12. Carboxylic acid

Question 1

Saturated VS Unsaturated fatty acid

Answer 1

• Saturated fatty acids have only single C-C bonds and unsaturated fatty acids have at least one C=C bond.
• The double bond put a kink in the chains. The kink make the intermolecular forces weaker which lowers the boiling point (smaller surface area between the molecules)
• Unsaturated fatty acid: linoleic acid (omega 6) and linoleic acid (omega 3)

Question 2

How is carboxylic acid obtained from alcohols and aldehydes?

Answer 2

Primary alcohols and aldehydes are normally oxidised to carboxylic acids using potassium dichromate(VI) solution in the presence of dilute sulphuric acid. During the reaction, the potassium dichromate(VI) solution turns from orange to green.

Question 3

Oxidative (carboxylic acid)

Answer 3

• The presence of hydrogen atom makes aldehydes very easy to oxidize (are good reducing agents)
• What is formed when aldehydes are oxidised? It depends on whether the reaction is done under acidic or alkaline conditions. Under acidic conditions, the aldehyde is oxidised to a carboxylic acid. Under alkaline conditions, this couldn’t form because it would react with the alkali. A salt is formed instead.

Question 4

Anaerobic Fermentation (carboxylic acid)

Answer 4

Composting without oxygen results in fermentation. This causes organic compounds to break down by the action of living anaerobic organisms. As in the aerobic process, these organisms use nitrogen, phosphorus, and other nutrients in developing cell protoplasm. However, unlike aerobic decomposition, this reduces organic nitrogen to organic acids and ammonia. Carbon from organic compounds, is released mainly as methane gas (CH4). A small portion of carbon may be respired as CO2.

Question 5

Reactions of carboxylic acids – obtaining of salts and esters

Answer 5

• Under alkaline conditions salts are formed

- Ethanoic acid reacts with ethanol in the presence of concentrated sulphuric acid as a catalyst to produce the ester