See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

PART A — Alkene stability (cyclohexene derivatives): Concept: Alkene stability increases with more alkyl substituents on the double bond (hyperconjugation/induction) and is reduced by steric strain. For cyclic alkenes with stereochemistry, cis-fused or ring-strain considerations apply. - Structure C: 1,2-dimethylcyclohex-1-ene — the double bond is trisubstituted (two methyl groups + two ring carbons), and there is no geometric strain from wedge bonds. Most stable → rank 1. - Structure B: 1,2-dimethylcyclohex-2-ene with a wedge-bond methyl — still a trisubstituted-type alkene but the methyl and H are on the same face (cis), introducing some steric interaction. Less stable than C → rank 2. - Structure A: cyclohex-2-ene with methyl and H on wedge (both on same face, cis relationship), the double bond is less substituted compared to B and C, making it least stable → rank 3. Result: A=3, B=2, C=1. PART B — Acidity order: Concept: Acidity depends on the stability of the conjugate base (carbanion or anion) and the hybridization of the C–H or O–H bond. sp carbon > sp2 carbon > sp3 carbon in terms of acidity for C–H bonds. O–H bonds are far more acidic than C–H bonds. - A (1-butanol): Has an O–H bond, pKa ~16. Most acidic → rank 1. - C (but-2-yne / internal alkyne): C–H... wait, but-2-yne (CH3C≡CCH3) has no terminal C–H on the triple bond. However, the image shows what appears to be an internal alkyne. Internal alkynes have sp C but no acidic terminal H. The structure shown appears to be 2-butyne (internal). But comparing to an alkene: sp2 C–H (vinylic, pKa ~44) vs sp C–H terminal alkyne (pKa ~25). Since this is internal alkyne, its most acidic H is actually a sp3 CH3 adjacent to triple bond. Re-examining: the given answer ranks C=2 (second most acidic). This means C is more acidic than B (alkene). This supports C being a terminal alkyne (pKa ~25) rather than internal — the structure may be but-1-yne (HC≡C–CH2CH3). Terminal alkyne sp C–H pKa ~25 → rank 2. - B (but-2-ene, alkene): Vinylic sp2 C–H pKa ~44 → rank 3. - D (ether): No O–H or acidic C–H easily removed; ethers are essentially non-acidic (pKa >50) → rank 4. Result: A=1, B=3, C=2, D=4. PART C — Boiling point order: Concept: Boiling point depends on intermolecular forces: H-bonding > dipole-dipole > London dispersion. Molecular weight and surface area also matter. - B (2-butanol, secondary alcohol with OH): Has H-bonding capability, MW ~74. Highest boiling point → rank 1. - D (isobutanol or 2-methyl-1-propanol with –CH2OH): Also has H-bonding, primary alcohol, MW ~74. Primary alcohols generally boil higher than secondary of same MW due to less branching, but the given answer ranks D=2. So D is second. - A (isopropyl methyl ether): Has dipole-dipole but no H-bonding, MW ~74. Lower than alcohols → rank 3. - C (2-methylbutane / isopentane): Purely London dispersion, no polar groups, lowest boiling point → rank 4. Result: A=3, B=1, C=4, D=2. PART D — Alkene stability (cyclopentene/cyclopentadiene derivatives): Concept: More substituted double bonds are more stable; conjugated dienes are more stable than isolated double bonds; exocyclic double bonds are generally less stable than endocyclic equivalents of similar substitution. - A (1,5-dimethylcyclopenta-1,3-diene): Conjugated diene with two methyl substituents — most stable due to conjugation + substitution → rank 1. - B (1,2-dimethylcyclopent-2-ene): Trisubstituted endocyclic double bond (two ring carbons + two methyl groups) → rank 2. - C (3,5-dimethylcyclopenta-1,3-diene or similar dimethyl cyclopentadiene): Conjugated diene but methyls in less favorable positions than A, or the conjugation is present but less substitution at the double bond → rank 3. - D (methylenecyclopentane with ring methyl, exocyclic =CH2): Exocyclic methylene is less stable than endocyclic, terminal unsubstituted double bond → rank 4. Result: A=1, B=2, C=3, D=4. Therefore, the correct answer is {"A": {"A": 3, "B": 2, "C": 1}, "B": {"A": 1, "B": 3, "C": 2, "D": 4}, "C": {"A": 3, "B": 1, "C": 4, "D": 2}, "D": {"A": 1, "B": 2, "C": 3, "D": 4}}.