Erythritol Tetranitrate Research Articles

Properties of Erythritol Tetranitrate from Molecular Dynamics Simulation.

The nonpolarizable force field for alkyl nitrates developed by Borodin et al. [J. Phys. Chem. B, 2008, 112, 734-742] has been employed to calculate selected properties of crystalline and liquid erythritol tetranitrate (ETN). The set of partial charges proposed by Borodin for pentaerythritol tetranitrate (PETN) was used except for a small correction to the H atom charges to ensure charge neutrality owing to the absence of the neopentyl carbon in ETN. The force field was used to compute the isothermal compression curve, lattice parameters, heat capacity, thermal expansivity, single crystal elastic constants, and Gruneisen parameters of crystalline ETN. The density- and temperature-dependent viscosities of liquid ETN are also reported. We anticipate that these data will be of some utility to the development of equations of state and thermomechanical models for ETN.

Nitrate ester derivatization for the generation of structurally informative ions via gas chromatography-mass spectrometry

Forensic investigations of explosives in post-blast and trace scenarios often utilize gas chromatography-mass spectrometry (GC–MS). Many high explosives (e.g., trinitrotoluene) provide structurally significant ions so that a compound can be confidently identified by GC–MS; however, GC–MS only provides functional group identification for the presence of nitrate esters (e.g., nitroglycerin (NG)), a class of high explosives that is frequently encountered in forensic casework. Nitrate esters vary drastically and are much more accurately identified by their component alcohol structure rather than merely the detection of the nitrate and nitrite ions. Herein, we demonstrate a two-step derivatization reaction requiring no purification steps or advanced sample preparation and characterize several of the reaction byproducts created along with the desired reaction product. In this process, nitrate esters are initially reduced to their component alcohol, and then subsequently silylated. The resulting product, when submitted to GC–MS with positive ion mode chemical ionization, provides mass spectra that characterizes the component alcohol by the pseudo-molecular ion of the reaction product. GC–MS with negative ion mode chemical ionization confirms the presence of a nitrate functional group by the characterization of the unreacted starting material. These results combine to identify nitrate esters in forensic settings, and as a proof of concept, we demonstrate the applicability of the derivatization reaction to pentaerythritol tetranitrate (PETN), NG, and erythritol tetranitrate (ETN) standards, as well as a formulated composition containing PETN-SEMTEX 1A, homemade ETN, and post-burn samples.

Highly Scalable and Inherently Safer Preparation of Di, Tri and Tetra Nitrate Esters Using Continuous Flow Chemistry.

Nitrate esters are important organic compounds having wide application in energetic materials, medicines and fuel additives. They are synthesized through nitration of aliphatic polyols. But the process safety challenges associated with nitration reaction makes the production process complicated and economically unviable. Herein, we have developed a continuous flow process wherein polyol and nitric acid are reacted in a microreactor to produce nitrate ester continuously. Our developed process is inherently safer and efficient. The process was optimized for industrially important nitrate esters containing two, three and four nitro groups. Substrates include glycol dinitrates: 1,2-propylene glycol dinitrate (PGDN), ethylene glycol dinitrate (EGDN), diethylene glycol dinitrate (DEGDN), triethylene glycol dinitrate (TEGDN); trinitrates: trimethylolethane trinitrate (TMETN), 1,2,4-butanetriol trinitrate (BTTN); and tetranitrates: erythritol tetranitrate (ETN). The optimized process for each molecule provided yield >90 % in a short residence time of 1 min corresponding to a space time yield of >18 g/h/mL of reactor volume.

Thermochemical analysis of improvised energetic materials by laser-heating calorimetry

Thermochemical analysis of six improvised energetic materials was carried out using laser-heating calorimetry to demonstrate the feasibility of this methodology to provide distinctive thermal signatures and information on the material shelf life. The chemicals evaluated were erythritol tetranitrate, hexamethylene triperoxide diamine (HMTD), poor-man's C-4 (blend of potassium chlorate and petroleum jelly), R-salt (represented by 1,3,5-trinitroso-1,3,5-triazinane), triacetone triperoxide (TATP), and urea nitrate. The measurement technique records the temperature rise with time, from which one can estimate the material endothermic/exothermic behavior, energy release rate, and total specific energy release (heating value, enthalpy of explosion), as well as the sample mass rate of change. Measurements were carried out in an inert nitrogen environment at laser heating rates up to 60 K/s with steady-state temperatures reaching about 933 K. Sample initial mass was between 1.0 mg and 4.0 mg. Experiments were carried out with freshly prepared samples, as well as refrigerated samples and those stored at room (laboratory) temperature for three years. Results indicated that the samples reacted rapidly between 0.50 s and 0.75 s, being initiated near the material decomposition temperature. The total specific energy release, using two different thermal-analysis models, was calculated and compared to values available in the literature. One model represents sample reaction and decomposition within the spherical reactor volume, while the second represents reactions emanating from sample in a pan centrally positioned within the sphere; the former model was found to be the more appropriate approach for these faster-reacting energetic materials. The thermal signatures (temperature-time derivatives with temperature) were different for each chemical, a feature that may be important for energetic material identification. The initiation and peak reaction temperatures were found to decrease with increasing initial sample mass. Also, the shelf life for TATP and HMTD was found not to degrade under nonideal conditions after three years.

A validated method for the analysis of sugars and sugar alcohols related to explosives via liquid chromatography mass spectrometry (LC-MS) with post-column addition

The analysis of eleven sugars and sugar alcohols was performed via liquid chromatography with mass spectrometric detection. A method for the separation of the sugars and sugar alcohols, with the specific emphasis on the separation of the isomeric pair sorbitol/mannitol, was developed. The method was validated, with the following studies included: limit of detection, stability, interference, and ionization suppression. The limits of detection ranged from 9.2x10-3 mM for maltitol up to 2.3 mM for erythrose (3.2 ppm up to 2.8 x102 ppm). The sugars and sugar alcohols were tested at low and high concentrations over 5 days for their stability. Most of the sugars were stable for at least two days at the high concentration, while 6 were stable at the low concentration indicating the need to analyze promptly. An interference study was conducted with nitrated sugars present, which may be present in the forensic application for which the method is intended. There was no interference observed from either mannitol hexanitrate (MHN) or erythritol tetranitrate (ETN). Finally, the effect of a sample collection matrix was evaluated for its potential to either suppress or enhance the analytical signal from the sugars and sugar alcohols. There was no significant enhancement/suppression observed, at high or low concentration, for any analyte except fructose. A field trial was made of forensic samples which demonstrated the potential of the procedure. The method was successfully used for the analysis of six post-blast samples, which indicated the presence of at least one sugar/sugar alcohol in five of those samples.

Investigation of the Impurities in Erythritol Tetranitrate (ETN) Using UHPLC‐QTOF

AbstractIn order to further gain a comprehensive chemical understanding of erythritol tetranitrate (ETN), the synthesis impurities of ETN were investigated using ultrahigh performance liquid chromatography with tandem high resolution mass spectrometry (UHPLC‐MS/MS). A total of 12 impurities were identified relating to the synthesis of ETN. We have synthesized pure analytical standards of erythritol‐1,4‐dinitrate (1,4‐EDiN) and erythritol‐1,2,4‐trinitrate (1,2,4‐ETriN). These isomerically pure standards have allowed for confirmation of the identity of some of the discovered impurities. Additionally, partially nitrated with sulfate substituted erythritol was identified which is theorized to have formed from the incomplete displacement of the formed sulfate group on the alcohol position during nitration.

Characterization of encapsulated energetic materials for trace explosives aids for scent (TEAS)

ABSTRACT Encapsulation is proposed as a safer way of handling energetic materials. Different encapsulation methods for explosives, such as solvent evaporation, spray coating and supercritical carbon dioxide assisted encapsulation, were explored. Explosive training aids, where energetic materials, such as triacetone triperoxide (TATP), erythritol tetranitrate (ETN) and trinitrotoluene (TNT), are encapsulated in a polymer matrix were developed, followed by comprehensive quality control testing, including differential scanning calorimetry (DSC), thermogravimetric analysis-infrared spectroscopy (TGA-IR), gas chromatography-mass spectrometry (GC-MS), high-resolution mass spectrometry (HRMS) and sensitivity testing, and finally field approved by canine units trained on the pure explosive.

ReaxFF Molecular Dynamics Simulation of Hydrostatic and Uniaxial Compression of Nitrate Energetic Materials.

The physical and chemical properties of typical nitrate energetic materials under hydrostatic compression and uniaxial compression were studied using the ReaxFF/lg force field combined with the molecular dynamics simulation method. Under hydrostatic compression, the P–V curve and the bulk modulus (B0) obtained using the VFRS equation of state show that the compressibility of the three crystals is nitroglycerine (NG) > erythritol tetranitrate (ETN) > 2,3-bis-hydroxymethyl-2,3-dinitro-1,4-butanediol tetranitrate (NEST-1). The a- and c-axis of ETN are easy to compress under the action of hydrostatic pressure, but the b-axis is not easy to compress. The b-axis of NEST-1 is the most compressible, while the a- and c-axis can be compressed slightly when the initial pressure increases and then remains unchanged afterward. The a-, b-, and c-axes of NG all have similar compressibilities. By analyzing the change trend of the main bond lengths of the crystals, it can be seen that the most stable of the three crystals is the N–O bond and the largest change is in the O–NO2 bond. The stability of the C–O bond shows that the NO3 produced by nitrates is not from the C–O bond fracture. Under uniaxial compression, the stress tensor component, the average principal stress, and the hydrostatic pressure have similar trends and amplitudes, indicating that the anisotropy behaviors of the three crystals ETN, NEST-1, and NG are weak. There is no significant correlation between maximum shear stress and sensitivity. The maximum shear stresses τxyand τyz of the ETN in the [010] direction are 1.5 GPa higher than τxz. However, the maximum shear stress of NG shows irregularity in different compression directions, indicating that there is no obvious correlation between the maximum shear stress and sensitivity.

Chemical attribution of the homemade explosive ETN - Part II: Isotope ratio mass spectrometry analysis of ETN and its precursors

In this follow-up study the collaboration between two research groups from the USA and the Netherlands was continued to expand the framework of chemical attribution for the homemade explosive erythritol tetranitrate (ETN). Isotope ratio mass spectrometry (IRMS) analysis was performed to predict possible links between ETN samples and its precursors. Carbon, nitrogen, hydrogen and oxygen isotope ratios were determined for a wide variety of precursor sources and for ETN samples that were prepared with selected precursors. The stability of isotope ratios of ETN has been demonstrated for melt-cast samples and two-year old samples, which enables sample comparison of ETN in forensic casework independent of age and appearance. Erythritol and nitric acid (or nitrate salt) are the exclusive donor of carbon and nitrogen atoms in ETN, respectively, and robust linear relationships between precursor and the end-product were observed for these isotopes. This allowed for defining isotopic enrichment ranges for carbon and nitrogen that support the hypothesis that a given erythritol or nitrate precursor was used to synthesize a specific ETN batch. The hydrogen and oxygen atoms in ETN do not originate from one exclusive donor material, making linkage prediction more difficult. However, the large negative enrichments observed for both isotopes do provide powerful information to exclude suspected precursor materials as donor of ETN. Additionally, combing the isotopic data of all elements results in a higher discrimination power for ETN samples and its precursor materials. Combining the findings of our previously reported LC–MS analysis of ETN with this IRMS study is expected to increase the robustness of the forensic comparison even further. The partially nitrated impurities can provide insight on the synthesis conditions while the isotope data contain information on the raw materials used for the production of ETN.

Linking chemical precursors to the synthesis of erythritol tetranitrate

Erythritol tetranitrate (ETN) is a homemade explosive with high explosive performance which can easily be synthesized using widely available chemical precursors. Ascertaining the manner in which ETN is synthesized and being able to trace the ETN back to its precursor materials may aid in the forensic identification. As a proof of concept, seven different types of ETN were synthesized with laboratory grade materials as well as commercially available chemicals from the hardware store and grocery store. The seven different types of solid ETN and the reaction quenches were analyzed using high performance liquid chromatography (HPLC). Partial least squares discriminant analysis (PLS-DA) was used to probe the different classes of ETN and reaction quenches. Several PLS-DA models were produced with the seven different types of ETN and quenches having their own classification, ETN and quenches based on their acid source, and ETN and the quenches based on their nitrate source. Regardless of which classification manner was used, there were no differences found between the different types of ETN or their reaction quenches. Moreover, it is demonstrated that there is inherent variability in the synthesis of ETN making HPLC an unreliable method to determine the source of the synthesis materials. Elemental impurities were measured in seven solid ETN samples and their reaction quenches by inductively coupled plasma mass spectrometry (ICP-MS). No differences were found between the solid ETN samples, but there were trace metals found in the reaction quenches which were found to be identifiers of the source material.

Synthesis of Erythritol Tetranitrate Derivatives: Functional Group Tuning of Explosive Sensitivity.

Understanding the factors that affect explosive sensitivity is paramount to the safe handling and development of new explosives molecules. Erythritol tetranitrate (ETN) is an explosive that recently has attracted significant attention in the explosives community because of its ease of synthesis and physical properties. Herein, we report the synthesis of ETN derivatives using azide, nitramine, and nitrate ester functional groups. Impact, spark, and friction sensitivity measurements, computationally calculated explosive properties, and the crystal structure analysis of the ETN derivatives are reported. Mixing explosive functional groups led to changes in the explosive sensitivity, explosive performance as well as physical properties including melting point and physical state at room temperature. Overall, we have demonstrated that combining functional groups can enable the tuning of explosive and physical properties of a molecule. This tunability can potentially aid in the development of new explosives in which characteristics are varied to meet certain specifications.

Chemical attribution of the home-made explosive ETN – Part I: Liquid chromatography-mass spectrometry analysis of partially nitrated erythritol impurities

Erythritol tetranitrate (ETN) was prepared independently by two research groups from the USA and the Netherlands. The partially nitrated impurities present in ETN were studied using liquid chromatography-mass spectrometry to address the ultimate challenge in forensic explosives investigations, i.e., providing chemical and tactical information on the production and origin of the explosive material found at a crime scene. Accurate quantification of the tri-nitrated byproduct erythritol trinitrate (ETriN) was achieved by in-lab production of an ETriN standard and using custom-made standards of the two isomers of ETriN (1,2,3-ETriN and 1,2,4-ETriN). Large differences in levels of ETriN were observed between the two sample sets showing that, even when similar synthesis routes are employed, batches from different production locations can contain different impurity profiles. In one of the sample sets the ratios of the lesser partially nitrated impurities, EDiN and EMN, in the ETN samples could be determined. The impurity profiles enable prediction of post-synthesis work-up steps by reduction of the level of partially nitrated products upon recrystallization. However, impurity analysis does not enable predictions with respect to raw material or synthesis route used. Nonetheless, characteristic impurity profiles obtained can be used in forensic casework to differentiate or link ETN samples. However, forensic interpretation can be complicated by acid catalyzed degradation which can cause changes in impurity levels over time. The high food-grade quality of the erythritol precursor materials did not provide other impurity markers using the LC-MS methods in this study. To expand our framework of chemical attribution a follow-up study will be reported that focuses on stable isotope analysis of ETN and its precursor materials that potentially allow predictions for forensic explosives intelligence.

Ranking the Drop-Weight Impact Sensitivity of Common Explosives Using Arrhenius Chemical Rates Computed from Quantum Molecular Dynamics Simulations.

Drop-weight impact tests are used routinely to characterize the handling safety of explosives. Numerous studies have sought to connect various physical and chemical properties of the energetic molecules and materials to their measured impact sensitivities. Wenograd in the early 1960s demonstrated that there is a strong dependency of the drop-heights on the critical temperatures required for explosives to undergo prompt reactions. Reactive quantum molecular dynamics simulations with the lanl31 density functional tight binding model have been used to compute the delay time before the thermal explosion of the secondary explosives erythritol tetranitrate (ETN), pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), trinitrotolune (TNT), and 3,3'-diamino-4,4'-azoxyfurazan (DAAF) as a function of the initial temperature and pressure. The delay time to explosion data are consistent with Arrhenius chemical kinetics, which is expected for thermally activated processes in materials and in accord with experimental measurements. The critical temperatures required for the materials to undergo prompt explosions display the same dependence on drop height as was observed by Wenograd. Hence, quantum-based reactive molecular dynamics simulations are potentially a tool for ranking the drop-weight impact sensitivity and handling safety of explosives.

Modifying Nitrate Ester Sensitivity Properties Using Explosive Isomers

Understanding explosive sensitivity is key to the safe handling and development of new explosives. Macro- and microscale studies have concluded that multiple physical and chemical factors affect sensitivity, both intermolecular and intramolecular. Stereoisomers are molecular pairs with the same bond connectivity but differing spatial arrangement of those bonds, and in certain cases can exhibit vastly different chemical and physical properties. Herein we report the synthesis of stereoisomers of erythritol tetranitrate (ETN) and the reported stereoisomers mannitol hexanitrate (MHN) and sorbitol hexanitrate (SHN). Isomers of ETN and MHN had altered physical properties such as melting point, state of matter, and crystal structure. These different physical properties caused changes in the impact sensitivity of the isomers. The melting point of the explosive was determined to be a key factor in the impact sensitivity measurements, altering the physical state of the explosive at room temperature or by potentially facilitating access to the more sensitive liquid state of the explosive.

Crystal Structure, Sensitiveness and Theoretical Explosive Performance of Xylitol Pentanitrate (XPN)

AbstractXylitol pentanitrate (XPN) is a little‐studied nitrate ester of similar molecular structure to the military energetic materials pentaerythritol tetranitrate (PETN) and nitroglycerin (NG). XPN was crystallised from a mixture of ethanol and water by slow evaporation and studied by single crystal X‐ray diffraction. XPN crystallises in the centrosymmetric monoclinic space group P21/n, with a calculated density of 1.852 g cm−3. Sensitiveness analysis of the energetic material revealed it to be a primary explosive, significantly more sensitive than PETN to friction and impact. The calculated heat of formation of XPN, −500.48 kJ mol−1, and the density were exploited utilising the Cheetah 7.0 suite of programs to predict explosive performance parameters. The theoretical explosive performance of XPN was comparable to the calculated explosive parameters of erythritol tetranitrate (ETN), PETN and cyclotrimethylene trinitramine (RDX).

Increased handling sensitivity of molten erythritol tetranitrate (ETN).

Erythritol tetranitrate (ETN) is a well-studied homemade explosive (HME), which is known for its ability to be melt-cast at a fairly low temperature. We have observed dramatically increased handling sensitivity of ETN in the molten state, using temperature controlled drop-weight impact sensitivity measurements. Impact testing was performed using ERL Type 12 drop hammer equipment using a 2.5 kg weight, a 0.8 kg striker, an anvil and sound detection equipment. Most experiments were performed in the absence of standard grit paper, due to the elevated temperature measurements with a liquid. At room temperature, ETN exhibited an impact sensitivity of 14.7 ± 3.4 cm, which changed to 1.0 ± 0.6 cm in the liquid state at 65 °C. The change in sensitivity in the liquid state was found to be reversible upon solidification, and did not appear to correlate with temperature. Control experiments were performed in the same setup using standard explosives pentaerythritol tetranitrate (PETN) and triacetone triperoxide (TATP). This is the most sensitive material that we have been able to measure using our instrumentation, and indicates that ETN be handled with extreme caution during the melt-casting process.

Generating highly specific spectra and identifying thermal decomposition products via Gas Chromatography / Vacuum Ultraviolet Spectroscopy (GC/VUV): Application to nitrate ester explosives

Gas chromatography/mass spectrometry (GC/MS) is a "workhorse" instrument for chemical analysis, but it can be limited in its ability to differentiate structurally similar compounds. The coupling of GC to vacuum ultraviolet (VUV) spectroscopy is a recently developed technique with the potential for increased detection specificity. To date, GC/VUV has been demonstrated in the analysis of volatile organic compounds, petroleum products, aroma compounds, pharmaceuticals, illegal drugs, and lipids. This paper is the first to report on the utility of GC/VUV for explosives analysis in general, and the first to report on thermal degradation within the VUV cell and its analytical utility. The general figures of merit and performance of GC/VUV were evaluated with authentic standards of nitrate ester explosives (e.g., nitroglycerine (NG), ethylene glycol dinitrate (EGDN), pentaerythritol tetranitrate (PETN), and erythritol tetranitrate (ETN)). In addition, the explosive analytes were thermally degraded in the VUV cell, yielding reproducible, complex and characteristic mixtures of gas phase products (e.g., nitric oxide, carbon monoxide, and formaldehyde). The relative amounts of the degradation products were estimated via spectral subtraction of library spectra. Lastly, GC/VUV was used to analyze milligram quantities of intact and burned samples of double-base smokeless powders containing nitroglycerine, diphenylamine, ethyl centralite, and dibutylphthalate

Application of a co-polymeric solid phase extraction cartridge to residues containing nitro-organic explosives

A validated solid phase extraction (SPE) cleanup procedure utilizing Bond Elut NEXUS co-polymeric cartridges has been applied to soil and swab samples containing pre- and post-blast residues of nitro-organic explosives. In addition, simulated samples were also processed by SPE to evaluate matrix rejection and interferences. The matrices were extracted with acetone, diluted with deionized water, and processed by SPE. The final extracts were then analyzed by gas chromatography with electron capture detection (GC/ECD) to screen for the compounds of interest, which included ethylene glycol dinitrate (EGDN), dimethyl dinitrobutane (DMDNB), 4-nitrotoluene (4-NT), nitroglycerin (NG), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), pentaerythritol tetra-nitrate (PETN), cyclotrimethylene trinitramine (RDX), 2,4,6-trinitrophenylmethylnitramine (tetryl), cyclotetra-methylene tetranitramine (HMX), erythritol tetranitrate (ETN), and cyclotrimethylene trinitrosoamine (R-salt). The expected explosives were detected in 97% of cases after processing through SPE and analysis by GC/ECD. Approximately one-third of the samples that screened positive by ECD were subjected to confirmation testing by gas or liquid chromatography/mass spectrometry (GC/MS or LC/MS). The results from these matrices were compared to results obtained by syringe filtration. SPE produced equal or better results than syringe filtration in both the ECD screening and MS confirmation tests, including the ability to detect higher signals for more explosives in the post-blast residue samples. The confirmation results also show that all of the expected explosives could be confirmed after processing by SPE, whereas only 83% of them were confirmed after syringe filtration. This study demonstrates the successful application of a validated method to the cleanup of organic explosive residues in complex matrices.

The correlations among detonation velocity, heat of combustion, thermal stability and decomposition kinetics of nitric esters

In this paper, the thermal stability and decomposition kinetics of 10 nitric esters including nitroglycerine (NG), pentaerythritol tetranitrate (PETN), trimethylolethane trinitrate (TMETN), dipentaerythritol hexanitrate (DiPEHN), trimethylolpropane trinitrate (TMPTN), xylitol pentanitrate (XPN), sorbitol hexanitrate (SHN), erythritol tetranitrate (ENT), mannitol hexanitrate (MHN) and nitroisobutylglycerol trinitrate (NiBGT) are investigated by non-isothermal TG and DSC. It has been shown that the mass loss processes of NG, TMETN and TMPTN are more dependent on the heating rate, and the simultaneous evaporation makes the initial temperatures for their mass loss lower than those of the other nitric esters. Based on the correlations among their thermal stability, activation energy, detonation velocity and heat of combustion, one could conclude that the oxygen coefficient (α) plays a positive role on the decomposition heat release efficiency (η d) when it is less than one, whereas when the α is greater than or equals to one, the fuel elements such as C and H contents would play a decisive role on η d. It has been further proved that the order of contribution rate of function groups on the tertiary carbon to the detonation velocity could be –CH3 < –NO2 < –C2H5 < –ONO2. In addition, the introduction of function groups to the tertiary carbon is in favor of increasing the thermal stability of nitric esters due to increase in symmetry and rigidity of their molecules. The proportion numbers (C s) of methylene group (–CH2–) to tertiary carbon or quaternary carbon will, to some extent, determine the thermal stability of the nitric esters.

Eutectics of Erythritol Tetranitrate

With the recent availability of erythritol as an artificial sweetener, the synthesis of erythritol tetranitrate (ETN) has become economically feasible. This paper examines the eutectics of ETN, to see if it can be a useful component in melt-casted explosive formulations. To this end, we report several novel ETN–energetic eutectics, correct ratios, and melt-temperature for a previously reported eutectic, and we examine a new eutectic composed of insensitive explosives.