Nitramine salts

Salt Ignition temperature 50% of explosions by 2 kg weight dropped from 

Urbanski, Zacharewicz and Pietrzyk [61] suggested the use of some methyl-enedi-isonitramine salts (CH2) (N202H)2 as primary explosives. 

The sodium salt of methylenedi-isonitramine was prepared by Traube [62] from acetone and nitric oxide in the presence of sodium alcoholate according to the following chain of reactions  

The sodium salt of methylenedi-isonitramine (II) is formed. In an aqueous solution this precipitates with the salts of heavy metals. Some of these salts (e.g. the thallium salt) have the properties of weak initiators. 

The structure of these compounds remained obscure for a long time. Traube originally assigned the structure —N—N—OH to the isonitramino group, but in further researches he found that isonitramines and the derivatives of nitrosohydro-xylamine which he prepared by the action of nitrous acid on -derivatives of hydro-xylamine were identical. He did not, however, draw from this any definite conclusions as to the structure of isonitramines in spite of the fact that by the synthesis of isonitraminoisobutyric acid, Gomberg [63] had confirmed the nitrosohydro-xylamine structure of the isonitramino group. 

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Another synthesis of the fully reduced ring system (510) results from the alkylatiotl of the nitramine salt of ethylenediamine (508) with 4,5-dichloro-l,3-diacetylimidazolidine (509) (79IZV1618). 

Best results are obtained in nitration by nitramine salts in chloroalkanes or acetonitrile. However, the use of more basic solvents, such as ethers and esters, ensures equally high yields in the nitration of both free nitra-mines and their salts [115]. 

Methyidichloroarsine Methylene glycol dinitrate Methyl ethyl ketone peroxide, >50% alpha-Methylglucoside tetranitrate alpha-Methylglycerol trinitrate Methyl nitramine (dry) metal salts of Methyl nitrate Methyl nitrite... 

The Na salt of MEDINA was fluorinated in w, the sain extd with methylene chloride, and the solv evapd to give a yellow oil whose IR spectrum showed absence of NH and the presence of NF absorption, and analysis indicated was a mixt (Ref 22). Nitramines in the presence of sulfuric acid are capable of nitrating reactive aromatic compds, but when acetanilide was treated with MEDINA in the presence of this acid, no nitroacetanilide was isolated. Instead compds indicating that the MEDINA had been fragmented and the fragments reacted with the acetanilide were isolated (Ref 12)... 

Scholl et al (Refs 3 4) prepared the same compds by treating ketoximes (such as pina-colone) with nitrogen tetroxide, but he assigned them the structure R2C=N-N02 and called them nitrimines. One of the compds described by him in Ref 4, p 27 is a weak expl. It is the Ag salt of pinacolone-nitraminic acid which puffs off on rapid heating (this compd described below under List of Nitrimines ). Further work on... 

This powerful but relatively insensitive explosive decomposes violently at 202° C, and gives lead and silver salts which are highly impact sensitive [1], Though not endothermic (AH°f —103.3 kJ/mol), as a bis-nitramine it has a rather high heat of decomposition (3.91 kJ/g) which it is calculated would attain an adiabatic decomposition temperature over 2250°C, with a 60-fold pressure increase in a closed system [2],... 

Eremenko and co-workers used nitryl fluoride for the deamination of amines at subambient temperatures in acetonitrile. The same reaction occurs with primary nitramines and their alkali metal salts bis-nitramines react to give the corresponding bis-nitrate esters. 

The reaction of primary aliphatic amines and nitramines with nitronium salts also leads to deamination and the formation of alkyl nitrates. 

The chemical properties of primary and secondary nitramines are important in relation to their use as explosives. Primary nitramines contain acidic hydrogen in the form of —N//NO2 and, consequently, in the presence of moisture, primary nitramines corrode metals and form metal salts, some of which are primary explosives. This is one reason why powerful explosives like methyinitramine (1) have not found practical use. Ethylenedinitramine (EDNA) (2) suffers from similar problems but its high brisance (VOD 8240 m/s, d = 1.66 g/cm ) and low sensitivity to impact have seen it used for some applications. 

If nitration under acidic conditions could only be used for the nitration of the weakest of amine bases its use for the synthesis of secondary nitramines would be severely limited. An important discovery by Wright and co-workers " found that the nitrations of the more basic amines are strongly catalyzed by chloride ion. This is explained by the fact that chloride ion, in the form of anhydrous zinc chloride, the hydrochloride salt of the amine, or dissolved gaseous hydrogen chloride, is a source of electropositive chlorine under the oxidizing conditions of nitration and this can react with the free amine to form an intermediate chloramine. The corresponding chloramines are readily nitrated with the loss of electropositive chlorine and the formation of the secondary nitramine in a catalytic cycle (Equations 5.2, 5.3 and 5.4). The mechanism of this reaction is proposed to involve chlorine acetate as the source of electropositive chlorine but other species may play a role. The success of the reaction appears to be due to the chloramines being weaker bases than the parent amines. 

Wright illustrated the effectiveness of chloride-catalyzed nitration for a number of amines of different basicity. Wright showed that weakly basic amines like iminodiacetonitrile and its dimethyl and tetramethyl derivatives are all nitrated in high yield with nitric acid-acetic anhydride mixtures in the absence of chloride ion. In contrast, the slightly more basic 3,3 -iminodipropionitrile is not appreciably nitrated with acetic anhydride-nitric acid, but the inclusion of a catalytic amount of the hydrochloride salt of the amine base generates the corresponding nitramine in 71 % yield. ... 

Unlike the direct nitration of amines under acidic conditions, nucleophilic nitration is an excellent route to both primary and secondary nitramines. In these reactions the amine or the conjugate base of the amine is used to attack a source of NO2. This source may be a nitrogen oxide, nitronium salt, cyanohydrin nitrate, alkyl nitrate ester or any other similar source of nitronium ion. 

Emmons and co-workers prepared a series of aliphatic secondary nitramines by treating amines with a solution of dinitrogen pentoxide in carbon tetrachloride at —30 C (Equation 5.9). The amine component needs to be in excess of two equivalents relative to the dinitrogen pentoxide if high yields of nitramine are to be attained. This is wasteful because at least half the amine remains unreacted. However, yields are high and there is no reason why the amine cannot be recovered as the nitrate salt. The method is particularly useful for the nitration of hindered secondary amines substrates such as those with branching on the a carbon. 

While nitramines are formed from the reaction of secondary amines with nitronium salts the success of the reaction depends on the basicity of the amine (Equation 5.11). Thus, amines of low to moderate basicity are A-nitrated in good yields. The nitration of more basic amines is slow and the nitrosamine is often observed as a significant by-product, a consequence of the partial reduction of the nitronium salt to the nitrosonium salt during the reaction. Increased reaction temperature is also found to increase the amount of nitrosamine formed. The amine substrate is usually used in excess to compensate for the release of the strong mineral acid formed during the reactions. Both nitronium tetrafluoroborate and the more soluble hexafluorophosphate are commonly used for A-nitrations. Solvents like acetonitrile, methylene chloride, nitromethane, dioxane, sulfolane, ethyl acetate and esters of phosphoric acid are commonly used. 

The reaction of nitronium salts with primary amines is not usually a feasible route to primary nitramines, except in the case of some electron-deficient arylamines . Picramide... 

Secondary nitramines are conveniently prepared from the nitrolysis of A, A-dialkylamides with nitronium salts in acetonitrile or ethyl acetate at 20 °C where the acyl group is converted into an acylium tetrafluoroborate (Equation 5.14). Problems can occur if commercial nitronium salts like the tetrafluoroborate are used without purification. The presence of nitrosonium salts can then lead to nitrosamines via nitrosolysis. Yields of secondary nitramine up to 90 % have been reported with solutions of nitronium tetrafluoroborate in acetonitrile di-n-butylnitramine is obtained in 82 % yield from the nitrolysis of corresponding acetamide. ... 

The nitrolysis of substituted methylenediamines with nitronium salts can lead to a number of products depending on the nature of the substituents within the substrate. Electron-withdrawing or resonance-stabilizing groups favour the expulsion of an immonium ion and the formation of a secondary nitramine in yields between 58 % and 78... 

A particularly useful synthesis of primary nitramines involves the nitration of the appropriate carbamate ester followed by ammonolysis with gaseous ammonia in diethyl ether. The ammonium salt of the nitramine precipitates in pure form and is carefully acidified to give the free nitramine. The corresponding carbamate esters are readily synthesized from the action of chlorocarboxylic acid esters on alkylamines in the presence of alkali hydroxides. 

Nitramine (161), the simplest member of the nitramines, can be prepared from ethyl carbamate (158) in three synthetic steps nitration of the latter with mixed acid or a solution of ethyl nitrate in concentrated sulfuric acid, followed by isolation of the resulting ethyl N-nitrocarbamate as the ammonium salt (159), hydrolysis with aqueous potassium hydroxide and subsequent acidification, yields nitramine (161). ... 

The dehydration of the nitrate salts of some primary and secondary amines can yield the corresponding nitramine. Dimethylnitramine has been prepared in 65 % yield from the dehydration of dimethylamine nitrate in acetic anhydride to which 4 mole % of anhydrous zinc chloride has been added." The same reaction in the absence of chloride ion only generates a 5 % yield of dimethylnitramine." Some arylnitramines derived from weakly basic amines have been prepared via the addition of the amine nitrate salts to acetic anhydride. " ... 

Metathesis reactions between iV-chloramines and silver nitrite in alkaline solution are reported to give the silver salt of the corresponding primary nitramine. The method is of little synthetic value. ... 

The alkylation of primary nitramines with alkyl halides is of little preparative value for the synthesis of secondary nitramines. Such reactions often result in a mixture of N- and 0-alkylated products. The product distribution appears to be very dependent on the nature of the cation of the nitramine used, with silver salts ° favouring 0-alkylation and alkali metal salts usually giving A-alkylation as the predominant product. However, this is not always the case. 

Tetryl has been synthesized by treating picryl chloride with the potassium salt of methyl-nitramine but the reaction is of theoretical interest only. ... 

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