Textbook Question
Show how you would synthesize the following alcohol by adding Grignard reagents to ethylene oxide.
(c)
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13. Alcohols and Carbonyl Compounds
Grignard Reaction
4:38 minutesProblem 15d
Textbook Question
Show how you would synthesize following tertiary alcohol by adding an appropriate Grignard reagent to a ketone.
d. 2-cyclopentylpentan-2-ol
Verified step by step guidance1
Identify the target molecule: The target molecule is 2-cyclopentylpentan-2-ol, which is a tertiary alcohol. Tertiary alcohols can be synthesized by reacting a ketone with a Grignard reagent.
Determine the structure of the ketone: To form the tertiary alcohol, the ketone must have the same carbon skeleton as the target molecule, minus the group added by the Grignard reagent. In this case, the ketone would be cyclopentyl methyl ketone (2-cyclopentylpropan-2-one).
Determine the Grignard reagent: The Grignard reagent must add the appropriate alkyl group to the ketone to form the tertiary alcohol. In this case, the Grignard reagent would be ethylmagnesium bromide (CH₃CH₂MgBr).
Write the reaction mechanism: The Grignard reagent (ethylmagnesium bromide) will attack the carbonyl carbon of the ketone (cyclopentyl methyl ketone), forming a tetrahedral alkoxide intermediate. This intermediate will then be protonated during the acidic workup to yield the tertiary alcohol.
Summarize the synthesis: Combine cyclopentyl methyl ketone with ethylmagnesium bromide in an anhydrous ether solvent, followed by an acidic workup (e.g., H₃O⁺), to synthesize 2-cyclopentylpentan-2-ol.
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Video duration:
4mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Grignard Reagents
Grignard reagents are organomagnesium compounds that are highly reactive and used in organic synthesis to form carbon-carbon bonds. They are created by reacting an alkyl or aryl halide with magnesium metal in anhydrous ether. When added to carbonyl compounds like ketones, they can facilitate the formation of alcohols through nucleophilic addition.
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Carbonation of Grignard Reagents
Nucleophilic Addition to Ketones
Nucleophilic addition is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophilic carbon atom in a carbonyl group. In the case of ketones, the carbonyl carbon is susceptible to attack by nucleophiles such as Grignard reagents, leading to the formation of an alkoxide intermediate. This intermediate can then be protonated to yield the corresponding alcohol.
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Synthesis of Tertiary Alcohols
Tertiary alcohols are synthesized from ketones by adding two alkyl groups to the carbon atom of the carbonyl. When a Grignard reagent reacts with a ketone, it adds to the carbonyl carbon, resulting in a tertiary alcohol after protonation. The specific structure of the Grignard reagent determines the final structure of the tertiary alcohol produced.
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01:44Forming alcohols through SN2 reactions.
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