Benzene and its compounds

Question 1

Describe the structure of Benzene

Answer 1

• The carbons are sp2 hybridised
• six spare electrons are delocalised
• planar
• head on overlapping
• ring of delocalised electrons above and below the carbon atoms.

Question 2

How to prepare bromobenzene?

Answer 2

By reacting bromine with benzene in the presence of AlBr3 as a catalyst.

Question 3

What are electron donating groups?

Answer 3

They are groups that direct the attack of the electrophile to the 2,4 positions, they activate attacks by electrophile because they donate electrons to benzene ring

Question 4

why are halogenoarenes less reactive than halogenoalkanes?

Answer 4

The carbon halogen bond is stronger in arenes because one of the lone pairs on the halogen atom overlaps with the pi system and gives the C-X bond a partial double bond character.

Question 5

How to form chloromethyl-benzene?

Answer 5

Boil benzene with Cl2 in the presence if U.V light

Question 6

How to form nitrobenzene?

Answer 6

Reflux benzene with nitric acid and sulfuric acid at temp between 25 and 60 C.

Question 7

What is an electron withdrawing group?

Answer 7

This group direct the electrophile to the 3 and 5 position. they deactivate the attack by electrophiles as they withdraw electrons from the benzene ring.

Question 8

Describe the formation of any alkyl benzene.

Answer 8

Heat a halogenoalkane with benzene in the presence of AlCl3

Question 9

Describe the acylation of benzene.

Answer 9

Heat an acyl chloride with benzene in the presence of AlCl3

Question 10

How to form carboxylic acid from methyl benzene?

Answer 10

Reflux methyl benzene with Alkaline potassium manganate and then acidify with sulfuric acid.

Question 11

How to form cyclohexane from benzene?

Answer 11

By heating with hydrogen in the presence of nickel or platinum catalyst

Question 12

How to form Phenol?

Answer 12

1. React phenyl amine with nitric acid (HNO2) in temp below 10 C to form a diazonium salt
2. Warm with H2O to form phenol

Question 13

What is the order of acidity of water, phenol and ethanol?

Answer 13

Phenol> water> ethanol

Question 14

How to form bromophenol and what are the observations?

Answer 14

React phenol with bromine and the bromine decolourises and a white ppt is formed

Question 15

What are the conditions for the nitration of phenol?

Answer 15

React phenol with dil nitric acid at room temperature.

Question 16

Why are the conditions for the nitration and bromination of phenol diff from benzene?

Answer 16

The OH group inc the reactivity of the benzene ring towards the electrophile