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(B) The reactivity of carbonyl compounds towards nucleophilic addition reactions (like addition of $HCN$) depends on steric and electronic factors. $1

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$III > II > I > IV$

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(B) The reactivity of carbonyl compounds towards nucleophilic addition reactions (like addition of $HCN$) depends on steric and electronic factors. $1.$ **Steric factor**: As the size and number of alkyl groups increase,the attack of the nucleophile on the carbonyl carbon becomes difficult. Thus,aldehydes are more reactive than ketones. $2.$ **Electronic factor**: Electron-donating groups ($+I$ effect) decrease the electrophilicity of the carbonyl carbon. Phenyl groups also decrease reactivity due to resonance. Comparing the given compounds: - $(III)$ $CH_3-CHO$ is an aldehyde (most reactive). - $(II)$ $CH_3-CO-CH_3$ is an aliphatic ketone. - $(I)$ $Ph-CO-CH_3$ is an aromatic ketone. - $(IV)$ $Ph-CO-CH_2-CH_3$ is an aromatic ketone with a larger alkyl group than $(I)$. Therefore,the order is: $III > II > I > IV$.

Column-$1$ (Reaction)	Column-$2$ (Product)
$A$. Benzaldehyde + $Zn-Hg/HCl$	$I$. Cyclohexanol
$B$. Benzoyl chloride + $H_2/Pd-BaSO_4$	$II$. Benzyl alcohol
$C$. Cyclohexanone + $NH_2NH_2/KOH$	$III$. Toluene
	$IV$. Benzaldehyde
	$V$. Cyclohexane

Give the reactivity order towards $HCN$ for the following compounds:
$(I)$ $Ph-CO-CH_3$
$(II)$ $CH_3-CO-CH_3$
$(III)$ $CH_3-CHO$
$(IV)$ $Ph-CO-CH_2-CH_3$

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Give the reactivity order towards $HCN$ for the following compounds: $(I)$ $Ph-CO-CH_3$ $(II)$ $CH_3-CO-CH_3$ $(III)$ $CH_3-CHO$ $(IV)$ $Ph-CO-CH_2-CH_3$