Ch_322a_11.015

Ch_322a_11.015 - Synthesis of Ethers The Sulfuric Acid...

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Synthesis of Ethers The Sulfuric Acid Dehydration Method Symmetrical ethers may be prepared from the dehydration of primary alcohols in the presence of sulfuric acid. The synthesis of commercially important ethers, such as diethyl ether, are carried out under carefully designed conditions that minimize side reactions. Reaction of Ethanol and Sulfuric Acid The major product produced in this reaction depends on the reaction conditions: CH 3 CH 2 OH H 2 SO 4 140 o C CH 2 =CH 2 H 2 SO 4 180 o C CH 3 CH 2 OCH 2 CH 3 diethyl ether ethene
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Mechanism: Acid-Catalyzed S N 2 CH 3 CH 2 OH : + H-O-SO 3 H fast CH 3 CH 2 OH 2 + HOSO 3 - (1) + (2) CH 3 CH 2 OH + CH 3 CH 2 -OH 2 + S N 2 CH 3 CH 2 OCH 2 CH 3 H + + H 2 O (3) CH 3 CH 2 OCH 2 CH 3 H + + H-O-H fast CH 3 CH 2 OCH 2 CH 3 + H 3 O + In the commercial synthesis of diethyl ether, ethanol is constantly added to the reaction mixture to maintain a high concentration of the needed nucleophile, and diethyl ether is removed.
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Limitations of the Sulfuric Acid Dehydration Synthesis In general, symmetrical ethers can be prepared from primary alcohols by this method: R-OH + R-OH R-O-R + H 2 O
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Ch_322a_11.015 - Synthesis of Ethers The Sulfuric Acid...

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