NITRATION OF A HALOARENE

 

 

NOTE

WEAR GLOVES AND LAB COAT DURING THE ENTIRE PROCEDURE

 

Haloarenes and their nitration products are irritating to sensitive skin areas.  If you should have these materials on your hands and then accidentally touch your face,  this can cause a severe burning sensation in the affected area.  If this should  happen,

 

IMMEDIATELY:

 

             1. Go to the restroom and wash the affected area with lots of soap and water.

                THE SOAP IN THE LAB IS NOT SUITABLE FOR THIS PURPOSE.

 

             2. Return to the lab and apply mineral oil to the affected area.

 

             3. The summary to this warning is NOT TO TOUCH ANY PART OF YOUR BODY

                WHILE PERFORMING THIS EXPERIMENT.

 

If you must leave the lab for any reason:

 

             1. First dispose of your gloves in the waste container

 

             2. Immediately go to the restroom and wash your hands

                thoroughly with soap and water.

 

                AGAIN, LAB SOAP WILL NOT DO A SUFFICIENT CLEANING

                JOB

 

             3. Upon returning to the lab, obtain another pair of

                gloves from the front of the room, and proceed with

                the experiment.

NITRATION OF A HALOARENE

 

 

Locker #

Compound

1, 10, 20, 4

 4 Bromobenzene

2, 12, 22, 9

1,4-Dichlorobenzene

3, 13, 19

1,3-Dichlorobenzene

5, 15

1-Bromo-4-chlorobenzene    

6, 16, 11

Chlorobenzene

7, 17, 21

1,4-Dibromobenzene

8, 18, 14

1,2 Dichlorobenzene

 

 

------------------------- FOR SAFETY REASONS --------------------------

 

  1.           Add 700mL of tap water to your 1 L Beaker.

  2.           Discard any acid washings, plus the contents of the filter flask (from step 9 below) into your 1 L Beaker, WITH STIRRING.

  3.           Wash the contents of your 1 L Beaker down the sink.

 

PROCEDURE

 

 1.            Obtain 0.025 mole of your haloarene ( See table above ) to a small beaker/graduated cylinder, and place it in your

                hood area.

 

 2.            Prepare a mixture of 5 mL conc HNO3 and 5 mL conc H2SO4 in a 25x150 mm test tube, take it back to your hood workstation and clamp it to your hotplate/stirrer, immersing the tube in a 150 mL beaker containing 100 mL tap water. Allow the tube to cool to 30 deg. C, measured using your glass thermomtter.

 

3.             To the test tube, add your haloarene, gently stirring  to mix the contents.  Continue to stir/agitate the test tube contents until the haloarene begins to transform into solid nitrohaloarene immersed in the acid mixture.  Keep the reaction mixture between 50 - 55 oC.  DO NOT ALLOW THE REACTION MIXTURE TO EXCEED 60 oC. 

 

4.             After the exothermic reaction has subsided, heat the test tube for 10 min. on your hot plate set at ~ 2.5 to maintain the temperature below 60oC during this period.

 

5.             Cool the test tube in an ice bath to room temperature

 

6.             Pour the reaction mixture into 50 mL of distilled water which is in a 150 mL beaker.

 

7.             Isolate the crude product by vacuum filtration.

 

8.             Wash the filter cake thoroughly with cold (0-10oC) distilled water and dry the filter cake by allowing the vacuum apparatus to draw air through it after you have finished washing.

 

9.             Place the washings into the 1L beaker.  Transfer the crystals to a TARED 50 mL beaker and obtain the weight of your wet product

 

10.                 Calculate the volume of 95%(v/v) ethanol needed to just dissolve the halobromobenzenes. You will need approx. 5 mL 95% ethanol per gram of crude product.  Round the amount of ethanol needed to the next 5 mL increment.   (e.g.: 5.6 g. x 5 mL/g = 28 mL => use 30 mL).  SHOW THIS CALCULATION IN THE PROCEDURE PORTION OF YOUR REPORT.

 

       11.    Bring this mixture to boiling to dissolve the crude product.  If the product does not completely dissolve boiling, add 5 mL of 95%(v/v) ethanol.  If solid still remains you will have to do a hot filtration.  Once your crude product has dissolved, set the flask onto your lab bench and allow the contents to cool slowly to room temperature.

 

  1. Isolate the nearly pure crystals of your product by vacuum filtration.  If there is solid material in the filter flask at this point, pour it into a beaker and vacuum filter this solution again through the funnel containing the first crop of nitrobromobenzene.  Save the filtrate.

 

  1. Wash the crystals with a little ICE COLD ethanol, allowing the washes to drain into the filter flask containing the filtrate.  The filtrate may now be poured into the recovered organic solvents container at the east end of the lab.

 

  1. Allow air to be drawn through the Buchner funnel for 5 min. then detach the vacuum hose from the filter flask, turn off the water and transfer the solid from the Buchner funnel onto 11cm filter paper which is on a watch glass.  Spread the solid over most of the filter paper, breaking large clumps into small particles and put it in your drawer to dry overnight.  Place another piece of filter paper lightly over the crystals to keep the dust out.

 

Thin‑Layer Chromatography

 

1.             Take a few crystals of haloarene isomer, place in a 5 ml beaker, and add 5 drops of acetone to the beaker to dissolve the crystals.  Do the same with your known haloarene standards

 

2.             Take a 2.5 x 7.5 cm strip of silica gel, mark the origin 1 cm from bottom and make 2 pencil marks lightly on the origin.

 

3.             Apply one drop of the solution containing the 4-nitro isomer on one spot & one drop of oil containing the 2-nitro isomer on the other spot.  Be sure that neither application results in a spot more than 2 mm in diameter.  Allow the strip to dry at your hood workstation .

 

4.             Place dried strip in jar containing the solvent solution Hexane: Chloroform 9:1.

 

5.             When the solvent system reaches  within 1 cm of the top of the strip, remove the strip, allow to dry at your hood workstation & view under ultraviolet light in the U.V. box.  Outline the spots with a pencil by stippling around each spot while the chromatogram is still in the U.V. box.

 

6.             Dispose of the remainder of your product into the jar provided at the front of the lab.