Identifying double bonds in organic molecules

Steps:

• Recall that a double bond involves two shared electron pairs between atoms, common in alkenes (C=C) or carbonyls (C=O).
• Examine each substance's structure: Substance 1 has a C=C bond; Substance 2 has a C=O bond; Substance 3 lacks double bonds (all single bonds); Substance 4 has a C=C bond.
• List substances with at least one double bond: 1, 2, and 4.
• Match to options: A includes 3 (wrong), B misses 1 and 2, D includes 3 but misses 2.

Why C is correct:

• Option C accurately lists substances 1, 2, and 4, each containing a double bond per structural formulas.

Why the others are wrong:

• A includes substance 3, which has only single bonds.
• B omits substances 1 and 2, both with double bonds.
• D includes substance 3 (no double bond) and excludes 2 (has C=O).

Final answer: C