In the previous section, we saw the nomenclature of substituted Benzene compounds. In this section, we will see isomerism.
We have seen the basics about isomerism in our earlier chemistry classes. Details here. The reader is advised to study those notes thoroughly. In our present discussion, we will see some advanced examples.
Chain isomerism
This can be explained in 3 steps:
1. Consider the three compounds in fig.12.62 below.
• Each of them have five C atoms. Also each of them have twelve H atoms. So they have the same molecular formula: C5H12
 |
| Fig.12.62 |
2. Even though they have the same molecular formula, they are different compounds.
• This is because, the carbon chains are different.
3. The phenomenon of two or more compounds having the same molecular formula but different carbon chains is known as chain isomerism. Such compounds are known as chain isomers.
Position isomerism
This can be explained in 3 steps:
1. Consider the two compounds in fig.12.63 below.
• Both of them have three C atoms, eight H atoms and one O atom. So they have the same molecular formula: C3H8O
 |
| Fig.12.63 |
• Also note that, they have the same functional group, which is: ㅡOH
2. Even though they have the same molecular formula, they are different compounds.
• This is because, the position of the ㅡOH functional group is different.
3. The phenomenon of two or more compounds having the same molecular formula but different positions of functional groups in the carbon chains is known as position isomerism. Such compounds are known as position isomers.
Functional group isomerism
This can be explained in steps:
1. Consider the two compounds in fig.12.64 below.
• Both of them have three C atoms, six H atoms and one O atom. So they have the same molecular formula: C3H6O
 |
| Fig.12.64 |
♦ The first compound has the functional group: >C=O
♦ The second compound has the functional group: ㅡCHO
2. Even though they have the same molecular formula, they are different compounds.
• This is because, the functional groups are different.
3. The phenomenon of two or more compounds having the same molecular formula but different functional groups is known as functional group isomerism. Such compounds are known as functional isomers.
Metamerism
This can be explained in 3 steps:
1. Consider the two compounds in fig.12.65 below.
• Both of them have four C atoms, ten H atoms and one O atom. So they have the same molecular formula: C4H10O
 |
| Fig.12.65 |
2. Even though they have the same molecular formula, they are different compounds.
• This is because, the alkyl chains on either sides of ㅡOㅡ are different.
3. The phenomenon of two or more compounds having the same molecular formula but different alkyl chains on either sides of the functional group is known as metamerism. Such compounds are known as metamers.
Stereoisomerism
This can be explained in 3 steps:
1. Consider two hydrocarbons having the same molecular formula.
• They have the same number of double bonds also.
• The positions of the double bonds are also same.
• So they appear to be same in all respects.
2. But in reality, the two compounds are different because, relative positions of atoms are different. We have seen such a case in the animation in fig.4.141 in section 4.25.
• This phenomenon is called stereoisomerism.
3. This type of isomerism can be further classified as geometrical isomerism and optical isomerism. We will see more details in later sections.
Based on the above discussion, we can prepare a chart showing how the phenomenon of isomerism is classified into various types. It is shown in fig.12.66 below:
 |
| Fig.12.66 |
• The link below gives the folder containing additional solved examples on this chapter.
• Part 1 is related to nomenclature and isomerism.
In the next section, we
will see the fundamental concepts in organic reaction mechanism.
Previous
Contents
Next
Copyright©2021 Higher secondary chemistry.blogspot.com
No comments:
Post a Comment