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 24a

Chapter 10, Problem 24a

Predict the products you would expect from the reaction of NaBH₄ with the following compounds. You may assume that these reactions take place in methanol as the solvent.
(a) CH₃–(CH₂)₈–CHO

Verified step by step guidance

Step 1: Recognize the type of reaction. Sodium borohydride (NaBH4) is a reducing agent commonly used to reduce aldehydes and ketones to their corresponding alcohols. Methanol serves as the solvent in this reaction.

Step 2: Identify the functional group in the given compound. The compound CH3-(CH2)8-CHO contains an aldehyde group (-CHO) at the end of the carbon chain.

Step 3: Understand the mechanism of the reduction. NaBH4 donates a hydride ion (H⁻) to the carbonyl carbon of the aldehyde group. This breaks the double bond between the carbon and oxygen, forming an alkoxide intermediate.

Step 4: Protonation of the alkoxide intermediate. The alkoxide ion formed in the previous step is protonated by methanol (the solvent), resulting in the formation of a primary alcohol.

Step 5: Predict the product. The aldehyde group (-CHO) in CH3-(CH2)8-CHO is reduced to a primary alcohol (-CH2OH), yielding CH3-(CH2)8-CH2OH as the final product.

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Key Concepts

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

Reduction Reactions

Reduction reactions involve the gain of electrons or the decrease in oxidation state by a molecule. In organic chemistry, this often refers to the conversion of carbonyl groups (like aldehydes and ketones) into alcohols. Sodium borohydride (NaBH4) is a common reducing agent that effectively reduces aldehydes to primary alcohols.

Sodium Borohydride (NaBH4)

Sodium borohydride is a mild reducing agent used primarily for the reduction of aldehydes and ketones to their corresponding alcohols. It is less reactive than lithium aluminum hydride, making it suitable for selective reductions in various solvents, including methanol. Its ability to donate hydride ions (H-) is crucial for the reduction process.

Aldehyde Structure and Reactivity

Aldehydes are characterized by the presence of a carbonyl group (C=O) bonded to at least one hydrogen atom. This structure makes them more reactive than ketones, as they can be easily reduced to alcohols. In the given compound, CH3-(CH2)8-CHO, the aldehyde group is at the terminal position, making it a primary aldehyde that will yield a primary alcohol upon reduction.

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Related Practice

Textbook Question

Predict the products you would expect from the reaction of NaBH₄ with the following compounds. You may assume that these reactions take place in methanol as the solvent.

(d)

1019

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Textbook Question

Predict the products you would expect from the reaction of NaBH₄ with the following compounds. You may assume that these reactions take place in methanol as the solvent.

1647

views

Textbook Question

Predict the products you would expect from the reaction of NaBH₄ with the following compounds. You may assume that these reactions take place in methanol as the solvent.

(e)

748

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Textbook Question

Point out the flaws in the following incorrect Grignard syntheses.

(c)

(d)

1062

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Textbook Question

Point out the flaws in the following incorrect Grignard syntheses.

(a)