Arrange the following compounds in decreasing order of reactivity towards nucleophilic addition reaction:
$I: HCHO$
$II: CH_3CHO$
$III: CH_3COCH_3$
$IV: PhCOCH_3$

The number of aldol reaction$(s)$ that occurs in the given transformation is :

Which of the following can be used to differentiate pentan$-2-$one and pentan$-3-$one?

Which of the following reactions are incorrect?
$(a)$ $CH_2(COOH)_2 \xrightarrow{\Delta} CH_3COOH + CO_2$
$(b)$ Aniline $\xrightarrow{CH_3Cl/AlCl_3}$ $p$-chloroaniline
$(c)$ Phenol $\xrightarrow{CHCl_3 + aq. NaOH}$ Salicylic acid
$(d)$ $CH_3CHO + NaHSO_3 \rightleftharpoons CH_3CH(OH)SO_3Na$
$(e)$ Benzene $\xrightarrow{CO, HCl, Anhydrous AlCl_3/CuCl}$ Benzaldehyde

The same product $(A)$ is formed in both of the following reactions:
$1. PhMgBr + CH_3-CN \xrightarrow{H_3O^{+}} (A)$
$2. Ph-COOH \xrightarrow{(1) \text{ excess } CH_3Li, (2) H_3O^{+}} (A)$
Identify product $(A)$.

Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reaction :
$(P)$ Benzaldehyde
$(Q)$ $p-$Tolualdehyde
$(R)$ $p-$Nitrobenzaldehyde
$(S)$ Acetophenone