Phenol

Question 1

What is phenol?

Answer 1

A type of organic chemical containing a hydroxyl group -OH, directly bonded to an aromatic ring.

Question 2

What is the simplest phenol member of the phenols?

Answer 2

C6H5OH

Question 3

Why is phenol classified as a weak acid?

Answer 3

• It partially disassociates which makes it a weak acid.
• It is also less soluble in water due to presence of non-polar benzene ring.
• After dissolving in water, phenol disassociates into phenoxide and a proton (H+).

Question 4

What is the order of acidity of phenol, ethanol and a carboxylic acid?

Answer 4

Goes in this ascending order

1. Ethanol
2. Phenol
3. Carboxylic acid for e.g. ethanoic acid

Ka value also increases as the acidity increases.

Question 5

How would you conduct a test that distinguishes between these products?

Answer 5

Sodium hydroxide - strong base
Sodium carbonate - weak base

1. Ethanol will not react with sodium hydroxide or sodium carbonate.
2. Carboxylic acids and phenol will react with solutions such as aqueous sodium hydroxide.
3. Only carboxylic acid is strong enough to react with sodium carbonate with produces carbon dioxide as a gas.
   
   • this helps distinguish between phenol and -COOH!!

Question 6

How does a neutralisation reaction with phenol work?

Answer 6

Phenol reacts with aqueous sodium hydroxide to form the salt, sodium phenoxide and water.

Question 7

How does electrophilic substitution reactions work with phenol? How many ways are there?

Answer 7

• There are two, bromination and nitration.
• Bromination is when phenol reacts with bromine water and forms a white precipitate and also decolourizes the solution. NO HALOGEN CARRIER IS REQUIRED.
• Nitration is when phenol reacts with dilute nitric acid at room temperature. This forms a mixture of 2-nitrophenol and 4-nitrophenol.

Question 8

How is phenol more reactive than benzene and why?

Answer 8

• Phenol does not require a halogen carrier compared to benzene or required conc. nitric/sulfuric acid.
• All reactions mentioned can be carried out at room temp. compared to benzene with nitration to speed rate of reaction.
• Increased reactivity caused by lone pair of electrons from oxygen p-orbitals of -OH group being donated into pi-system.
  
  • This increases electron density of benzene ring in phenol. Also attracts electrophiles more strongly than with benzene.
• Aromatic ring in phenol is more susceptible to attacks from electrophiles than benzene. With the bromine reaction, electron density is sufficient to polarise bromine molecules and so no halogen carrier catalyst is required.

Question 9

What test would you conduct to tell if a solution is a phenol or an alkene?

Answer 9

• Bromine water test
• Phenol will decolourise bromine water but will also form a white precipitate.
• Alkene will decolourise bromine water and there will not be a white precipitate.

Question 10

What is phenol used for in everyday appliances?

Answer 10

• Phenols are used in everyday antiseptics.

However can harm the skin