Ch.10 - Structure and Synthesis of Alcohols

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch.10 - Structure and Synthesis of Alcohols

Problem 26c

Chapter 10, Problem 26c

Show how you would synthesize the following alcohol by reducing appropriate carbonyl compound.
c. 2-methylhexan-3-ol

Verified step by step guidance

Identify the target alcohol: The compound 2-methylhexan-3-ol is a secondary alcohol, meaning the hydroxyl group (-OH) is attached to a carbon atom that is bonded to two other carbon atoms. This suggests that the precursor is likely a ketone.

Determine the corresponding carbonyl compound: To synthesize 2-methylhexan-3-ol, the corresponding carbonyl compound would be 2-methylhexan-3-one. This is because reducing a ketone with a reducing agent will yield a secondary alcohol.

Choose an appropriate reducing agent: Common reducing agents for converting ketones to secondary alcohols include sodium borohydride (NaBH₄) or lithium aluminum hydride (LiAlH₄). NaBH₄ is often preferred for mild conditions.

Write the reaction mechanism: The reduction involves the nucleophilic attack of the hydride ion (H⁻) from the reducing agent on the carbonyl carbon of 2-methylhexan-3-one. This forms an alkoxide intermediate, which is then protonated by water or an acid to yield 2-methylhexan-3-ol.

Summarize the synthesis: Start with 2-methylhexan-3-one as the carbonyl compound. Treat it with NaBH₄ in a suitable solvent (e.g., ethanol or methanol) to reduce the ketone to 2-methylhexan-3-ol. Finally, perform a workup step to isolate the alcohol product.

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Key Concepts

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

Reduction of Carbonyl Compounds

Reduction is a chemical reaction that involves the gain of electrons or a decrease in oxidation state. In organic chemistry, carbonyl compounds, such as aldehydes and ketones, can be reduced to alcohols using reducing agents like lithium aluminum hydride (LiAlH4) or sodium borohydride (NaBH4). Understanding the mechanism of this reduction is crucial for synthesizing alcohols from carbonyl precursors.

Structure of 2-methylhexan-3-ol

2-methylhexan-3-ol is a secondary alcohol with a specific carbon skeleton. It consists of a six-carbon chain (hexane) with a methyl group (–CH3) attached to the second carbon and a hydroxyl group (–OH) on the third carbon. Recognizing the structure helps in identifying the appropriate carbonyl compound to reduce in order to achieve the desired alcohol.

Choice of Carbonyl Compound

To synthesize 2-methylhexan-3-ol, one must select the correct carbonyl compound to reduce. The appropriate precursor is 2-methylhexan-3-one, a ketone, which upon reduction will yield the target alcohol. Understanding the relationship between the structure of the desired alcohol and its corresponding carbonyl compound is essential for successful synthesis.

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Related Practice

Textbook Question

Predict the products you would expect from the reaction of LiAlH₄ followed by hydrolysis with the following compounds. You may assume that these reactions take place in methanol as the solvent.

(e)

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Textbook Question

Predict the products you would expect from the reaction of LiAlH₄ followed by hydrolysis with the following compounds. You may assume that these reactions take place in methanol as the solvent.

(d)

891

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Textbook Question

Show how you would synthesize the following alcohol by reducing appropriate carbonyl compound.

(d)

816

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Textbook Question

Give IUPAC names for the following compounds.

1759

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