Nitration without nitric acid

Some nitramines may be prepared without treating amines with nitric acid. The classical example is the so-called E-method of cyclonite preparation in which a nitramine is formed by dehydration of a mixture of paraformaldehyde and ammonium nitrate, i.e. without using either amine or nitric acid (this will be discussed more fully on p. 109). When a nitramine is required with a non-nitrated aromatic ring which readily undergoes nitration with nitric acid, Bamberger s method [45], involving the oxidation of diazo compounds (13), may be applied. 

The first attempts to esterify cellulose by means of nitric acid consisted in treating cellulose with the acid without any dehydrating agents. Vieille [1] discovered in 1882 that on nitration with nitric acid alone the rate of reaction and the nitrogen Content of the nitrocellulose increased as the concentration of HN03 was increased ... 

In practice, there is too much activation in 17 and attempted nitration oxidised the molecule. The amine must be acetylated first and then, without isolation of 18, can be nitrated (with nitric acid alone) to give 19. Hydrolysis of the amide gives 14 in excellent yield.8... 

Nitroindazoles, the products of nitration with nitric acid in acetic anhydride, are easily rearranged to 3-nitro derivatives that make these isomers fairly accessible [28], This method has been modified by Pozharskii [38] with a main goal to increase the yield of the reaction product. So 3-nitroindazole has been obtained without the intermediate 2-nitroindazole. 

In early period, methyl nitrate was prepared by nitration reaction between methanol and urea nitrate-contained nitric acid or mixed acid of nitric acid and sulphuric acid (40 60) at 18 °C for 20 0 min [50]. The density of nitric acid is 1.4 g/cm without nitrogen dioxide. After nitration, the products were washed by water to pH 7 and carefully distilled at 40 or 18 °C to obtain methyl nitrate. The yield of the nitration reaction is 45-80 %. The production period of the preparation method is long and the yield is very low. 

Alkylphosphonic acids and the majority of substituted alkylphosphonic acids are very stable and can be recrystallised from 6 N HCl or boiled for several hours with caustic soda without change. Arylphosphonic acids are often different, however. The aromatic ring in phenylphosphonic acid can be nitrated with nitric acid undergoing changes at 100°C and sulphonated with SO3 [22]. 

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. 

Accepting, for the moment without further evidence, that the nitro-nium ion formed by heterolysis of nitric acid is the active reagent in the solutions imder discussion, it remains to consider briefly why nitration in such solutions depends on the concentrations of nitric acid to such high powers (fig. 3.1), and why different solvents behave so differently (table 3.2). 

Although the term ester used without a modifier is normally taken to mean an ester of a carboxylic acid alcohols can react with inorganic acids m a process similar to the Fis cher esterification The products are esters of inorganic acids For example alkyl nitrates are esters formed by the reaction of alcohols with nitric acid... 

Nitrations can be performed in homogeneous media, using tetramethylene sulfone or nitromethane (nitroethane) as solvent. A large variety of aromatic compounds have been nitrated with nitronium salts in excellent yields in nonaqueous media. Sensitive compounds, otherwise easily hydroly2ed or oxidized by nitric acid, can be nitrated without secondary effects. Nitration of aromatic compounds is considered an irreversible reaction. However, the reversibihty of the reaction has been demonstrated in some cases, eg, 9-nitroanthracene, as well as pentamethylnitrobenzene transnitrate benzene, toluene, and mesitylene in the presence of superacids (158) (see Nitration). 

Ferrous Sulfdte Titration. For deterrnination of nitric acid in mixed acid or for nitrates that are free from interferences, ferrous sulfate titration, the nitrometer method, and Devarda s method give excellent results. The deterrnination of nitric acid and nitrates in mixed acid is based on the oxidation of ferrous sulfate [7720-78-7] by nitric acid and may be subject to interference by other materials that reduce nitric acid or oxidize ferrous sulfate. Small amounts of sodium chloride, potassium bromide, or potassium iodide may be tolerated without serious interference, as can nitrous acid up to 50% of the total amount of nitric acid present. Strong oxidizing agents, eg, chlorates, iodates, and bromates, interfere by oxidizing the standardized ferrous sulfate. 

Environmental aspects, as well as the requirement of efficient mixing in the mixed acid process, have led to the development of single-phase nitrations. These can be divided into Hquid- and vapor-phase nitrations. One Hquid-phase technique involves the use of > 98% by weight nitric acid, with temperatures of 20—60°C and atmospheric pressure (21). The molar ratios of nitric acid benzene are 2 1 to 4 1. After the reaction is complete, excess nitric acid is vacuum distilled and recycled. An analogous process is used to simultaneously produce a nitrobenzene and dinitrotoluene mixture (22). A conversion of 100% is obtained without the formation of nitrophenols or nitrocresols. The nitrobenzene and dinitrotoluene are separated by distillation. 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

Nitrating cellulose with pure HNO is the simplest method of obtaining CN. In practice, nitration does not occur with acid concentrations below 75%. At acid concentrations <75%, an unstable compound (so called Knecht compound) is formed which has been described as a molecular complex or an oxonium salt of the nitric acid (72). HNO concentrations of 75—85% yield CN with 5—8% N, which dissolve in excess acid. CN with % N of 8—10% are formed at acid concentrations of 85—89%. Above 89%, a heterogeneous nitration occurs without apparent swelling of the cellulose fibers. CN with 13.3% N can be obtained with 100% HNO. Addition of inorganic salts to 100% HNO can raise the % N to 13.9. 

Standardisation. Pipette 10.0 mL of the sodium tetraphenylborate solution into a 250 mL beaker and add 90 mL water, 2.5 mL 0.1 M nitric acid, 1.0 mL iron(III) nitrate solution, and 10.0 mL sodium thiocyanate solution. Without delay stir the solution mechanically, then slowly add from a burette 10 drops of mercury(II) nitrate solution. Continue the titration by adding the mercury(II) nitrate solution at a rate of 1-2 drops per second until the colour of the indicator is temporarily discharged. Continue the titration more slowly, but maintain the rapid state of stirring. The end point is arbitrarily defined as the point when the indicator colour is discharged and fails to reappear for 1 minute. Perform at least three titrations, and calculate the mean volume of mercury(II) nitrate solution equivalent to 10.0 mL of the sodium tetraphenylborate solution. 

See also under Nitration in this Vol Nitric Acid Explosives. According to Stettbacker (Ref 20), solns of aromatic nitrocompds in fuming nitric acid are very powerful expls, which are inexpensive and simple to prepare. Such solns can be kept for several months in Fe or A1 containers, even in sunlight, without decompg. These mixts can be transported in closed containers without danger of press rise... 

Kinetic studies with benzene in acetic anhydride containing 0.4-2 M nitric acid at 25 °C show the reaction to be first-order in benzene and approximately second-order in nitric acid this falls to first-order in nitric acid on addition of sulphuric acid, which also increases the first-order rate coefficient (first-order in benzene) from 4.5 x 10-4 to 6.1 x 10 4. By contrast the addition of as little as 0.001 M sodium nitrate reduced the rate to 0.9 x 10-4 without affecting the kinetic order70. These results were, therefore, interpreted as nitration by nitronium ion via equilibria (21a) and (22). 

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