Nitric reaction

Rudisill, T.S. 2000. Initiation temperature for runaway TBP/nitric reaction. WSRC-TR-2000-00427, 110. Aiken, SC Westinghouse Savarmah River Company. 

Catalytic gas-phase reactions play an important role in many bulk chemical processes, such as in the production of methanol, ammonia, sulfuric acid, and nitric acid. In most processes, the effective area of the catalyst is critically important. Since these reactions take place at surfaces through processes of adsorption and desorption, any alteration of surface area naturally causes a change in the rate of reaction. Industrial catalysts are usually supported on porous materials, since this results in a much larger active area per unit of reactor volume. 

The most widely used reactions are those of electrophilic substitution, and under controlled conditions a maximum of three substituting groups, e.g. -NO2 (in the 1,3,5 positions) can be introduced by a nitric acid/sul-phuric acid mixture. Hot cone, sulphuric acid gives sulphonalion whilst halogens and a Lewis acid catalyst allow, e.g., chlorination or brom-ination. Other methods are required for introducing fluorine and iodine atoms. Benzene undergoes the Friedel-Crafts reaction. ... 

Nitro-compounds are prepared by the direct action of nitric acid. The reaction is greatly facilitated if a mixture of nitric and sulphuric acid is used. 

Tin slowly dissolves in dilute hydrochloric, nitric and sulphuric acids, and is in fact the only Group IV element to do so. The reactions with more concentrated acid are rapid. With hydrochloric acid. 

Both white and red phosphorus dissolve in, for example, concentrated nitric acid to form phosphoricfV) acid, the reaction between hot acid and white phosphorus being particularly violent. 

In the presence of catalyst, usually platinum, ammonia is oxidised by oxygen (and air) to nitrogen oxide. NO. This reaction, used to obtain nitric acid from ammonia (p. 238), can be demonstrated in the laboratory using the apparatus shown in Figure 9.4 the oxygen rate should be slow. 

The reaction between copper and nitric acid, 1 part concentrated acid and 1 part water, gives impure nitrogen monoxide ... 

If this reaction takes place in air, the evolved nitrogen monoxide is oxidised to the dioxide and this dissolves again as in equation (9.1) hence virtually complete conversion of nitrogen dioxide to nitric acid can occur (see nitric acid, below). With alkalis, a mixture of nitrite and nitrate is formed ... 

Nitric acid is prepared in the laboratory by distilling equal weights of potassium nitrate and concentrated sulphuric acid using an air condenser, the stem of which dips into a flask cooled by tap water. The reaction is ... 

On the large scale, nitric acid is now made in large quantities by the catalytic oxidation of ammonia, employing the reaction ... 

Addition of silver nitrate to a solution of a bromide in nitric acid produces a cream-coloured precipitate of silver bromide, soluble in ammonia (but not so readily as silver chloride). The reaction may be used quantitatively, as for a chloride. 

About 0.5 g of iodine is placed in a small flask fitted with a long reflux air condenser and 15 cm of fuming nitric acid (b.p. 380 K) are added. The mixture is then heated on a water bath at 385-390 K in a fume cupboard until the reaction seems to be complete. This takes about an hour. The solution is then transferred to an evaporating basin and evaporated to dryness on a steam bath. The iodic acid... 

This reaction consists of the condensation of two molecular equivalents of a 1,3 diketone (or a J3-keto-ester) with one equivalent of an aldehyde and one of ammonia. Thus the interaction of ethyl acetoacetate and acetaldehyde and ammonia affords the 1,4-dihy dro-pyridine derivative (1), which when boiled with dilute nitric acid readily undergoes dehydrogenation and aromatisation" to gb e the diethyl ester of collidine (or 2,4,6-trimethyl-pyridine-3,5 dicarboxylic acid (II)). For the initial condensation the solid aldehyde-ammonia can conveniently be used in place of the separate reagents. 

D) No general reaction can be cited for the preparation of crystalline derivatives of Class (iii). Triphenylamine, when nitrated in acetic acid with fuming nitric acid, gives tri-/>-nitrophenylamine, m.p. 280°. The presence of substituents in the phenyl groups may however complicate or invalidate nitration. 

The simpler nitrop>arafIins (nitromethane, nitroethane, 1- and 2-nitroproj)ane) are now cheap commercial products. They are obtained by the vapour phase nitration of the hydrocarbons a gaseous mixture of two mols of hydrocarbon and 1 mol of nitric acid vapour is passed through a narrow reaction tube at 420-476°. Thus with methane at 476° a 13 per cent, conversion into nitro methane is obtained ethane at 420° gives a 9 1 mixture of nitroethane (b.p. 114°) and nitromethane (b.p. 102°) propane at 420° afifords a 21 per cent, yield of a complex mixture of 1- (b.p. 130-6°) and 2-nitropropane (b.p. 120°), nitroethane and nitromethane, which are separated by fractional distillation. 

The evil>smelling residue in the reaction flask is best removed by the cautious addition of concentrated nitric acid. 

Fit a 3-litre rovmd-bottomed flask with a long reflux condenser and a dropping funnel (1). Place a mixture of 400 ml. of concentrated nitric acid and 600 ml. of water in the flask and heat nearly to boiling. Allow 100 g. (116 ml.) of cycZopentanone (Section 111,73) to enter the hot acid dropwise, taking care that the first few drops are acted upon by the acid, otherwise an explosion may occur the addition is complete in 1 hour. Much heat is evolved in the reaction so that the flame beneath the flask must be considerably lowered. Omng to the evolution of nitrons fumes, the reaction should be carried out in the fume cupboard or the fumes... 

Nitrations are usually carried out at comparatively low temperatures at higher temperatures there may be loss of material because of the oxidising action of the nitric acid. For substances which do not nitrate readily with a mixture of concentrated nitric and sulphuric acids ( mixed acid ), the intensity of the reaction may be increased inler alia by the use of fuming sulphuric acid (containing up to 60 per cent, of sulphur trioxide) or by fuming nitric acid. Thus nitrobenzene is converted by a mixture of fuming nitric acid and concentrated sulphuric acid into about 90 per cent, of wi-dinitrobenzene and small amounts of the o- and p-isomers the latter are eliminated in the process of recrystallisation ... 

A brief account of aromatic substitution may be usefully given here as it will assist the student in predicting the orientation of disubstituted benzene derivatives produced in the different substitution reactions. For the nitration of nitrobenzene the substance must be heated with a mixture of fuming nitric acid and concentrated sulphuric acid the product is largely ni-dinitrobenzene (about 90 per cent.), accompanied by a little o-dinitrobenzene (about 5 per cent.) which is eliminated in the recrystallisation process. On the other hand phenol can be easily nitrated with dilute nitric acid to yield a mixture of ortho and para nitrophenols. It may be said, therefore, that orientation is meta with the... 

Place 18 g. (12 ml.) of fuming nitric acid, sp. gr. 1 5, and 30 g. (16-5 ml.) of concentrated sulphuric acid and a few fragments of broken glass in a 250 or 500 ml. round-bottomed flask. Add gradually, in small portions, 14 g. of p-nitrotoluene do not allow the temperature to rise above 50 and cool the flask, if necessary, by immersion in cold water. Place a small funnel in the mouth of the flask and heat on a water bath at 90-95° for 30 minutes. Allow to cool almost to the laboratory temperature and pour the reaction mixture slowly into about 500 ml. of ice water containing a few small pieces of ice. Filter the crude dinitrotoluene through a Buchner funnel at the pump, wash it thoroughly with cold water, and drain as completely as possible. RecrystalUse from the minimum volume of hot methyl alcohol (flask, reflux condenser, and water bath experimental details as in Section IV,12). The yield of pure 2 4-dinitrotoluene, m.p. 71°, is 12 -5 g. 

Add 25 g. of finely-powdered, dry acetanilide to 25 ml. of glacial acetic acid contained in a 500 ml. beaker introduce into the well-stirred mixture 92 g. (50 ml.) of concentrated sulphuric acid. The mixture becomes warm and a clear solution results. Surround the beaker with a freezing mixture of ice and salt, and stir the solution mechanically. Support a separatory funnel, containing a cold mixture of 15 -5 g. (11 ml.) of concentrated nitric acid and 12 -5 g. (7 ml.) of concentrated sulphuric acid, over the beaker. When the temperature of the solution falls to 0-2°, run in the acid mixture gradually while the temperature is maintained below 10°. After all the mixed acid has been added, remove the beaker from the freezing mixture, and allow it to stand at room temperature for 1 hour. Pour the reaction mixture on to 250 g. of crushed ice (or into 500 ml. of cold water), whereby the crude nitroacetanilide is at once precipitated. Allow to stand for 15 minutes, filter with suction on a Buchner funnel, wash it thoroughly with cold water until free from acids (test the wash water), and drain well. Recrystallise the pale yellow product from alcohol or methylated spirit (see Section IV,12 for experimental details), filter at the pump, wash with a httle cold alcohol, and dry in the air upon filter paper. [The yellow o-nitroacetanihde remains in the filtrate.] The yield of p-nitroacetanihde, a colourless crystalline sohd of m.p. 214°, is 20 g. 

Phenol may be nitrated with dilute nitric acid to 3deld a mixture of o- and nitrophenols the 3deld of p-nitrophenol is increased if a mixture of sodium nitiute and dilute sulphuric acid is employed. Upon steam distilling the mixture, the ortho isomer passes over in a substantially pure form the para isomer remains in the distillation flask, and can be readily isolated by extraction with hot 2 per cent, hydrochloric acid. The preparation of m-nitrophenol from wt-nitroaniline by means of the diazo reaction is described in Section IV,70. 

Method 1. Place 20 g. of crude benzoin (preceding Section) and 100 ml. of concentrated nitric acid in a 250 ml. round-bottomed flask. Heat on a boiling water bath (in the fume cupboard) with occasional shaking until the evolution of oxides of nitrogen has ceased (about 1 -5 hours). Pour the reaction mixture into 300-400 ml. of cold water contained in a beaker, stir well until the oil crystallises completely as a yellow solid. Filter the crude benzil at the pump, and wash it thoroughly with water to remove the nitric acid. RecrystaUise from alcohol or methylated spirit (about 2-5 ml. per gram). The yield of pure benzil, m.p. 94-96°, is 19 g. 

Introduce a solution of 15 g. of the diazo ketone in 100 ml. of dioxan dropwise and with stirring into a mixture of 2 g. of silver oxide (1), 3 g. of sodium thiosulphate and 5 g. of anhydrous sodium carbonate in 200 ml. of water at 50-60°. When the addition is complete, continue the stirring for 1 hour and raise the temperature of the mixture gradually to 90-100°. Cool the reaction mixture, dilute with water and acidify with dilute nitric acid. Filter off the a-naphthylacetic acid which separates and recrys-talhse it from water. The yield is 12 g., m.p. 130°. 

Reaction with alcoholic silver nitrate. To carry out the test, treat 2 ml. of a 2 per cent, solution of silver nitrate in alcohol with 1 or 2 drops (or 0 05 g.) of the compound. If no appreciable precipitate appears at the laboratory temperature, heat on a boiling water bath for several minutes. Some organic acids give insoluble silver salts, hence it is advisable to add 1 drop of dilute (5 per cent.) nitric acid at the conclusion of the test most silver salts of organic acids are soluble in nitric acid. 

Benzene and some of its derivatives react with solutions of mercuric nitrate in concentrated nitric acid to give nitrophenols. These reactions, known as oxynitrations may proceed by mercuration followed by nitroso-demercuration the resulting nitroso compound becomes a diazonium compound and then a phenol, which is nitrated. ... 

Nitric acid being the solvent, terms involving its concentration cannot enter the rate equation. This form of the rate equation is consistent with reaction via molecular nitric acid, or any species whose concentration throughout the reaction bears a constant ratio to the stoichiometric concentration of nitric acid. In the latter case the nitrating agent may account for any fraction of the total concentration of acid, provided that it is formed quickly relative to the speed of nitration. More detailed information about the mechanism was obtained from the effects of certain added species on the rate of reaction. 

Nitration in aqueous solutions of nitric acid Added water retards nitration in concentrated nitric acid without disturbing the kinetic order of the reaction. The rate of nitration of nitrobenzene was depressed sixfold by the addition of 5 % of water, (c. 3 2 mol 1 ), but because of the complexity of the equilibria involving water, which exist in these media, no simple relationship could be found between the concentration of water and its effect on the rate. 

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