Question

Give chemical test to distinguish:
(i) Ethyl alcohol and sec-propyl alcohol
(ii) Acetaldehyde and acetic acid

Answer 1

(i) Ethyl alcohol and sec-propyl alcohol are distinguished by Lucas reagent (a mixture of conc. HCl and anhydrous zinc chloride). Secondary alcohols such as sec-propyl alcohol gives turbidity within 5-10 minutes. Primary alcohols such as ethyl alcohol do not give turbidity at all, at room temperature.
$ROH+HCl\stackrel{ZnC{l}_2}{\to }RCl+H_{2}O$
(ii) Acetaldehyde and acetic acid are distinguished by Tollen's reagent (ammoniacal silver nitrate solution). Tollens' reagent oxidises acetaldehyde to acetic acid and the reagent itself is reduced to silver. This test is known as silver mirror test and is used to distinguish aldehdyes from ketones.