbered to identify the parent alkane and to locate the positions of the carbon atoms at which branching takes place due to the substitution of alkyl group in place of hydrogen atoms. ๐๐ก๐ ๐ง๐ฎ๐ฆ๐๐๐ซ๐ข๐ง๐ ๐ข๐ฌ ๐๐จ๐ง๐ ๐ข๐ง ๐ฌ๐ฎ๐๐ก ๐ ๐ฐ๐๐ฒ ๐ญ๐ก๐๐ญ ๐ญ๐ก๐ ๐๐ซ๐๐ง๐๐ก๐๐ ๐๐๐ซ๐๐จ๐ง ๐๐ญ๐จ๐ฆ๐ฌ ๐ ๐๐ญ ๐ญ๐ก๐ ๐ฅ๐จ๐ฐ๐๐ฌ๐ญ ๐ฉ๐จ๐ฌ๐ฌ๐ข๐๐ฅ๐ ๐ง๐ฎ๐ฆ๐๐๐ซ๐ฌ. Thus, the numbering in the above example should be from left to right (branching at carbon atoms 2 and 6) and not from right to left (giving numbers 4 and 8 to the carbon atoms at which branches are attached).
3.The names of alkyl groups attached as a branch are then prefixed to the name of the parent alkane and position of the substituents is indicated by the appropriate numbers. If different alkyl groups are present, they are listed in alphabetical order. Thus, name for the compound shown above is: 6-ethyl-2- methylnonane. [Note: the numbers are separated from the groups by hyphens and there is no break between methyl and nonane.]
4. If two or more identical substituent groups are present then the numbers are separated by commas. The names of identical substituents are not repeated, instead prefixes such as di (for 2), tri (for 3), tetra (for 4), penta (for 5), hexa (for 6) etc. are used. While writing the name of the substituents in alphabetical order, these prefixes, however, are not considered. Thus, the following compounds are named as:
5. If the two substituents are found in equivalent positions, the ๐ฅ๐จ๐ฐ๐๐ซ ๐ง๐ฎ๐ฆ๐๐๐ซ ๐ข๐ฌ ๐ ๐ข๐ฏ๐๐ง ๐ญ๐จ ๐ญ๐ก๐ ๐จ๐ง๐ ๐๐จ๐ฆ๐ข๐ง๐ ๐๐ข๐ซ๐ฌ๐ญ ๐ข๐ง ๐ญ๐ก๐ ๐๐ฅ๐ฉ๐ก๐๐๐๐ญ๐ข๐๐๐ฅ ๐ฅ๐ข๐ฌ๐ญ๐ข๐ง๐ . Thus, the following compound is 3-ethyl-6-methyloctane and not 6-ethyl-3-methyloctane.
6. The branched alkyl groups can be named by following the above mentioned procedures. However, the ๐๐๐ซ๐๐จ๐ง ๐๐ญ๐จ๐ฆ ๐จ๐ ๐ญ๐ก๐ ๐๐ซ๐๐ง๐๐ก ๐ญ๐ก๐๐ญ ๐๐ญ๐ญ๐๐๐ก๐๐ฌ ๐ญ๐จ ๐ญ๐ก๐ ๐ซ๐จ๐จ๐ญ ๐๐ฅ๐ค๐๐ง๐ is numbered 1 as exemplified below.
The name of such branched chain alkyl group is placed in parenthesis while naming the compound. While writing the trivial names of substituentsโ ๐ข๐ง ๐๐ฅ๐ฉ๐ก๐๐๐๐ญ๐ข๐๐๐ฅ ๐จ๐ซ๐๐๐ซ, ๐ญ๐ก๐ ๐ฉ๐ซ๐๐๐ข๐ฑ๐๐ฌ ๐ข๐ฌ๐จ- ๐๐ง๐ ๐ง๐๐จ- ๐๐ซ๐ ๐๐จ๐ง๐ฌ๐ข๐๐๐ซ๐๐ ๐ญ๐จ ๐๐ ๐ญ๐ก๐ ๐ฉ๐๐ซ๐ญ ๐จ๐ ๐ญ๐ก๐ ๐๐ฎ๐ง๐๐๐ฆ๐๐ง๐ญ๐๐ฅ ๐ง๐๐ฆ๐ ๐จ๐ ๐๐ฅ๐ค๐ฒ๐ฅ ๐ ๐ซ๐จ๐ฎ๐ฉ. ๐๐ก๐ ๐ฉ๐ซ๐๐๐ข๐ฑ๐๐ฌ ๐ฌ๐๐- ๐๐ง๐ ๐ญ๐๐ซ๐ญ- ๐๐ซ๐ ๐ง๐จ๐ญ considered to be the part of the fundamental name. The use of `color{brown}("๐๐ ๐")` and related common prefixes for naming alkyl groups is also allowed by the IUPAC nomenclature as long as these are not further substituted.
In multisubstituted compounds, the following rules may aso be remembered:
โข If there happens to be two chains of equal size, then that chain is to be selected which contains more number of side chains.
โข After selection of the chain, numbering is to be done from the end closer to the substituent.
๐๐ฒ๐๐ฅ๐ข๐ ๐๐จ๐ฆ๐ฉ๐จ๐ฎ๐ง๐๐ฌ: A saturated monocyclic compound is named by prefixing โcycloโ to the corresponding straight chain alkane. If side chains are present, then the rules given above are applied. Names of some cyclic compounds are given below