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

Grignard Reaction

Organic Chemistry

13. Alcohols and Carbonyl Compounds

Grignard Reaction

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3:21 minutes

Problem 39d

Textbook Question

Show how you would use Grignard syntheses to prepare the following alcohol from the indicated starting material and any other necessary reagents.
(d) 2-cyclohexylethanol from bromocyclohexane

Verified step by step guidance

Step 1: Begin by preparing the Grignard reagent. React bromocyclohexane with magnesium (Mg) in anhydrous ether to form cyclohexylmagnesium bromide. This reaction involves the insertion of magnesium into the carbon-bromine bond.

Step 2: Identify the electrophile needed to react with the Grignard reagent to form the desired alcohol. In this case, you need an aldehyde or ketone that will lead to 2-cyclohexylethanol upon reaction. Ethylene oxide (an epoxide) is a suitable choice because it will open up to form a primary alcohol with the Grignard reagent.

Step 3: React the Grignard reagent (cyclohexylmagnesium bromide) with ethylene oxide in anhydrous ether. The nucleophilic attack of the Grignard reagent on the epoxide ring opens the ring, forming a magnesium alkoxide intermediate.

Step 4: Perform an acidic workup by adding dilute acid (e.g., HCl or H2SO4) to the reaction mixture. This step protonates the alkoxide intermediate, converting it into the desired alcohol, 2-cyclohexylethanol.

Step 5: Purify the product by standard organic chemistry techniques, such as extraction, drying, and distillation, to isolate 2-cyclohexylethanol in its pure form.

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Key Concepts

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

Grignard Reagents

Grignard reagents are organomagnesium compounds, typically represented as R-MgX, where R is an organic group and X is a halogen. They are highly reactive and can act as nucleophiles, allowing them to react with electrophiles such as carbonyl compounds. In the synthesis of alcohols, Grignard reagents can add to carbonyl groups, leading to the formation of alcohols after hydrolysis.

Nucleophilic Addition

Nucleophilic addition is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbon atom, typically found in carbonyl groups. This process is crucial in the formation of alcohols from carbonyl compounds, as the nucleophile (like a Grignard reagent) adds to the carbonyl carbon, resulting in an alkoxide intermediate that can be protonated to yield the final alcohol product.

Synthesis of Alcohols

The synthesis of alcohols can be achieved through various methods, including the reduction of carbonyl compounds or the reaction of Grignard reagents with carbonyls. In the case of preparing 2-cyclohexylethanol from bromocyclohexane, the Grignard reagent formed from bromocyclohexane can react with an appropriate carbonyl compound, followed by hydrolysis, to yield the desired alcohol.