(cycloalkanes). All alkanes have the general molecular formula C n H 2nþ2 and
are called saturated hydrocarbons. Saturated hydrocarbons contain only
single bonds, and are also commonly referred to as aliphatic or acyclic
alkanes (alkanes without rings). Thus, the alkane family is characterized by
the presence of tetrahedral carbon (sp
3 ) atoms. Methane (CH 4 ) and ethane
(C 2 H 6 ) are the first two members of the alkane family. A group derived from
an alkane by removal of one of its hydrogen atoms is known as an alkyl
group, for example the methyl group (CH 3 À À) from methane (CH 4 ) and the
ethyl group (CH 3 CH 2 À À) from ethane (CH 3 CH 3 ).
The IUPAC nomenclature of alkanes
In general, organic compounds are given systematic names by using the
order prefix–parent–suffix, where prefix indicates how many branching
groups are present, parent indicates how many carbons are in the longest
chain and suffix indicates the name of the family. Common names as well as
systematic names are used for alkanes and their derivatives. However, it is
advisable to use systematic names or the IUPAC (International Union of
Pure and Applied Chemistry) nomenclature, which can be derived from a
simple set of rules.
The IUPAC naming of the alkanes is based on a prefix indicating the
number of carbon atoms in the chain (as shown below) followed by the
suffix -ane. For example, if a chain contains three carbons the parent name is
propane, if four carbons the parent name is butane and so on. The
remaining parts of the structure are treated as substituents on the chain.
Numbers are used to indicate the positions of the substituents on the parent
carbon chain.
Prefix
Number of carbon atoms
Prefix
Number of carbon atoms
Meth1
Hept7
Eth2
Oct8
Prop3
Non9
But4
Dec10
Pent5
Undec11
Hex6
Dodec12
First, one has to identify and name the groups attached to the chain, and
number the chain so that the substituent gets the lowest possible number. For
example, one of the isomers of pentane is 2-methylbutane, where the parent
chain is a four-carbon butane chain, and is numbered starting from the end
nearer the substituent group (methyl group). Therefore, the methyl group is
indicated as being attached to carbon atom number 2.
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CH4 ORGANIC FUNCTIONAL GROUPS
are called saturated hydrocarbons. Saturated hydrocarbons contain only
single bonds, and are also commonly referred to as aliphatic or acyclic
alkanes (alkanes without rings). Thus, the alkane family is characterized by
the presence of tetrahedral carbon (sp
3 ) atoms. Methane (CH 4 ) and ethane
(C 2 H 6 ) are the first two members of the alkane family. A group derived from
an alkane by removal of one of its hydrogen atoms is known as an alkyl
group, for example the methyl group (CH 3 À À) from methane (CH 4 ) and the
ethyl group (CH 3 CH 2 À À) from ethane (CH 3 CH 3 ).
The IUPAC nomenclature of alkanes
In general, organic compounds are given systematic names by using the
order prefix–parent–suffix, where prefix indicates how many branching
groups are present, parent indicates how many carbons are in the longest
chain and suffix indicates the name of the family. Common names as well as
systematic names are used for alkanes and their derivatives. However, it is
advisable to use systematic names or the IUPAC (International Union of
Pure and Applied Chemistry) nomenclature, which can be derived from a
simple set of rules.
The IUPAC naming of the alkanes is based on a prefix indicating the
number of carbon atoms in the chain (as shown below) followed by the
suffix -ane. For example, if a chain contains three carbons the parent name is
propane, if four carbons the parent name is butane and so on. The
remaining parts of the structure are treated as substituents on the chain.
Numbers are used to indicate the positions of the substituents on the parent
carbon chain.
Prefix
Number of carbon atoms
Prefix
Number of carbon atoms
Meth1
Hept7
Eth2
Oct8
Prop3
Non9
But4
Dec10
Pent5
Undec11
Hex6
Dodec12
First, one has to identify and name the groups attached to the chain, and
number the chain so that the substituent gets the lowest possible number. For
example, one of the isomers of pentane is 2-methylbutane, where the parent
chain is a four-carbon butane chain, and is numbered starting from the end
nearer the substituent group (methyl group). Therefore, the methyl group is
indicated as being attached to carbon atom number 2.
62
CH4 ORGANIC FUNCTIONAL GROUPS