Textbook Question
Show how you would synthesize the following primary alcohol by adding an appropriate Grignard reagent to formaldehyde.
(c)
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13. Alcohols and Carbonyl Compounds
Grignard Reaction
2:38 minutesProblem 19c
Textbook Question
Show how you would synthesize the following alcohol by adding Grignard reagents to ethylene oxide.
(c) 
Verified step by step guidance1
Step 1: Identify the target alcohol structure. The alcohol shown has a cyclohexane ring with a methyl group and a CH2CH2OH group attached to the same carbon. This suggests that the synthesis involves forming a secondary alcohol at the carbon attached to the ring.
Step 2: Recognize the role of ethylene oxide in the synthesis. Ethylene oxide is an epoxide that reacts with Grignard reagents to form alcohols. The reaction involves nucleophilic attack by the Grignard reagent on the epoxide, followed by protonation to yield the alcohol.
Step 3: Determine the Grignard reagent needed. To form the CH2CH2OH group, the Grignard reagent must contain the cyclohexane ring and the methyl group already attached to the same carbon. This can be achieved by using cyclohexylmethyl magnesium bromide (C6H11CH2MgBr) as the Grignard reagent.
Step 4: Perform the reaction. Add the Grignard reagent (C6H11CH2MgBr) to ethylene oxide under anhydrous conditions. The nucleophilic carbon in the Grignard reagent will attack the less hindered carbon of the epoxide, opening the ring and forming a new C-C bond.
Step 5: Protonate the intermediate. After the epoxide ring opens, the resulting alkoxide intermediate is protonated using a mild acid (e.g., HCl or H2O) to yield the final alcohol product, which matches the target structure.
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2mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Grignard Reagents
Grignard reagents are organomagnesium compounds represented as R-MgX, where R is an organic group and X is a halogen. They are highly reactive and serve as nucleophiles in organic synthesis, allowing for the formation of carbon-carbon bonds. When added to electrophiles, such as carbonyl compounds or epoxides, they can facilitate the synthesis of alcohols and other functional groups.
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Carbonation of Grignard Reagents
Ethylene Oxide
Ethylene oxide is a three-membered cyclic ether that is highly reactive due to its strained ring structure. It can undergo nucleophilic attack, making it a useful substrate for reactions with Grignard reagents. When a Grignard reagent attacks ethylene oxide, it opens the epoxide ring, leading to the formation of an alcohol after subsequent protonation.
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Nucleophilic Attack
Nucleophilic attack is a fundamental reaction mechanism in organic chemistry where a nucleophile donates an electron pair to an electrophile, forming a new bond. In the context of Grignard reagents and ethylene oxide, the nucleophile (Grignard reagent) attacks the electrophilic carbon in the epoxide, resulting in ring opening and the formation of a new carbon-carbon bond, ultimately leading to the desired alcohol.
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