Question

The reduction of benzoyl chloride with $Pd$ and $BaS{{O}_{4}}/CaS{{O}_{3}}$ Produces:
a.) Benzyl chloride
b.) Benzoic acid
c.) Benzaldehyde
d.) All the above

Answer 1

Hint: The above given is a named reaction in which $Pd$ reduces the reactant while $BaS{{O}_{4}}/CaS{{O}_{3}}$ the reduction reaction. Using the above information try to find that what happens when the reaction takes place in the presence of both $Pd$ and $BaS{{O}_{4}}/CaS{{O}_{3}}$

Complete Solution :
Given that reduction of the benzoyl chloride takes place in the presence of $Pd$ and $BaS{{O}_{4}}/CaS{{O}_{3}}$
- Here the reactant is the benzoyl chloride whose molecular formula is ${{C}_{6}}{{H}_{5}}-COCl$ . When this is treated in the presence of palladium then it gets reduced to aldehyde group and further undergoes reduction to form benzene and which further can convert into alkane that is cyclohexane because palladium is one of the strong reducing agents.
- If we introduced $BaS{{O}_{4}}/CaS{{O}_{3}}$ which is poisoned with sulfur then this tries to prevent the further reduction of the compound.
- So when ${{C}_{6}}{{H}_{5}}-COCl$ is treated with palladium then it gets converted into benzaldehyde and then we introduced $BaS{{O}_{4}}/CaS{{O}_{3}}$ in the reaction to prevent the further reduction of the formed product.

The reaction is as follows
${{C}_{6}}{{H}_{5}}-COCl+{{H}_{2}}\xrightarrow{Pd/BaS{{O}_{4}}/CaS{{O}_{2}}}{{C}_{6}}{{H}_{5}}CHO+HCl$
- This reaction is known as Rosenmund reaction.
So the final product of the reaction is Benzaldehyde.
So, the correct answer is “Option C”.

Note: This reaction is also known as controlled reduction reaction. We can get the desired products not only by using certain reagents and catalysts but also the catalytic poisons so that we can stop the reaction at a certain time to obtain the desired products as we discussed in the above problem.