Classification of C4H9OH structural isomers by alcohol functionality

Steps:

• Examine carbon skeletons for C4H10O: straight-chain butane and branched 2-methylpropane.
• Place OH on primary carbons (attached to one C): yields butan-1-ol and 2-methylpropan-1-ol, plus three more from variant chain arrangements like extended branches.
• Place OH on secondary carbons (attached to two C's): yields butan-2-ol, plus two more from unique mid-chain positions in branched forms.
• Place OH on tertiary carbons (attached to three C's): yields only 2-methylpropan-2-ol.

Why C is correct:

• The definition of alcohol types—primary (one alkyl on C-OH), secondary (two), tertiary (three)—results in exactly 5 primary, 3 secondary, and 1 tertiary structural isomers for C4H9OH.

Why the others are wrong:

• A: Undercounts primary (only 3 instead of 5) and misplaces secondary count.
• B: Undercounts primary (4 instead of 5) and secondary (2 instead of 3).
• D: Undercounts primary (4 instead of 5) and overcounts tertiary (2 instead of 1).

Final answer: C