Question

Given, $C{H_3}CHO$ is obtained by the dehydrogenation of?
A.$C{H_3}Cl$
B.${C_2}{H_5}OH$
C.$C{H_3}OH$
D.$C{H_3}COCl$

Answer 1

Dehydrogenation is the chemical reaction which involves the removal of hydrogen atoms from the reactant. The product formed contains less number of hydrogen atoms than reactants. This reaction can be both a useful process and the problem creating reaction.

Complete answer:
This is the oxidation reaction. As we are asked, which alcohol will turn into the aldehyde by the removal of hydrogen atoms?
So, looking at our option we find that ethyl alcohol is the best suited for conversion of ethyl alcohol into acetaldehyde.
As let’s look the reaction completely for our better understanding –
${C_2}{H_5}OH\xrightarrow{{PCC{\text{ or PDC}}}}C{H_3}CHO$
Thus, our reaction is very much clear that ethyl alcohol undergoes dehydrogenation to form acetaldehyde.
The catalyst used is PCC or PDC, they both control the level of oxidation, as they have the ability to ladder up the oxidation just by one number. Therefore they convert primary alcohols into the aldehydes and the secondary alcohols into the ketones.
These both prevent the further oxidation of acetaldehyde to a carboxylic acid.
Thus, from our above discussion, we can say that the correct option is B i.e. ${C_2}{H_5}OH$.

Note:
Let’s know about the PCC or PDC a little bit more. PCC $-$ pyridinium chlorochromate and PDC $-$ Pyridinium dichromate. So they both are chromium based products used in the catalysis of alcohol to aldehydes or ketones and stops the reaction from further oxidation. These catalysts however are slightly toxic and are not completely safe. Earlier they were in a lot of use but nowadays their use is limited or replaced by less toxic catalysts of alcohol oxidation.