Illustrate the reducing property of acetaldehyde with examples.

Explanation

(i) Clemmensen reduction : Aldehydes and Ketones when heated with zinc amalgam and concentrated hydrochloric acid gives hydrocarbons.
Example :
`underset("Acetaldehyde")(CH_(3)-underset(O)underset(||)(C)-H^(+)4(H))underset("Conc."HCl)overset(Zn^(-)Hg)tounderset("Ethane")(CH_(3)-CH_(3)pmH_(2)O)`
`underset("Acetone")(CH_(3)-underset(O)underset(||)(C)-CH_(3))+4(H)underset("Conc."HCl)overset(Zn^(-)Hg)tounderset("Propane")(CH_(3)CH_(2)CH_(3)+H_(2)O)`
(ii) Wolff-Kishner Reduction : Aldehydes and Ketones when heated with hydrazine `(NH_(2)NH_(2))` and sodium ethoxide, hydrocarbons are formed Hydrazine acts as a reducing agent and sodium ethoxide as a catalyst.
Example :
`underset("Acetaldehyde")(CH_(3)-underset(O)underset(||)(C)-H)+4(H)underset(C_(2)H_(5)ONa)overset(NH_(2)NH_(2))tounderset("Ethane")(CH_(3)-CH_(3)+H_(2)O)+N_(2)`
`underset("Acetone")(CH_(3)-underset(O)underset(||)(C)-CH_(3))+4(H)underset(C_(2)H_(5)ONa)overset(NH_(2)NH_(2))toCH_(3)CH_(2)CH_(3)+H_(2)O+N_(2)`
Aldehyde (or) ketones is first converted to its hydrazone which on heating with strong base gives hydrocarbons.
(iii) Reduction to pinacols : Ketones, on reduction with magnesium amalgam and water, are reduced to symmetrical diols known as pinacol.
`underset("Acetone")(CH_(3)-underset(CH_(3))underset(|)(C)=O)+underset("Acetone")(O=underset(CH_(3))underset(|)(C)-CH_(3))+2(H)underset(H_(2)O)overset(Mg//Hg)tounderset("(pinacol)")underset("2,3 dimethyl butane 2,3-diol")(CH_(3)-underset(OH)underset(|)overset(CH_(3))overset(|)(C)-underset(OH)underset(|)overset(CH_(3))overset(|)(C)-CH_(3))`