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Preparation of ethers by acid dehydration of secondary and tertiary alcohols is not a suitable method. Give reason. |
Answer» Solution :Acid-catalysed dehydration of `1^(@)` alcohols to ethers occurs by `S_(N)2` reaction involving nucleophilic attack by the alcohol molecule on the protonated alcohol molecule.  Under these conditions, `2^(@) and 3^(@)` alcohols, however, give alkenes rather than ethers. the reason being that due to sterric hindrance, nucleophilic attack by the alcohol molecule on the protonated alcohol molecule does not occur, INSTEAD protonated `2^(@) and 3^(@)` alcohols lose a molecule of water to FORM stable `2^(@) and 3^(@)` carbocations. these carbocations prefer to loss a proton to form alkenes rather than UNDERGOING nucleophilic attack by alcohol molecule to form ethers. 
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