Points to remember in Reduction

(2) $\mathrm{NaBH}_{4}, \mathrm{EtOH}$

Aldehyde $\longrightarrow 1^{\circ}$ Alcohol

Ketone $\longrightarrow 2{ }^{\circ} \mathrm{Alcohol}$

Acid halide $\longrightarrow 1^{\circ}$ Alcohol

(3) $\mathrm{Na} / \mathrm{EtOH}$ (Bouveault–Blanc reduction)

Aldehyde $\longrightarrow 1^{\circ}$ Alcohol$\quad$ Ketone $\longrightarrow 2^{\circ}$ Alcohol

Acid halide $\longrightarrow 1^{\circ}$ Alcohol $\quad$ Ester $\longrightarrow$ Alcohol + Alcohol

$RCN \longrightarrow RCH_{2} NH_{2}$

(4) $\mathrm{Na}-\mathrm{Hg} / \mathrm{HCl}$ or

$\mathrm{Al}[\mathrm{OCHMe}]_{3}$ (MPV Reduction)

Aldehyde $\longrightarrow 1^{\circ}$ Alcohol $\quad$ Ketone $\longrightarrow 2^{\circ}$ Alcohol

(5) Rosenmund Reduction

(6) Birch reduction

(Li/Na/K + Liquid $\mathrm{NH}_{3}$ )

Note : Terminal alkynes not reduced

(7) Stephen’s Reduction

$R-C \equiv N \xrightarrow[(2) H_{2} O]{(1) SnCl_{2} / HCl} {R}-{CH} = O$

Note : DIBAL-H is also used for same conversion.

(8) Clemmensen Reduction

Avoid if acid sensitive groups are present in molecule. e.g. $\mathrm{C}=\mathrm{C}, \mathrm{C} \equiv \mathrm{C}, \mathrm{OH}, \mathrm{OR}$,

(9) Wolff-Kishner Reduction

Avoid if base sensitive groups are present in molecule. e.g. COOR, $\mathrm{COX}, \mathrm{CONH}_{n}$,

$-\mathrm{CO}-\mathrm{O}-\mathrm{CO}-\mathrm{R}-\mathrm{X}$

(11) Red Phosphorus and HI

Almost all functional groups containing compounds converts into corresponding alkane by red $\mathrm{P}+\mathrm{HI}$.

• $R-CH_{2} OH \longrightarrow R - CH_{3} $

• $R-CHO \longrightarrow R-CH_{3}$

• $R_{2} CO \longrightarrow R_{2} CH_{2} $ (Alkane)

(12) DIABAL-H reduction

$\mathrm{R}-\mathrm{C} \equiv \mathrm{N} \xrightarrow{\mathrm{DIBAL}-\mathrm{H}} \mathrm{R}-\mathrm{CH}=\mathrm{O}$

At ordinary temperature esters reduced to alcohols but at low temperature esters reduced to aldehyde.

Hydrogenation