Ethanol to Propanol - Increasing Carbon Atoms by One

Ethanol has two carbon atom and propanol has three. Therefore we have to increase number of carbon atoms by one. Also note that both ethanol and propanol are alcohols.

How to increase number of carbon atoms by one?

There are several reactions to increase carbon atoms by one.

1. Formaldehyde and grignard reagent reaction
2. Carbon dioxide and grignard reagent reaction
3. Alkyl halides and aqueous alcoholic KCN reaction

According to the question or given reagent you have to select one of the above reaction.

Ethanol to propanol

In this tutorial we are going to prepare propanol by following methods.

1. Carbon dioxide and ethyl magnesium bromide
2. bromoethane and aqueous alcoholic KCN reaction

ethyl magnesium bromide - CH₃CH₂MgBr

ethyl bromide - CH₃CH₂Br

Ethanol to propanol from carbon dioxide and ethyl magnesium bromide

Steps of converting ethanol to propanol is explained below.

grignard reagent preparing

Ethanol reacts with PBr₃ to give bromoethane. Then bromoethane reacts with Mg / dry ether to give grignard reagent.

Grignard and carbon dioxide reaction

Grignard reacts with carbon dioxide to give carboxylic acid ( propanoic acid).

Reducing carboxylic acid to alcohol

Propanoic acid is the carboxylic acid we use in this reaction. Propanoic acid is reduced to propanol by LiAlH₄ / ether.

Ethanol to propanol from ethyl bromide and aqueous alcoholic KCN

Propanol to ethanol

Number of carbon atoms is reduced by one. Have to follow several steps to convert propanol to ethanol.

• Propanol is heated with a dehydrator to produce propene.
• Then, propanol is oxidized by acidic KMnO₄ to ethanoic acid.
• Finally, ethanoic acid is reduced by LiAlH₄ to ethanol.