Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

13. Alcohols and Carbonyl Compounds

Oxidizing Agent

Organic Chemistry

13. Alcohols and Carbonyl Compounds

Oxidizing Agent

Previous problemNext problem

7:07 minutes

Problem 61

Textbook Question

Chromic acid oxidation of an alcohol (Section 11-2A) occurs in two steps: formation of the chromate ester, followed by an elimination of H⁺ and chromium. Which step do you expect to be rate-limiting? Careful kinetic studies have shown that Compound A undergoes chromic acid oxidation over 10 times as fast as Compound B. Explain this large difference in rates.

Verified step by step guidance

Step 1: Understand the chromic acid oxidation mechanism. Chromic acid oxidation of alcohols involves two key steps: (1) formation of a chromate ester intermediate, and (2) elimination of H+ and chromium to form the oxidized product. The rate-limiting step is typically the formation of the chromate ester, as it involves bond formation and rearrangement.

Step 2: Analyze the structures of Compound A and Compound B. Compound A has a secondary alcohol group, while Compound B has a primary alcohol group. The steric and electronic environment around the alcohol group influences the rate of chromate ester formation.

Step 3: Consider steric hindrance. Compound A has a methyl group adjacent to the alcohol, which can stabilize the transition state during chromate ester formation. In contrast, Compound B lacks this stabilizing group, making the transition state less favorable and slowing down the reaction.

Step 4: Evaluate electronic effects. The methyl group in Compound A can donate electron density through hyperconjugation, stabilizing the intermediate formed during chromate ester formation. Compound B does not have this stabilizing effect, contributing to its slower reaction rate.

Step 5: Conclude the explanation. The large difference in rates between Compound A and Compound B is due to the steric and electronic stabilization provided by the methyl group in Compound A, which facilitates faster formation of the chromate ester intermediate, the rate-limiting step in the reaction.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chromic Acid Oxidation Mechanism

Chromic acid oxidation of alcohols involves a two-step mechanism. The first step is the formation of a chromate ester, where the alcohol reacts with chromic acid to form a transient intermediate. The second step involves the elimination of H+ and chromium species, leading to the formation of the carbonyl compound. Understanding this mechanism is crucial for identifying which step may be rate-limiting.

Rate-Limiting Step

The rate-limiting step in a reaction mechanism is the slowest step that determines the overall reaction rate. In the context of chromic acid oxidation, identifying whether the formation of the chromate ester or the elimination step is rate-limiting is essential for predicting reaction kinetics. This concept is fundamental in understanding how different factors can influence the speed of chemical reactions.

Kinetic Studies and Reactivity

Kinetic studies involve measuring the rates of reactions to understand how different compounds react under similar conditions. The observation that Compound A undergoes chromic acid oxidation over 10 times faster than Compound B suggests significant differences in their structures or steric effects, which can influence the stability of intermediates and transition states. This concept helps explain variations in reactivity among different alcohols.

Watch next

Master Reagents with a bite sized video explanation from Johnny

Start learning