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How will you bring about the following conversion?
Salicylaldehyde from phenol. Propan–2–ol from Grignard’s reagent.
(i)[1.0]
Salicylaldehyde from phenol.
(ii)[1.0]
Propan–2–ol from Grignard’s reagent.
Answer
Answer (i)
AIEquation: $\mathrm{C_{6}H_{5}OH} + \mathrm{CHCl_{3}} + 3\mathrm{NaOH} \xrightarrow{\text{Reimer-Tiemann}\text{ }\text{reaction}\text{,}\text{ }\text{aq.}\text{ }\text{NaOH}\text{,}\text{ }\text{340}\text{ }\text{K}} \mathrm{C_{6}H_{4}(OH)CHO} + 3\mathrm{NaCl} + 2\mathrm{H_{2}O}$
Reimer-Tiemann reaction: phenol is heated with chloroform and aqueous NaOH, then acidified.
Answer (ii)
AIEquations: $\mathrm{CH_{3}MgI} + \mathrm{CH_{3}CHO} \xrightarrow{\text{dry}\text{ }\text{ether}} \mathrm{CH_{3}CH(OMgI)CH_{3}}$ $\mathrm{CH_{3}CH(OMgI)CH_{3}} + \mathrm{H_{2}O} \xrightarrow{\text{hydrolysis}} \mathrm{CH_{3}CH(OH)CH_{3}} + \mathrm{Mg(OH)I}$
Methylmagnesium iodide adds to ethanal to give an adduct, which is hydrolysed to propan-2-ol.
From ISC 2019 Chemistry Paper 1, question 7(b).