Textbook Question
Predict the product of the following sulfonylation reactions.
(b)
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12. Alcohols, Ethers, Epoxides and Thiols
Leaving Group Conversions - Sulfonyl Chlorides
2:45 minutesProblem 12a
Textbook Question
Show how 1-propanol can be converted into the following compounds by means of a sulfonate ester:
a. CH3CH2CH2SCH2CH3
Verified step by step guidance1
Step 1: Begin by converting 1-propanol (CH3CH2CH2OH) into a sulfonate ester. This can be achieved by reacting 1-propanol with a sulfonyl chloride, such as p-toluenesulfonyl chloride (TsCl), in the presence of a base like pyridine. This reaction replaces the hydroxyl group (-OH) with a tosyl group (-OTs), forming CH3CH2CH2OTs.
Step 2: The sulfonate ester (CH3CH2CH2OTs) is now a good leaving group, which facilitates substitution reactions. To introduce the desired thiol group (-SCH2CH3), perform a nucleophilic substitution reaction (SN2 mechanism) using ethanethiol (CH3CH2SH) as the nucleophile.
Step 3: In the SN2 reaction, the ethanethiol attacks the carbon attached to the tosyl group in CH3CH2CH2OTs, displacing the tosyl group and forming CH3CH2CH2SCH2CH3. Ensure the reaction is carried out in an appropriate solvent, such as acetone, to favor the SN2 mechanism.
Step 4: After the reaction, purify the product (CH3CH2CH2SCH2CH3) using techniques such as distillation or chromatography to remove any unreacted starting materials and by-products.
Step 5: Confirm the structure of the final product (CH3CH2CH2SCH2CH3) using spectroscopic methods such as NMR or IR to verify the presence of the thiol group and the absence of the tosyl group.
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2mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sulfonate Esters
Sulfonate esters are derivatives of alcohols where the hydroxyl group (-OH) is replaced by a sulfonate group (-OSO2R). They are important in organic synthesis as they can be converted into various nucleophiles through nucleophilic substitution reactions. This transformation enhances the leaving group ability, facilitating the formation of carbon-carbon bonds or other functional groups.
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Nucleophilic Substitution Reactions
Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule with a nucleophile. In the context of sulfonate esters, the sulfonate group acts as a good leaving group, allowing nucleophiles to attack the carbon atom bonded to it. This mechanism is crucial for converting 1-propanol into more complex structures, such as the desired thioether in the question.
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Thioether Formation
Thioethers, also known as sulfides, are organic compounds containing a sulfur atom bonded to two alkyl or aryl groups. The formation of thioethers from alcohols typically involves the reaction of a sulfonate ester with a thiol (R-SH). Understanding this reaction is essential for synthesizing the target compound from 1-propanol, as it illustrates how to create carbon-sulfur bonds effectively.
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