[limonade]

Is there another method of synthesizing M Nitroaniline , other than reduction of dinitro benzene in presence of Na2S2 ?

[orgopete]

Probably, but certainly not as direct. What is wrong with the dinitrobenzene route?

[limonade]

Nothing is wrong with it. It would be faster. I just wanted to see if it was possible to do something indirect perhaps using sulfonation as a blocking group?

[mjpam]

Is the m-dinitrobenzene a given starting material or a step in a synthetic schema?

[limonade]

Nope. I'm just starting with benzene.

[mjpam]

Nope. I'm just starting with benzene.

Then how do you pan on getting a dinitrobenzene, given that nitration is strongly deactivating?

[limonade]

Wouldn't using HNO3 H2SO4 twice work, since  the first nitration would give me a deactivating group, meta directing, and then nitrating a second time gives me meta dinitrobenzene? Unless I am doing something wrong....

[shalikadm]

Sorry if Iam hijacking your thread..

Wouldn't using HNO3 H2SO4 twice work, since  the first nitration would give me a deactivating group, meta directing, and then nitrating a second time gives me meta dinitrobenzene? Unless I am doing something wrong....

I think the nitration happens step by step.First benzene to nitrobenzene then nitrobenzene to dinitrobenzene. So the second step  would be rather hard as nitro group is strongly deactivating the aromatic ring. So I would stuck to mjpan's idea

Then how do you pan on getting a dinitrobenzene, given that nitration is strongly deactivating?

how its about nitrating banzamide or acetophenone...would it be rather easy and effective...?
If its an easy nitration, it would suggest limonade a synthesis path using a meta derecting group

[orgopete]

Well, you could try this. Make aniline and nitrate it under strongly acidic conditions. Protonation of the aniline will make it a meta directing anilinium group. You' have to look up how effective in terms of yield this would be.

There are many other ways to do it, but dinitration and reduction has been done before, so you can look up the efficiency of the process and determine what yields you'd need to compete with it.

[mjpam]

Wouldn't using HNO3 H2SO4 twice work, since  the first nitration would give me a deactivating group, meta directing, and then nitrating a second time gives me meta dinitrobenzene? Unless I am doing something wrong....

Apparently, you can dinitrate benzene directly, but you have to use fuming nitric acid--a mixture of nitric acid and dinitrogen tetroxide, which is ever nastier than the sulfuric acid-nitric acid (if that's possible). My only concern would be if the sodium sulfide reduction would be selective.

[408]

Apparently, you can dinitrate benzene directly, but you have to use fuming nitric acid--a mixture of nitric acid and dinitrogen tetroxide, which is ever nastier than the sulfuric acid-nitric acid (if that's possible). My only concern would be if the sodium sulfide reduction would be selective.

Fuming nitric acid is not a mixture of HNO3 and N2O5.  You have confused it with oleum being a mix of sulfuric and SO3.  N2O5 is not too bad to work with.  Pain in the ass to make though.

But you can get by with a hot mixed acid nitration, no fuming necessary. 

Well, you could try this. Make aniline and nitrate it under strongly acidic conditions. Protonation of the aniline will make it a meta directing anilinium group. You' have to look up how effective in terms of yield this would be.

There are many other ways to do it, but dinitration and reduction has been done before, so you can look up the efficiency of the process and determine what yields you'd need to compete with it.

Even in concentrated acids, aniline will only be in equilibrium with the anilinium cation.  But the anilinium is so unreactive that significant nitration takes place on the small amounts of aniline in the acids.  You get a 50/50 mix of meta/(ortho/para mix)

Wouldn't using HNO3 H2SO4 twice work, since  the first nitration would give me a deactivating group, meta directing, and then nitrating a second time gives me meta dinitrobenzene? Unless I am doing something wrong....

Yes it will.  Nitrobenzene is not deactivated enough to be inert towards a good, hot mixed acid nitration.

Just stick with the sulfide reduction of dinitro.  It works.  Alternatively bubble H2S through an ammonia solution of the dinitro until 1 equiv of H2S has been absorbed.  But this is toxic. 

Anyway, I have the syntheses below from a backup of roguesci.org (a long-defunct website)

Dinitrobenzene:
To prepare dinitrobenzene, heat a mixture of 14 mL of concentrated sulfuric acid and 10 mL of concentrated nitric acid in an open Erlenmeyer flask in a boiling water bath in an area with good ventilation. 10 g of nitrobenzene is added gradually over a period of 30 minutes. The mixture is allowed to cool somewhat, then drowned in cold water. The dinitrobenzene should separate as a solid. Crush it under water with a stirring rod, wash with water, and recrystallize from ethyl alcohol or nitric acid. Dinitrobenzene crystallizes from nitric acid in beautiful needles which are practically colorless. Further purification by removing the ortho and para isomers can be achieved by reacting the product with sodium sulfite, it is not necessary to do this, but it will give a highly refined product. The dinitrobenzene is added to a 33% sodium hydroxide solution and heated to 50 °C while vigorously stirring. The temperature must be monitored with a thermometer to insure it does not rise above 80-85 °C. The total washing time is 30 minutes. During the washing, the pH must be alkaline, test often with pH paper. If at any point the pH is not alkaline, add more sodium hydroxide solution. Next, sulphitation of dinitrobenzene is done by adding cold water to the above alkaline solution until the temperature falls to 66 °C. Then, a solution of sodium sulfite, prepared by mixing a 40% solution of sodium bisulfite with half its volume of 33% sodium hydroxide solution, is added. Maintain the temperature at 66-73 °C while stirring for 2 hours. Afterwards, cool the mix to 50 °C and the purified dinitrobenzene will precipitate into large crystals. The majority of the liquor can be decanted off and the crystals poured over a filter to collect them. Wash the crystals thoroughly by repeated rinsing with water. The final product can be dried at 135 °C under reduced pressure.

m-nitroaniline
Dissolve 10 g of m-dinitrobenzene in 40 mL of ethyl alcohol in a round-bottomed 250-mL Florence flask. Place the flask into a salt-ice bath to cool it down; some dinitrobenzene should separate out. The solution is then treated with 9 mL of 27-30% ammonium hydroxide. You must use only concentrated ammonium hydroxide, adding extra dilute hydroxide will not work in this case. Remove the flask from the ice bath and allow it to warm to room temp before proceeding with the next step.
     For the synthesis to be most effective it is necessary to weigh the flask (that includes the contents of the flask), the following reaction is complete when the weight of the flask has increased by 6 g. Saturate the mixture in the flask by bubbling in hydrogen sulfide gas; stop when it appears no more is being absorbed. The saturated mixture is now refluxed for 30 minutes. Allow the flask to cool to room temperature, and again saturate the mixture with hydrogen sulfide, followed by refluxing. Continue the process of saturating and refluxing until the weight increase of 6 g is achieved.
     The mixture is now diluted with water, the resulting precipitate is collected on a filter, washed with water, and extracted several times by warming with dilute hydrochloric acid. The acidic extractions now contain the nitroaniline, it can be precipitated by neutralizing the liquid with ammonium hydroxide. The crystals are collected by filtration, and then recrystallized from water. The yield is about 70-80%.



EDIT:

here is a nice paper on the preps of dinitrobenzen http://pubs.acs.org/doi/abs/10.1021/ed016p35

[orgopete]

Well, you could try this. Make aniline and nitrate it under strongly acidic conditions. Protonation of the aniline will make it a meta directing anilinium group. You' have to look up how effective in terms of yield this would be.

There are many other ways to do it, but dinitration and reduction has been done before, so you can look up the efficiency of the process and determine what yields you'd need to compete with it.

Even in concentrated acids, aniline will only be in equilibrium with the anilinium cation.  But the anilinium is so unreactive that significant nitration takes place on the small amounts of aniline in the acids.  You get a 50/50 mix of meta/(ortho/para mix)

Right, and I asked why not use the sulfide reduction, as the alternates were less efficient. I suggested what I believe could have been a shorter alternate and you quote what I believe to be a literature result. In that case, what are the isolated literature yields of m-nitroaniline from benzene so we can see how much worse even this direct nitration of an anilinium ion is to the sulfide reduction (and any other potential multistep process). I am curious as to how really poor a selective reduction of dinitrobenzene is, it is quoted in many textbooks.

Actually, let me start. The prep here (http://www.scribd.com/mobile/doc/102683462) give a 57% isolated yield for the reduction step. M-nitro aniline is used as a starting material in some commercial processes and it isn't even an OrgSyn prep. Surely, the preparation of m-nitroaniline must not be the actual question, is it?