Some Commercially Important Alcohols

Among all alcohols, two stand out for their large-scale industrial and everyday use: methanol and ethanol.

1. Methanol

Methanol ($\text{CH}_3\text{OH}$) was once called "wood spirit" because it used to be manufactured by heating wood strongly in the absence of air (destructive distillation). The modern industrial route instead hydrogenates carbon monoxide catalytically under high pressure and temperature, using a mixed zinc oxide–chromium(III) oxide catalyst:

Methanol is a colourless liquid boiling at 337 K.

Methanol is strongly poisonous. Swallowing even a small amount can cause blindness, and larger amounts can be fatal.

Despite this toxicity, methanol has real industrial value — it is used as a solvent in paints and varnishes, and it is the main starting material for manufacturing formaldehyde.

2. Ethanol

Ethanol ($\text{C}_2\text{H}_5\text{OH}$) is manufactured commercially by fermentation, the oldest and still the classic method, starting from naturally occurring sugars. Molasses, sugarcane juice, or fruits such as grapes supply sugars that are first converted into glucose and fructose (both sharing the molecular formula $\text{C}_6\text{H}_{12}\text{O}_6$) by the enzyme invertase. These simple sugars are then broken down by a second enzyme, zymase — present in yeast — into ethanol:

Fermentation in wine-making

Wine-making illustrates this process directly: grapes supply both the sugar and, on their skin, the yeast needed for fermentation. As the grapes ripen, their sugar content rises while yeast builds up on the outer skin. Crushing the grapes brings the sugar and the enzyme into contact, and fermentation begins. The process runs under anaerobic conditions (absence of air), releasing carbon dioxide as it proceeds.

Two practical limits govern this process:

• Zymase stops working once the alcohol content of the mixture crosses about 14 percent, which caps how strong a fermented drink can naturally become.
• If air is allowed into the fermenting mixture, atmospheric oxygen oxidises the ethanol to ethanoic acid, spoiling the taste of the alcoholic drink.

Properties, uses and denaturation

Ethanol is a colourless liquid with a boiling point of 351 K. It is used as a solvent in the paint industry and as a starting material in preparing many other carbon compounds. …