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Which of the following reactions will not result in the formation of carbon-carbon bonds?
A
Friedel-Crafts acylation
B
Reimer-Tiemann reaction
C
Cannizzaro reaction
D
Wurtz reaction
Detailed Solution
Friedel–Crafts acylation: $C_6H_6 + RCOCl \xrightarrow{AlCl_3} C_6H_5COR$; a new ring carbon–acyl carbon bond is formed.
Reimer–Tiemann reaction: phenol + $CHCl_3$ + NaOH gives salicylaldehyde; a –CHO group is attached to the ring through a new C–C bond.
Wurtz reaction: $2RX + 2Na \rightarrow R-R + 2NaX$; two alkyl groups are joined by a new C–C bond.
Cannizzaro reaction: an aldehyde without α-hydrogen undergoes disproportionation in concentrated alkali; one molecule is oxidised to the acid salt and another is reduced to the alcohol by hydride transfer, e.g., $2HCHO + KOH \rightarrow HCOOK + CH_3OH$. Only C–H and C–O bonds change.
Hence the Cannizzaro reaction does not form a carbon–carbon bond.
Reimer–Tiemann reaction: phenol + $CHCl_3$ + NaOH gives salicylaldehyde; a –CHO group is attached to the ring through a new C–C bond.
Wurtz reaction: $2RX + 2Na \rightarrow R-R + 2NaX$; two alkyl groups are joined by a new C–C bond.
Cannizzaro reaction: an aldehyde without α-hydrogen undergoes disproportionation in concentrated alkali; one molecule is oxidised to the acid salt and another is reduced to the alcohol by hydride transfer, e.g., $2HCHO + KOH \rightarrow HCOOK + CH_3OH$. Only C–H and C–O bonds change.
Hence the Cannizzaro reaction does not form a carbon–carbon bond.