Structural isomers of C4H10O containing an -OH group

Steps:

• Determine carbon skeletons for C4H10: straight-chain butane (CH3-CH2-CH2-CH3) and branched 2-methylpropane ((CH3)2CH-CH3).
• Attach -OH to different carbon positions on each skeleton, ensuring the formula remains C4H10O and -OH bonds to a carbon (not hydrogen).
• List alcohols: butan-1-ol (primary, straight), butan-2-ol (secondary, straight), 2-methylpropan-1-ol (primary, branched), 2-methylpropan-2-ol (tertiary, branched).
• Count unique structures: four total.

Why C is correct:

• Alcohols are organic compounds with -OH attached to carbon; C4H10O yields exactly four distinct structural isomers fitting this definition.

Why the others are wrong:

• A: Excludes branched-chain alcohols, counting only two straight-chain ones.
• B: Misses the tertiary alcohol, undercounting by one.
• D: Overcounts by including non-alcohol isomers like ethers (e.g., diethyl ether).

Final answer: C