Molecular bonding and electron pairs in tiglic acid

Steps:

• Parse the structure CH3-CH=CH-COOH to reveal the alkene (C=C) and carboxylic acid (-COOH with C=O and -OH).
• Construct the Lewis structure, counting bonds (sigma/pi) and lone pairs on oxygens.
• Evaluate sigma/pi counts, lone pair distribution, and molecular geometry for planarity.
• Test each statement against these features to identify the accurate one.

Why B is correct:

• Per the octet rule in the Lewis structure, the hydroxyl oxygen (sp³ hybridized, bonded to C and H) holds exactly two lone pairs.

Why the others are wrong:

• A: Only one π bond exists in the C=C double bond; the C=O contributes another, making the statement inaccurate for exactly two.
• C: The molecule has 11 σ bonds total (5 C-H, 3 C-C, 2 C-O, 1 O-H), far exceeding four.
• D: Methyl hydrogens adopt tetrahedral geometry, positioning them out of the chain's sp² plane.

Final answer: B