Question

The final product for the following reaction is

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Hot copper at 573 K dehydrogenates a primary alcohol to an aldehyde. Count the carbon atoms of ethanol.

Answer 1

The Correct Option is A

Step 1: Identify the type of alcohol.
The reactant is CH\(_3\)CH\(_2\)OH, which is ethanol. The carbon that bears the OH group is attached to only one other carbon, so ethanol is a primary alcohol.

Step 2: Recall the effect of Cu at 573 K.
When alcohol vapour passes over copper at 573 K, the alcohol loses hydrogen. This is catalytic dehydrogenation.
A primary alcohol gives an aldehyde. A secondary alcohol gives a ketone. A tertiary alcohol gives an alkene, because it has no H on the carbon carrying OH.

Step 3: Write the reaction.
\[ \mathrm{CH_3CH_2OH} \xrightarrow{\mathrm{Cu},\ 573\ \mathrm{K}} \mathrm{CH_3CHO} + \mathrm{H_2} \]
The product is ethanal (acetaldehyde). It has two carbon atoms, with a CHO group attached to a CH\(_3\) group.

Step 4: Check option (1).
This is CH\(_3\)-CHO, ethanal. It matches the product. So option (1) is correct.

Step 5: Check option (2).
This is CH\(_3\)-CO-CH\(_3\), acetone. It has three carbons, and ethanol has only two. It would come from propan-2-ol. So option (2) is wrong.

Step 6: Check option (3).
This is H-CHO, methanal. It has one carbon, and it would come from methanol. Ethanol does not lose a carbon here. So option (3) is wrong.

Step 7: Check option (4).
This is propanal, CH\(_3\)CH\(_2\)CHO, with three carbons. It would come from propan-1-ol. So option (4) is wrong.

Final Answer:
Ethanol is dehydrogenated to ethanal, which is option (1). \[ \boxed{\text{Option (1)}} \]