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Explain the mechanism of esterification. Write the reactions involved in dehydration of 1^(@), 2^(@) and 3^(@) alcohols |
Answer» Solution :The esterification of carboxylic acid with alcohol is nucleophillic acyclic substution. The carboxylic acid is protonated on its carboxyl oxygen atom. Alcohol acts as a nucleophile and attacks carboxyl CARBON thus loss of proton gives ester hydrates.  Further one of the -OH group of ester hydrate gets protonated and LOOSES a molecule of water  Reaction involved in dehydration of `1^(@), 2^(@)` and `3^(@)` alcohols. Primary alcohol is dehydrated by heating with 95% `H_(2)SO_(4)` at 443 K `H underset("Ethanol")(- underset(H)underset(|)overset(H)overset(|)(C ) - underset(H)underset(|)overset(H)overset(|)(C )-O) - H underset(443K)overset(95% H_(2) SO_(4))(to) H underset("Ethene")-(overset(H)overset(|)(C ) = overset(H)overset(|)(C ) )- H` Secondary alcohol is dehydratd by heating with 60% `H_(2) SO_(4)` at 373 K `H underset("Propane" 2 - ol)(-underset(H)underset(|)overset(H)overset(|)(C )- underset(OH)underset(|)overset(H)overset(|)(C ) - underset(H)underset(|)overset(H)overset(|)(C ) -) H underset(373K)overset(60% H_(2) SO_(4))(to) CH_(3) - CH = CH_(2) + H_(2) O` `CH_(3) - underset(|)underset(OH)(CH) - CH_(2) - CH_(3) underset(373 K)overset(60% H_(2) SO_(4))(to)`  Tertiary alcohol is dehydrated by heating with 20% `H_(2)SO_(4)` at 373 K `underset(2-"methly - 2 Propanol")(CH_(3) - underset(CH_(3))underset(|)overset(CH_(3))overset(|) - OH) underset(373 K)overset(20% H_(2) SO_(4))(to) underset("2-methyl prop -2-ene")(CH_(3) - underset(CH_(3))underset(|)overset(CH_(2))overset(||) + H_(2) O)` |
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