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What is dehydration of alcohols ? Give the chemical reaction showing dehydration of primary (1^(@)), secondary (2^(@)) and tertiary(3^(@))alcohols.

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Solution :Removal of water from an alcohol is called dehydration of alcohol. Alcohols having a `beta`-hydrogenis heated with DEHYDRATING agents like concentrated `H_(2)SO_(4) (or H_(3)PO_(4) or P_(2)O_(5) or Al_(2)O_(3)).` The ease of dehydration of alcohols is in the following order :
tert-alcohol `(3^(@))gt` SECONDARY `(2^(@)) gt` primary `(1^(@))`
(1) Primary `(1^(@))` alcohol is dehydrated by HEATING it with `95% H_(2)SO_(4)` at 443 K.
`H-underset("Ethanol")(underset(H)underset(|)overset(H)overset(alpha|)C-underset(OH)underset(|)overset(H)overset(beta|)C)-H underset(443K)overset(95%H_(2)SO_(4))to H-underset("Ethene") (overset(H)overset(|)C=overset(H)overset(|)C-H)+H_(2)O`
(2) Secondary alcohol `(2^(@))` is dehydrated by heating with `60% H_(2)SO_(4)` at373 K.
`H-underset("Propan-2-o1")(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 underset("Propene")(CH_(3)-CH)=CH_(2)+H_(2)O`

(3) A tertiary alcohol can be easily dehydrated by heating with `20% H_(2)SO_(4)`at 363 K.
`H-underset("2-Methylproan-2-o1")(underset(H)underset(|)overset(H)overset(beta|)C-underset(OH)underset(|)overset(CH)overset(alpha|)C-underset(H)underset(|)overset(H)overset(beta|)C-H) underset(363K)overset(20%H_(2)SO_(4))tounderset("Propene")(CH_(3)-overset(CH_(3))overset(|)C=CH_(2)+H_(2)O)`


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