Question

Complete the following equations:
(i)\; \(\mathrm{CH_3CHO} \xrightarrow{\;CH_3MgBr\;} (A) \xrightarrow{\;(B)\;} CH_3\!-\!CHOH\!-\!CH_3 \xrightarrow[\ \Delta\ ]{\;K_2Cr_2O_7/H_2SO_4\;} (C) \xrightarrow[\ \Delta\ ]{\;NH_2OH\;} (D)\)
(ii)\; \(\mathrm{C_6H_5CN + H_2O \xrightarrow{\;dil.\ H_2SO_4\;} (E)}\)

Hint:

Grignard addition to aldehydes gives alkoxides \(\rightarrow\) on hydrolysis secondary alcohols.
Secondary alcohols oxidize to ketones with \(\mathrm{K_2Cr_2O_7/H_2SO_4}\), and ketones give oximes with \(\mathrm{NH_2OH}\).
Nitriles hydrolyze (acidic) to carboxylic acids.

Answer 1

(i) Sequence from ethanal via Grignard, oxidation and oxime formation:
\(\mathrm{CH_3CHO + CH_3MgBr \rightarrow CH_3\!-\!CH(OMgBr)\!-\!CH_3}\) \(\Rightarrow\) \(\boxed{(A)=\mathrm{CH_3\!-\!CH(OMgBr)\!-\!CH_3}}\) (magnesium alkoxide).
\((B)=\) acidic hydrolysis \((H_2O/H^+)\) \(\Rightarrow\) \(\mathrm{CH_3\!-\!CHOH\!-\!CH_3}\) (isopropyl alcohol).
Oxidation: \(\mathrm{CH_3\!-\!CHOH\!-\!CH_3 \xrightarrow{K_2Cr_2O_7/H_2SO_4,\ \Delta} CH_3\!-\!CO\!-\!CH_3}\) \(\Rightarrow\) \(\boxed{(C)=\mathrm{(CH_3)_2CO}}\) (acetone).
Oxime formation: \(\mathrm{(CH_3)_2CO + NH_2OH \xrightarrow{\Delta} (CH_3)_2C{=}NOH + H_2O}\) \(\Rightarrow\) \(\boxed{(D)=\mathrm{acetoxime}}\).
(ii) Hydrolysis of benzonitrile:
\(\mathrm{C_6H_5CN + 2H_2O \xrightarrow{dil.\ H_2SO_4} C_6H_5COOH + NH_3}\) \(\Rightarrow\) \(\boxed{(E)=\mathrm{benzoic\ acid}}\).