Dissociation of benzene dication [C6H6]2+: exploring the potential energy surface

The singlet potential energy surface for the dissociation of benzene dication has been explored, and its three major dissociation channels have been studied: C6H6(2+) --> C3H3(+) + C3H3(+), C4H3(+) + C2H3(+), and C5H3(+) + CH3(+). The calculated energetics suggest that the products will be formed with considerable translational energy because of the Coulomb repulsion between the charged fragments. The calculated energy release in the three channels shows a qualitative agreement with the experimentally observed kinetic energy release. The formation of certain intermediates is found to be common to the three dissociation channels.     

The crystal structures of 1-allyl-1-bromo-3,4-benzo-1-telluracyclopentane [C8H8Te(C3H5)Br], 1-phenacyl-1-bromo-3,4-benzo-1-telluracyclopentane [C8H8Te(C8H7O)Br] and 1-deuteromethyl-1-iodo-3,4-benzo-1-telluracyclopentane [C8H8Te(CD3)I]; the trans effect in organotellurium bromides and iodides

The crystal structures of the title compounds have been determined from three-dimensional X-ray counter data.C₈H₈Te(CH₂CHCH₂)Br (I) is orthorhombic, space group Pbca with a 9.642(1), b 25.586(7), c 9.680(3) Å, Z = 8. The structure has been refined to R 5.2% for 1262 observed reflections.C₈H₈Te(CH₂COPh)Br (II) is orthorhombic, space group Pccn with a 23.593(6), b 14.337(3), c 9.180(2) Å, Z = 8. R = 5.5% for 1374 reflections.C₈H₈Te(CD₃)I (III) is orthorhombic, space group Pbca with a 11.200(3), b 15.976(2), c 23.328(3) Å, Z = 16. R = 5.6% for 2142 reflections.In I and II, tellurium is coordinated in an approximately octahedral geometry by the organic residues and three halogen contacts, with TeC and TeBr distances in the ranges 2.14(1)–2.19(1) Å and 3.328(2)–3.368(2) Å in (I) and 2.12(1)–2.18(1) Å and 3.292(2)–3.391(2) Å in II.In III, each of the two crystallographically independent complexes has tellurium coordinated in a distorted octahedral geometry. The TeC bond lengths are 2.10(2)–2.16(2) Å. In each case two TeI distances are in the range 3.596(2)–3.688(2) Å and a third, longer interaction (3.870(2) and 4.112(2) Å) completes the coordination.In each of the structures I–III the three covalent TeC bonds are oriented cis within the octahedra and exert a trans bond-lengthening effect on the Tehalogen interactions, precluding covalent-type bonding; the structures are essentially ionic, (C₈H₈TeR)⁺ cations and halide anions forming extended arrays.     

A comparative study on the synthesis of the 1H[1]benzothieno[2,3-d]-imidazole and 1H[1]benzothieno[2,3-d]-v-triazole

Alternate routes for the synthesis of the new title compounds are described. The experimental procedure for the isolation of the unstable 2,3-diaminobenzo[b]thiophene as the dichloride salt is presented.     

Isomerisation of hydrocarbon ions III–[C8H8]+·, [C8H8]2+, [C6H6]+· AND [C6H5]+ IONS

Collisional activation spectra of [C₈H₈]⁺·, [C₈H₈]²⁺, [C₆H₆]⁺· and [C₆H₅]⁺ ions from fifteen different sources are reported. Decomposing [C₈H₈]⁺· ions of ten of these precursors isomerise to a mixture of mainly the cyclooctatetraene and, to a smaller extent, the styrene structure. Three additional structures are observed with [C₈H₈]⁺· ions from the remaining precursors. [C₈H₈]^2+., [C₈H₈]⁺·, [C₆H₆]⁺· and [C₆H₅]⁺· ions mostly decompose from common structures although some exceptions are reported.     

The energy surface for isomeric [C2H3O]+ ions: Further experimental evidence

Mass spectra from collisionally activated dissociation (CAD) of [C₂H₃O]⁺ ions, including isotopically labeled analogs, provide further information on the isomers [CH₃C?O⁺] (a), [CH₂?C?O⁺H] (b), [⁺CH₂CH?O] (c) and (d). Our data generally support the recent conclusions from theory by Radom and coworkers and from experiment by Terlouw, Holmes and coworkers. Most acetyl-containing molecular ions form a ions in high purity only at low energies, consistent with isomerization of higher energy molecular ions to form the more stable enol which dissociates to b. Isomer d, prepared from (CICH₂)₂CHOH, undergoes facile hydrogen scrambling, presumably through a degenerate 1,2-hydrogen shift. Theory suggests that c undergoes spontaneous isomerization to a and d; although [C₂H₃O]⁺ ions from BrCH₂CHO appear to consist of a and ～15% d, the latter are formed without substantial hydrogen scrambling.     

Potential energy profiles for unimolecular reactions of organic ions: [C3H8N]+ and [C3H7O]+

The unimolecular decompositions of two isomers of [C₃H₈N]⁺, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} {\rm CH} = \mathop {\rm N}\limits^ + {\rm H}_2 $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} \mathop {\rm N}\limits^ + {\rm H = CH}_{\rm 2} $\end{document}, are discussed in terms of the potential energy profile over which reaction may be considered to occur. The energy needed to promote slow (metastable) dissociations of either ion is found to be less than that required to cause isomerization to the other structure. This finding is supported by the observation of different decomposition pathways, different metastable peak shapes for C₂H₄ loss, the results of ²H labelling studies, and energy measurements on the two ions. The corresponding potential energy profile for decomposition of the oxygen analogues, \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} {\rm CH}_{\rm 2} {\rm CH =\!= }\mathop {\rm O}\limits^ + {\rm H} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} \mathop {\rm O}\limits^ + {\rm = CH}_{\rm 2} $\end{document}, is compared and contrasted with that proposed for the [C₃H₈N]⁺ isomers. This analysis indicates that for the oxygen analogues, the energy needed to decompose either ion is very similar to that required to cause isomerization to the other structure. Consequently, dissociation of either ion is finely balanced with rearrangement to the other and similar reactions are observed. Detailed mechanisms are proposed for loss of H₂O and C₂H₄ from each ion and it is shown that these mechanisms are consistent with ²H and ¹³C labelling studies, the kinetic energy release associated with each decomposition channel, the relative competition between H₂O and C₂H₄ loss and energy measurements.     

A study of [C7H8]+˙ and [C7H8]2+ ions formed from different precursor molecules

On the basis of unimolecular and collisionally activated decompositions, as well as their charge stripping behaviour, [C₇H₈]⁺˙ and [C₇H₈]²⁺ ions from a variety of precursors have been studied. In particular, structural characteristics of molecular ions of toluene, cycloheptatriene, norborna-2,5-diene and quadricyclane have been compared to those of [C₇H₈]⁺˙ and [C₇H₈]²⁺ rearrangement fragment ions obtained from n-butylbenzene, 2-phenylethanol and n-pentylbenzene. Severe interferences from [C₇H₇]^2+˙ ion fragmentations have been observed and rationalized.     

Molar heat capacity and thermodynamic properties of 1-cyclohexene-1,2-dicarboxylic anhydride [C8H8O3]

The molar heat capacity C_p,m of 1-cyclohexene-1,2-dicarboxylic anhydride was measured in the temperature range from T=(80 to 360) K with a small sample automated adiabatic calorimeter. The melting point T_m, the molar enthalpy Δ_fusH_m and the entropy Δ_fusS_m of fusion for the compound were determined to be (343.46 ± 0.24) K, (11.88 ± 0.02) kJ · mol⁻¹ and (34.60 ± 0.06) J · K⁻¹ · mol⁻¹, respectively. The thermodynamic functions [H_(T)−H_(298.15)] and [S_(T)−S_(298.15)] were derived in the temperature range from T=(80 to 360) K with temperature interval of 5 K. The mass fraction purity of the sample used in the adiabatic calorimetric study was determined to be 0.9928 by using the fractional melting technique. The thermal stability of the compound was investigated by differential scanning calorimeter (DSC) and thermogravimetric (TG) technique, and the process of the mass-loss of the sample was due to the evaporation, instead of its thermal decomposition.     

Theoretical study on the [Si, C, N, O] potential energy surface

The structures, energetics, spectroscopies, and stabilities of the doublet [Si, C, N, O] radical are explored at the density functional theory and ab initio levels. Sixteen isomers are located, connected by 29 interconversion transition states. At the CCSD(T)/6-311+G(2df)//QCISD/6-311G(d)+ZPVE level, the lowest lying isomer is a linear SiNCO 1 (0.0 kcal/mol) mainly featuring a cumulene | . Si = N = C = O. The second and third low-lying isomers are bent OSiCN 2 (8.8) and bent OSiNC 3 (11.1), respectively. All the three low-lying isomers 1, 2, 3, and another high-lying species 5 (75.4) with a linear SiCNO structure are shown to have considerable kinetic stability and may be experimentally observable. The predicted results of isomers 1 and 2 are consistent with the previous mass spectrometry experiments. Moreover, the fourth low-lying species SiOCN 4 (23.9) with bent structure is expected to be observable in low-temperature environments. The bonding nature of the five isomers 1, 2, 3, 4, and 5 is analyzed. The calculated results are compared with those of the analogous molecules C(2)NO and Si(2)NO. Implications in interstellar space and N,O-doped SiC vaporization processes are also discussed.     

一个新的二维配位聚合物:{Cu_2[C_(10)H_8Cl_2NO_4]_2[C_(10)H_8N_2]_3}_n的合成及其晶体结构

采用铜(Ⅱ)盐和3,5-二氯水杨醛缩丝氨酸以及4,4′-联吡啶在乙醇水溶液中合成了具有二维层状的配位聚合物.通过元素分析、红外光谱对该配位聚合物进行了表征,并利用X射线单晶衍射仪对其结构进行了鉴定.晶体结构表明,该标题配合物属三斜方晶系,空间群C2/c,晶胞参数为a=2.711(3)nm,b=2.711(3)nm,c=4.977(5)nm;α=90.00°,β=90.00°,γ=120.00°,V=3.167 8 nm3,Z=18,Dc=1.173 g.cm-3,F(000)=11 448,μ=0.807 mm-1,R1=0.078 8,wR2=0.187 2.     

Study on kinetics of the pyrolysis process of aluminum sulfate

Abstract

Using high aluminum gangue as a raw material, aluminum sulfate 18 hydrate was made by the sulfuric acid leaching method under certain conditions. The product was characterized using X-ray diffraction (XRD) analysis of the phases, x-ray-fluorescence (XRF) analysis of the aluminum and sulfur content and thermogravimetric analysis of the crystallized water [Al₂(SO₄)₃·18H₂O]. Change characteristics of the crystal form and morphology during pyrolysis of octadecahydrate aluminum sulfate were studied by thermogravimetric Analysis (TGA), differential scanning calorimetry (DSC), differential thermogravimetry (DTG), XRD and scanning electron microscope (SEM). The theoretical basis for the preparation of metallurgical alumina from octadecahydrate aluminum sulfate was provided. According to the characteristics of the crystal structure change, the pyrolysis process of octadecahydrate aluminum sulfate can be separated into three stages. The first stage (dehydration stage 87–250?°C) had a weight loss rate of 40.5% and a loss of 15 water molecules; the weight loss rate of the second stage (dehydration stage 280–414?°C) was 8.1% with three water molecules lost; the weight loss rate of the third stage (decomposition stage 770–900?°C) was 36.1%, where three SO₃ molecules were lost. The pyrolysis products were mainly Al₂O₃. The activation energies of the three reaction stages were calculated using the Coats-Redfern method as 90.02?kJ/mol, 205.74?kJ/mol and 284.40?kJ/mol, respectively.     

Exploring new species on the [H,S, Se,Cl] potential energy surface

This investigation is concerned with the characterization of seleno‐sulfide‐halogen model systems, the isomerization processes, and the dissociation into diatomic fragment channels on the [H, S, Se, Cl] potential energy surface. Structural, energetic, and vibrational data were obtained at the CCSD(T) and MP2 levels of theory with the series of correlation consistent basis sets and extrapolated to the complete basis set (CBS) limit. For the frequencies, additional computations were performed to include the contribution of anharmonic effects, and for the determination of the heats of formation, important corrections incorporating core‐valence correlation effects and relativistic effects (scalar and spin‐orbit) were taken into account. CCSD(T)/CBS relative stability (kcal mol^?1) follows the order: HSSeCl (0.0), HSeSCl (8.80), SSeHCl (23.52), and SeSHCl (25.87). The cis‐rotational barrier for the two lowest isomers is practically identical (10.14 and 10.09 kcal mol^?1), whereas for the trans barrier, we obtained 9.25 (HSSeCl) and 8.45 (HSeSCl) kcal mol^?1. Dissociation of HSSeCl (HSeSCl) into HS (HSe) + SeCl (SCl) requires 59.70 (56.30) kcal mol^?1. For the most stable isomer, we predict a value of the heat of formation at 298.15 K of 2.53 kcal mol^?1. One of the outcomes of this research is that the MP2 results are consistent with those of CCSD(T). The MP2 method turns out to be a reliable alternative for a first exploration of larger catenated species, although it accounts for a lesser fraction of correlation effects. © 2012 Wiley Periodicals, Inc.     

The decompositions of metastable [C4H8O]+˙ ions and the [C4H8O]+˙ potential surface

Collisionally activated decomposition (CA) spectra of [C₄H₈O]⁺˙ ions and the products of their metastable decompositions are used to refine a previously presented picture of the reactions of [C₄H₈O]⁺˙ ions. Metastable [C₄H₈O]⁺˙ isomers predominantly rearrange to the 2-butanone ion and decompose by loss of methyl and ethyl, although up to 38% of the methyl losses take place by other pathways to form \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{2}} = {\rm{CHCH = }}\mathop {\rm{O}}\limits^{\rm{ + }} {\rm{H}}{\rm{.}} $\end{document} . The CA spectra of many of the [C₄H₈O]⁺˙ ions with the oxygen on the first carbon are very similar, consistent with those ions isomerizing largely to common structures before or after collision. However, several of these ions have unique CA spectra, so they must remain structurally distinct from the majority of the [C₄H₈O]⁺˙ ions below energies required for decomposition. The CA spectra of ions with the oxygen on the second carbon are distinct from those of ions with the oxygen on the first carbon, so there is limited interconversion of the non-decomposing forms of the two types of ions. A potential energy diagram for the reactions of metastable [C₄H₈O]⁺˙ ions is constructed from appearance energy measurements. As would be expected, the relative importances of most of the [C₄H₈O]⁺˙ isomerizations seem to be inversely related to the activation energies for those processes. Some parallels between the isomerizations of [C₄H₈O]⁺˙ ions and those of related ions are pointed out.     

阴离子开放骨架磷酸盐[A14P5O19(OH)][C6H18N2]和[Ga8P8PO32F5.5][C6H18N2]2[H30+]1.5水热合成中的对映体拆分

以外消旋的2-甲基-1,5-戊二胺(MPMD)为结构导向剂,在水热条件下合成出新磷酸铝化合物[Al4P5O19(OH)][C6H18N2](AlPO-MPMD)和新磷酸镓化合物[Ga8P8O32F5.5][C6H18N2]2[H30+]1.5(GaPO-MPMD).采用单晶x射线衍射结构分析、粉末x射线衍射分析(XRD)、热重-差热分析(TGA-DTA.A)、固体核磁共振(MAs NMR)、旋光分析(Optical rotation)以及振动圆二色光谱分析(Vibrational circular dichroism,VCD)等技术对产物进行了表征.对产物的VCD实验光谱和理论模拟光谱对比分析及旋光分析表明,在水热合成过程中,具有S构象的手性结构导向剂分子比具有R构象的手性结构导向剂分子更多地进入无机化合物骨架中,显示了手性对映体分子在该水热条件下的原位手性拆分.     

Monocarbaborane anion chemistry. The elusive C-arylated [PhCB11H11]-, [PhCB9H9]- and [PhCB8H8]- anions

B10H14 and PhCHO yield [6-Ph-nido-6-CB9H11]- (94%), from which the nine-vertex C-phenyl monocarbaborane anion [4-Ph-closo-4-CB8H8]- (68%) can be obtained by heating at 200 degrees C, and from which the twelve- and ten-vertex analogues [1-Ph-closo-1-CB11H11]- (50%) and [4-Ph-closo-4-CB9H9]- (25%) can be obtained by heating at 210 degrees C with BH3(NEt3).     

A concerted mechanism for uncatalysed transfer of carbon substituents from diimides to C = C and C[triple bond]C

We present high-level computational predictions regarding a novel uncatalysed, yet feasible, C-C bond forming reaction.     

Formation of N-butane in the pyrolysis of ethylene [1]

Yields of n-C₄H₁₀ have been measured from the flow pyrolysis of C₂H₄ at 897 (±7) K. From 77 to 720 Torr the order of n-C₄H₁₀ formation was found to be 2.0±0.3 The rate constant for the reaction, was estimated to be 2.4(±0.6)×10^–4l mol^–1s^–1.

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-C₄H₁₀ C₂H₄ 897 (±7) . -C₄H₁₀ 77 720 2.0±0.3. 2C₂H₄C₂H₃+C₂H₅ 2,4 (±0,6)×10^{–4 –1–1}.