Structure/Enthalpy of Formation Relationships for Hydrocarbons Containing Benzene Rings

Simple protocols to convert molecular mechanics (MMX/PCMODEL), semiempirical PM3, and HF ab initio energies to accurate heats of formation for hydrocarbons with benzene rings are described. The data set consists of every hydrocarbon benzene derivative with an experimentally determined ΔH_f^o (g), and the ΔH_f^o (g)'s cover a range of -140 to +410 kJ/mol. The molecular structures are comprised of numerous structural types. Hierarchical sets of molecular structure parameters are defined to describe these molecules. The independent variables include atom types (level 1), group and ring terms (level 2), nonbonded atom interactions (level 3), and the calculated MMX, PM3 or ab initio HF energies, which contribute a final level 4 parameter for rectification of the ΔH_f^o (g) data. The additivity, level 1-3 parameters give an excellent correlation of the experimental ΔH_f^o (g)'s, average error = 3.4 kJ, and maximum error = 12.1 kJ. However, the correlations are further enhanced by addition of any level 4 parameter, with maximum improvement coming at the 6-31G*//STO-3G HF level of calculation.     

Theoretical Study on Thermodynamic and Detonation Properties of Polynitrocubanes

We investigated the heat of formation (Δ_fH) of polynitrocubanes using density functional theory B3LYP and HF methods with 6‐31G*, 6‐311+G**, and cc‐pVDZ basis sets. The results indicate that Δ_fH firstly decreases (nitro number m=0–2) and then increases (m=4–8) with each additional nitro group being introduced to the cubane skeleton. Δ_fH of octanitrocubane is predicted to be 808.08 kJ mol⁻¹ at the B3LYP/6‐311+G** level. The Gibbs free energy of formation (Δ_fG) increases by about 40–60 kJ mol⁻¹ with each nitro group being added to the cubane when the substituent number is fewer than 4, then Δ_fG increases by about 100–110 kJ mol⁻¹ with each additional group being attached to the cubic skeleton. Both the detonation velocity and the pressure for polynitrocubanes increase as the number of substituents increases. Detonation velocity and pressure of octanitrocubane are substantially larger than the famous widely used explosive cyclotetramethylenetetranitramine (HMX).     

A convenient method to estimate the rate of heat evolution in fermentation

The estimation of heat of fermentation is discussed with reference to experimental data obtained in glucose-, ammonia- and oxygen-limited chemostat cultures of a specific bacterium and also to previous data published by other workers. Whatever the microbial or cultural conditions might be, the heat of fermentation can be easily estimated from TOD (total oxygen demand) measurement, accompanied by the concept of available electrons. If aerobic pathways are dominant in a particular fermentation, the specific rate of heat evolution, Q_H, can be calculated approximately from Q_H = Q_o2 (?δH_o^7ast;), where ? 7delta;H_o^* = 106 kcal/mol O₂, using only Q_o2 values without the need for either TOD or calorimetric determination.     

Molecular Orbital Based Design Guideline for Hypergolic Ionic Liquids

Currently, monomethyl hydrazine is the most widely used hypergolic rocket fuel. Due to its high toxic vapor, there is a thrust towards developing low‐toxic hypergolic fuels. Ultra‐low vapor pressure ionic liquids are one such potential category of fuels. However, designing ionic liquid with ignition delay comparable to monomethyl hydrazine is a challenge, because fundamental understanding of the hypergolic nature of ionic liquids is far from clear. This work used the computed energy gap values between the highest occupied molecular orbitals (HOMO) of the anions for a series of ionic liquids and the lowest occupied molecular orbital (LUMO) of HNO₃, and variation in the computed relative heats of formation, ΔH_f, of these anions to develop correlations to predict hypergol activity between an ionic liquid fuel and nitric acid as the oxidizer. The observed trends in HOMO LUMO energy gap and ΔH_f values can be used successfully to verify not only hypergolicity of known systems but also the lack of this phenomenon in OH⁻ and BF₄⁻ based ionic liquids. It was shown that through suitable substitution of electron withdrawing or electron donating groups in the anion, the energy gap and the ΔH_f values could be tailored into an optimal range that would have a high probability for the new system to exhibit hypergolic reactivity. To validate our method, we suggest herein new ionic liquid structures for synthesis and experimental screening.     

Diffusion of benzene vapor in blends of poly(vinyl acetate) and poly(methyl acrylate)

Sorption and diffusion of benzene in miscible blends of poly(vinyl-acetate), PVAc, and poly(methyl acrylate), PMA, have been studied. The polymer-polymer interaction parameter values calculated from equilibrium vapor sorption data were all negative, indicating favorable interaction between the two polymers. The sorption of benzene vapor into these blends was measured at a temperature above the T_g's of the pure polymers and found to obey Fickian kinetics. The mutual diffusion coefficients were estimated from the initial slopes of the sorption curves. The concentration dependent diffusion coefficients were fitted to the empirical relation D = D_o exp(αC) which satisfactorily correlated the data. Values of the constant D_o were found to vary continuously with blend composition, while the α values did not. These experimental data were analyzed employing Fujita's free volume theory. It was found that the data was consistent with this theory. If the f_o values for the blends are assumed to be the weighted average of the component polymers, then the β parameter values for the blends also obey the additivity rule.     

Simple Method for Prediction of the Standard Gibbs Free Energy of Formation of Energetic Compounds

A reliable simple method for prediction of the standard Gibbs energy of formation (Δ_fG^θ) of energetic compounds containing nitroaromatic, acyclic, and cyclic nitramine, nitrate ester, and nitroaliphatic compounds is introduced herein. The method is based on the contribution of elemental composition (Δ_fG_elem^θ) and the correcting function for the presence of additive and non‐additive molecular fragments (Δ_fG_corr^θ). In presence of some molecular moieties, Δ_fG_corr^θ may increase or decrease the value of Δ_fG_elem^θ, depending on the intermolecular interactions. The experimental root‐mean‐square error (RMSE) of the novel correlation (22.7 kJ mol⁻¹) is quite good. For some energetic compounds, where the computed values of two complex models of the quantitative structure‐property relationship (QSPR) theory were available, the experimental RMSE developed by the new method is smaller than the values obtained by QSPR method.     

Modeling of thermodynamics of substituted toluene derivatives and benzylic radicals via group additivity

The thermodynamic properties of unsubstituted, mono‐, and di‐substituted toluene derivatives and benzylic radicals with hydroxy, methoxy, formyl, vinyl, methyl, and ethyl substituents are calculated with the bond additivity corrected (BAC) post‐Hartree‐Fock CBS‐QB3 method. Benson's group additivity (GA) scheme is extended to toluene derivatives by determining six group additive value (GAV) and five non‐nearest neighbor interaction (NNI) parameters through least‐squares regression to a database of thermodynamic properties of 168 compounds and to benzylic radicals by defining 6 GAV and 14 NNI parameters based on a set of 168 radicals. Comparison between CBS‐QB3/BAC and GA‐calculated thermodynamic values shows that the standard enthalpies of formation generally agree within 4 kJ mol^?1, whereas the entropies and the heat capacities generally deviate <4 J mol^?1 K^?1. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3649–3661, 2018     

Taming the Beast: Measurement of the Enthalpies of Combustion and Formation of Triacetone Triperoxide (TATP) and Diacetone Diperoxide (DADP) by Oxygen Bomb Calorimetry

Low‐melting paraffin wax was successfully used as a phlegmatizing agent to perform semi‐micro oxygen bomb calorimetry of spectroscopically pure samples of the sensitive explosive peroxides TATP and DADP. The energies of combustion (Δ_cU) were measured and the standard enthalpies of formation (Δ_fH°) were derived using the CODATA values for the standard enthalpies of formation of the combustion products. Whilst the measured Δ_fH° of DADP (Δ_fH°=−598.5 ± 39.7 kJ mol⁻¹) could not be compared to any existing literature value, the measured Δ_fH° value of TATP (Δ_fH°=+151.4 ± 32.7 kJ mol⁻¹) did not correlate well with the only existing experimental value and confirmed that TATP is an endothermic cyclic peroxide.     

Determination of the Initiating Capability of Detonators Containing TKX‐50, MAD‐X1, PETNC,DAAF, RDX,HMX or PETN as a Base Charge,by Underwater Explosion Test

A comprehensive investigation to determine the initiation power of detonators containing as a base charge the novel explosives: dihydroxylammonium 5,5′‐bis(tetrazolate‐1N‐oxide) – TKX‐50, dihydroxylammonium 5,5′‐bis(3‐nitro‐1,2,4‐triazolate‐1N‐oxide) – MAD‐X1, pentaerythritol tetranitrocarbamate – PETNC and 3,3′‐diamino‐4,4′‐azoxyfurazan – DAAF in comparison with RDX, HMX and PETN was undertaken. In order to estimate the initiation power of the detonators, the underwater initiating capability test was used. The total energy as a sum of the primary shock wave energy and the bubble gas energy was determined for each of these explosives, by measuring the overpressure of the shock waves generated in water. Moreover, the complete synthesis for novel explosives is presented. The thermal behavior of the explosives was investigated using DSC (differential scanning calorimetry). The gas phase absolute molar enthalpies at 298 K and 10⁵ Pa were calculated theoretically using the modified complete basis set method (CBS‐4M; M referring to the use of minimal population localization) with the Gaussian 09 software. Gas phase standard molar enthalpies of formation (ΔH_f°_(g)) at 298 K were computed using the atomization energy method. Standard molar enthalpies of formation (▵H_(s)°) were calculated using ΔH_f°_(g) and the standard molar enthalpies of sublimation by applying Trouton’s rule. The Chapman‐Jouguet (CJ) characteristics based on calculated ▵H_(s)° values were computed using the EXPLO5 V6.01 thermochemical computer code. For the calculations the theoretical maximum densities and densities obtained during the experiments presented in this work were used.     

Conductometric Probe Analysis of the Effect of Benzyldimethylhexadecylammonium Chloride on the Micellization Behavior of Dodecyltrimethylammonium Bromide in Aqueous/Urea Solution: Investigation of Concentration and Temperature Effect

Surfactant mixtures are used in many different industrial formulations. In this study, the mixed micelle formation behavior of 2 different cationic surfactants, namely dodecyltrimethylammonium bromide (DTAB) and benzyldimethylhexadecylammonium chloride (BDHAC), in the absence and presence of urea at various temperatures (298.15–318.15 K) was studied using the conductometric method. The attractive interaction between DTAB and BDHAC was estimated from the values of critical micelle concentration (CMC) and the CMC for ideal mixing (CMC^id). Urea increases the CMC value as a result of the enrichment in the surface charge of the micelles/mixed micelles. The values of micellar mole fraction (X₁^Rub [Rubingh], X₁^M [Motomura], X₁^Rod [Rodenas]) and ideal micellar (X₁^id) of surfactant BDHAC were obtained by different models and are shown to exhibit the high contribution or effective involvement of BDHAC in mixed micelles and increase with increasing BDHAC mole fraction (α₁). Activity coefficients (f₁ and f₂) were also evaluated from the relevant formula given in the literature. The negative values of the interaction parameters (β) show the attractive interaction among the studied components. Excess Gibbs free energy (?G_ex) of micellization revealed that the stability of mixed micelles is higher in aqueous solution than in urea solution. The thermodynamic parameters, namely the Gibbs free energy change, enthalpy change, and entropy change (?G^o_m, ΔH^o_m, and ?S^o_m, respectively), were also calculated from the conventional standard equations.     

Removal of Basic Blue 3 by sorption onto a weak acid acrylic resin

A weak acid acrylic resin was used as an adsorbent for the investigation of Basic Blue 3 (BB3) adsorption kinetics, isotherms, and thermodynamic parameters. Batch adsorption studies were carried out to evaluate the effect of pH, contact time, initial concentration (28–100 mg/g), adsorbent dose (0.05–0.3 g), and temperature (290–323 K) on the removal of BB3. The adsorption equilibrium data were analyzed by the Langmuir, Temkin, and Freundlich isotherm models, with the best fitting being the first one. The adsorption capacity (Q_o) increased with increasing initial dye concentration, adsorbent dose, and temperature; the highest maximum Q_o (59.53 mg/g) was obtained at 323 K. Pseudo‐first‐order and pseudo‐second‐order kinetic models and intraparticle diffusion models were used to analyze the kinetic data; good agreement between the experimental and calculated amounts of dye adsorbed at equilibrium were obtained for the pseudo‐second‐order kinetic models for the entire investigated concentrations domain. Various thermodynamic parameters, such as standard enthalpy of adsorption (ΔH^o = 88.817 kJ/mol), standard entropy of adsorption (ΔS^o = 0.307 kJ mol^?1 K^?1), and Gibbs free energy (ΔG^o < 0, for all temperatures investigated), were evaluated and revealed that the adsorption process was endothermic and favorable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Performance Assessment of Some Isomers of Saturated Polycyclic Hydrocarbons for Use as Jet Fuels

The performance of jet fuel depends on the density (ρ), condensed phase heat of formation (▵_fH°(c)), and specific impulse (I_SP). Exo‐tricyclo[5.2.1.0(2,6)]decane (C₁₀H₁₆) or JP‐10 is now used as a suitable synthetic liquid jet fuel because it has the approximated values of ρ=1.1 g cm⁻³ and ▵_fH°(c)=− 123 kJ mol⁻¹ and a broad range between the melting and boiling points, i.e. T_bp–T_mp=196.2 K. This work introduces a suitable pathway for calculation of the values of ρ, ▵_fH°(c), and I_SP of 13 well‐known isomers of JP‐10 and a series of saturated polycyclic hydrocarbons with general formula of C_nH_n′ (5≤n≤12) in order to specify high performance jet fuels. Although 13 compounds have larger values of I_SP*ρ than JP‐10, only two compounds, tetraspiro[2.0.0.0.2.1.1.1]undecane and tetracyclo[3.2.0.0(2,7).0(4,6)]heptane, are suitable as jet fuels.     

Mechanisms and kinetics of thermal degradation of poly(butylene succinate‐co‐propylene succinate)s

Poly(butylene succinate) (PBSu) and two PBSu‐rich poly(butylene succinate‐co‐propylene succinate)s were studied. Copolyesters were characterized as random copolymers, based on ¹³C‐NMR spectra. TGA‐FTIR was used to monitor the degradation products at a heating rate of 5°C/min under N₂. FTIR spectra revealed that the major products were anhydrides, which were formed following two cyclic intramolecular degradation mechanisms by the breaking of the weak O‐CH₂ bonds around succinate groups. Thermal stability at heating rates of 1, 3, 5, and 10°C/min under N₂ was investigated using TGA. The model‐free methods of the Friedman and Ozawa equations are useful for studying the activation energy of degradation in each period of mass loss. The results reveal that the random incorporation of minor propylene succinate units into PBSu did not markedly affect their thermal resistance. Two model‐fitting mechanisms were used to determine the mass loss function f(α), the activation energy and the associated mechanism. The mechanism of autocatalysis nth‐order, with f(α) = α^m(1 ? α)ⁿ, fitted the experimental data much more closely than did the nth‐order mechanism given by f(α) = (1 ? α)ⁿ. The obtained activation energy was used to estimate the failure temperature (T_f). The values of T_f for a mass loss of 5% and an endurance time of 60,000 h are 160.7, 155.5, and 159.3°C for PBSu and two the copolyesters, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A Comparative Study on the Aggregation and Thermodynamic Properties of Anionic Sodium Dodecylsulphate and Cationic Cetyltrimethylammonium Bromide in Aqueous Medium: Effect of the Co-solvent N-Methylacetamide

The effect of co‐solvent N‐methylacetamide (NMA) (0.035, 0.046, 0.127, and 0.258 mol kg^?1) on the micellization behaviour of anionic surfactant sodium dodecylsulphate (SDS) (3.21–10.35 mmol kg^?1) and cationic surfactant cetyltrimethylammonium bromide (CTAB) (0.19–3.72 mmol kg^?1) in aqueous solution was explored by employing conductivity measurements at different temperatures (298.15–313.15 K). The critical micelle concentration (CMC) values for SDS and CTAB in aqueous solutions of NMA were determined from the conductivity versus surfactant concentration plots. The variations in the CMC values of SDS with NMA concentration are in striking contrast to those observed in the case of CTAB. The various relevant thermodynamic parameters of micellization, viz. standard enthalpy change, ΔH_m^o, standard entropy change, ΔS_m^o, and standard Gibbs free energy change, ΔG_m^o, were determined using the temperature variation of the CMC values and counterion binding. The results not only relate these thermodynamic parameters to the consequences of intermolecular interactions but are also able to differentiate between SDS–water–NMA and CTAB–water–NMA systems in terms of contributions from head groups as well as alkyl chains of surfactants.     

Interaction Study of Anionic Surfactant with Aqueous Non‐Ionic Polymers from Conductivity,Density and Speed of Sound Measurements

In the present study, we have investigated in detail the interactions of the anionic surfactant sodium dodecyl sulfate (SDS) with aqueous polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP) and various PEG + PVP mixtures at 293.15, 303.15 and 313.15 K by applying conductivity, density and speed of sound techniques. From experimentally measured data, the critical micelle concentration (CMC) values, standard free energy of micellization (ΔG_m^o), standard enthalpy of micellization (ΔH_m^o), standard entropy of micellization (ΔS_m^o), isentropic compressibilities (κ_s), apparent molar volumes (?_v) and apparent molar isentropic compressions (?_k) of SDS in aqueous polymer mixtures have been calculated. The nature of the process of micellization has been evidenced from the magnitude of ΔG_m^o, ΔH_m^o and ΔS_m^o values. The trends of variations obtained in the various parameters have been explained in terms of the electrostatic as well as hydrophobic interactions pertaining in SDS?PEG/PVP?water systems.     

Adsorptive removal of dibenzothiophene from petroleum distillates using pomegranate leaf (Punica granatum) powder as a greener adsorbent

In this study, adsorption performance of pomegranate leaf powder (PLP) for the removal of dibenzothiophene (DBT) from petroleum distillates is presented. Morphology and elemental composition, surface chemistry, and textural property of the PLP were checked using scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), and N₂ physi-sorption at 77?K, respectively. Model oil contained 0.1?g DBT in 100?mL hexane was used for the performance evaluation and conducted in batch mode. The results show DBT removal of 70.55%, with the adsorbent retaining about 97.81% of its capacity after fourth cycle of usage. Results from SEM-EDX and FTIR indicate that DBT was adsorbed on the surface of PLP. Adsorption isotherm data fitted onto Freundlich and Langmuir isotherms models show very good coefficient of determination (R²) values of 0.9952 (for Langmuir) and 0.9979 (for Freundlich), indicating suitability of the models to describe the process. The adsorption kinetics of DBT onto PLP follows pseudo-second-order kinetics and the experimental q_e (53.66?mg/g) values obtained is very close to the model-estimated value q_e (55.55?mg/g). The negative value of ΔG^o and the positive values of ΔH^o obtained in the thermodynamic studies indicate that adsorption of DBT onto the PLP is an endothermic and spontaneous process at the temperatures studied.     

Process kinetics of UASB reactors treating non‐inhibitory substrate

The degradation of a non‐inhibitory substrate (sucrose) in upflow anaerobic sludge bed (UASB) reactors with different superficial flow velocites (u_s) was performed to generate experimental data. Additionally, a kinetic model accounting for the mass fraction of methanogens (f) and granule size distribution in UASB reactors is also proposed. At the volumetric loadings of 2.65–21.16 g COD dm^?3 day^?1, both the COD removal efficiency and granule size of the UASB reactors increase with increasing u_s. The f values determined experimentally increase from 0.13–0.24 to 0.27–0.43 if the volumetric loading is increased from 2.65 to 5.29 g COD dm^?3 day^?1. With a further increase in volumetric loading, the f values decline because of the accumulation of volatile fatty acids (VFAs). The predicted residual concentrations of VFAs and COD are in fairly good agreement with the experimental data. From the calculated effectiveness‐factor values, the influence of mass transfer resistance of the substrate sucrose on the overall substrate removal rate should not be neglected. From parametric sensitivity analyses together with the simulated concentration profiles, methanogenesis is the rate‐limiting step. Copyright © 2003 Society of Chemical Industry     

A Determination of the Hansen Solubility Parameters of Hexanitrostilbene (HNS)

The temperature‐dependent solubility of hexanitrostilbene (HNS) [CAS# 20062‐22‐0] was determined in ten solvents and solvent blends using the Tyndall effect. Thermodynamic modeling of the data yielded Flory interaction parameters, the molar enthalpy of mixing, the molar entropy of mixing, and the molar Gibbs energy of mixing. All solutions exhibited endothermic enthalpies and positive entropies of mixing. The presence of water in some of the solvent blends made dissolution increasingly endothermic and disfavored solubility. The solubilities of HNS at 25 °C were used to determine the three‐component Hansen solubility parameters (HSP) (δ_D=18.6, δ_P=13.5, δ_H=6.1 MPa^1/2) and the radius of the solubility sphere (R₀=5.8 MPa^1/2). The HSP determined for HNS using group‐additivity (δ_D=21.0, δ_P=13.3, and δ_H=8.6 MPa^1/2) also correctly predicted the optimum solvents for this explosive.     

Study of stability and thermodynamic properties for polychlorinated dihydrophezines by density functional theory

The thermodynamic properties of 76 polychlorinated dihydrophezines (PCDPs) in the gaseous state at 298.15 K and 101.325 kPa, have been calculated using the density functional theory (the BHANDHLYP/6‐31G*) with Gaussian 03 program. Based on these data, the isodesmic reactions were designed to calculate the standard formation heat (Δ_fH^θ), standard Gibbs free energy of formation (Δ_fG^θ) of PCDPs in the gaseous state. The relations of these thermodynamic parameters with the number and position of chlorine substituents (N_PCS) were discussed, and it was found that there exist good correlation between thermodynamic parameters, including heat capacity at constant volume , entropy (S^θ), enthalpy (H^θ), free energy (G^θ), Δ_fH^θ, Δ_fG^θ, and N_PCS. The relative stability order of PCDP congeners was theoretically proposed based on the relative magnitude of their Δ_fG^θ. In addition, the values of molar heat capacity at constant pressure (C_p,m) for PCDP congeners have been calculated.     

Calculation of the Detonation Velocities and Detonation Pressures of Dinitrobiuret (DNB) and Diaminotetrazolium Nitrate (HDAT‐NO3)

The enthalpies of combustion (Δ_combH) of dinitrobiuret (DNB) and diaminotetrazolium nitrate (HDAT‐NO₃) were determined experimentally using oxygen bomb calorimetry: Δ_combH(DNB)=5195±200 kJ kg⁻¹, Δ_combH(HDAT‐NO₃)=7900±300 kJ kg⁻¹. The standard enthalpies of formation (Δ_fH°) of DNB and HDAT‐NO₃ were obtained on the basis of quantum chemical computations at the electron‐correlated ab initio MP2 (second order Møller‐Plesset perturbation theory) level of theory using a correlation consistent double‐zeta basis set (cc‐pVTZ): Δ_fH°(DNB)=−353 kJ mol⁻¹, −1 829 kJ kg⁻¹; Δ_fH°(HDAT‐NO₃)=+254 kJ mol⁻¹, +1 558 kJ kg⁻¹. The detonation velocities (D) and detonation pressures (P) of DNB and HDAT‐NO₃ were calculated using the empirical equations by Kamlet and Jacobs: D(DNB)=8.66 mm μs⁻¹, P(DNB)=33.9 GPa, D(HDAT‐NO₃)=8.77 mm μs⁻¹, P(HDAT‐NO₃)=33.3 GPa.