Bromo
Tatiana Pachova BSc‐2, chemistry
Assistant : Chandan Dey
Sciences II – lab. A
Nitration of bromobenzene (n°28)
1. INTRODUCTION 1.1)
1.2)
Purpose The objective of this experiment is to synthesize the p‐bromonitrobenzene
(bromo‐1‐nitro‐4‐benzene) out of bromobenzene, by nitration. Scheme Br
Br
HNO3 / H2SO4
Mechanism The first step is the formation of the NO2 from the nitric acid: NO2
1.3)
O
O
S
N
HO
O
O
HO
O
N
+ H2O + HSO4-
OH
O
The second step is the nucleophile attack of the bromobenzene on the NO2. The temperature is moderated to avoid the formation of ortho and meta products:
Br
Br
O
+ H+
N
O
NO2
2. PROCEDURE
2.1)
Reaction In a 100mL twin‐neck bottom flask a mixture of nitric acid and sulfuric acid was prepared (cooled down with an ice bath). The flask was then equipped with a thermometer (not to let the temperature go over 50‐60°C) and a refrigerator.
Bromobenzene was added in small proportions (1mL at a time) through the refrigerator and the solution was well agitated between each addition. Then, the solution was heated for 20min at 100°C. After heating, the mixture was left to cool down a little and then poured on 150g of ice. The crystals left on the flask were dissolved in 10mL of hot ethanol and added to the suspension.
Isolation The solid product was isolated by filtration, washed 3 times in water and recrystallized in 50mL of ethanol.
2.2)
3. DISCUSSION AND RESULTS 3.1)
Observations When the bromobenzene was added, the solution turned yellow. The final product was also yellow crystals. Yield molar mass [g/mol] n th [mmol] n exp [mmol] yield [%]
3.2)
202.99
76
35.0
46%
7.1124g of final product were collected
Assistant : Chandan Dey
Sciences II – lab. A
Nitration of bromobenzene (n°28)
1. INTRODUCTION 1.1)
1.2)
Purpose The objective of this experiment is to synthesize the p‐bromonitrobenzene
(bromo‐1‐nitro‐4‐benzene) out of bromobenzene, by nitration. Scheme Br
Br
HNO3 / H2SO4
Mechanism The first step is the formation of the NO2 from the nitric acid: NO2
1.3)
O
O
S
N
HO
O
O
HO
O
N
+ H2O + HSO4-
OH
O
The second step is the nucleophile attack of the bromobenzene on the NO2. The temperature is moderated to avoid the formation of ortho and meta products:
Br
Br
O
+ H+
N
O
NO2
2. PROCEDURE
2.1)
Reaction In a 100mL twin‐neck bottom flask a mixture of nitric acid and sulfuric acid was prepared (cooled down with an ice bath). The flask was then equipped with a thermometer (not to let the temperature go over 50‐60°C) and a refrigerator.
Bromobenzene was added in small proportions (1mL at a time) through the refrigerator and the solution was well agitated between each addition. Then, the solution was heated for 20min at 100°C. After heating, the mixture was left to cool down a little and then poured on 150g of ice. The crystals left on the flask were dissolved in 10mL of hot ethanol and added to the suspension.
Isolation The solid product was isolated by filtration, washed 3 times in water and recrystallized in 50mL of ethanol.
2.2)
3. DISCUSSION AND RESULTS 3.1)
Observations When the bromobenzene was added, the solution turned yellow. The final product was also yellow crystals. Yield molar mass [g/mol] n th [mmol] n exp [mmol] yield [%]
3.2)
202.99
76
35.0
46%
7.1124g of final product were collected