A simple correlation for predicting heats of fusion of nitroaromatic carbocyclic energetic compounds

In this paper, it is shown that heats of fusion of nitroaromatic carbocyclic energetic compounds can be predicted by using some structural parameters. Elemental composition and the contribution of some specific polar functional groups would be needed in the new method. Predicted heats of fusion using the method described herein for 41 nitroaromatic carbocyclic compounds are compared with experimental data. Calculated heats of fusion have a root mean square (rms) deviation of 3.01 kJ/mol and average deviation of 2.35 kJ/mol for these energetic compounds.     

A simple procedure for calculating condensed phase heat of formation of nitroaromatic energetic materials

A simple procedure has been introduced for calculating solid and liquid heats of formation of nitroaromatic energetic compounds. This model assumes that the heat of formation of a nitroaromatic compound of composition C(a)H(b)N(c)O(d) can be expressed as a new correlation which depends on elemental composition and various structural and special functional group parameters. Condensed phase heats of formation predicted using the method described herein and complicated quantum mechanical computations [B.M. Rice, J. Hare, Thermochem. Acta 384 (2002) 377] have a root mean square (rms) deviation of 5.9 and 11.1 kcal/mol for 19 well-known organic nitroaromatic compounds. Predicted heats of formation for 29 polycyclic nitroaromatic energetic compounds have a rms deviation from experiment of 10.6 kcal/mol. The results show that the present method gives comparable prediction respect to the other methods such as complex quantum mechanical computation.     

Theoretical prediction of condensed phase heat of formation of nitramines, nitrate esters, nitroaliphatics and related energetic compounds

An empirical approach is presented for calculation heats of formation of nitramines, nitrate esters, nitroaliphatics and related energetic compounds which contain at least one of the functional groups including N-NO(2), C-ONO(2) or nonaromatic C-NO(2). This approach is based on elemental composition and various structural and functional group parameters of C(a)H(b)N(c)O(d) energetic compounds. Heat of formation for 78 nitrocompounds including nitramines, nitrate esters, nitroaliphatics and the data obtained is compared with experimental data. Root mean square (rms) of deviation for 19 well known of mentioned energetic compounds are also compared with complex quantum mechanical computations which show 23.8 and 21.3 kJ/mol for new and quantum mechanical methods, respectively. Predicted condensed phase heats of formation for remainder 59 energetic molecules with complex molecular structures have a rms deviation from experiment of 42.3 kJ/mol.     

Heats of sublimation of nitramines based on simple parameters

In this work, a simple procedure is introduced to determine heats of sublimation of nitramines as an important class of explosives. Molecular weight and one structural parameter of nitramines would be needed in the new method. Calculated heats of sublimation for well-known explosives such as HMX [1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane], RDX [1,3,5-trinitro-1,3,5-triazacyclohexane] and TETRYL [1-(methylnitramino)-2,4,6-trinitrobenzene] as well as new nitramines CL-20 [2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane] and TNAZ [1,3,3-trinitroazatidine] show good agreement with experimental data. R-squared value or the coefficient of determination of new correlation is 0.945. The root-mean-square deviation (RMS) from experiment for the predicted heats of sublimation by new method is 10.10 kJ/mol.     

Determining heats of detonation of non-aromatic energetic compounds without considering their heats of formation

A new procedure is introduced for calculating heats of detonation of non-aromatic energetic compounds through ratios of oxygen to carbon and hydrogen to oxygen as well as the contribution of some structural parameters. There is no need to use heats of formation of non-aromatic energetic compounds that are usually needed by the other methods. Moreover, this much simple method does not use any experimental and computed data of energetic materials. Predicted heats of detonation for 28 non-aromatic energetic compounds have a root mean square (rms) of deviation of 0.54 kJ/g from experiment, which show good agreement with respect to measured values. The new method is the simplest procedure for predicting heats of detonation and provides reliable results which are comparable with the other methods.     

Quick estimation of heats of detonation of aromatic energetic compounds from structural parameters

In this paper, a simple procedure is introduced for a quick and reliable estimation of detonation heats of aromatic energetic compounds without considering heats of formation of energetic compounds. This method does not use any experimental or computed data of energetic materials. The methodology assumes that the heat of detonation of an energetic compound with composition of C(a)H(b)N(c)O(d) can be obtained from the number of nitrogens, ratios of oxygen to carbon and hydrogen to oxygen as well as the contribution of some specific functional groups. There is no need to use any assumed decomposition products to calculate heats of detonation for energetic compounds. Predicted heats of detonation of pure energetic compounds with the product H(2)O in the liquid state for 31 aromatic energetic compounds have a root mean square (rms) of deviation of 0.32 kJ/g from experiment. The new method gives good results with respect to two empirical methods which use measured heats of formation of explosives with two sets of decomposition gases.     

Simple empirical method for prediction of impact sensitivity of selected class of explosives

A new approach is described in this work to predict impact sensitivity of a variety of polynitroaliphatics, polynitroaromatics and the explosives containing N-NO2. This paper introduces some simple correlations for prediction of impact sensitivity of C(a)H(b)N(c)O(d) explosives using a, b, c, d, molecular weight and structure information of the explosive. The new correlations are applied to test different polynitroaromatics, benzofuroxans and nitramines. The results are compared with experimental data and some models of complex quantum mechanics computation. Predicted impact sensitivities for 46 explosives have a root mean square (rms) of deviation from experiment of 24 cm, which show good agreement with respect to measured values as compared to five different quantum mechanical models. Impact sensitivities for 58 polynitroaliphatics and related explosives are also calculated, and have a rms deviation from experiment of 40 cm.     

Prediction of the condensed phase heat of formation of energetic compounds

A new reliable simple model is presented for estimating the condensed phase heat of formation of important classes of energetic compounds including polynitro arene, polynitro heteroarene, acyclic and cyclic nitramine, nitrate ester and nitroaliphatic compounds. For CHNO energetic compounds, elemental compositions as well as increasing and decreasing energy content parameters are used in the new method. The novel correlation is tested for 192 organic compounds containing complex molecular structures with at least one nitro, nitramine or nitrate energetic functional groups. This work improves the predictive ability of previous empirical correlations for a wide range of energetic compounds. For those energetic compounds where group additivity method can be applied and outputs of quantum mechanical computations were available, it is shown that the root mean square (rms) deviation of the new method is lower.     

Simple method for prediction of activation energies of the thermal decomposition of nitramines

A novel general method has been introduced to predict activation energies of thermal decomposition of nitramines as an important class of energetic compounds. It is shown that the activation energies of acyclic nitramines can be expressed as a function of optimized elemental composition. The resultant relationship as a core correlation can be corrected for cyclic nitramines that contain more than five member ring. R(2) value or the coefficient of determination of the new correlation is 0.94. The new correlation has the root mean square (rms) and the average deviations of 5.67 and 3.98 kJ/mol, respectively, for 14 nitramines with different molecular structures. The new method is also tested for some cyclic and acyclic nitramines with complex molecular structures, e.g. two new nitramines 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW) and 4,10-dinitro-2,4,6-tetroxa-4,10-diaazaisowurtzitane (TEX), so that it can predict relatively good results as compared to the experimental values.     

Prediction of shock sensitivity of explosives based on small-scale gap test

A new method is described to predict shock sensitivity of C(a)H(b)N(c)O(d) explosives without using any experimental data. It can determine shock sensitivity based on small-scale gap test as the pressure required to initiate material pressed to 90%, 95% and 98% of theoretical maximum density. Three essential parameters would be needed in the new scheme which contain a+b/2-d, the existence of alpha-C-H linkage in nitroaromatic compounds or NNO(2) functional group and difference of the number of amino and nitro groups attached to aromatic ring. Predicted shock sensitivities in some well-known explosives have a root mean square (rms) deviation of 3.97, 4.02 and 5.89kbar of experiment to initiate pressure of material pressed to 90%, 95% and 98% of theoretical maximum density, respectively.     

Reliable estimation of performance of explosives without considering their heat contents

In this paper, a new approach is introduced to calculate detonation pressure of large class of explosives based elemental composition and specific structural groups rather than using their heats of formation. It is shown here how the loading density, atomic composition and some structural parameters can be integrated into an empirical formula for predicting the detonation pressure of pure and explosive formulations over a wide range of loading densities. The results show good agreement with experimental values so that the deviations are within about experimental errors. The calculated values of new method are also compared with the computed results obtained by complex computer code using BKWR and BKWS equations of state. Predicted detonation pressures have root-mean-square (rms) deviation for new method, BKWR and BKWS equations of state are 6.5, 11.7 and 7.4kbar, respectively.     

New approach for predicting melting point of carbocyclic nitroaromatic compounds

A simple correlation has been introduced to estimate melting point of carbocyclic nitroaromatic compounds. The methodology assumes that melting point of a carbocyclic nitroaromatic compound with general formula C(a)H(b)N(c)O(d) can be expressed as a function of the number of hydrogen and nitrogen atoms as well as the contribution of some specific functional groups and the existence of ortho or para isomers in disubstituted benzene ring. Predicted melting points using the method described herein and group contribution method of Joback and Reid [K.G. Joback, R.C. Reid, Chem. Eng. Commun. 57 (1987) 233] have the average deviation of 5.0 and 37.6%, respectively, for 60 carbocyclic nitroaromatic compounds. The proposed new method clearly exhibits a much better accuracy.     

Quantitative Measurements in Continuous-Flow HPLC/NMR

Two methods for the quantitative determination of compounds in continuous-flow HPLC/NMR are described. The first method uses an internal standard (caffeine) of known concentration directly mixed into the mobile phase, while with the second method, a known amount of internal standard is injected onto the column during the chromatographic run. The latter method was validated using several nitroaromatic compounds and explosives. Deviations between the injected and calculated amounts of analytes are usually below 10% while the relative standard deviation ranges from 2% in the upper microgram range to 40% at the limit of detection.     

Theoretical investigation on the heats of formation and the interactions among the isocyano groups in polyisocyanoprismanes C(6)H(6-n)(NC)(n) (n=1-6)

A series of polyisocyanoprismanes, C(6)H(6-n)(NC)(n) (n=1-6), has been designed computationally. We have calculated the heats of formation (HOFs) of the title compounds by using density functional theory (DFT) with 6-31G** basis set. We chose [3]prismane C(6)H(6)-D(3h) as a reference compound in the process of designing isodesmic reactions. The relationship between the HOFs and the molecular structures is discussed. The results have shown that the HOFs of the title compounds gradually increase with increasing number of isocyano groups. On average, the contribution of one isocyano group to the heat of formation is about 232.3 kJ/mol and 234.1 kJ/mol at the B3LYP and B3P86 levels, respectively. The relative stabilities of the title compounds are discussed in terms of the calculated HOFs, the energy gaps between the frontier orbitals, and the bond dissociation energies. The interactions of the isocyano groups in these polyisocyanoprismanes are also discussed. The results have not only shown that these compounds may be used as high-energy-density materials, but also provide some useful information for further syntheses.     

A new method for predicting the heats of combustion of polynitro arene, polynitro heteroarene, acyclic and cyclic nitramine, nitrate ester and nitroaliphatic compounds

A new method is presented for estimating the gross and net heats of combustion of important classes of energetic compounds including polynitro arene, polynitro heteroarene, acyclic and cyclic nitramine, nitrate ester and nitroaliphatic compounds. Elemental compositions as well as the presence of some specific polar groups and molecular fragments are important parameters in the new model. The novel method can be easily used for any complex organic compounds with at least one nitro, nitramine or nitrate functional groups by which the predictions of their heats of combustion by the available methods are inaccurate or difficult. The predicted results show that this method gives reliable predictions of heats of combustion with respect to group additivity method and computed values based on atom-type electrotopological state indices for several energetic compounds where the models can be applied.     

Effect of the allotropic transition in titanium on its interatomic interaction energy

The variation of interatomic interaction energy during allotropic transition in titanium is established by analyzing the stress and temperature dependences of durability. This energy is ≈458 kJ/mol in bodycentered β-Ti at a temperature of T > 1155 K, which agrees well with the titanium sublimation heat, and ≈305 kJ/mol in hexagonal close-packed α-Ti at T < 1155 K. Literature data confirming the conclusions drawn are discussed.     

两性纤维素对持久性污染物的吸附特征

研究两性纤维素对Pb2+、阳离子翠蓝GB、酸性红B和R盐四种持久性污染物吸附过程的动力学和热力学问题,对吸附机理进行探讨.实验结果表明,两性纤维素对上述四种化合物的吸附过程的热力学参数依次为:△H 9.33 kJ/mol、2.88 kJ/mol、5.96 kJ/mol、7.95 kJ/mol;△S 76.8 J/mol...     

Prediction of impact sensitivity of nitroaliphatic, nitroaliphatic containing other functional groups and nitrate explosives

This paper describes a new method for prediction of impact sensitivity of nitroaliphatic, nitroaliphatic containing other functional groups and nitrate explosives. The new procedure is based on some structural parameters of C(a)H(b)N(c)O(d) explosives. Three essential parameters would be needed in this scheme which contain a+b/2-d and the number of nitrogens as well as the number of RC(NO(2))(2)CH(2) structural parameters attached to oxygen of carboxylate functional groups where R is alkyl groups. The results are compared with experimental data and some empirical correlations. Predicted impact sensitivities for 58 explosives have a root mean square (rms) of deviation from experiment of 27 cm, which show good agreement with respect to measured values as compared to previous empirical models.     

New method for calculating densities of nitroaromatic explosive compounds

A new model has been introduced for simple calculation of crystal density of an important class of organic explosives, namely nitroaromatic energetic compounds. This model is based on the fundamental correlation. The introduced procedure has been applied to 60 well-known and new synthesized organic nitroaromatic explosives. The results show that the present method gives comparable prediction respect to well-developed group additivity method for estimation of crystal density of organic explosives. The introduced simple method can be applied to any complex nitroaromatic explosive that contains the elements of carbon, hydrogen, nitrogen and oxygen with no difficulties.     

Disposable electrochemical sensor for determination of nitroaromatic compounds by a single-run approach

Environmental and security applications have generated major demands for effective field-deployable tools for detecting nitroaromatic compounds, such as chloramphenicol (an antibiotic), parathion (an organophosphate nerve agent), and TNT (2,4,6-trinitrotoluene, an explosive) in a fast, simple, sensitive, reliable, and cost-effective manner. We report here a single-run approach for such a purpose. The reduction potential of different nitroaromatic compounds was found to systematically shift with the substituent group at an electrochemically preanodized screen-printed carbon electrode. The preanodization treatment makes the peak sharp and hence provides a precise way to identify the substituent effect on nitroaromatic compounds. By using potential shifts as analytical characteristics of nitroaromatic compounds, a suitable internal standard can be chosen based on the criteria of well-separated peak potential and rarely found in the real sample of interest. Simply by measuring the ratio of peak currents between analytes of interest and internal standard, the analysis can be done in a single-run measurement. Both the matrix effect and the variation of electrode during the preparation process can be canceled out in this approach and thus allows for a high-precision analysis. Just by placing a 20-microL drop on a single-use amperometric sensor strip incorporating a three-electrode configuration is enough for rapid and sensitive detection of nitroaromatic compounds by square-wave voltammetry. For example, the linear detection range can be up to 100 microM with a detection limit of 0.42 microM (S/N = 3) in the detection of chloramphenicol. This approach was successfully demonstrated in real sample analysis to verify the applicability of the method. The promising performances open new possibilities for rapid determination of nitroaromatic compounds in environmental and biological samples.