<Emphasis Type="Italic">Ab initio</Emphasis> study of the reaction path of the reaction HNCO+CN

We report ab initio UMP2 calculations of the reaction of CN with HNCO using 6-311G(d,p) basis sets. The obtained results show that the reaction has two product channels: HNCO+CN→HCN+NCO (1) and HNCO+CN→HNCN+CO (2). Channel (1) is a hydrogen abstraction reaction, which is a concerted process. The calculated potential energy barrier is 20.80 kJ/mol at UMP2(full)/6-311G(d,p) level. In the range of reaction temperature (1000-2100 K), the conventional transition theory rate constant for channel (1) ranges from 0.32×10⁻¹¹ to 6.9×10⁻¹¹cm³· mol⁻¹· s⁻¹, which is close to the experimental value. Channel (2) is a stepwise reaction involving an intermediate during the process of reaction. The UMP2(full)/6-311G(d,p) potential energy barrier is 83.42 kJ/mol for the rate-controlling step, which is much higher than that of channel (1).     

Thermochemical Properties and Decomposition Kinetics of Ammonium Magnesium Phosphate Monohydrate

Ammonium magnesium phosphate monohydrate NH4MgPO4·H2O was prepared via solid state reaction at room temperature and characterized by XRD, FT-IR and SEM. Thermochemical study was performed by an isoperibol solution calorimeter, non-isothermal measurement was used in a multivariate non-linear regression analysis to determine the kinetic reaction parameters. The results show that the molar enthalpy of reaction above is （28.795 ± 0.182） kJ/mol （298.15 K）, and the standard molar enthalpy of formation of the title complex is （-2185.43 ± 13.80） kJ/mol （298.15 K）. Kinetics analysis shows that the second decomposition of NH4MgPO4·H2O acts as a double-step reaction： an nth-order reaction （Fn） with n=4.28, E1=147.35 kJ/mol, A1=3.63×10^13 s^-1 is followed by a second-order reaction （F2） with E2=212.71 kJ/mol, A2= 1.82 × 10^18 s^-1.     

Kinetics and mechanism of the reduction of monochloramine by hydroxylamine and hydroxylammonium ion

The kinetics and mechanism by which monochloramine is reduced by hydroxylamine in aqueous solution over the pH range of 5–8 are reported. The reaction proceeds via two different mechanisms depending upon whether the hydroxylamine is protonated or unprotonated. When the hydroxylamine is protonated, the reaction stoichiometry is 1:1. The reaction stoichiometry becomes 3:1 (hydroxylamine:monochloramine) when the hydroxylamine is unprotonated. The principle products under both conditions are Cl^–, NH⁺₄, and N₂O. The rate law is given by ?[d[NH₂Cl]/dt] = k₊[NH₃OH⁺][NH₂Cl] + k₀[NH₂OH][NH₂Cl]. At an ionic strength of 1.2 M, at 25°C, and under pseudo‐first‐order conditions, k₊= (1.03 ± 0.06) ×10³ L · mol^?1 · s^?1 and k₀=91 ± 15 L · mol^?1 · s^?1. Isotopic studies demonstrate that both nitrogen atoms in the N₂O come from the NH₂OH/NH₃OH⁺. Activation parameters for the reaction determined at pH 5.1 and 8.0 at an ionic strength of 1.2 M were found to be ΔH? = 36 ± 3 kJ · mol^–1 and Δ S? = ?66 ± 9 J · K^?1 · mol^?1, and Δ H? = 12 ± 2 kJ · mol^?1 and Δ S? = ?168 ± 6 J · K^?1 · mol^?1, respectively, and confirm that the transition states are significantly different for the two reaction pathways. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 124–135, 2006     

Mass spectrum and heat of formation of isocyanic acid. Production of [hco]+ from discrete electronic state of molecular ion

The appearance potentials for the transition ([HNCO]^+·→ [HCO]⁺ + N), determined for the reaction in the ion source and in the first field free region (15·84 and 15·52 eV) correspond, respectively, to the vertical and adiabatic third ionisation potential of HNCO, as determined by photoelectron spectroscopy. The formyl ion and nitrogen radical are formed in the ground state, which requires predissociation of a quartet molecular ion of HNCO. A heat of formation δHf(HNCO)g = ?25 ± 3 kcal mol^·1 was determined from the appearance potential and kinetic energy release for the metastable ion [HCO]⁺, and from the difference in appearance potentials for the ion [NH]⁺· produced from the isoelectronic molecules HNCO and HN₃.     

Theoretical investigation on identical anionic halide‐exchange SN2 reaction processes on N‐haloammonium cation NH3X+ (X = F,Cl, Br,and I)

CCSD(T) calculations have been used for identically nucleophilic substitution reactions on N‐haloammonium cation, X^? + NH₃X⁺ (X = F, Cl, Br, and I), with comparison of classic anionic S_N2 reactions, X^? + CH₃X. The described S_N2 reactions are characterized to a double curve potential, and separated charged reactants proceed to form transition state through a stronger complexation and a charge neutralization process. For title reactions X^? + NH₃X⁺, charge distributions, geometries, energy barriers, and their correlations have been investigated. Central barriers ΔE for X^? + NH₃X⁺ are found to be lower and lie within a relatively narrow range, decreasing in the following order: Cl (21.1 kJ/mol) > F (19.7 kJ/mol) > Br (10.9 kJ/mol) > I (9.1 kJ/mol). The overall barriers ΔE relative to the reactants are negative for all halogens: ?626.0 kJ/mol (F), ?494.1 kJ/mol (Cl), ?484.9 kJ/mol (Br), and ?458.5 kJ/mol (I). Stability energies of the ion–ion complexes ΔE_comp decrease in the order F (645.6 kJ/mol) > Cl (515.2 kJ/mol) > Br (495.8 kJ/mol) > I (467.6 kJ/mol), and are found to correlate well with halogen Mulliken electronegativities (R² = 0.972) and proton affinity of halogen anions X^? (R² = 0.996). Based on polarizable continuum model, solvent effects have investigated, which indicates solvents, especially polar and protic solvents lower the complexation energy dramatically, due to dually solvated reactant ions, and even character of double well potential in reactions X^? + CH₃X has disappeared. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Pyrolysis of vinylacetylene between 300 and 450°C

Vinylacetylene was pyrolyzed at 300–450°C in a packed and an unpacked static reactor with a pinhole bleed to a quadrupole mass spectrometer. The reactant and C₈H₈ products were monitored continuously during a reaction by mass spectrometry. In some runs, the products were also analyzed by gas chromatography after the run. In these runs CH₄, C₂H₆, C₃H₆, and C₂H₄ were also detected. The reaction for vinylacetylene removal and C₈H₈ formation is homogeneous, second order in reactant, and independent of the presence of a large excess of N₂ or He. However, C₈H₈ formation is about half-suppressed by the addition of the free-radical scavengers NO or O₂. The rate coefficient for total vinylacetylene removal is 1.7 × 10⁶ exp(?79 ± 13 kJ/mol RT) L/mol · s. The major reaction for C₄H₄ removal is polymerization. In addition four C₈H₈ isomers, carbon, and small hydrocarbons are formed. The three major C₈H₈ isomers are styrene, cyclooctatetraene (COT), and 1,5? dihydropentalene (DHP). The C₈H₈ compounds are formed by both molecular and free-radical processes in a second-order process with an overall k ? 3 × 10⁸ exp(?122 kJ/mol RT) L/mol · s (average of packed and unpacked cell results). The molecular process occurs with an overall k = 8.5 × 10⁷ exp (?118 kJ/mol RT) L/mol · s. The COT, DHP, and an unidentified isomer (d), are formed exclusively in molecular processes with respective rate coefficients of 4.4 × 10⁴ exp(?77 kJ/mol RT), 1.7 × 10⁵ exp(?89 kJ/mol RT), and 3.1 × 10⁹ exp(? 148 kJ/mol RT) L/mol · s. The styrene is formed both by a direct free-radical process and by isomerization of COT.     

Mutual combination of ClO radicals

The mutual combination reaction is proposed as the rate-limiting step in the removal of ClO radicals at moderate pressures. The third--order rate constants measured at room temperature were k₁(Ar) = 3.51 ± 0.14 × 10⁹ l²/mol²·ec; k₁(He) ≈ 2.8 × 10⁹ l²/mol²·sec, and k₁(O₂) ≈ 7.9 × 10⁹ l²/mol²·sec. There is also an independent second-order reaction for which k₃ ≈ 8 × 10⁶ l/mol·sec. A new absorption spectrum has been observed in the ultraviolet and attributed to Cl₂O₂. The extinction coefficient for Cl₂O₂ has been measured at six wavelengths, and, between 292 and 232 nm, it increases from 0.4 × 10³ to 2.9 × 10³ l/mol·cm. In the presence of the chlorine atom scavengers OClO or Cl₂O, Cl₂O₂ exists in equilibrium with ClO. The equilibrium constant Ke₁ = 3.1 ± 0.1 × 10⁶ l/mol at 298 K, and, with ΔS₁⁰ estimated to be ?133 ± 11 J/K·mol, ΔH₁⁰ = ?69 ± 3 kJ/mol and ΔH_f⁰(Cl₂O₂) = 136 ± 3 kJ/mol.     

The recombination of iodine atoms in the presence of nitric oxide

The recombination of iodine atoms following the flash photolysis of iodine in the presence of nitric oxide is interpreted through the mechanism with k₁ = 3.5 × 10⁹ l.²/mol²·sec; k₂ ≈ 1 × 10¹¹ l./mol·sec; k₃ = 2.1 × 10⁷ l./mol·sec at 298°K; E₃ = 11 kJ/ mol; and ΔH°₁ = 76 ± 6 kJ/mol. Lower and upper limits for the equilibrium constant are also established. The absorption spectrum of INO has been extended down to 223 nm and extinction coefficients for the region of 223–310 nm and 360–460 nm have been measured.     

Absolute rate constants for reactions of free radicals in the high-temperature photolysis of formamide vapor. Part I. Carbamyl radicals

The photolysis of formamide vapor at 2062 Å has been studied in a flow system with results essentially similar to those obtained previously under static conditions and higher conversions. The rotating-sector technique has been applied to the radical-chain decomposition of formamide under conditions (305°C, 11.5 torr) such that decomposition of the carbamyl (NH₂CO) radical was rate controlling, so that [NH₂CO] ? [NH₂]. A rate constant of (3.1 ± 1.0) × 10¹⁰(M·sec)^?1 was obtained for bimolecular chain termination by carbamyl radicals. A concurrent first-order radical loss, probably at the surface, was taken into account by the treatment described by Shepp. Both oxamide and HNCO were tentatively identified as termination products, suggesting the occurrence of both combination and disproportionation, but quantitative estimates of the relative rates were not possible. From the rate constant for chain termination, and relative rate constants obtained previously, Arrhenius parameters A_∞ = (5.9 ± 2.0) × 10¹² sec^?1 and A₀ = (1.04 ± 0.35) × 10¹⁴ (M·sec)^?1 were estimated for the unimolecular decomposition of carbamyl radicals in the high and low pressure limits.     

Rate constant and activation energy for the gaseous reaction between hydroxyl and formaldehyde

The rate constant k₄ has been measured at 268°, 298°, and 334° K for the reaction CH₂O + 2OH → CO + 2H₂O relative to that for OH + OH (k₂) by competition experiments in a discharge flow tube using mass-spectrometric analysis. Based on k₂ = 2.24 × 10^?12cm³/molec·sec at 298°K and E₂ = 4 kJ/mol, k₄ = (6.5 ± 1.5) × 10^?12cm³/molec·sec at 298°K and E₄ = (6 ± 2)kJ/mol.     

碳酸盐共沉淀法可控制备超高倍率锂离子电池正极材料LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2

采用碳酸盐共沉淀法通过调节NH_3·H_2O用量来实现可控制备超高倍率纳米结构LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料。NH_3·H_2O用量会对颗粒的形貌、粒径、晶体结构以及材料电化学性能产生较大的影响。X射线衍射(XRD)分析和扫描电镜(SEM)结果表明,随着NH_3·H_2O用量的降低,一次颗粒形貌由纳米片状逐渐过渡到纳米球状,且nNH_3·H_2O∶(nNi+nCo+nMn)=1∶2样品晶体层状结构最完善、Li~+/Ni~(2+)阳离子混排程度最低。电化学性能测试结果也证实了nNH_3·H_2O∶(nNi+nCo+nMn)=1∶2样品具有最优异的循环稳定性和超高倍率性能。具体而言,在2.7~4.3 V,1C下循环300次后的放电比容量为119 m Ah·g~(-1),容量保持率为81%,中值电压基本无衰减(保持率为97%)。在100C(18 Ah·g~(-1))的超高倍率下,放电比容量还能达到56 m Ah·g~(-1),具有应用于高功率型锂离子电池的前景。此NH_3·H_2O比例值对于共沉淀法制备其他高倍率、高容量的正/负极氧化物材料具有一定的工艺参考价值。     

Ab initio potential energy surface and excited vibrational states for the electronic ground state of Li2H

A 285-point multi-reference configuration-interaction involving single and double excitations (MRS-DCI) potential energy surface for the electronic ground state of Li₂H is determined by using 6-311G (2df, 2pd) basis set. A Simons-Parr-Finlan polynomial expansion is used to fit the discrete surface with a X² of 4.64 × 10^-6. The equilibrium geometry occurs at R_e =0.172 nm and <LiHLi =94.10. The dissociation energy for reaction Li₂H(²A)⇑ Li₂(¹⌆_g)+H(²S) is 243.910 kJ/mol. and that for reaction Li₂H(²A)⇑HLi(¹be)+Li(²S) is 106.445 kJ/mol. The inversion barrier height is 50.388 kJ/mol. The vibrational energy levels are calculated using the discrete variable representation (DVR) method. Project supported by the National Natural Science Foundation of China (grant No. 29673029) and by the Special Doctoral Research Foundation of the State Education Commission of China.     

Determination of hemoglobin at a novel NH2/ITO ion implantation modified electrode

A novel electrode was prepared by implanting NH₂ ⁺ into an ITO film (NH₂/ITO). Gold nanoparticles were deposited on the surface of NH₂/ITO electrode. The NH₂/ITO and Au/NH₂/ITO electrodes were used to determine hemoglobin (Hb) immobilized on the electrodes surfaces. The relationship of the reductive peak current value of Hb among different electrodes was: Hb/ITO:Hb/Au/ITO:Hb/NH₂/ITO:Hb/Au/NH₂/ITO=1:1.5:2:4. The linkage between the –NH₂ implanted into ITO film and the –COOH of Hb was recognized to be the reason for the increase of active Hb coverage on NH₂/ITO electrode compared with the ITO electrode. Increase of active Hb coverage on Au/NH₂/ITO compared with Au/ITO was attributed to the different amount of gold nanoparticles deposited. The determination of Hb at an Au/NH₂/ITO electrode was optimized. Calibration curve was obtained over the range of 1.0 × 10⁻⁸ – 1.0 × 10⁻⁶ mol · L⁻¹ with a detection limit of 1.0 × 10⁻⁸ mol · L⁻¹. Results showed that the novel NH₂/ITO and Au/NH₂/ITO electrodes exhibited good stability, reproducibility besides better electrochemical performance. Correspondence: Jing Bo Hu, Department of Chemistry, Beijing Normal University, Beijing 100875, China     

碳酸盐共沉淀法可控制备超高倍率锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2

采用碳酸盐共沉淀法通过调节NH₃·H₂O用量来实现可控制备超高倍率纳米结构LiNi_1/3Co_1/3Mn_1/3O₂正极材料。NH₃·H₂O用量会对颗粒的形貌、粒径、晶体结构以及材料电化学性能产生较大的影响。X射线衍射（XRD）分析和扫描电镜（SEM）结果表明,随着NH₃·H₂O用量的降低,一次颗粒形貌由纳米片状逐渐过渡到纳米球状,且n_NH3·H2O：（n_Ni+n_Co+n_Mn）=1：2样品晶体层状结构最完善、Li⁺/Ni²⁺阳离子混排程度最低。电化学性能测试结果也证实了n_NH3·H2O：（n_Ni+n_Co+n_Mn）=1：2样品具有最优异的循环稳定性和超高倍率性能。具体而言,在2.7~4.3 V,1C下循环300次后的放电比容量为119 mAh·g^-1,容量保持率为81%,中值电压基本无衰减（保持率为97%）。在100C（18 Ah·g^-1）的超高倍率下,放电比容量还能达到56 mAh·g^-1,具有应用于高功率型锂离子电池的前景。此NH₃·H₂O比例值对于共沉淀法制备其他高倍率、高容量的正/负极氧化物材料具有一定的工艺参考价值。     

Why is N···Be distance of NH3H+···DBeH shorter than that of NH3D+···HBeH? paradoxical geometrical isotope effects for partially isotope‐substituted dihydrogen‐bonded isotopomers

The partial isotope substitution for the change of geometrical parameters, interaction energies, and nuclear magnetic shielding tensors (σ) of dihydrogen‐bonded NH₃X⁺···YBeH (X, Y = H, D, and T) systems is analyzed. Based on the theoretical calculation, the distance between heavy atoms R_N···Be of NH₃H⁺···DBeH is clearly found to be shorter than that in NH₃D⁺···HBeH. Such apparently paradoxical geometrical isotope effect (GIE) on R_N···Be is revealed by the cooperative effect of two kinds of (1) primary covalent‐bonded GIE and (2) secondary dihydrogen‐bonded one. We have demonstrated that (1) the covalent bond lengths become shorter by heavier isotope‐substitution and (2) the dihydrogen‐bonded distance R_X···Y becomes shorter by heavier Y and lighter X isotope‐substitution due to the difference of electronic structure reflected by the nuclear distribution. We have also found that interaction energy of NH₃H⁺···DBeH is stronger than that of NH₃D⁺···HBeH and isotopic deshielding effect of magnetic shielding becomes large in lighter isotope. © 2013 Wiley Periodicals, Inc.     

Dy(Tyr)(Gly)3Cl3·3H2O的热化学和热分解动力学研究

以氯化镝、甘氨酸和L-酪氨酸为原料合成了配合物Dy(Tyr)(Gly)₃Cl₃·3H₂O. 用溶解-反应热量计测得配合物在298. 15K时的标准摩尔生成焓为–(4287. 10±2. 14) kJ / mol. 并用TG-DTG技术对配合物进行了非等温热分解动力学研究, 推断出配合物第二步热分解反应的动力学方程为: dα/dT＝3. 14 ×10²⁰ s^-1/βexp(-209. 37 kJ / mol /RT)(1-α)².     

The Protonation of Acetamide and Thioacetamide in Super­acidic Solutions: Crystal Structures of [H3CC(OH)NH2]+AsF6– and [H3CC(SH)NH2]+AsF6–

Acetamide and thioacetamide react with the superacid solutions HF/MF₅ (M = As, Sb) under formation of the corresponding salts [H₃CC(OH)NH₂]⁺MF₆^– and [H₃CC(SH)NH₂]⁺MF₆^– (M = As, Sb), respectively. The reaction of DF/AsF₅ with acetamide and thioacetamide lead to the corresponding deuterated salts [H₃CC(OD)ND₂]⁺AsF₆^– and [H₃CC(SD)ND₂]⁺AsF₆^–, respectively_. The salts are characterized by vibrational and NMR spectroscopy, and in the case of [H₃CC(OH)NH₂]⁺AsF₆^– and [H₃CC(SH)NH₂]⁺AsF₆^– also by single‐crystal X‐ray analyses. The [H₃CC(OH)NH₂]⁺AsF₆^– ( 1 ) salt crystallizes in the triclinic space group P$\bar{1}$ with two formula units per unit cell, and the [H₃CC(SH)NH₂]⁺AsF₆^– ( 2 ) salt crystallizes in the monoclinic space group P2₁/c with four formula units per unit cell. In both crystal structures three‐dimensional networks are observed which are formed by intra‐ and intermolecular N–H ··· F and O–H ··· F or S–H ··· F hydrogen bonds, respectively. For the vibrational analyses, quantum chemically calculated spectra of the cations [H₃CC(OH)NH₂ · 3HF]⁺ and [H₃CC(SH)NH₂ · 2HF]⁺ are considered.     

Ab initio study on the mechanism of reaction HNCO+NH_2

Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that the reactions have two product channels: NH2+ HNCO→NH3+NCO (1) and NH2+HNCO-N2H3+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48 kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300-2700 K, transition theory rate constant for reaction (1) is 1.68 × 1011- 3.29 × 1011 mL · mol-1· s-1, which is close to the experimental one of 5.0 ×1011 mL× mol-1· s-1 or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes, cis and trans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (for cis-mode) and 147.43 kJ/mol (for trans-mode), respectively, which is much higher than     

[Mn(H_2P_2O_7)_3]~(3-)引发淀粉与丙烯腈接枝聚合反应的动力学研究

以[Mn(H_2P_2O_7)_3]~(3-)为引发剂,研究了丙烯腈与玉米淀粉的接枝共聚反应。由实验结果求出了反应速率与引发剂浓度、单体浓度、淀粉浓度和反应温度的关系,推导并验证了接枝反应动力学模型,探讨了反应机理,求得了接枝反应活化能。     

Mechanism of Ethylene Migratory Insertion and Dimerization Catalyzed by δ‐Alkyl Platinum Complexes–A DFT Study

The mechanism of ethylene insertion reactions catalyzed by cationic δ‐alkyl platinum complexes has been studied at the B3LYP level of density functional theory. The initial steps of the reactions proceed via the coordination of ethylene to the reactants L₂Pt(II)R⁺, where L₂=none, (NH₃)₂, (CHNH)₂; R=H, CH₃, C₂H₅ in which ethylene coordinates strongly to the complexes PtCH⁺₃ and PtC₂H⁺₅ (coordination energies (CE) are 296.52 and 229.28 kJ/mol, respectively), while nitrogen‐containing ligands decrease the energies: Pt(NH₃)₂CH⁺₃ (CE: 180.04 kJ/mol), Pt(NH₃)₂C₂H⁺₅ (CE: 97.86 kJ/mol), Pt(CHNH)₂CH⁺₃ (CE : 176.31 kJ/mol) and Pt(CHNH)₂C₂H⁺₅ (CE: 91.00 kJ/mol). Moreover, ethylene insertion into the Pt‐alkyl bond, which is the rate‐determining step, is endothermic with barrier heights for L₂PtCH₃(C₂H₄)⁺ decreasing in the order: PtCH⁺₃ (164.18 kJ/mol)>(NH₃)₂ PtCH⁺₃ (129.95 kJ/mol)>(CHNH)₂ PtCH⁺₃ (115.27 kJ/mol), which has the same tendency for the ethyl case. The insertion product will continually undergo β‐hydride elimination, which is exothermic. On the other hand, the effects of solvent (dichloromethane, THF and benzene) are investigated with PCM method, but the inclusion of the effects in the computations only slightly affects the results. Beside that, a complete catalytic cycle for ethylene dimerization is studied in detail and the calculations agree well with known energetic and recognized tendencies.