The coupling of an alkyne with an aryl halide in the presence of a palladium catalyst and triethylamine is called a Sonogashira reaction. What reactants couple to form this product?

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Step 1: Recognize that the Sonogashira reaction involves the coupling of an alkyne with an aryl halide in the presence of a palladium catalyst and a base such as triethylamine.

Step 2: Analyze the product structure provided in the image. The product contains a phenyl group (benzene ring) attached to a terminal alkyne group with an ethyl substituent.

Step 3: Identify the two reactants required for the Sonogashira reaction. The phenyl group suggests the use of an aryl halide, such as bromobenzene or iodobenzene. The terminal alkyne group with an ethyl substituent suggests the use of ethynylbenzene (C≡C-CH2CH3).

Step 4: Write the general reaction scheme for the Sonogashira reaction: Ar-X + R-C≡CH → Ar-C≡C-R, where Ar-X is the aryl halide and R-C≡CH is the terminal alkyne.

Step 5: Confirm that the reactants bromobenzene (or iodobenzene) and ethynylbenzene (C≡C-CH2CH3) would couple under Sonogashira reaction conditions to form the product shown in the image.

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Key Concepts

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

Sonogashira Reaction

The Sonogashira reaction is a cross-coupling reaction that involves the coupling of an alkyne with an aryl halide using a palladium catalyst and a base, typically triethylamine. This reaction is significant in organic synthesis for forming carbon-carbon bonds, particularly in the construction of complex molecules and materials.

Palladium Catalysis

Palladium is a transition metal that serves as a catalyst in various organic reactions, including the Sonogashira reaction. Its ability to facilitate the formation and breaking of carbon-carbon bonds makes it essential for promoting the coupling of alkynes and aryl halides, enhancing reaction rates and selectivity.

Aryl Halides

Aryl halides are organic compounds that contain a halogen atom (such as chlorine, bromine, or iodine) bonded to an aromatic ring. In the context of the Sonogashira reaction, these compounds act as electrophiles, reacting with nucleophilic alkynes to form new carbon-carbon bonds, which are crucial for synthesizing more complex organic structures.