Analyzing molecular bonds and electron pairs in tiglic acid

Steps:

• Parse the structure CH3-CH=CH-COOH to identify atoms and bonds: four carbons, one C=C double bond, one COOH group with C=O double bond.
• Count π bonds: one from C=C (σ + π), one from C=O (σ + π).
• Draw Lewis structure for lone pairs: carbonyl O has two lone pairs, hydroxyl O has two lone pairs.
• Assess geometry: sp2 carbons in chain suggest planarity for heavy atoms, but sp3 methyl hydrogens deviate.

Why B is correct:

• In the Lewis structure of the carboxylic acid, the carbonyl oxygen (double-bonded) has two lone pairs, and the hydroxyl oxygen (single-bonded to C and H) has two lone pairs, totaling four per the octet rule.

Why the others are wrong:

• A: Only one carbon-carbon π bond exists; the C=O π bond is in the functional group, not counted as a second in this context.
• C: The methyl group's sp3-hybridized hydrogens are not coplanar with the sp2 chain due to tetrahedral geometry.

Final answer: B