Picric-A
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Reducing and Diazotization problems
I am attempting to synthesis Resorcinol from Benzene.
To do this i dinitrate benzene with fuming nitric/conc sulphuric under reflux.
I then tryed to reduce this using Zn/HCl. After about one hour reflux, i tryed to steam distill a product out however none came. What have i done
wrong?
Also, will the Diazotization of the phenyldiamine be similar to Diazotization of aniline, just double the quantity of NaNO2 ect..?
thanks
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DJF90
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If you distill a solution of salt in water, how much salt do you think will co-distill...?
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Nicodem
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And even if you would have tried to steam distil m-phenylenediamine instead of its salt, what is the reference that says it can be steam distilled?
This may or may not be possible, but without providing a reference you are making us waste our time searching or just making us frustrated.
What is the reference for the double diazotation?
And besides, I must have repeated at least a hundred times that threads started without a single reference go to the Beginnings section. Why do I have
to move them there when you can start them there in the first place?
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Nicodem
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Thread Moved
14-6-2009 at 11:01 |
benzylchloride1
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I think that commercial resorcinol is produced from benzene by the alkaline fusion of sodium 1,3-benzene sulfonate. This would require fuming sulfuric
acid, you can produce the monosulfonic acid by heating benzene with sulfuric acid. The ring is then deactivated and requires rigerous conditions to
add the second sulfonic acid group. The disulfonic acid is then isolated as the sodium salt and fused with potassium hydroxide. Potassium hydroxide
has more solvent power then sodium hydroxide when it comes to these reactions. The fused mass is then added to water, chilled and carefully acidified.
The resorcinol may precipitate out or may require isolation by solvent extraction. Meta-phenylenediamine is prepared by the reduction of
m-nitrobenzene with tin and hydrochloric acid. The tin is then removed as the sulfide with H2S . See Vogels, if you dare to attempt this procedure. Reduction with dithionite may work also; this can be obtained by washing Wink iron
stain remover with a large amount of methanol and then drying. The dithionite is practically colorless and odorless. Bis diazotization of diamines
works, see Vogels again, but the hydrolysis to the phenol generally proceeds in very low yield;<45%. I have tried it with aniline and was not
impressed. I have read of a method of hydrolysis that uses a copper (II) salt, but this requires several hundred grams of the copper salt for a few
grams of amine. At least this procedure results in fairly high yields.
Since you have reduced the m-dinitrobenzene to m-phenylenediamine, I would add an excess of sodium hydroxide solution. The zinc salts will precipitate
and then redissolve. Allow the mixture to cool and then extract with a organic solvent of your choice; toluene, ether, etc. Dry the extract with some
anhydrous magnesium sulfate, filter and distill off the solvent. Hopefully if your reaction worked, you will have some diamine to work with.
Another possible method of resorcinol synthesi was mentioned in an older thread, resorcinol from paracetamol. This synthesis could work, if the
hydroxyl group was first protected with an ether functional group. Nitration of p-acetamidophenol results in a red tar and a violent reaction. Fuming
nitric acid causes a hypergolic reaction. Expect very low yields because of the number of steps. This would be an interesting project to start from
250g of p-acetamidophenol, recrystallized from a bottle of 500 500mg tablets of generic tylenol. You would learn much by carrying out this synthesis
and have a lot of fun in the process. See the resorcinol thread in the organic chemistry forum.
Here is the procedure for the nitration of the second intermediate in the synthesis.
Synthesis:
• Add 1.0 g of phenacetin to 10 mL of glacial acetic acid in a 50 mL Erlenmeyer flask. Clamp flask in a water bath at 30oC prepared in a 400 mL
beaker.
• Add 0.5 mL of concentrated HNO3 dropwise. Carefully stir mixture with glass rod between additions. Continue to stir reaction occasionally for 20
minutes at room temperature.
• Pour 20 mL of ice-cold deionized water into flask. Cool flask in an ice bath for an additional 15 minutes, and then filter with suction. Wash
the product on the filter paper with 10 mL of cold deionized water.
• Remove a small sample (~ 1 mg) of your crude product for HPLC analysis and a small sample for TLC analysis. DO NOT DISCARD FILTRATE- it will be
used later in the experiment!
• Transfer the filter paper to a watch glass and place in the oven for 5 minutes, while you perform the extraction below.
• Obtain dried crude crystals from oven, determine final weight (1A) and calculate % yield (1B) of crude crystals.
Extraction:
• Transfer the filtrate from above to a 250 mL Erlenmeyer flask.
• Neutralize the filtrate by adding 20-25 mL of 20% NaOH. Check by litmus paper to ensure that the solution is basic (red litmus turns blue). Swirl
to mix completely
• Transfer neutralized filtrate to separatory funnel. Add 30 mL of ethyl acetate, cap, agitate, and allow layers to separate. Draw off the bottom
aqueous layer, and transfer the top ethyl acetate layer to a clean 125 mL Erlenmeyer flask. Dry over MgSO4.
• Suction filter the solution to remove the drying agent. Rinse the drying agent from the Erlenmeyer flask and the funnel using an additional 10 mL
of ice cold ethyl acetate.
• Remove a drop of the extract filtrate for a TLC sample (add 1 mL of reagent acetone) and a drop for an HPLC sample (add 1 mL of HPLC solvent).
• Transfer the filtrate to a 150 mL beaker, preweighed with 2-3 boiling chips. Evaporate all of the solvent on a warm hotplate (setting of 2-3).
Obtain a final weight (2A) and calculate % yield (2B) of the product isolated during the extraction.
Recrystallization:
• Combine the crude crystals from the synthesis with the crystals isolated above (after the column) in the same beaker.
• Dissolve the crude crystals in the minimum amount of hot ethanol (~ 5mL). Place the beaker directly on a warm hotplate. Once dissolved, add hot
deionized water until the solution becomes cloudy (10 mL maximum).
• Allow flask to cool to room temperature, and then place in an ice bath for 15 min.
• Filter with suction.
• Remove a small amount (~1 mg) of your pure product and submit it for HPLC analysis. Remove a small amount (~1 mg) of your pure product and
prepare a TLC sample.
• After allowing the recrystallized product to dry in the oven for 5 min, determine the final weight (3A) and calculate the percent yield of your
pure product (3B).
[Edited on 19-6-2009 by benzylchloride1]
[Edited on 19-6-2009 by benzylchloride1]
Attachment: Total Synthesis of resorcinol from tylenol.skc (6kB)
This file has been downloaded 811 times
Amateur NMR spectroscopist
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