Synthesis of m-nitrophenol from nitrobenzene

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BACKGROUND

Principle: In the first step nitrobenzene converts to m-dinitrobenzene due to electrophilic aromatic substitution in presence of nitrating reagents. It is a slow process and more difficult to add the second NO2+ because the nitro substitutent is a powerful deactivator. Since NO2 is a meta director, the resultant dinitrobenzene is almost exclusively 1,3-dinitrobenzene. In second step selective hydrogenation of one of the nitro group is occurring which forms m-nitroaniline in presence of ammonium hydrogensulphide, sodiumsulphide or sodiumhydrogensulphide, which exhibit a useful selective reducing action to smoothly reduce one nitro group in a polynitro compound to yield the corresponding nitroamine. Finally in third step an aryl diazonium salt is produced from reaction of m-nitroaniline with sodium nitrite and sulphuric acid. Then hydrolysis occurs forming m-nitrophenol, sulphuric acid and nitrogen gas due to nucleophilic attack.1

Aim: To prepare m-nitrophenol from nitrobenzene.

Reaction:

Step 1:



Step 2:


Step 3:



Mechanism:

Step 1:



Step 2:


 

 

 

 

Step 3:




Use:
It is a chemical reagent used in various organic synthesis via the etherification of phenols. Also used in the synthesis of kinase inhibitors against epidermal growth factor receptor T790M mutation.

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REQUIREMENTS

Chemicals:     Conc. sulphuric acid

Nitric acid

Nitrobenzene

Rectified sprit

Sodium sulphide

Sodium bicarbonate

Methanol

Sodium nitrite

HCl

Apparatus:     Conical flask

Round bottom flask

Condenser

Beaker

Pipette

Glass rod

Buchner funnel

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PROCEDURE

Step 1: Preparation of m-dinitrobenzene from nitrobenzene

Place 37.5 g (21 ml) of concentrated sulphuric acid and 22.5 g (15 ml) of fuming nitric acid, in a round-bottomed flask; add few fragents of porcelain pieces. Attach a reflux condenser and place the apparatus in a fume cupboard. Add slowly, in portions of about 3 ml, 15 g (12.5 ml, 0.122mol) of nitrobenzene; after each addition, shake the flask to ensure thorough mixing. Heat the mixture, with frequent shaking, on a boiling water bath for 30 min. Allow the mixture to cool somewhat and pour it cautiously with vigorous stirring into about 500 ml of cold water; the dinitrobenzene soon solidifies. Filter with suction, wash thoroughly with cold water and allow to drain as completely as possible. If the m.p. is below 89-90 °C, recrystallize using hot rectified sprit and using reflux condenser. Add 80-100 ml of rectified spirit and heat on a water bath until all the crystalline solid dissolves. If the resulting solution is not quite clear, filter it through a fluted filter paper on a large funnel which has previously been warmed or through a warm Buchner funnel. Colourless crystals of m-dinitrobenzene (15 g, 73%) are deposited on cooling.

Step 2: Preparation of m-nitroaniline from m-dinitrobenzene

Dissolve 18 g (0.075 mol) of crystallised sodium sulphide, Na2S-9H2O, in 50 ml of water; add 6.0 g (0.0714 mol) of finely powdered sodium hydrogen carbonate in small portions with constant stirring. When the carbonate has dissolved completely, add 50 ml of methanol and cool below 20 °C. Filter off the precipitated sodium carbonate at the pump, using a small Buchner funnel; if necessary add 2-3 g of filter-aid to the reaction mixture before filtering, and prepare a bed of filter-aid in the Buchner funnel since this will aid the retention of the finely divided solid. Wash the precipitate with three 8 ml portions of methanol. Retain the filtrate and washings: these contain about 3.9 g of NaSH in solution and must be used forthwith for the reduction. Dissolve 6.7g (0.04 mol) of m-dinitrobenzene in 50 ml of hot methanol in a 250-ml round-bottomed flask and add, with shaking, the previously prepared methanolic solution of sodium hydrogen sulphide. Attach a reflux condenser and boil the mixture for 20 min; ignore any further sodium carbonate which may precipitate. Allow the reaction mixture to cool and fit the condenser for distillation. Distil off most of the methanol (100-120 ml) from a water bath. Pour the liquid residue with stirring into about 200 ml of cold water. Collect the yellow crystals of m-nitroaniline by suction, wash with water and recrystallise from 75 percent aqueous methanol. The yield of bright yellow crystals, m.p. 114°C, is 3.7 g (69%).

Step 3: Preparation of m-nitrophenol from m-nitroaniline

Add 101 g (55 ml) of concentrated sulphuric acid cautiously to 75 ml of water contained in a 1-litre beaker and introduce 35 g (0.25 mol) of finely powdered m-nitroaniline. Add 100-150g of finely crushed ice and stir until the m-nitroaniline has been converted into the sulphate and a homogeneous paste results.

Cool to 0-5 °C by immersion of the beaker in a freezing mixture, stir mechanically and add a cold solution of 18 g (0.26 mol) of sodium nitrite in 40 ml of water over a period of 10 min until a permanent colour is immediately given to potassium iodide-starch paper: do not allow the temperature to rise above 5-7 °C during the diazotisation. Continue the stirring for 5-10 min and allow to stand for 5 min; some m- nitrobenzenediazonium sulphate may separate. Decant the supernatant liquid from the solid as far as possible. In a 1 litre round-bottomed flask take 165 ml of concentrated sulphuric acid to 150 ml of water. Heat the mixture just to boiling. Add the supernatant liquid (diazonium solution) from the separatory funnel supported over the flask at such a rate that the mixture boils very vigorously (about 30 min). Then add the residual damp solid (or suspension) in small portions; avoid excessive frothing. When all the diazonium salt has been introduced, boil for a further 5 min and pour the mixture into a 1-litre beaker set in ice-water, and stir vigorously to obtain a homogeneous crystal maga. When cold, filter at the pump, drain well and wash with four 20 ml portions of ice-water. Recrystallise by dissolving the crude product in hot dilute hydrochloric acid (1:1 by volume), decant from any residual dark oil, filter and cool to 0 °C, when light yellow crystals separate. Spread these upon a large sheet of filter paper, and dry in the air in a warm room. The mother-liquor deposits a further crop (about 2g) upon standing for 24 hours. The yield of m-nitrophenol, m.p. 96 °C, is 23 g (66%).

Calculation:

Here limiting reagent is nitrobenzene; hence yield should be calculated from its amount.

Molecular formula of nitrobenzene = C6H5NO2

Molecular formula of 3-nitrophenol = C6H5NO3

Molecular weight of nitrobenzene = 123 g/mole

Molecular weight of 3-nitrophenol = 139 g/mole

Theoretical yield:

123 g nitrobenzene forms 139 g 3-nitrophenol

Therefore, 15 g nitrobenzene will form …….? (X) g 3-nitrophenol

X =(139 ×15)/123 = 16.95 g

Theoretical yield = 16.95 g

Practical yield = ————- g

% Yield = (Practical Yield)/(Theoretical Yield) × 100

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CONCLUSION

m-nitrophenol was synthesized and the percentage yield was found to be………..%

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REFERENCES

  1. Vogel’s Textbook of Practical Organic Chemistry by Brian S. Furniss, Antony J. Hannaford, Peter W. G. Smith & Austin R. Tatchell; Fifth Edition; Page No. 855, 895, 927.