$\text { Identify the reagent used in following conversion. }$

$\text { Identify the reagent used in following conversion. }$

1. $\mathrm{CO}, \mathrm{HCl} / \mathrm{AlCl}_3$
2. $\mathrm{CrO}_2 \mathrm{Cl}_2 \cdot \mathrm{H}_3 \mathrm{O}^{+}$
3. $\mathrm{AlH}(\mathrm{i}-\mathrm{Bu})_2, \mathrm{H}_3 \mathrm{O}^{+}$
4. $\mathrm{CrO}_3,\left(\mathrm{CH}_3 \mathrm{CO}\right)_2 \mathrm{O}$

Asked in: MHT CET 2021 (21 Sep Shift 1)

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