Q.Complete the reaction and write the name of the product. $CH_3CH_2OH \xrightarrow[620K]{Al_2O_3} ?$

Passing ethanol vapour over hot alumina at 620 K brings about dehydration (not dehydrogenation) of the alcohol, eliminating water to give ethylene.

Reaction:

$CH_3CH_2OH \xrightarrow[620\,K]{Al_2O_3} CH_2=CH_2 \uparrow + H_2O$

Mechanism/explanation: $Al_2O_3$ is a mildly acidic, dehydrating catalyst. At the higher temperature of 620 K, it promotes elimination of a water molecule from ethanol (loss of $-OH$ from C1 and $-H$ from the adjacent C2), forming the carbon–carbon double bond of ethylene. This is an example of catalytic dehydration of a primary alcohol.

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