(a) (i) $\; \mathrm{CH}_3 \mathrm{C} \equiv \mathrm{N} + \text{ DIBAL-H } + \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{CH}_3 \mathrm{CHO}$ $\mathrm{NH}_2 \mathrm{OH} + \mathrm{H}^+ \rightarrow \mathrm{CH}_3 \mathrm{CH} = \mathrm{N} - \mathrm{OH}$ $\mathrm{H}_2 \mathrm{O}$ A-Acetaldehyde B-Acetaloxide (ii) The IUPAC name is 3-bromobenzaldehyde. (iii) Phenol and Benzoic Acid can be distinguished by iron chloride $(\mathrm{FeCl}_3)$ test. As phenol gives violet colouration with neutral $\mathrm{FeCl}_3$ solution while benzoic acid gives buff coloured precipitate of ferric benzoate. $\;6\mathrm{C}_6\mathrm{H}_5\mathrm{OH} + \mathrm{FeCl}_3 \rightarrow \left[ \mathrm{Fe}(\mathrm{OC}_6\mathrm{H}_5)_6 \right]^{3-} + 3\mathrm{H}^+$ $\;\; \text{Violet complex}\; + 3\mathrm{HCl}$ $\;3\mathrm{C}_6\mathrm{H}_5\mathrm{COOH} + \mathrm{FeCl}_3 \rightarrow (\mathrm{C}_6\mathrm{H}_5\mathrm{COO})_3\mathrm{Fe} + 3\mathrm{HCl}$ Violet complex $+ 3\mathrm{HCl}$ $\underset{\text{Benzoic acid}}{3\mathrm{C}_6\mathrm{H}_5\mathrm{COOH}} + \mathrm{FeCl}_3 \rightarrow \underset{\text{Buff coloured ppt.}}{(\mathrm{C}_6\mathrm{H}_5\mathrm{COO})_3\mathrm{Fe}} + 3\mathrm{HCl}$ $+ 3\mathrm{HCl}$ OR (b) (i) Benzoic acid to benzaldehyde - Firstly benzoic acid is converted into benzoyl chloride by adding sulphonyl chloride and then by Rosenmund reduction reaction using $\mathrm{Pd}-\mathrm{BaSO}_4$ converted into benzaldehyde. (ii) Propan-1-ol to 2-bromo propanoic acid -Firstly propanol is converted into propanoic acid by oxidizing in presence of alk. $\mathrm{KMnO}_4$ and then by using Red Phosphorous/ $\mathrm{NaOH}$ and Bromine gas is further converted into 2-Bromo-propanoic acid $\underset{\text{Propanol}}{\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{OH}} \xrightarrow[\mathrm{KMnO}_4]{\text{alkaline}}$ $\underset{\text{Propanoic acid}}{\mathrm{CH}_3-\mathrm{CH}_2-\overset{\mathrm{O}}{\overset{\parallel}{\mathrm{C}}}-\mathrm{OH}} + \mathrm{Br}_2 \xrightarrow[\mathrm{NaOH}]{\text{red P}}$ $\underset{\text{2-Bromopropanoic acid}}{\mathrm{CH}_3-\underset{\mathrm{Br}}{\underset{\vert}{\mathrm{CH}}}-\mathrm{COOH}}$ (iii) Ethanal or Acetaldehyde into But-2-en-1-al Aldol condensation (in presence of dil $\mathrm{NaOH}$ ) followed by dehydration. $\underset{\text{Ethanal}}{2\mathrm{CH}_3\mathrm{CHO}} \xrightarrow{\text{dil NaOH}} \underset{\text{Acetaldehyde}}{\mathrm{CH}_3-\overset{\mathrm{OH}}{\overset{\vert}{\mathrm{CH}}}-\mathrm{CH}_2-\mathrm{CHO}}$ $\xrightarrow[\mathrm{-H_2O}]{\Delta} \underset{\text{But-2-en-1-al}}{\mathrm{CH}_3-\mathrm{CH}=\mathrm{CH}-\mathrm{CHO}}$