The number of alcoholic isomers with the formula $C_4{H}_{10}O$ (structural only) is

To analyze the number of structural alcoholic isomers for the molecular formula C₄H₁₀O, we need to consider all the possible ways the carbon and hydroxyl groups can be arranged while keeping the molecular formula intact. This means we are looking for alcohols (compounds that contain one hydroxyl group, –OH) that have different connectivity, not just different spatial arrangements (i.e., not stereoisomers, only structural isomers).

Step 1: Consider the Carbon Skeletons

For C₄H₁₀, we can have:

1. A straight-chain (butane, C–C–C–C)
2. A branched chain (isobutane, C–C(C)–C)

Each of these backbones can support various placements of the hydroxyl group to create distinct alcohols.

Step 2: Place the –OH Group on Different Carbons

1. Straight-Chain Butanol Isomers:

• 1-Butanol: OH group on the first carbon.
• 2-Butanol: OH group on the second carbon.

Since placing the OH on the third carbon yields the same structure as 2-butanol, there are no new isomers.

2. Branched-Chain Butanol Isomers:

• 2-Methyl-1-propanol: A methyl group and the OH group are on adjacent primary and secondary carbons.
• 2-Methyl-2-propanol: The OH group is on the tertiary carbon, surrounded by three methyl groups.

Total Count of Structural Isomers:

• Straight-chain alcohols: 2
• Branched-chain alcohols: 2

Total isomers: 4

Correct Answer - The correct answer is d) 4.