In the presence of dil. $HCl$,compound $A$ is converted to a constitutional isomer $(B)$. Compound $B$ is:

Which one of the following reactions can be used for the preparation of $\beta$-hydroxy acid derivatives?

The product$(s)$ formed when $m$-chlorobenzaldehyde is heated with concentrated $NaOH$ is/are:

An organic compound $A$ on reaction with $PCC$ $(\text{Pyridinium chlorochromate})$ gives a compound $B$. $B$ on further reaction with $I_2$ and $NaOH$ forms tri-iodomethane. Identify the compound $A$.

Haloform reaction is characteristic of

The aldehydes which will not form a single Grignard product with one equivalent of Grignard reagent are:
$(a)$ Benzaldehyde
$(b)$ $4$-Formylbenzoic acid
$(c)$ $4$-Methoxybenzaldehyde
$(d)$ $4$-(Hydroxymethyl)benzaldehyde