Equilibrium conditions of clathrate hydrates formed from carbon dioxide and aqueous acetone solutions

Equilibrium conditions of clathrate hydrates formed from carbon dioxide and aqueous acetone solutions were experimentally measured at temperatures between 269.2 and 281.4 K and pressures up to 3.98 MPa. The acetone concentrations in solutions were investigated from 0.04 to 0.40 mass fractions. The experimental results suggested a transition in hydrate structure from structure I to another structure for acetone solutions between 0.04 and 0.12 mass fractions of acetone. The hydrate structure was suggested to be structure II which was the most stable with a 0.16 mass fraction acetone solution. For more than 0.16 mass fraction of acetone, the equilibrium conditions of the hydrate were shifted to lower temperatures as acetone concentrations increased.     

荧光光谱法测定多种复杂样品中的维生素B2

运用丙酮-(NH4)2SO4-H2O双水相萃取法对复杂样品进行预处理,然后用荧光光谱法在521nm处测量有机相的荧光强度,建立一种分离、测定复杂样品中维生素B<,2>的新方法.在最适条件下,该方法的线性范围为2.0×10<'-7>-1.4×10<'-2>mg/mL,检出限为1×10<'-6>mg/mL.该方法具有操作简...     

Acetone promoted 1,4-migration of an alkoxycarbonyl group on a syn-1,2-diamine

A 2-protected cis-amino mitosene undergoes an irreversible acetone promoted isomerization and converts to the 1-isomer. Kinetic studies and DFT calculations of the reaction are reported. An organocatalytic mechanism is proposed, involving a covalent intermediate formed by reaction of the mitosene and acetone.     

Y掺杂的ZnO纳米纤维材料的制备及其气敏传感器作用机理

采用静电纺丝法成功制备了Y掺杂的ZnO纳米纤维.并通过X射线衍射(XRD),扫描电子显微镜(SEM),能量色散X射线(EDX),透射电子显微镜(TEM)以及热重差热分析(TG-DTA)等手段对样品的结构和形貌进行了表征分析.同时用纯的ZnO和Y掺杂的ZnO纳米纤维制备了传感器,对浓度为(1-200)×10^-6 (体积分数)丙酮的气敏特性进行了测试分析.测试结果表明,可以通过简单控制纳米纤维中Y的含量,来微调该传感器的气敏特性.同时也发现通过Y掺杂, ZnO纳米纤维对丙酮的气敏特性有所改善,表现出很高的响应.纯ZnO和Y掺杂ZnO制成的传感器对几种潜在干扰气体表现出良好的选择性,比如氨气、苯、甲醛、甲苯以及甲醇.本文最后也讨论了该传感器的气敏作用机理.     

丙酮对Pd电极上异丙醇电氧化的毒化作用

采用循环伏安法和计时电流法研究了丙酮浓度和反应温度对Pd电极上异丙醇直接电氧化的影响. 研究发现, 丙酮对Pd电极上异丙醇电氧化存在严重的毒化作用, 并提出了其发生竞争吸附的毒化作用机理.     

A shock-tube and theory study of the dissociation of acetone and subsequent recombination of methyl radicals

The dissociation of acetone: CH₃COCH₃ → CH₃CO + CH₃, quickly followed by CH₃CO → CH₃ + CO, has been examined with Laser-Schlieren measurements in incident shock waves over 32-717 Torr and 1429-1936 K using 5% acetone dilute in krypton. A few very low pressure experiments (∼10 Torr) were used in a marginal effort to resolve the extremely fast vibrational relaxation of this molecule. This effort was partly motivated as a test for molecular, “roaming methyl” reactions, and also as a source of methyl radicals to test the application of a recent high-temperature mechanism for ethane decomposition [J.H. Kiefer, S. Santhanam, N.K. Srinivasan, R.S. Tranter, S.J. Klippenstein, M.A. Oehlschlaeger, Proc. Combust. Inst. 30 (2005) 1129-1135] on the reverse methyl combination. The gradient profiles show strong initial positive gradients and following negative values fully consistent with methyl radical formation and its following recombination. Thus C-C fission is certainly a large part of the process and molecular channels cannot be responsible for more than 30% of the dissociation. Rates obtained for the C-C fission show strong falloff well fit by variable reaction coordinate transition state theory when combined with a master equation. The calculated barrier is 82.8 kcal/mol, the fitted 〈ΔE〉_down = 400 (T/298) cm⁻¹, similar to what was found in a recent study of C-C fission in acetaldehyde, and the extrapolated k_∞ = 10^25.86 T^−2.72 exp(−87.7 (kcal/mol)/RT), which agrees with the literature rate for CH₃ + CH₃CO. Large negative (exothermic) gradients appearing late from methyl combination are accurately fit in both time of onset and magnitude by the earlier ethane dissociation mechanism. The measured dissociation rates are in close accord with one earlier shock-tube study [K. Sato, Y. Hidaka, Combust. Flame 122 (2000) 291-311], but show much less falloff than the high pressure experiments of Ernst et al. [J. Ernst, K. Spindler, H.Gg. Wagner, Ber. Bunsenges. Phys. Chem. 80 (1976) 645-650].     

Solid–liquid equilibria of the ternary system m-nitrobenzoic acid + p-nitrobenzoic acid + acetone

Solubility data and the density of equilibrium liquid phase for the ternary system m-nitrobenzoic acid + p-nitrobenzoic acid + acetone were determined at 283.1 K and 313.1 K, and the phase diagrams of the system were constructed. Two solid phases, pure solid m-nitrobenzoic acid and p-nitrobenzoic acid are confirmed by the Schreinemaker's wet residue method. The crystallization regions of m-nitrobenzoic acid and p-nitrobenzoic acid increase as the temperature decreases. At the same temperature, the crystallization region of p-nitrobenzoic acid is larger than that of m-nitrobenzoic acid.     

Towards hybrid silicon-organic molecular electronics: The stability of acetone on the Si(0 0 1) surface

We present the results of a combined study using scanning tunneling microscopy (STM) and density functional theory (DFT) of the interaction of acetone [(CH₃)₂CO] with the Si(0 0 1) surface. Three distinct adsorbate features were observed using atomic-resolution STM. One of the features appears as a bright protrusion located above a Si-Si dimer, while the other two are asymmetric about the dimer row and involve a second neighboring Si-Si dimer. One of the two asymmetric features has a protrusion located between the two dimers, while the other has a protrusion which is located at the site of a single dimer and exhibits a dimer sized depression on the adjacent dimer. DFT calculations have been performed for two structures; the four-membered ring structure and dissociation structure. Our calculations show that the bright single-dimer sized feature observed in the STM images could be attributed to either of these two calculated structures. However, neither of the two calculated structures can explain the appearance of the two-dimer wide asymmetric features observed in the experiment.     

Reactivity of silica-supported zirconium neopentyl fragments with trimethylphosphine and acetone: Formation of unexpected reaction products

The reactivity of trimethylphosphine with (SiO)_xZrNp_4−x species (x = 1-3) synthesized on silica dehydroxylated at various temperatures has been studied. Only the bi-grafted (SiO)₂ZrNp₂ complex reacts, leading to the formation of a surface alkylidene and evolution of neopentane. In presence of acetone the three neopentyl zirconium species react by the same way with evolution of neopentane and formation of enolate (SiO)_xZr[OC(CH₃)(CH₂)]_4−x species.     

Ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate,an efficient solvent for extraction of acetone from aqueous solutions

(Liquid + liquid) equilibrium (LLE) of the chemical system of {water + acetone + 1-Hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF₆) ionic liquid} was studied at different temperatures of (293.2, 298.2 and 303.2) K and under atmospheric pressure of 81.5 kPa. The results show that HMIMPF₆ provides the acetone distribution coefficient and separation factor values within (0.8813 to 1.2351) and (3.0 to 54.4), respectively; indicating the high capability of the ionic liquid for extraction of acetone from aqueous solutions. In most cases, acetone solubility in the ionic liquid is higher than in water, especially at higher solute concentrations. Meanwhile, higher separation factor is relevant to the lower temperature due to lower (water + ionic liquid) miscibility. The consistency of tie line data, at each temperature, was examined with Othmer–Tobias correlation. The values were nicely reproduced with the well-known NRTL and UNIQUAC models. Accordingly, the required thermodynamic properties of HMIMPF₆ were obtained by the Density Functional Theory (DFT) calculations, carried out at the M06/6-311++G⁷ level of theory. The root mean square deviations (RMSD) between experimental and model concentration values were 0.0192 and 0.0255, respectively; indicating close agreement of the both models.