M- Nitroaniline

Physical Properties. All solid, sparingly soluble in cold water, freely soluble in hot water. o-Nitroaniline, NO2C6H4NH2, orange, volatile in steam m-nitroaniline, yellow, also volatile in steam />-nitroaniline, yellow, non-volatile in steam. 

It is convenient to include under Aromatic Amines the preparation of m-nitroaniline as an example of the selective reduction of one group in a polynitro compound. When wt-dinitrobenzene is allowed to react with sodium polysulphide (or ammonium sulphide) solution, only one of the nitro groups is reduced and m-nitroanUine results. Some sulphur separates, but the main reaction is represented by ... 

Account for the fact that p-nitroaniline (pKa = 1.0) is less basic than m-nitroaniline (pKa = 2.5) by a factor of 30. Draw resonance structures to support your argument. (The p/Ca values refer to the corresponding ammonium ions.)... 

OB to C02 -54,3%, mp explds at approx 1S4°, hygr crysts. Prepd by dissolving m-nitroaniline in an excess of dil perchloric acid (d 1.12g/cc), the excess being such that, at the end of the reaction, free acid is present. A sufficient quantity nf Na nitrite in solid form or in a sstd soLp. is added to effect diazotization. The mixt is cooled during the Na nitrite addition ,... 

Metafor 3- Mononitrophenol Monoclinic prisms from eth or dil HC1 mp 97° bp 194° at 70mm, decomps when distd at ordinary pressure d 1.485g/cc at 20°, 1.2797 at 100°. Does not volatilize with steam cannot be prepd by the nitration of phenol. Can be obtained by boiling diazotized m-nitroaniline with w and sulfuric acid (Ref 3). SI sol in w, sol in ale. Highly toxic by ingestion and inhalation Refs 1) Beil 6, 222-24, (116), [212-14]... 

Resonance effects are also important in aromatic amines. m-Nitroaniline is a weaker base than aniline, a fact that can be accounted for by the —7 effect of the nitro group. But p-nitroaniline is weaker still, though the —I effect should be less because of the greater distance. We can explain this result by taking into account the canonical form A. Because A contributes to the resonance hybrid, " the electron density of the unshared pair is lower in p-nitroaniline than in m-nitroaniline, where a canonical form such as Ais impossible. The basicity is lower in the para compound for two reasons, both... 

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. of finely-powdered m-nitroaniline (Section IV,44). Add 100-150 g. 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° by immersion of the beaker in a freezing mixture, stir mechanically, and add a cold solution of 18 g. of sodium nitrite in 40 ml. of water over a period of 10 minutes until a permanent colour is immediately given to potassium iodide - starch paper do not allow the temperature to rise above 5-7° during the diazotisation. Continue the stirring for 5-10 minutes and allow to stand for 5 minutes some m-nitrophen ddiazonium sulphate may separate. Decant the supernatant liquid from the solid as far as possible. 

A. l-(m-Nitrophenyl)-3,3-dimethyltriazene. To a 3-1. threenecked flask containing 276 g. (2 moles) of technical grade tn-nitroaniline (Note 1) are added 250 ml. of concentrated hydrochloric acid and 500 ml. of hot water. The contents of the flask are heated to about 85° to dissolve the m-nitroaniline then 550 ml. of concentrated hydrochloric acid is added, and the solution is cooled rapidly. A stirrer, a thermometer, and a longstemmed dropping funnel are attached to the flask, and its contents are then cooled to —3 to —5° by means of a salt-ice bath. A solution of 144 g. (2.09 moles) of sodium nitrite in 350 ml. of water is added dropwise under the surface of the acid solution... 

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