The intermediates for the Swern oxidation, a reaction introduced in Section 13.9.4, are shown. Provide the arrow-pushing mechanism that rationalizes the formation of each intermediate and the final product(s).

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Identify the first step where dimethyl sulfide reacts with chlorine gas (Cl2) to form a chlorosulfonium ion. The lone pair on sulfur attacks one of the chlorine atoms, resulting in the formation of a chlorosulfonium ion and a chloride ion.

In the next step, the chlorosulfonium ion reacts with the alcohol. The oxygen of the alcohol attacks the sulfur atom of the chlorosulfonium ion, forming an alkoxysulfonium ion intermediate.

The chloride ion acts as a base and abstracts a proton from the alkoxysulfonium ion, leading to the formation of a neutral sulfoxide intermediate and hydrochloric acid (HCl).

The sulfoxide intermediate undergoes deprotonation by triethylamine (Et3N), which acts as a base. This step generates a sulfur ylide intermediate and a protonated triethylamine.

Finally, the sulfur ylide intermediate undergoes a rearrangement to form the desired ketone or aldehyde product, along with dimethyl sulfide as a byproduct. This step involves the migration of the alkyl group from the carbon to the oxygen, completing the Swern oxidation process.

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Key Concepts

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

Swern Oxidation

Swern oxidation is a method for converting alcohols into aldehydes or ketones using a combination of oxalyl chloride and a base, typically triethylamine. This reaction is notable for its mild conditions and selectivity, making it a valuable tool in organic synthesis. Understanding the overall reaction mechanism is crucial for predicting the formation of intermediates and final products.

Arrow-Pushing Mechanism

The arrow-pushing mechanism is a way to illustrate the movement of electrons during chemical reactions. In this notation, arrows indicate the direction of electron flow, helping to visualize bond formation and breaking. Mastery of this technique is essential for accurately depicting the steps involved in the Swern oxidation and understanding how intermediates are formed.

Reaction Intermediates

Reaction intermediates are transient species that form during the conversion of reactants to products in a chemical reaction. They are often unstable and exist only for a short duration. Identifying these intermediates is key to understanding the mechanism of the Swern oxidation, as they provide insight into the steps leading to the final products.

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