The Kinds of Isomers

The Kinds of Isomers

General ly isomers are distinguished into structural isomer and spatial isomer. Structural isomer are molecules that have the same chemical formula and have the same atoms in each molecule, but the order of atoms in which the molecules are different. The differences of order of the atoms produces the completely different molecular structures. Meanwhile, the spatial isomer relate to the configuration of atoms in the moleculer space.

Isomer structure consist of the constructive isomer, position isomer, and function group isomer. In this chapter we will be studied only about position isomer and constructive isomer, while function isomer will be studied later. Constructive isomer happens because by the difference of atoms on the compound having the same molecule formula, while position isomer happens because by the position difference of a certain group (for example alkyl group and double or triple bonds) on compounds having the same molecular formula.

Example :

Constructive isomer in molecule C6H14 forming 3-methyl-pentane and 2,3-dimethyl-butane.

a. CH3-CH2-CH2-CH(CH3)-CH3
.......2-methyl-pentane
b. CH3-CH2-CH2(CH3)-CH2-CH3
.......2,3-dimethyl-butane.

Position isomer in molecule C6H12 form 1-hexene and 3-hexene.

a. CH2=CH-CH2-CH2-CH2-CH3
b. b. CH3-CH2-CH=CH-CH2-CH3

Spatial isomers consist of geometric isomer and optical isomer. In this chapter will be discussed about the geometric isomer only, that happens because the existence of the defference of certain group direction on the compounds having the same molecular formula.

Example :

C2H5 ........C2H5
l ..................l
C======C
l ..................l
H ...............H
Cis-3-hexene

C2H5..... H
l ...............l
C=====C
l ...............l
H .............C2H5
Trans-3-hexene

Execise :

1. Write down the structural formula and IUPAC name of all alkane isomers with molecular formula of C7H16.

2. Write down the structural formula and IUPAC name of all alkane isomers with molecular formula of C7H16

3. Write down the structural formula and IUPAC name of all alkene isomers with molecular formula of C5H12

4. Among the following compounds, write the structural formula and determine the compound having the geometric isomer.

a. 1-pentene
b. 2-hexene
c. 2-methyl-2-pentene
d. 3-ethyl-4,7-dimethyl-2,5-undekadiene
e. 2,2,4-trimethyl-3,5,7-oktadekatriene