Limonene's molecular formula from structure

Steps:

• Count carbon atoms: the cyclohexene ring has 6, plus 4 from the isopropenyl side chain, totaling 10 carbons.
• Count hydrogen atoms: ring with one double bond and substituents accounts for 14, plus 2 from the =CH2, totaling 16 hydrogens.
• Confirm unsaturation: two double bonds (one in ring, one exocyclic) match C10H16 for a bicyclic equivalent monoterpene.
• Verify against standard: limonene is a known monoterpene with formula C10H16.

Why B is correct:

• B states C10H16, matching the general formula for monoterpenes with two degrees of unsaturation (CnH2n-4 for n=10).

Why the others are wrong:

• A (C10H18): Matches one double bond only, ignoring the exocyclic one.
• C (C10H14): Implies three double bonds or a triple bond, overstating unsaturation.
• D (C10H20): Suggests fully saturated, like decane, ignoring all double bonds.

Final answer: B