Nitrobenzene is a clear, yellow liquid with a sweet odor and is made by the nitration of benzene. It can be used for further nitration into Di- and Tri- nitrobenzenes and is also used for making aniline. It has limited use because most chemicals that need the benzene ring can be made from other chemicals that will better suit it. Nitrobenzene is extremely toxic by inhalation so good ventilation must be present at all times.
C6H6 + HNO3---> C6H5NO2 + H2O
|70% Nitric acid||100ml Burette or Pipette|
|96% Sulfuric acid||Seperatory funnel|
|Calcium chloride||250ml flask|
|Distilled water||Distilation apparatus|
Into a 1000ml flask, insert a thermometer and pour 75mls of 70% nitric acid and 85mls of sulfuric acid. Swirl this until its completely mixed. Some heat will be evolved so place this in an ice bath for a few minutes while you fill your burette. Set the burette up on a ringstand and fill with 60mls of benzene. If you use a 50ml burette (like me) fill it to the 50ml line and then once you have added 10ml of the benzene to the nitration mixture, just fill it back up to the 50ml line. Pull the flask out of the ice bath and swirl it some more. Add your benzene in 1-2ml portions and then swirl the flask. During additions it is not uncommon to see red or orange colors being formed where the benzene was added. These will disappear with swirling. Repeat this until the flask starts to warm up above 50C. When this happens place the flask in the ice bath (be careful doing this, and make sure you have good glassware) until the temperature drops below 25C. Repeat the last 2 steps until all of the benzene has been added. Set the flask up for reflux in a water bath. Bring the water bath (not the contents of the flask) up to 60C and leave it there for 1-2 hours, swirling the flask often.
After the time has passed, cool the flask to room temperature. You will see two layers; a clearish yellow layer on top and a different colored layer on the bottom. The top layer is your crude nitrobenzene. Pour the mixture into a seperatory funnel and wait for it all to settle. When it has, dump the waste acids (bottom layer) into a 1000ml beaker. Add distilled water to the nitrobenzene and shake it in the seperatory funnel. The nitrobenzene will now be the bottom layer. Drain the nitrobenzene into an intermediary container (such as a flask) and dump the water into the 1000ml beaker with the waste acids.. Repeat the last 2 steps 2 more times to wash most of the acids away. Do not use anything to neutralize the acids such as sodium bicarbonate. It is very soluble in nitrobenzene and will dissolve into it. After this, pour the nitrobenzene into the 250ml flask and throw in some powdered calcium chloride. Swirl this a bit. Bring some water to a boil and hold this flask above it until the contents go clear. You can now distill this. Discard the first 5mls that come over. After all the nitrobenzene has come over, store it in a glass bottle that is tighly closed. Yeild is high, but I never measured it any of the times I performed this synthesis.