Question

Explain dehydration of alcohols. 

OR 

What is dehydration of alcohols? 

Give the chemical reactions showing dehydration of primary (1°), secondary (2°) and tertiary (3°) alcohols.

Answer 1

Removal of water from an alcohol is called dehydration of alcohol. 

Alcohols having a /ihydrogen is heated with dehydrating agents like concentrated H₂SO₄(or H₃PO₄ or P₂O₅ or Al₂O₃). 

The ease of dehydration of alcohols is in the following order : 

Tert-alcohol (3°) > secondary (2°) > primary (1°) 

(1) Primary (1°) alcohol is dehydrated by heating it with 95% H₂SO₄ at 453 K.

(2) Secondary alcohol (2°) is dehydrated by heating with 60% H₂SO₄ at 373 K.

(3) A ternary alcohol can be easily dehydrated by heating with 20% H₂SO₄ at 363 K.

An alcohol can be dehydrated by passing vapours alcohols over heated alumina (Al₂O₃).