Q33E - Organic Chemistry (Mcmurry)

Question

Draw and name all monobromo derivatives of pentane  ${\mathbf{C}}_5{\mathbf{H}}_{11}\mathbf{Br}$.

Step-by-Step Solution

Answer

There are 8 monobromo derivatives of pentane, namely;

1. 1-Bromopentane
2. 2-Bromopentane
3. 3- bromopentane
4. 1- bromo-2-methyl butane
5. 2-Bromo-2-methyl butane
6. 2-Bromo-3 methyl butane
7. 1-bromo-3-methyl butane
8. 2,2-dimethyl-1-Bromo pentane

Step 1: Isomerism

Chemical compounds which have identical chemical formula but have different chemical structures, different properties, are known to be exhibiting isomerism. Therefore, the compounds which exhibit isomerism are called isomers. 

It is of two types- structural and stereoisomerism. Here we will be talking about structural isomerism. In structural isomerism the constituent atoms are linked in different ways in each isomer. For example- Alkane with formula ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$  can have three isomers, showing chain isomerism ( type of isomerism where the molecular formula of isomers is same but they have different length of C chains).

Step 2: Monobromo derivatives of pentane

Look at all the structure of pentane given above, and find, which hydrogen atoms in the structure can you replace with bromine in order to get the monobromo derivatives of pentane.

structures you will get on replacing, one hydrogen atom in the above given pentane structures are- 

1. 1-Bromopentane

2.

2-Bromopentane 

3.

3- bromopentane

4.

1-bromo-2-methyl butane

5.

2-Bromo-2-methyl butane

6.

2-Bromo-3 methyl butane

7.

1-bromo-3-methyl butane

8.

2,2-dimethyl-1-Bromo pentane

So, Monobromo pentane can have 8 isomers showing position isomerism (type of structural isomerism where the molecular formula of isomers is same but they have different positions of functional groups attached).