In the experiment procedure, there are two procedures; 1. Add slowly 36ml of ben
ID: 707363 • Letter: I
Question
In the experiment procedure, there are two procedures;
1. Add slowly 36ml of benzene. At this step, benzene should be added about 31ml at a time by dropping funnel, and then the contents of the flask should be thoroughly mixed. The temperature of the mixture must not be allowed to rise above 50°C(celsius), and it should be kept under control.(NO2 gas could be generated)
2. After quantity of benzene had been added, set up a reflux water condenser to the flask. After that, place it in a water bath and maintain at 60°C(celsius) for 40minutes with vigorous stirring. At this step, the flask should be withdrawn from the water bath intermediately and vigorously shaken in order to break up the nitrobenzene layer, otherwise it could be float on the dense acid alyer.
I thought that at procedure 1, temeperature under 50°C is to prevent the side reaction of synthesis of dinitrobenzene. However, at procedure2, why should we keep 60°C ? Above 50°C, side reaction of synthesis of dinitrobenzene will occur, so we should keep under 50°C. Why should we maintain 60°C then? Are there any other reasons for keeping 60°C?
Explanation / Answer
In procedure 1 there is no arrangement is done for the recovery of product. As the product is formed the high temperatures favors the furthur reaction i.e., formation of NO2
But in procedure 2 as soon as the product is formed vapor from the boiling point rises to the inside column of the reflux condensor and it is cooled by the jacket of water from outside. Then the product is recovered and remaining solvent is sent back to the flask. So by arranging the reflux condensor the product is taken out time to time where there is no scope of furthur reactions. So 60c of temperatures can be maintained to enhance the production of nitrobenzene in procedure2.