Ch. 11 - Organometallic Compounds

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

Bruice 8th Edition

Ch. 11 - Organometallic Compounds

Problem 42a

Chapter 12, Problem 42a

Which of the following compounds cannot be prepared by a Heck reaction?

Verified step by step guidance

Step 1: Understand the Heck reaction. The Heck reaction is a palladium-catalyzed coupling reaction between an aryl or vinyl halide and an alkene, resulting in the formation of a substituted alkene. The reaction typically requires a halide (such as bromide or iodide) and an alkene with a terminal double bond.

Step 2: Analyze compound A. Compound A contains two conjugated double bonds. This structure can be formed via a Heck reaction because it involves the coupling of a halide with a terminal alkene, leading to conjugation.

Step 3: Analyze compound B. Compound B contains a double bond in the middle of the chain, not at the terminal position. The Heck reaction generally requires a terminal alkene for the coupling process, so this compound cannot be prepared by a Heck reaction.

Step 4: Analyze compound C. Compound C contains a double bond adjacent to a carbonyl group. This structure can be formed via a Heck reaction because the carbonyl group can stabilize the intermediate formed during the reaction, making it feasible.

Step 5: Conclude that compound B cannot be prepared by a Heck reaction due to the lack of a terminal double bond, which is a key requirement for this reaction.

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Key Concepts

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

Heck Reaction

The Heck reaction is a palladium-catalyzed coupling reaction between an aryl or vinyl halide and an alkene, resulting in the formation of substituted alkenes. This reaction is significant in organic synthesis for constructing complex molecules and is particularly useful for forming carbon-carbon bonds. Understanding the mechanism and the types of substrates that can participate is crucial for predicting the products formed.

Substrate Compatibility

In the context of the Heck reaction, substrate compatibility refers to the ability of specific reactants to undergo the reaction successfully. Factors such as sterics, electronics, and the presence of functional groups influence whether a compound can be synthesized via this method. Recognizing which substrates are suitable helps in determining the feasibility of preparing a desired compound.

Functional Group Tolerance

Functional group tolerance in organic reactions indicates how well different functional groups can coexist in a reaction without interfering with the desired transformation. In the Heck reaction, certain functional groups may be incompatible, leading to side reactions or failure to produce the desired product. Understanding this concept is essential for predicting which compounds can be synthesized and which cannot.

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Related Practice

Textbook Question

A student added an equivalent of 3,4-epoxy-4-methylcyclohexanol to a solution of methylmagnesium bromide in diethyl ether, and then added dilute hydrochloric acid. He expected that the product would be 1,2-dimethyl-1,4-cyclohexanediol. He did not get any of the expected product. What product did he get?

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Textbook Question

Metathesis of which of the following sets of alkenes leads to the highest yield of a single alkene?

1. 1-butene and 1-pentene

2. 2-butene and 3-hexene

3. 2-butene and 1-pentene

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Textbook Question

Dimerization is a side reaction that occurs during the preparation of a Grignard reagent. Propose a mechanism that accounts for the formation of the dimer.

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Textbook Question

Using the given starting material, any necessary inorganic reagents, and any carbon-containing compounds with no more than two carbons, indicate how each of the following compounds can be prepared:

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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

For those compounds that can be prepared by a Heck reaction, what starting materials are required?

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