Alcohols

What are the 2 ways that alcohols can be produced?

Hydration, fermentation

General formula for alcohols

CnH2n+1OH

What catalyst, temperature and pressure is needed for hydration to make alcohols?

Concentrated phosphoric acid (H3PO4), 300°C, 60-70atm

Equation for production of ethanol by hydration

ethene + water —> ethanol

How is ethanol made by fermentation?

Enzymes break down starch from crops into sugar which can then be fermented to for ethanol

Why is the fermentation method to make ethanol carbon neutral?

The CO2 given out when it is burned is taken in by plants during photosynthesis (net carbon output is 0)

Equation for production of ethanol by fermentation

C6H12O6 —> C2H5OH + CO2

What enzyme is needed to convert glucose to ethanol?

Yeast

What are disadvantages of production of ethanol by fermentation?

Slower and lower percentage yield

Why is fermentation cheaper than hydration?

It takes place at lower temperatures

What types of alcohols can be oxidised?

1° and 2°

Why can 3° alcohols not be oxidised?

C-C bond would have to be broken rather than C-H bond

What oxidising agent is needed for oxidation of primary alcohols?

Acidified potassium dichromate (Cr2O7 2-)

Equation for partial oxidation of 1° alcohols (example propanol)

Propan-1-ol + [O] —> propanal + H2O

Equation for full oxidation of primary alcohols (example propanol)

Propan-1-ol + 2[O] —> propanoic acid + H2O

What colour change is observed when oxidising alcohols using acidified potassium dichromate?

Orange to green

What is produced when you oxidise a secondary alcohol?

Ketone

what are the conditions needed for oxidation of secondary alcohols?

Potassium dichromate, heat under reflux

Equation for oxidation of secondary alcohols (example propanol)

Propan-2-ol + [O] —> Propanone + H2O

Why should you never seal the end of the condenser during reflux?

Build up of gas pressure can cause the apparatus to explode

Why are anti-bumping granules added to the flask in reflux and distillation?

To prevent vigorous, uneven boiling by making small bubbles form instead of large bubbles