VANKOPPEN S03
CHAPTER 22 ORGANIC CHEMISTRY
Nomenclature
Straight Chain Alkanes
Name
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Formula
CH 4
C2H 6
C3H 8
C4H 10
C5H 12
C6H 14
C7H 16
C8H 18
C9H 20
Boiling Point (oC)
– 164
– 89
– 42
– 0.5
36
69
98
126
151
Name
Decane
Undecane
Dodecane
Tridecane
Tetradecane
Pentadecane
.
.
.
Formula
C10H 22
C11H 24
C12H 26
C13H 28
C14H 30
C15H 32
1. Find the longest possible continuous chain of carbon atoms in the molecule. The molecule will be named as a
derivative of the alkane. In the following figure a chain of three carbon atoms can be found, so the molecule is
a derivative of propane.
2– methyl propane (systematic name)
or
isobutane (common name)
2. The hydrocarbon groups attached to the chain are called alkyl groups. Their names are obtained by dropping
the ending -ane from the corresponding alkane and replacing it with -yl. From methane (CH4) the methyl
group, – CH3, is derived.
Alkyl side groups
Name
Formula
Methyl
Ethyl
Propyl
Isopropyl
Butyl
Isobutyl
sec-butyl
tert-butyl
– CH3
– CH2CH 3
– CH2CH 2CH 3
– CH(CH3) 2
– CH2CH 2CH 2CH 3
– CH2CH(CH 3) 2
– CH(CH3)(CH 2CH 3)
– C(CH 3) 3
3. Number the carbon atoms along the chain identified in rule 1. The # 1 carbon is the end carbon closest to a side
group. Identify the alkyl groups by the number of the carbon atom at which each is attached to the chain.
For example: The methyl group in the molecule in the above Figure is attached to the second carbon atom of
the three carbon atoms in the propane chain: the molecule is therefore called 2-methyl propane.
4. If more than one alkyl group of the same type is attached to the chain, use the prefixes di–, tri–, tetra–,
penta– etc. to specify the total number of such attached groups in the molecule.
For example: 2,2,3–trimethylbutane has two methyl groups attached to the second carbon atom and one to the
third carbon atom of the four-atom butane chain. It is an isomer of n-heptane (C 7 H 16 )
Note: the name of the molecule starts with the position numbers, followed by a hyphen, followed by the
prefix (if any) followed by the substituent name and finally the main chain name.
5. If several types of alkyl groups appear, name them in alphabetical order. Note: Prefixes that indicate a
number, di-, tri-, tetra-, tert-, sec-, etc. are ignored in alphabetizing substituents. However, prefixes that
define the shape, such as iso, neo, cyclo are NOT ingnored.