Ch. 11 - Organometallic Compounds

Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook

Bruice 8th Edition

Ch. 11 - Organometallic Compounds

Problem 57a(6)

Chapter 12, Problem 57a(6)

a. Show the reagents required to form the primary alcohol in each of the following reactions.

Verified step by step guidance

Step 1: Identify the starting material and the product. The starting material is an aldehyde (ethanal, CH₃CHO), and the product is a primary alcohol (ethanol, CH₃CH₂OH).

Step 2: Recognize the type of reaction. This is a reduction reaction where the aldehyde is reduced to a primary alcohol.

Step 3: Select the appropriate reducing agent. Common reducing agents for this transformation include sodium borohydride (NaBH₄) or lithium aluminum hydride (LiAlH₄).

Step 4: Consider the reaction conditions. NaBH₄ is typically used in protic solvents like ethanol or water, while LiAlH₄ requires anhydrous conditions and is often used in ether solvents such as diethyl ether.

Step 5: Write the reaction mechanism. The reducing agent donates hydride ions (H⁻) to the carbonyl carbon of the aldehyde, breaking the C=O double bond and forming the primary alcohol.

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Key Concepts

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

Carbonyl Compounds

Carbonyl compounds contain a carbon atom double-bonded to an oxygen atom (C=O). They are classified into aldehydes and ketones, depending on the carbonyl's position in the molecule. Aldehydes, like the one shown in the reaction, have at least one hydrogen atom attached to the carbonyl carbon, making them more reactive in nucleophilic addition reactions.

Nucleophilic Addition

Nucleophilic addition is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbon atom, such as that in a carbonyl group. This reaction typically leads to the formation of alcohols when the carbonyl compound is reduced. In the context of the question, a nucleophile will add to the carbonyl carbon, resulting in the formation of a primary alcohol.

Reagents for Alcohol Formation

To convert a carbonyl compound into a primary alcohol, specific reagents are required. Commonly, lithium aluminum hydride (LiAlH4) or sodium borohydride (NaBH4) are used as reducing agents. These reagents donate hydride ions (H-) to the carbonyl carbon, effectively reducing it and resulting in the formation of a primary alcohol.

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Reagents

Related Practice

Textbook Question

The Reformatsky reaction is an addition reaction in which an organozinc reagent is used instead of a Grignard reagent to add to the carbonyl group of an aldehyde or a ketone. Because the organozinc reagent is less reactive than a Grignard reagent, a nucleophilic addition to the ester group does not occur.

The organozinc reagent is prepared by treating an α-bromo ester with zinc.

Describe how each of the following compounds can be prepared, using a Reformatsky reaction:

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Textbook Question

What product is obtained from ring-opening metathesis polymerization of each of the following compounds? (Hint: In each case, the product is an unsaturated hydrocarbon with a high molecular weight.)

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Textbook Question

A dibromide loses only one bromine when it reacts with sodium hydroxide. The dibromide forms toluene (C₆H₅-CH₃) when it reacts with magnesium shavings in ether followed by treatment with dilute acid. Give possible structures for the dibromide.

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Textbook Question

What starting material is required in order to synthesize each of the following compounds by ring-closing metathesis?

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Textbook Question

What are the products of the following reactions? Show all stereoisomers that are formed.

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