(a) Write the equation involved in the following reactions: (i) Rosenmund reduction (ii) Etard reaction (iii) Stephen reaction

RCOCl + H$\displaystyle _2$ $\displaystyle \xrightarrow{\text{Pd} \cdot \text{BaSO}_4}$ RCHO + HCl

$\displaystyle + \mathrm{CrO_2Cl_2}$ $\displaystyle \xrightarrow{\mathrm{CS_2}}$ $\displaystyle \xrightarrow[\Delta]{\mathrm{H_3O^+}}$

R—CN $\displaystyle \xrightarrow{\text{SnCl}_2 + \text{HCl}}$ RCH=NH $\displaystyle \xrightarrow{\text{H}_3\text{O}^+}$ RCHO + NH$\displaystyle _3$

F-CH$\displaystyle _2$COOH, due to -I effect of F.

CH$\displaystyle _3$COOH, acetate ion is more resonance stabilised than phenoxide ion.

Heat both the compounds with NaOH and I$\displaystyle _2$, pentan-$\displaystyle 2$-one gives yellow ppt. of iodoform while pentan-$\displaystyle 3$-one does not.