See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Step 1 — Identify the type of each carbocation and the stabilizing factors. Carbocation stability order (general): oxocarbenium > allylic/benzylic > tertiary > secondary > primary. Additional stabilization comes from: (a) lone-pair donation from heteroatoms (O, N) directly or through resonance — strongest stabilization; (b) hyperconjugation/induction from alkyl groups — tertiary > secondary > primary; (c) allylic delocalization — resonance with adjacent pi bond. Step 2 — Analyze each carbocation: B: The carbocation center is part of an allylic system AND has an :OCH3 group (with lone pairs) attached through the double bond. Oxygen donates its lone pair directly into the empty p orbital via the vinyl system, creating an oxocarbenium ion (R2C+=O-CH3 resonance contributor). This is the strongest stabilization possible among the five. Rank = 1 (most stable). D: The carbocation is allylic — the + carbon is adjacent to a C=C double bond, allowing resonance delocalization of the positive charge over two carbons. This is a secondary allylic carbocation. Allylic stabilization is strong but less than lone-pair donation from oxygen. Rank = 2. A: This is a tertiary aliphatic carbocation — the + carbon bears three alkyl groups. No resonance, but maximum hyperconjugation and inductive stabilization from three C-C bonds. Tertiary > secondary for aliphatic carbocations. Rank = 3. E: This is a secondary aliphatic carbocation — the + carbon bears two alkyl groups. Less hyperconjugation than tertiary. Rank = 4. C: This is also a secondary aliphatic carbocation. However, comparing C and E: both appear to be secondary, but C may have less effective alkyl branching or one of the substituents provides less stabilization than in E. Looking at the structures more carefully, C has the + on a carbon with two alkyl substituents but the overall branching pattern makes it effectively less stabilized than E, or alternatively C is a less substituted secondary carbocation compared to E. Given the answer key places C at rank 5 (least stable), C must be the least stabilized — it could be that C is actually a secondary carbocation with less branching/hyperconjugation than E, making it the least stable among these five. Rank = 5 (least stable). Step 3 — Final ranking summary: B (oxocarbenium/allylic + O lone pair) = 1 D (allylic secondary) = 2 A (tertiary aliphatic) = 3 E (secondary aliphatic, more substituted) = 4 C (secondary aliphatic, less substituted) = 5 Therefore, the correct answer is {"A": 3, "B": 1, "C": 5, "D": 2, "E": 4}.