Draw all the structural isomers for the molecular formula C4H9Br.
The Correct Answer and Explanation is:
Structural Isomers of C₄H₉Br
The molecular formula C₄H₉Br represents butyl bromide isomers, which consist of four carbon atoms, nine hydrogen atoms, and one bromine atom. These isomers differ in the arrangement of their carbon skeleton and the position of the bromine atom. There are four distinct structural isomers for this formula:
1. 1-Bromobutane (n-Butyl Bromide)
Structure:
CH₃ – CH₂ – CH₂ – CH₂ – Br
In this isomer, the bromine atom is attached to the first carbon of a straight-chain butane.
2. 2-Bromobutane
Structure:
CH₃ – CH₂ – CH(Br) – CH₃
Here, the bromine atom is attached to the second carbon of a straight-chain butane.
3. 1-Bromo-2-methylpropane (Isobutyl Bromide)
Structure:
CH₃ – CH(Br) – CH₂ – CH₃
This isomer has a branched chain where the bromine is attached to the primary carbon next to a methyl group.
4. 2-Bromo-2-methylpropane (tert-Butyl Bromide)
Structure:
(CH₃)₃C – Br
In this case, the carbon skeleton is fully branched, with the bromine attached to the central tertiary carbon.
Explanation:
Structural isomers are compounds with the same molecular formula but different connectivity of atoms. For C₄H₉Br, all isomers consist of four carbons, nine hydrogens, and one bromine atom, but the position of the bromine and the carbon skeleton vary.
These isomers fall into different categories:
- Straight-chain isomers: 1-bromobutane and 2-bromobutane
- Branched-chain isomers: 1-bromo-2-methylpropane and 2-bromo-2-methylpropane
The differences in structure influence the physical and chemical properties of these compounds, such as boiling point, reactivity, and solubility. For example, tert-butyl bromide is more reactive in certain substitution reactions due to the stability of the carbocation intermediate.
Thus, understanding these isomers is important in organic synthesis and reaction mechanisms.
