How many isomers are possible for C5H12?
a 1
b 2
c 3
d 4
e 10
The correct answer and explanation is :
The correct answer is d) 4.
Here’s the explanation:
The molecular formula C5H12 represents a molecule with five carbon atoms and twelve hydrogen atoms, which is an alkane (since it follows the general formula for alkanes, CnH2n+2). Since alkanes have only single bonds between carbon atoms, their structure can be varied by changing the arrangement of the carbon atoms, leading to different isomers. These structural isomers can differ in the branching of the carbon chain.
Let’s look at the possible isomers for C5H12:
- Pentane: This is the straight-chain isomer, where all five carbon atoms are connected in a continuous chain (CH3-CH2-CH2-CH2-CH3). This is the simplest form and the parent structure for the others.
- Isopentane (Methylbutane): This is a branched isomer where the main chain has four carbon atoms, and the fifth carbon is attached to the second carbon of the chain (CH3-CH(CH3)-CH2-CH3). This branching creates a different shape compared to the straight-chain version.
- Neopentane (Dimethylpropane): This is another branched isomer in which the carbon chain forms a central carbon atom that is attached to four methyl groups (CH3-CH2-C-CH3) on the central carbon atom. This results in a more compact and symmetrical structure.
- 2,2-Dimethylpropane: This is a unique branched structure with the same number of carbon atoms and hydrogens, but this time, the branching occurs at the second carbon of the chain. It is considered a different isomer due to the position of the methyl groups.
These are the four distinct structural isomers of C5H12. Each structure has the same molecular formula, but their physical and chemical properties (such as boiling point, melting point, and reactivity) can be different because of the varying shapes and structures of the molecules.
Thus, there are 4 isomers of C5H12, which makes option d) 4 the correct answer.