Question

Aldehydes, Ketones and Carboxylic acids are Carbonyl compounds.
(a) Aldehydes differ from Ketones in their oxidation reactions. Illustrate with one example.
(b) How will you prepare benzaldehyde by Gatterman-Koch reaction?
(c) Write the reactions of carboxylic acid with the following reagents. (Write the chemical equations)
(i) Thionyl chloride $\left(SO{Cl}_2\right)$
(ii) Chlorine in presence of small amount of red phosphorous.
(iii) Lithium Aluminium hydride $\left(LiAl{H}_4\right)$/ether.

Answer 1

$\left(a\right)$ Aldehydes has hydrogen as one of the substituents of carbon. Ketones don't have that hydrogen. The presence of that hydrogen atom makes aldehydes very easy to oxidise.

$\left(b\right)$ Refer IMAGE $01$

Benzene on reaction with carbon monoxide and $HCl$ in the presence of $AlC{l}_3$ or $CuCl$ gives Benzaldehyde.

$\left(c\right)$

$\left(i\right)$ Carboxylic acid reacts with thionyl chloride which gives acyl chloride and $S{O}_2$ gas and $HCl$.

$C{H}_{3}COOH+SOC{l}_2⟶C{H}_{3}COCl+S{O}_2+HCl$

$\left(ii\right)$ Chloride presence of small amount of red phosphorous gives $\alpha -chloro$ substituted products. This reaction is also called as $HVZ$ (Hell-Volhard-Zelinsky) reaction. Refer IMAGE $02$.

$\left(iii\right)$ Carboxylic acid on reduction with $LiAl{H}_4$ gives corresponding Alcohols as $LiAl{H}_4$ is strong reducing agent. Refer IMAGE $03$.