Question

Electrophilic aromatic substitution // Nitration of Bromobenzene

Used: nitric acid, sulfuric acid, and bromobenzene

Post-lab Question #1: The procedure for this experiment cautions you to keep the temperature below 60°C.

a) Why is it important to keep the temperature below 60°C? (1 point)

b) If it’s important to keep the temperature below 60°C, why do we evenheat the reaction at all? Why don’t we just do the reaction at roomtemperature? Explain your answer using reaction principles.

Answer 1

a) This reaction is carried out to produce monosubstituted product, i.e. either ortho or para nitro benzene. If we increase the temperature above 60 degree celcius, nitration at both ortho and para position are possible and thus we will get disubstituted product (1-bromo-2,4-dinitrobenzene) as an impurity. To avoid this side reaction, the temperature needs to be below 60 degrees.

b) If we carry reaction at room temperature, reaction will be very slow, to observe any appreciable amount of product formation. The reaction has some threshhold activation energy, only when that much energy is provided (here by heating), the reaction can move in forward direction. So we need to heat up the reaction.