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The enthalpy of formation (ΔfH0) of molecules CH3-(CH2)n-CH2F, where 3≤n≤5, CH3-(CH2)n-CHF2 (3≤n≤4), CH2F-(CH2)3-CH2F, CHF2-(CH2)3-CHF2, CF3-(CH2)3-CHF2, CF3-(CH2)3-CF3, CHF2-(CH2)3-CH2F, CF3-(CH2)3-CH2F, fluorinated isobutane C4HmFk, where 0≤m≤9, k = 10-m, and neopentane C5HmFk, where 0≤m≤11, k = 12-m has been calculated by the G4 method. Within the ΔHf0 for molecules of fluoroethanes, fluorobutanes, and fluoropropanes this values has been formed learning sample, which totally includes 180 values. The calculation scheme for the enthalpy of formation of fluorine-containing molecules M have been proposed: ΔHf0add(M) = ΔHf0(R) + a∙ΔHf0(F-F)1,2 + b∙ΔHf0(F-F)1,3 + c∙ΔHf0(F-F)1,4, where ΔHf0(R) is contribution of group R into the enthalpy of formation (R = СH3, CH2, CH, С, CH2F, CHF2, CF3, CHF, CF2, CF), ΔHf0(F-F)1,2, ΔHf0(F-F)1,3, ΔHf0(F-F)1,4 are contributions of interaction of two fluorine atoms, which bounded with the carbon atoms from one, two and three С-С bounds, respectively, a, b, c are numbers of fluorine-fluorine interactions from one, two and three С-С bounds, respectively. All the group contributions have been computed. The comparison have been shown that new scheme is more effective than the simple group-additive methods.

In this work, the spherically propagating flame method was applied to the measurements of laminar flame propagation for the flame synthesis precursors. The laminar burning velocities of a typical precursor of silica nanoparticles, i.e. tetramethylsilane (TMS, Si(CH 3) 4), were measured, and a comparative study was carried out on its hydrocarbon counterpart, neopentane. The laminar burning velocities of the two fuels were measured at the initial pressure of 1 atm, initial temperature of 323 K and equivalence ratios of 0.7–1.5. The results show that the laminar burning velocities of TMS are much higher than those of neopentane, showing remarkable fuel molecular structure effects. Kinetic models of TMS and neopentane combustion were constructed and validated against the new experimental data in this work. Based on the rate of production analysis and sensitivity analysis, the critical pathways in the flames of TMS and neopentane were revealed. The fictitious diluent gas method was adopted to provide insight into the fuel molecular structure effects on the laminar burning velocities of TMS and neopentane. It is concluded that the relatively high adiabatic flame temperature of TMS is the driven force of the rapid laminar flame propagation of TMS compared with neopentane, while the chemical effect also promotes the laminar flame propagation of TMS, especially under near stoichiometric conditions. [ABSTRACT FROM AUTHOR]

• T-R FTIR spectroscopy of Neopentane. • Rovibrational analysis of obtained spectra in the MIR region. • Analysis by use of tensorial formalism based software. • New spectroscopic constants to be used for spectra simulations. High resolution (0.0014 cm−1) infrared spectra of neopentane (2,2-dimethylpropane) have been recorded at 203 K at the Canadian Light Source. Spectra were recorded in the infrared (8.3–6.4 μm) with 8 m of optical path. Neopentane is a spherical top molecule with T d (tetrahedral) symmetry. A low temperature is favorable for a detailed rotational analysis of its fundamental bands. This study focuses on the analysis of 3 band systems of neopentane. The first system is a dyad consisting of a ν 15 fundamental band and a ν 7 + ν 19 combination band located at 1472.5 and 1489 cm−1, respectively. The second system is a ν 16 fundamental band located at 1369.4 cm−1 with uncertain band origin. The third band system is a dyad of a ν 17 fundamental and a ν 8 + ν 18 combination band. Only the ν 17 fundamental band was analyzed in this last system due to the weaker intensity of the combination band. For all spectral simulations and calculations an 'XTDS' program based on tensorial formalism by the Dijon molecular spectroscopy group was used. A subprogram 'SPVIEW', paired with XTDS, was used for spectral assignment. [ABSTRACT FROM AUTHOR]

• High resolution absorption spectra of neopentane, C(CH 3) 4. • Cross sections for neopentane broadened by N 2. • Measurements performed for 203–294 K. • Useful for analysis of spectra of Titan. Spectra of neopentane, 2,2-dimethylpropane, C(CH 3) 4 , were recorded in the 1200–1650 cm-1 region by high resolution Fourier transform spectroscopy at the Canadian Light Source (CLS) and converted to absorption cross sections. Samples were at 203, 233, 266 and 294 K with 0, 10, 30 and 100 Torr of nitrogen broadening gas. The previously published cross sections in the CH stretching region (2550–3350 cm−1) [JQSRT 251, 107034 (2020)] were recalibrated and checked with two additional spectra recorded at Old Dominion University in the 1000–5000 cm−1 region. Local mode calculations for the CH stretching modes were carried out, and interactions with the overtones of the CH 2 scissor vibrations were included to obtain agreement with experiment. [ABSTRACT FROM AUTHOR]

• Bit metamorphism evaluation of biomarker thermodynamic stabilities. • Thermal stress influence on maturity parameters. • Identification of bit metamorphism from gas composition. In this study, the effects of drill-bit metamorphism (DBM) on oil in a kerogen-free system is examined to provide an insight into the relative thermodynamic stabilities of biomarkers and aromatic hydrocarbons, free from the contributions of newly generated hydrocarbons that complicate studies based on source rock intervals. Mud gas from the upper 20 m of fractured basement in the 25/8-19 A well of the Iving Discovery exhibits compositional variations attributable to DBM, such as abundant alkenes and neopentane, and C isotopic fractionation. Molecular, and particularly biomarker, distributions from corresponding core extracts are compared to those in unaltered test oil from immediately overlying Triassic sandstone, after normalization to diahopane, which is suggested to be relatively resistant towards thermal degradation. The variations in these relative abundances, determined by GC–MS analysis, correspond to some of the previously observed or theoretically postulated thermodynamic stability trends among biomarkers, such as depletion increasing with C-number among extended hopanes, and enrichment of rearranged vs regular hopanes. Some other trends are not as expected, such as the similar sensitivities of diasteranes towards removal as regular steranes, and greater depletion of short-chain triaromatic steroids compared to their C 26 –C 28 homologues. Triaromatic dinosteroids and their 28-nor counterparts are enriched relative to diahopane, whereas during normal maturation their concentrations have been found to decline towards the end of the oil window in a similar way to biomarkers in general. Among cheilanthanes, C 29 and C 30 members are particularly depleted when compared to C 28. Methylated naphthalenes are more readily removed than corresponding phenanthrenes and dibenzothiophenes, but all such polycyclic aromatics are at least as depleted as regular hopanes and steranes, suggesting a level of thermal destruction similar to that observed above ∼1.2% vitrinite reflectance under natural maturation conditions. The influence of oil-based mud (OBM) on core extracts is limited, although contributions are recognized for C 29 and C 30 17α-hopanes and 17β-moretanes, 5α,14α,17α-20 R isomer of the C 27 –C 30 steranes, C 20 and C 21 cheilanthanes, gammacerane and 3β-methyl-17α-hopanes. [ABSTRACT FROM AUTHOR]

This work reports a comparative study on jet-stirred reactor (JSR) pyrolysis of tetramethylsilane (TMS) and neopentane at 1.04 bar and 770–1070 K. Gas chromatography (GC) was used to detect pyrolysis products and measure their mole fraction profiles versus heating temperature. TMS was observed to decompose about 70 K later than neopentane, showing a slower reactivity than its hydrocarbon counterpart. Hydrocarbon products such as methane, ethylene, ethane and propene were detected in the TMS pyrolysis, while besides TMS, no other Si-containing species was observed. Methane, acetylene, ethylene and isobutene were observed as dominant products in the neopentane pyrolysis. The pyrolysis models of TMS and neopentane were developed and validated against the present data, as well as the previous pyrolysis data of TMS. The available rate constants of Si C bond dissociation reaction were evaluated based on the mole fraction profiles of TMS in the present and previous pyrolysis work over a wide temperature region. The influence of methane-elimination reactions on the decomposition of TMS and neopentane was also discussed. Rate of production (ROP) analysis and sensitivity analysis were performed to provide insight into the fuel decomposition chemistry in both the TMS and neopentane pyrolysis. The Si C/C C bond dissociation reactions and methane-elimination reactions were concluded to be the crucial fuel consumption pathways in both the TMS and neopentane pyrolysis. [ABSTRACT FROM AUTHOR]