Question

Why is dinitration not a serious problem in this procedure?

Nitration of Bromobenzene. (EAS)

Procedure: mix 1ml concentrated sulfuric acid and 1mil concentrated nitric acid in a long-necked round bottom flask. Add a small stir bar, then place the flask in a 50mL beaker half-filled with water sitting on a magnetic stirrer. Using a connector, secure the flask to a ring stand and begin stirring the contents.

Add .5ml bromobenzene dropwise while stirring the mixture. It is important to keep the reaction mixture realatively cool, so do not add the bromobenzene too rapidly. After the addition is complete, the let the mixture stir for 3-4minutes than dd another .5 added, at hwich time the reaction mixture should be allowed to stir for 10 additional minutes.

Pour the cold reaction mixture in 10ml of ice cold DI water in a 50ml beaker thus precicptating the 1-bromo-4-nitrobenzene. Recover the product by fultration using a buchner funnel. A small amount of ice cold water may be used to rinse the last of the product from the beaker. Recrystalliz the product using 95% ethyl alcohol and spread out the crystals on a pre-weighed piece of ilter paper to dry. When dry, determine the melting point range and run an IR.

Answer 1

Solution :-

Whenthe bromobenzene is reacted with the nitrating mixture H2SO4 + HNO3 then it gives the nitration of the aromatic ring.

so when the reaction is set up with 1 :2 mole ratio

means if the excess nitrating mixture is used then it can give the dinitrobromobenzene product.