Alcohols

What is the functional group of alcohols?

-OH

What are the first four alcohols and its structural formula?

• Methanol (CH₃OH)

• Ethanol (CH₃CH₂OH)

• Propanol (CH₃CH₂CH₂OH)

• Butanol (CH₃CH₂CH₂CH₂OH)

What are the three ways that ethanol can be oxidised?

1. Complete combustion (burning in air or oxygen)

2. Microbial oxidation (reaction with air) to form ethanoic acid

3. Heating with potassium dichromate (VI) in dilute sulfuric acid to form ethanoic acid

Predict the result of ethanol reacting with heated potassium dichromate in dilute sulfuric acid

orange —> green

What are the 2 ways that ethanol can be manufactured?

• Hydration (steam)

• Fermentation

Describe the process of hydration

ethene + water —(catalyst)—> ethanol

What are the conditions required for hydration?

• Presence of phosphoric acid catalyst

• 300 ‘C

• pressure 60-70 atm

What are the advantages and disadvantages of hydration?

+ Pure ethanol

+ Continuous process (quick and little labour)

- non -renewable (finite)

- high temp (more energy)

Describe the process of fermentation

glucose —(yeast)—> ethanol + carbon dioxide

What are the conditions required for fermentation?

• Absence of air

• optimum temp. 30’C

• enzymes in yeast

What are the advantages and disadvantages of fermentation?

+ renwable (sustainable)

+ low temp (less energy)

+ carbon neutral (carbon released = carbon absorbed)

- impure ethanol (requires distillation)

- batch process (slow and labour intense)

Why is the optimum temp for fermentation around 25-50’C

If too low = yeast would be inactive

If too high = enzymes in yeast would be denatured

Why does fermentation require the absence of air?

the ethanol would be oxidised into ethanoic acid instead