Question

$RCHO + 4[H]\xrightarrow{{Zn - Hg/conc.HCL}}R - C{H_3} + {H_2}O$
The above reaction is called as:
A. Wurtz reaction
B. Clemmensen reaction
C. Wolff-kishner reduction
D. Friedel-crafts alkylation

Answer 1

Among the various functional groups, organic compounds containing carbon-oxygen double bond( ) are called carbonyl groups, which is one of the most important functional groups in organic chemistry.

Complete step by step solution:
in aldehydes the carbonyl group is bonded to a carbon and hydrogen denoted by –CHO. Therefore the above given compound shall be identified as an aldehyde. It is being further reacted to form a hydrocarbon, that is formation of an all C-C chain. We observe that the oxygen in the carbonyl group is being reduced to hydrogen. Hence it is a reduction reaction.
Aldehydes can be reduced to both alcohols and hydrocarbons. In the above reaction though we see that it has been reduced to a hydrocarbon. Therefore the carbonyl group of aldehydes is reduced to -$C{H_2}$ group on treatment with zinc-amalgam and concentrated hydrochloric acid is termed as a clemmensen reaction.
Same reaction if taking place under hydrazine an amine group, then further treating with potassium hydroxide in a high boiling solvent such as ethylene glycol is termed as wolf-kishner reaction. It too reduces the aldehyde to form a hydrocarbon.
Since aldehydes and ketones both possess the carbonyl functional group therefore undergo similar chemical reactions. Therefore when ketones are synthesized from benzene or substituted benzene after treating with acid chloride in the presence of anhydrous aluminium chloride. This reaction is known as friedel crafts alkylation.

**Therefore from above we can conclude that the correct option is B. Clemmensen reaction

Note: **
Aldehydes are useful in quite some of the industrial products such as formaldehyde and benzaldehyde are used in bakelite, urea and perfumery, dye respectively.