2.3.6 Preparing Alkohol

Alcohols can be prepared by using 2 methods

1. Hydration of alkene
2. Fermentation

Hydration of Alkene

1. When we discuss the chemical properties of alkenes, we have learned that, when alkenes undergo addition reaction with steam, alcohol will be produced. (see hydration of alkenes).
2. Equations below shows the hydration of ethene and propene to produce ethanol and propanol respectively.

Hydration of Ethene

Hydration of Propene

Fermentation

1. This method only applies to ethanol.
2. Fermentation is the chemical process which microorganism such as yeast act on carbohydrate to produce ethanol and carbon dioxide.
3. When yeast is added to sugar (example: glucose), fermentation occurs. During fermentation, the yeast produce an enzyme called zymase. The zymase enzyme breaks down the glucose molecules to simpler molecule, namely ethanol and carbon dioxide.
   \[{C_6}{H_{12}}{O_6}\xrightarrow{{yeast}}2{C_2}{H_5}OH + 2C{O_2}\]
4. Yeast is killed by ethanol concentrations in excess of about 15%, and that limits the purity of the ethanol that can be produced.