Alcohols and Carboxylic Acids

Alcohols

• Alcohols contain the -OH group.

• They form a homologous series with the general formula $C<em>nH</em>{2n+1}OH$.

• The -OH functional group determines their similar reactivity.

Ethanol

• Ethanol is a common alcohol found in alcoholic drinks.

• It is a good, volatile solvent used in glues, printing inks, perfumes and aftershave.

Production of Ethanol

1. Fermentation (Biological):

   • Glucose is converted to ethanol using yeast in the absence of air:
     $C<em>6H</em>{12}O<em>6 (aq) \rightarrow 2C</em>2H<em>5OH (aq) + 2CO</em>2 (g) + \text{energy}$

   • Enzymes in yeast catalyze the exothermic reaction.

   • The process works with substances containing sugar, starch, or cellulose (e.g., sugarcane, maize, potatoes, wood).

   • Yeast stops working when ethanol concentration is too high, or the mixture gets too warm.

   • Ethanol is separated by fractional distillation.

2. Hydration of Ethene (Chemical):

   • Ethene reacts with steam (water) in an addition reaction:
     $C<em>2H</em>4 (g) + H<em>2O (g) \rightleftharpoons C</em>2H_5OH (l)$

   • Conditions: 570°C, 60-70 atm, phosphoric acid catalyst.

   • The reaction is reversible and exothermic.

   • High pressure and low temperature favor yield, but high temperature is used for decent reaction rate.

Ethanol as Fuel

• Ethanol burns well in oxygen:
  $C<em>2H</em>5OH (l) + 3O<em>2 (g) \rightarrow 2CO</em>2 (g) + 3H_2O (l) + \text{heat}$

• It is increasingly used as a fuel because it can be made cheaply from waste plant material and offers an alternative to petroleum.

Carboxylic Acids

• Carboxylic acids are a homologous series of organic acids with the general formula $C<em>nH</em>{2n}O_2$ or $R-COOH$.

• The -COOH functional group is called the carboxyl group.

Ethanoic Acid

• Ethanoic acid is made by oxidizing ethanol.

Production of Ethanoic Acid

1. Fermentation (Biological):

   • Ethanol oxidizes to ethanoic acid in the presence of air and bacteria (acid fermentation).

   • This method is used to make vinegar (a dilute solution of ethanoic acid).

2. Using Oxidizing Agents (Chemical):

   • Ethanol is oxidized rapidly by warming it with potassium manganate(VII) in the presence of acid.

   • Manganate(VII) ions are reduced to $Mn^{2+}$ ions (color change: purple to colorless).

   • Potassium dichromate(VI) can also be used.

Reactions of Ethanoic Acid

1. Turns litmus red.

2. Dissociates in water, releasing $H^+$ ions, making it a weak acid:
   $CH<em>3COOH (aq) \rightleftharpoons CH</em>3COO^- (aq) + H^+ (aq)$

3. Reacts with metals, bases, and carbonates to form salts (e.g., with sodium hydroxide):
   $CH<em>3COOH (aq) + NaOH (aq) \rightarrow CH</em>3COONa (aq) + H_2O (l)$

4. Reacts with alcohols to form esters (condensation reaction):

   • Example:
     $CH<em>3COOH (l) + C</em>3H<em>7OH (l) \rightleftharpoons CH</em>3COOC<em>3H</em>7 (l) + H_2O (l)$

   • Sulfuric acid acts as a catalyst in this reversible reaction.

   • Water molecule is lost during the reaction.

   • Alcohol part of the name comes first, but second in the formula.