Identifying Limonene's Molecular Structure

Steps:

• Recall limonene is a monoterpene with formula C10H16, featuring a cyclohexene ring.
• Identify key features: double bond in ring at position 1-2, methyl group at C1, isopropenyl group (-C(CH3)=CH2) at C4.
• Compare options to match ring size, substitution, and unsaturation.
• Select structure with correct connectivity and no extra bonds.

Why B is correct:

• Matches IUPAC name 1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene, with one endocyclic and one exocyclic double bond.

Why the others are wrong:

• A: Incorrect ring substitution; methyl at wrong position.
• C: Saturated ring, violating C10H16 formula.
• D: Extra double bond, exceeding monoterpene unsaturation.

Final answer: B