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 formed by reacting magnesium with alkyl or aryl halides. They are highly reactive nucleophiles that can add to carbonyl compounds, leading to the formation of alcohols upon hydrolysis. In this synthesis, bromocyclohexane will react with magnesium to form the Grignard reagent, which is essential for the subsequent steps.

Nucleophilic Addition

Nucleophilic addition is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbon atom, typically in a carbonyl group. In the case of preparing 2-cyclohexylethanol, the Grignard reagent will act as the nucleophile, attacking a suitable carbonyl compound to form an intermediate alcohol. Understanding this mechanism is crucial for predicting the outcome of the reaction.

Alcohol Formation

The formation of alcohols from carbonyl compounds is a key transformation in organic synthesis. After the nucleophilic addition of the Grignard reagent to the carbonyl, the resulting alkoxide intermediate can be protonated by water or an acid to yield the final alcohol product. In this case, the reaction will yield 2-cyclohexylethanol, demonstrating the utility of Grignard reagents in alcohol synthesis.

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Related Practice

Textbook Question

Show two ways you could synthesize each of the following secondary alcohol by adding an appropriate Grignard reagent to an aldehyde.

(c)

Textbook Question

Show how you would synthesize following tertiary alcohol by adding an appropriate Grignard reagent to a ketone.

c. 1-ethylcyclopentanol

Textbook Question

Show how you would add Grignard reagent to acid chloride or ester to synthesize the following alcohols.

c. dicyclohexylphenylmethanol

Textbook Question

Show how you would synthesize the following alcohol by adding Grignard reagents to ethylene oxide.

(c)

Textbook Question

Show how this 1° alcohol can be made from the following:

(e) an alkene

(f) ethylene oxide

Textbook Question

Show how you would synthesize the following primary alcohol by adding an appropriate Grignard reagent to formaldehyde.

(b)

Textbook Question

Show how you would synthesize following tertiary alcohol by adding an appropriate Grignard reagent to a ketone.

d. 2-cyclopentylpentan-2-ol

Textbook Question

Point out the flaws in the following incorrect Grignard syntheses.

(c)

(d)

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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

Key Concepts

Grignard Reagents

Nucleophilic Addition

Alcohol Formation

Watch next

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