Structure of Nitrate Esters

The basic feature of nitrate esters is the nitroxyl group of -C-O-NO2. The ester group in nitrate esters is of an oxygen atom connecting with a carbon atom, that is, the nitrate esters belong to (9-nitro compounds. This was confirmed by the hydrolysis or reduction of nitrate esters to alcohols [3, 13, 14], as the following reaction equation. 

The essential difference between nitrate esters and nitro compounds can be found in the reaction. In the same reaction conditions, nitro compounds would be converted to amines. Though the structure of ester group (-NO2) is the same as the nitro group (C-NO2) in nitro compounds, the reactivity of nitrate esters is higher and the product distribution after hydrolysis reaction is more complicated. It indicates that nitrate esters might have the structure of hyperoxide group -R-O-O-NO. 

However, the hyperoxide structure was not found in nitrate esters after multiple chemical structure analysis techniques [1, 3, 15]. The only structure of nitrate esters 

The structure of nitrate esters was further characterized by techniques of Raman spectroscopy, Infrared spectroscopy, Electron Diffraction, dipole moment, and X-ray. The results supported the finding of no hyperoxide structure in nitrate esters. Symmetrical structure was demonstrated for nitrate esters. 

The bond length and bond angle of nitrate esters are similar with those of nitro 

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Nitrous acid is only produced in the hydrolysis of nitrate esters with peroxide structure. Under the influence of hydrolytic reagent, the structure of nitrate esters would be changed to peroxide structure. Thus, nitrous acid would be produced in the process. 

Stability of nitrate esters is a factor to decide if they can be long-term stored [44]. Because of their structure, they could be decomposed by hydrolysis and spontaneously burned to cause explosion. The higher the purity of esters is, the lower the risk of decomposition is. The stability depends on the chemical structure of nitrate esters. For example, the stability for most pure nitrate esters, such as methylene glycol dinitrate, nitroglycerine, glycol dinitrate, 1,3-propanediol dinitrate, pentae-rythritol tetranitrate, and cellulose nitrate, is acceptably high. 

Examination of the structures of nitrate ester explosives shows that they contain abundant carbon derived from polyhydric alcohols (e.g. glycerol, pentaerythritol) which are readily assimilable by bacteria. Moreover nitrate esters also contain abundant nitrogen and thus they may also serve to supply this element for microbial growth. A... 

Due to its symmetrical structure, Pentaery-thritol Tetranitrate is highly resistant to many reagents. Thus PETN differs from the majority of nitrate esters by not being readily decompd by sodium sulfide at 50°. On the other hand, it is decompd quite quickly by boiling in a ferrous... 

Olah and co-workers ° conducted a comprehensive study into the use of N-nitropyridinium salts for nitration. Such salts are easily prepared from the slow addition of the appropriate heterocyclic base to an equimolar suspension of nitronium tetrafluoroborate in acetonitrile. Olah studied the effect on nitration of changing both the structure of the heterocyclic base and the counter ion. Three of these salts (20, 21, 22) illustrated above have been synthesized and used for the 0-nitration of alcohols with success. Transfer nitrations with Al-nitropyridinium salts are particularly useful for the preparation of nitrate esters from acid-sensitive alcohols and polyols because conditions are essentially neutral. 

The combustion wave structure of RDX composite propellants is homogeneous and the temperature in the solid phase and in the gas phase increases relatively smoothly as compared with AP composite propellants. The temperature increases rapidly on and just above the burning surface (in the dark zone near the burning surface) and so the temperature gradient at the burning surface is high. The temperature in the dark zone increases slowly. However, the temperature increases rapidly once more at the luminous flame front. The combustion wave structure of RDX and HMX composite propellants composed of nitramines and hydrocarbon polymers is thus very similar to that of double-base propellants composed of nitrate esters.[1 1... 

HMX composite propellants are composed of crystalline HMX particles and polymeric materials, and so their physical structures are heterogeneous. On the other hand, nitropolymer propellants are composed of mixtures of nitrate esters such as NC and NG, and their physical structures are homogeneous. Moreover, HMX pro-... 

Polymeric materials used as fuel components of pyrolants are classified into two types active polymers and inert polymers. Typical active polymers are nitropoly-mers, composed of nitrate esters containing hydrocarbon and oxidizer structures, and azide polymers, containing azide chemical bonds. Hydrocarbon polymers such as polybutadiene and polyurethane are inert polymers. When both active and inert polymers are mixed with crystalline oxidizers, polymeric pyrolants are formed. 

A hypothetical structure of complexes of nitrate esters with one to four nitrate groups was also advanced [19]. It was suggested that TMPD be used for analytical detection (including TLC) of nitrate esters (20. ... 

A comparison of the effect of the structure of phosphate esters on uranium extraction from nitrate media shows that the esters from secondary alcohols give higher uranium distribution coefficients (D s) than those from primary alcohols, phenyl esters extract uranium less strongly than alkyl esters, and benzyl esters are intermediate in extractant strength for uranium (24). 

Lead compounds are effective in increasing the burning rate (super-rate burning) of double-base propellants. A similar super-rate burning effect is observed when lead compounds are added to composite propellants consisting of nitramine particles and polymeric binder. Though the chemical structures and properties of nitramines are different from those of nitrate esters, super-rate burning effects are obtained by the use of the same lead compounds. 

The present work was undertaken as part of a wider programme to isolate bacteria competent in the biodegradation of nitrate esters and to determine the kinetics of metabolite production during the biodegradation process. The enrichment substrates used were GTN, PETN and propane-2-yl nitrate (isopropyl nitrate, IPN). The last was chosen because it is a readily available mononitrate which is structurally related to GTN, and it is analogous to propane-2-yl sulphate which is known to undergo bacterial biodegradation (Crescenzi e/a/., 1984, 1985 [18, 19]). 

Nitrocellulose, of the resins used in these end uses and in car refinishing, is the nitrate ester of cellulose. The structure is linear and a wide range of (high) molecular weights is available as well as various degrees of nitration ... 

Sliver. Frepd by addn of Ag nitrate soin to a soln of the Na salt (see above) (Refs 3 10) ign point 181° (Ref 12). When treated with alkyl iodides it gives alkyl esters. From the reaction with Me iodide a colorless and a yellow dimethyl ester were isolated (Ref 3). The UV spectra of the colorless (called a) and the yellow (called 3) esters are given in Ref 9 it is concluded that the color of the / ester is due to a nitroso group, hence its structure is probably (CH301 Q2CH2... 

A group of flavoenzyme reductases mediate the reduction both nitrate esters and C= C double bonds generally activated with carbonyl or nitro functions. The structures of the substrates vary widely (references in Faber 1997). 

The chemical structures of some common mifttary explosives are shown in Figure 1. These include the nitrate esters such as nitrocellulose (NC), NG, EGDN, and (PETN) nitroarenes such as trinitrotoluene (TNT, CH3—C6H2(N02)3), picric acid (HO—C5H2(N02)3), and 2,4,6-trinitrophenylmethylnitramine (tetryl) and nitramines such as RDX (C3H6N6O6), HMX (C4H8N8O8), and hexanitrohexa-azaisowurtzitane (CL— 20). Of these, only CL— 20 is new , that is, less than 50 years old [3]. Mixtures of oxidizers and fuels, such as AN and FO (called ANFO), are also secondary explosives. 

Drees and co-workers synthesized a number of energetic azido plasticizers whose structures are based on those of known nitrate ester plasticizers. EGBAA (3), DEGBAA (4), TMNTA (5) and PETKAA (6) are synthesized from the corresponding chloroacetate esters with sodium azide in DMSO. 

Typical materials containing oxygen and nitrogen atoms are nitrate esters, such as nitrocellulose (NC) and nitroglycerin (NG). Nitrate esters contain -O-NO2 chemical bonds in their structures. The oxidizer component is represented by the oxygen atoms and the fuel components are the carbon and hydrogen atoms. The oxidized combustion products are COj and HjO, the AHjp values of which are -8.94 MJ... 

Though nitroglycerin (NG) is a liquid nitrate ester rather than a nitropolymer, it becomes a polymeric material when it is mixed with plasticizers. Like NC, NG is composed of a hydrocarbon structure with -O-NO2 bonds as oxidizer fragments. 

BAMO is also copolymerized with nitratomethyl methyl oxetane (NIMO) to formulate the energetic liquid polymer BAMO-NIMO. Since NIMO is a nitrate ester containing an -O-NO2 bond in its molecular structure, BAMO-NIMO copolymer is more energetic than BAMO-THF copolymer. The chemical structures of BAMO and NIMO are both based on the oxetane structure, and the structure of the BAMO-NIMO copolymer is shown in Fig. 4.10. 

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