Swern Oxidation - Organic Chemistry, Reaction Mechanism
TLDRThis video delves into the Swern oxidation mechanism, a technique for converting primary and secondary alcohols into aldehydes and ketones. It features the use of reagents like oxalyl chloride and DMSO, and highlights the reaction's unique ability to selectively oxidize alcohols in complex molecules, such as 1,5-diols, without cyclization. The presenter also shares a valuable purification tip involving dimethyl sulfide and cautions about the reaction's strong odor, emphasizing the need for proper waste treatment.
Takeaways
- 🧪 The Swern oxidation is a method for converting primary alcohols to aldehydes and secondary alcohols to ketones.
- 🔬 The reaction involves reagents oxalyl chloride and DMSO, with DMSO acting as both a solvent and a reagent due to its unique structure and resonance form.
- ❄️ The reaction is initiated at -78 degrees Celsius using a dry ice and acetone slush bath to stabilize the intermediates.
- 🌀 The first step is an addition-elimination reaction between DMSO and oxalyl chloride, resulting in the formation of a chlorosulfonium intermediate.
- 💥 Loss of CO2, CO, and chloride occurs during the formation of the chlorosulfonium intermediate, which is a key step in the mechanism.
- 🔄 The alcohol is then added to react with the electrophile, forming a new bond and creating another intermediate.
- 🚫 The hydrogens on the sulfur in the intermediate are acidic, and triphenylamine is used as a weak base to deprotonate them, preventing unwanted SN2 reactions.
- 🔄 An intramolecular hydrogen transfer leads to the formation of the desired aldehyde and dimethyl sulfide as a byproduct.
- 🌡 The reaction requires warming from -78 degrees to 0 degrees to facilitate the hydrogen transfer step.
- 🧴 Dimethyl sulfide is easily removed due to its volatility, simplifying the purification of the aldehyde product.
- ⚠️ The Swern oxidation produces smelly compounds, necessitating careful waste and glassware treatment with bleach to avoid unpleasant odors.
- 🎩 A unique advantage of the Swern oxidation is its ability to selectively oxidize both primary and secondary alcohols in a 1,5-diol setup to form a 1,5-dicarbonyl compound, which is useful for further synthetic steps.
Q & A
What is the Swern oxidation used for?
-The Swern oxidation is used for converting primary and secondary alcohols into aldehydes and ketones, respectively.
What are the two key reagents used in the Swern oxidation?
-The two key reagents used in the Swern oxidation are oxalyl chloride and DMSO (dimethyl sulfoxide).
Why is oxalyl chloride considered an activating agent in the Swern oxidation?
-Oxalyl chloride is considered an activating agent because it helps in the formation of a good leaving group, which is essential for the reaction to proceed.
What is the role of DMSO in the Swern oxidation?
-DMSO acts as a nucleophile in the reaction, participating in an addition-elimination reaction with the acid chloride functional group.
Why is the Swern oxidation initiated at -78 degrees Celsius?
-The Swern oxidation is initiated at -78 degrees Celsius to form a reactive intermediate, which is stable at this low temperature.
What is the purpose of adding triphylamine in the Swern oxidation?
-Triphylamine is added to the reaction to act as a weak base that deprotonates the acidic hydrogens on the sulfur, facilitating the formation of the desired product.
Why is the Swern oxidation considered to have a 'cool trick' for 1,5-diols?
-The 'cool trick' refers to the ability of the Swern oxidation to selectively oxidize both primary and secondary alcohols in a 1,5-diol to form a 1,5-dicarbonyl compound, which can be useful for further synthetic steps.
What is the final product of the Swern oxidation when a primary alcohol is used?
-The final product of the Swern oxidation when a primary alcohol is used is an aldehyde.
What is the byproduct formed during the Swern oxidation process?
-The byproduct formed during the Swern oxidation process is dimethyl sulfide.
Why is it necessary to treat solvent waste and glassware with bleach after performing a Swern oxidation?
-Solvent waste and glassware need to be treated with bleach after a Swern oxidation to remove the smell from the reaction, as the process involves very smelly compounds.
What is the advantage of using DMSO in the Swern oxidation in terms of purification?
-The advantage of using DMSO in the Swern oxidation is that the byproduct, dimethyl sulfide, is volatile and easy to remove, which simplifies the purification of the aldehyde product.
Outlines
🧪 Swern Oxidation Mechanism and Reaction Insights
This paragraph delves into the Swern oxidation process, a chemical reaction used to convert primary and secondary alcohols into aldehydes and ketones, respectively. The video script introduces the reagents involved, including oxalyl chloride and DMSO, and describes their roles in the reaction. It explains the initial steps of the mechanism at low temperatures, the formation of key intermediates, and the subsequent steps leading to the desired products. The script also touches on the use of triphenylamine as a base and the final intramolecular hydrogen transfer that results in the formation of the carbon-oxygen double bond. It concludes with a caution regarding the smelly byproduct, dimethyl sulfide, and its advantages in purification due to its volatility.
🔍 Advanced Swern Oxidation Techniques for 1,5 Diols
The second paragraph discusses a specific application of the Swern oxidation in the context of 1,5 diols, which are compounds with both a primary and a secondary alcohol group. The script outlines the potential issues with other oxidation methods that may lead to unwanted cyclization and the formation of lactols or lactones. It highlights the Swern oxidation's ability to selectively oxidize both alcohol groups, preventing cyclization and allowing for the synthesis of 1,5 dicarbonyl compounds, which are valuable intermediates in organic chemistry. The paragraph concludes with a note on the video's intention to continue exploring chemical mechanisms in future content.
Mindmap
Keywords
💡Swern Oxidation
💡Primary Alcohol
💡Secondary Alcohol
💡Oxalyl Chloride
💡DMSO
💡Nucleophilic Addition Elimination
💡Leaving Group
💡Chlorosulfonium Species
💡Triphylamine
💡Intramolecular Hydrogen Transfer
💡Dimethyl Sulfide
💡1,5-Diol
Highlights
Introduction to the Swern oxidation mechanism and its unique advantages over other oxidation methods.
Use of oxalyl chloride as an activating agent in the Swern oxidation process.
Utilization of DMSO as a reagent with its structure and resonance form emphasized for understanding the mechanism.
The reaction setup at -78 degrees Celsius using dry ice and acetone as a slush bath for the initial step.
Formation of a chlorosulfonium intermediate as a key step in the Swern oxidation.
Loss of CO2, carbon monoxide, and chloride gas during the intermediate formation.
Incorporation of the alcohol into the reaction to form a new bond with the electrophile.
The acidity of hydrogens on sulfur and their role in the reaction mechanism.
Introduction of triphylamine as a weak base to facilitate the reaction without causing SN2 reactions.
Formation of a sulfur-based ylid as part of the Swern oxidation process.
The final step involving intramolecular hydrogen transfer to form the desired aldehyde.
Generation of dimethyl sulfide as a byproduct, which is easy to remove and aids in purification.
Caution regarding the smelly nature of the Swern oxidation and the need for bleach treatment of waste.
The Swern oxidation's ability to selectively oxidize both primary and secondary alcohols in a 1,5-diol setup.
Prevention of unwanted cyclization in 1,5-diols using the Swern oxidation.
The Swern oxidation's unique trick to form 1,5-dicarbonyl species for further synthetic applications.
Conclusion and intention to follow up with more mechanism videos in the future.
Transcripts
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