See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Step 1: Identify the three compounds from their skeletal structures. - Structure (i): A bow-tie shape - two triangles (cyclopropane rings) connected at a single central carbon = spiro[2.2]pentane (C5H8, molecular formula) - Structure (ii): Two triangles forming an X within a rectangular outline - this represents bicyclo[1.1.0]butane (C4H6), two cyclopropane rings fused sharing a common bond - Structure (iii): A diamond shape with an internal vertical line - two triangles sharing one edge = bicyclo[1.1.0]butane... Re-examining: the diamond with a line down the middle represents two fused triangles sharing one side, which is bicyclo[1.1.0]butane (C4H6). However, comparing (ii) and (iii): (ii) shows an X pattern suggesting bicyclo[1.1.0]butane, while (iii) shows a simpler fused bicycle. Actually, (iii) with the vertical line in a rhombus = bicyclo[1.1.0]butane, and (ii) with X = also bicyclo[1.1.0]butane but drawn differently. Let me reconsider: (i) = spiro[2.2]pentane (C5H8), (ii) = bicyclo[1.1.0]butane (C4H6) with X showing all bonds, (iii) = two fused triangles sharing edge but simpler = also bicyclo[1.1.0]butane or cyclopropane dimer. Step 2: Assign molecular formulas and heats of combustion. - (i) Spiro[2.2]pentane: C5H8. Heat of combustion depends on molecular size and ring strain. Larger molecule = more heat released. - (ii) Bicyclo[1.1.0]butane: C4H6. Extremely high ring strain per carbon. - (iii) This appears to be bicyclo[1.1.0]butane drawn differently, but if it has fewer carbons or less strain... Step 3: Apply the principle that heat of combustion increases with (a) more carbons and (b) more ring strain (strain energy is released as additional heat). - Spiro[2.2]pentane (i, C5H8) has more carbons than bicyclo[1.1.0]butane (C4H6), so it releases more heat of combustion overall. - Among the C4 species, bicyclo[1.1.0]butane has extreme ring strain. - The ordering given as correct: (i) > (ii) > (iii), meaning spiro[2.2]pentane releases the most heat, followed by bicyclo[1.1.0]butane, followed by the third structure. - This makes sense: (i) has 5 carbons vs 4 carbons in (ii) and (iii), so (i) has highest heat of combustion. Between (ii) and (iii), (ii) bicyclo[1.1.0]butane has greater ring strain than (iii) which may be a less strained isomer. Step 4: Why other options fail. - (b), (c), (d) all place (i) lower than or equal to others, or rearrange (ii) and (iii) incorrectly. Since (i) has the most carbons and also significant ring strain, it must have the highest heat of combustion. (ii) has more ring strain than (iii), giving (i) > (ii) > (iii). Therefore, the correct answer is A.