See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: The stability of canonical (resonance) structures depends on factors such as: (1) completeness of octets, (2) minimization of formal charges, (3) electronegativity of atoms bearing charges, and (4) separation of charges. Step 1: Analyze Structure I. Structure I has a C=O double bond (carbonyl) and a carbanion (negative charge) on the CH2 carbon. The negative charge is on carbon, which is not highly electronegative. However, there is no charge separation on the more electronegative oxygen, and all atoms satisfy their valences reasonably. The carbonyl is stable, but the carbanion on carbon is somewhat unfavorable. Step 2: Analyze Structure II. Structure II has both a positive charge on carbon and a negative charge on oxygen AND a negative charge on CH2. This structure has charge separation and a carbon with a positive charge (carbocation) which violates the octet rule at carbon (only 6 electrons). Having two negative charges and one positive charge simultaneously makes this structure the least stable. Charge separation on carbon (low electronegativity bearing positive charge next to negatively charged oxygen) is highly unfavorable. Step 3: Analyze Structure III. Structure III has a negative charge on oxygen (O has negative charge, O^- ) and a C=CH2 double bond. The negative charge resides on oxygen, which is the most electronegative atom in the structure. Negative charge on a more electronegative atom confers greater stability. There is no positive charge anywhere, and oxygen can accommodate the negative charge well. This makes Structure III the most stable among the three. Step 4: Establish order. - III is most stable: negative charge on electronegative oxygen, C=CH2 double bond, no positive charges. - I is next: has a stable C=O, but carbanion on CH2 (carbon bearing negative charge is less favorable than oxygen bearing it). - II is least stable: has charge separation, carbocation (incomplete octet on carbon), and two negative charges simultaneously. Thus the order is: III > I > II. Why other options fail: - Option (a) I > III > II: Incorrect because III is more stable than I (negative charge on O vs. on C). - Option (c) II > III > I: Incorrect because II is the least stable due to carbocation and multiple charge separation. - Option (d) II > I > III: Incorrect for the same reason as (c). Therefore, the correct answer is B.