Organometallic Cumulative Practice: Study with Video Lessons, Practice Problems & Examples

In organometallic chemistry, understanding both product prediction and retrosynthesis is crucial. Predicting products involves recognizing various reactions, including 1,2-addition and nucleophilic acyl substitution, which may require multiple steps. Retrosynthesis focuses on identifying necessary reagents to synthesize a target compound, utilizing knowledge of organometallic reactions. Mastery of these concepts enhances problem-solving skills and deepens comprehension of reaction mechanisms, such as electrophilic additions and the role of Grignard reagents in organic synthesis.

Intro to Predict the Product

Now we're going to do some predict the product practice problems involving all the different reactions that organometallics can undergo. Keep in mind that some of these reactions will be multiple step reactions. So what that means is that you may have to draw back from previous lessons in order to really figure out the entire thing. At the end, just like always, I'll explain the answers to every problem. Let's go ahead and begin with problem 1.

Predict the product of the reaction

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Predict the product of the reaction

• A.
• B.
• C.
• D.

Predict the product of the reaction

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• B.
• C.
• D.

Predict the product of the reaction

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• B.
• C.
• D.

Intro to Retrosynthesis

Now let's focus on some practice problems involving organometallics, but going the other way around, we want to do some retrosynthesis now. What that means is that you're going to try to figure out what reagents it's going to take to make the final product. Think about all of the different reactions of organometallics we talked about and see how you can use them to your advantage in the next few questions. So let's go ahead and try to do the first one.

Propose a synthesis to accomplish the following transformation

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• D.

Propose a synthesis to accomplish the following transformation

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• B.
• C.
• D.

Predict the product of the reaction

• A.
• B.
• C.
• D.

Here’s what students ask on this topic:

What are the common reactions involving Grignard reagents in organometallic chemistry?

Grignard reagents (RMgX) are highly versatile in organometallic chemistry. Common reactions include:

• 1,2-Addition: Grignard reagents add to carbonyl compounds (aldehydes, ketones) to form alcohols.
• Nucleophilic Acyl Substitution: They react with esters to form tertiary alcohols.
• Carboxylation: Reaction with CO₂ to form carboxylic acids.
• Formation of C-C Bonds: React with alkyl halides to form new carbon-carbon bonds.

These reactions are fundamental in organic synthesis, enabling the construction of complex molecules.

How do you predict the product of a reaction involving organometallic compounds?

Predicting the product of a reaction involving organometallic compounds requires understanding the reactivity of the organometallic reagent and the functional groups present in the substrate. Key steps include:

• Identify the nucleophilic center in the organometallic reagent.
• Determine the electrophilic center in the substrate.
• Consider possible reaction pathways, such as 1,2-addition or nucleophilic acyl substitution.
• Account for any subsequent steps, such as protonation or rearrangement.

By following these steps, you can systematically predict the reaction product.

What is retrosynthesis and how is it applied in organometallic chemistry?

Retrosynthesis is a strategy used to plan the synthesis of complex molecules by breaking them down into simpler precursor structures. In organometallic chemistry, it involves:

• Identifying the target molecule.
• Determining the key bonds that need to be formed.
• Working backward to identify suitable organometallic reagents and reactions that can form these bonds.
• Considering alternative pathways and selecting the most efficient route.

This approach helps in designing a synthetic route by utilizing the unique reactivity of organometallic compounds.

What are the key differences between 1,2-addition and nucleophilic acyl substitution in organometallic reactions?

1,2-Addition and nucleophilic acyl substitution are two distinct reaction mechanisms:

• 1,2-Addition: Involves the addition of a nucleophile (e.g., Grignard reagent) to the carbonyl carbon of aldehydes or ketones, resulting in the formation of alcohols.
• Nucleophilic Acyl Substitution: Involves the substitution of a leaving group (e.g., halide) in acyl compounds (e.g., esters) by a nucleophile, leading to the formation of new carbonyl-containing compounds.

The key difference lies in the type of substrate and the nature of the product formed.

How do Grignard reagents react with carbon dioxide?

Grignard reagents react with carbon dioxide in a carboxylation reaction to form carboxylic acids. The reaction proceeds as follows:

1. The Grignard reagent (RMgX) attacks the electrophilic carbon in CO₂, forming a carboxylate intermediate.
2. The intermediate is then protonated during an acidic workup to yield the carboxylic acid (RCOOH).

This reaction is useful for converting alkyl halides into carboxylic acids.