Aromatic Aldehydes Ketones and Acids - Result Question 4
####5. Major products of the following reaction are
(2019 Main, 10 April I)
(a) $CH _3 OH$ and $HCO _2 H$
(b) $CH _3 OH$ and
(c) $HCOOH$ and
(d)
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Answer:
Correct Answer: 5. (b)
Solution:
- The given reaction is a crossed Cannizzaro reaction which is a redox reaction too. Oxidation number of carbon atom of the $-CHO$ groups of $Ph-CHO$ and $H-CHO$ are +1 and zero respectively. So, $HCHO$ is the stronger reducing agent than $PhCHO$. As a result, $HCHO$ is oxidised to $HCOONa$ (by donation of hydride, $\left.H^{-}\right)$and $PhCHO\left(H^{-}\right.$acceptor $)$is reduced to $PhCH _2 OH$.
$$ \begin{aligned} & Ph-\stackrel{+1}{C} HO+HC \stackrel{0}{C} HO \xrightarrow[-1]{50 % NaOH} \ & Ph-\stackrel{-1}{C} H _2 OH+\stackrel{+2}{HC} OO _O^{Na} \ & \downarrow H _3 O^{+} \ & PhCH _2 \stackrel{\circ}{O} H+HCOOH \ & \text { (Major products) } \end{aligned} $$
The reaction proceed via following mechanism.
