Textbook Question
What products would you expect from the following reactions?
(a)
35. Transition Metals
Heck Reaction
3:27 minutesProblem 17a
Textbook Question
What is the product of each of the following reactions?
a. 
Verified step by step guidance1
Step 1: Identify the reaction type. This is a typical example of a palladium-catalyzed cross-coupling reaction, specifically a Heck reaction. The Heck reaction involves the coupling of an aryl halide (in this case, iodobenzene) with an alkene (here, acrylonitrile) in the presence of a palladium catalyst and a base.
Step 2: Analyze the reactants. The aryl halide (iodobenzene) will act as the electrophile, while the alkene (acrylonitrile) will act as the nucleophile. The palladium catalyst facilitates the formation of a carbon-carbon bond between the two reactants.
Step 3: Predict the regioselectivity. In the Heck reaction, the alkene typically undergoes substitution at the less sterically hindered position. For acrylonitrile, the substitution will occur at the terminal carbon of the double bond, as it is less hindered.
Step 4: Consider the stereochemistry. The Heck reaction often leads to the formation of the trans product due to the anti-addition mechanism of the palladium catalyst.
Step 5: Combine the pieces. The product will be a substituted alkene where the phenyl group from iodobenzene is attached to the terminal carbon of acrylonitrile, forming a trans-stilbene-like structure with the nitrile group intact.
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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 halide and an alkene, resulting in the formation of a substituted alkene. This reaction is significant in organic synthesis for constructing carbon-carbon bonds and is widely used in the pharmaceutical and materials industries. The reaction typically requires a base and a ligand to stabilize the palladium catalyst.
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Heck Reaction
Palladium Catalysis
Palladium catalysis involves the use of palladium as a catalyst to facilitate various organic reactions, including cross-coupling reactions like the Heck reaction. Palladium can exist in multiple oxidation states, allowing it to participate in different steps of the reaction mechanism, such as oxidative addition, transmetalation, and reductive elimination. The choice of ligands and reaction conditions can significantly influence the efficiency and selectivity of the reaction.
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Substitution Reactions
Substitution reactions involve the replacement of one functional group in a molecule with another. In the context of the Heck reaction, the aryl halide undergoes substitution where the halogen is replaced by an alkene moiety. Understanding the mechanisms of substitution reactions, including nucleophilic and electrophilic pathways, is crucial for predicting the products of reactions and designing synthetic routes in organic chemistry.
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