DP Chemistry (first assessment 2025)
Question 22M.2.HL.TZ1.b(ii)
| Date | May 2022 | Marks available | [Maximum mark: 2] | Reference code | 22M.2.HL.TZ1.b(ii) |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | b(ii) | Adapted from | N/A |
b(ii).
[Maximum mark: 2]
22M.2.HL.TZ1.b(ii)
Explain why the reaction produces more (CH3)3COH than (CH3)2CHCH2OH.
[2]
Markscheme
carbocation formed from (CH3)3COH is more stable / (CH3)3C+ is more stable than (CH3)2CHCH2+ ✔
«because carbocation has» greater number of alkyl groups/lower charge on the atom/higher e- density
OR
«greater number of alkyl groups» are more electron releasing
OR
«greater number of alkyl groups creates» greater inductive/+I effect ✔
Do not award any marks for simply quoting Markovnikov’s rule.
Examiners report
Poor performance, particularly in light of past feedback provided in similar questions since there was repeated reference simply to Markovnikov's rule, without any explanation.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.4—Electron-pair sharing reactions » Reactivity 3.4.12—The relative stability of carbocations in the addition reactions between hydrogen halides and unsymmetrical alkenes can be used to explain the reaction mechanism. Predict and explain the major product of a reaction between an unsymmetrical alkene and a hydrogen halide or water.