Adsorption of Freon 113

Summary The adsorption of Freon 113 (1,1,2 trichloro-1,2,2 trifluoroethane) at 260–310 K on Graphon was measured and compared with the adsorption of krypton at 104–120 K on the same surface. The adsorption isotherms, and resulting thermodynamics, for both adsorbates were similar over the entire pressure range studied. Surface area analysis of the data suggests that the Freon molecule occupies approximately 2.5 times the area of the krypton molecule on Graphon. Further, the Freon molecules are hindered in their rotational freedom on this surface at these temperatures, with their dipole axes aligning perpendicular to the surface of the Graphon.

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Zusammenfassung Es wurde die Adsorption von Freon 113 (1,1,2 Trichlor-1,2,2 Trifluoräthan) an Graphon bei 260–310 °K gemessen und mit der Adsorption von Krypton bei 104–120 °K auf der gleichen Grenzfläche gemessen. Die Adsorptionsisothermen und die daraus resultierenden thermodynamischen Daten waren für beide Adsorbate im gesamten untersuchten Druckbereich ähnlich. Eine Analyse der Daten legt nahe, daß ein Freonmolekiil annähernd das 2,5fache der Fläche eines Kryptonmoleküls auf Graphon beansprucht. Es ist anzunehmen, daß die Freonmoleküle auf dieser Oberfläche und bei diesen Temperaturen in ihren Rotationsfreiheitsgraden gehindert sind und ihre Dipolachsen senkrecht zur Oberfläche liegen.

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With 9 figures and 2 tables     

Radiation synthesis of tetrafluoroethylene telomers with functional hydroxyl and amino end groups in Freon 113

The kinetics of radiation telomerization of tetrafluoroethylene in Freon 113 with ethanol and ammonia additives have been studied by kinetic calorimetry. Tetrafluoroethylene telomers with terminal hydroxyl and amino groups have been obtained. The molecular structure, properties, and composition of the telomers have been investigated by IR spectroscopy, thermogravimetry, and elemental analysis.     

Transformations and Tautomeric Equilibrium among Different Intermediates in Proline-Catalyzed Reactions of Aldehydes or Ketones

The enamines, iminium ions, and oxazolidinones are thought to be the key intermediates in the proline-catalyzed reactions of aldehydes or ketones, but there is an extensive contro-versy about their roles. Here, the corresponding transition states connecting any two of the three kinds of species are located at the ωB97XD/6-311++G** level of theory. The calcula-tions demonstrate that the oxazolidinones are the predominant species in both the gas phase and solvents; there exists tautomeric equilibrium among these species and the equilibriums are controlled by the employed solvents and temperature in the reaction. These results demonstrate that the concentration and role of the mentioned species are controlled by the employed solvent and temperature. A new reaction pathway is presented herein for the trans-formation between iminium ions and oxazolidinones through iminium ion-water complex and oxazolidinone-water complex. The calculations demonstrate that the rate-limiting step in proline-catalyzed Mannich reaction between acetaldehyde/keteones and N-Boc imines is the formation of the C-C bond rather than the intermediates tautomerization. These calcula-tions rationalize the available experimental observations and can be valuable in optimizing the experimental conditions of asymmetric organic-catalyzed reactions of aldehydes or ke-tones.     

Stereospecific Synthesis of Intermediates for 11-Aza-11-deoxy and 11-Azaprostaglandin Analogues from L-Arabinose

The syntheses of chiral synthons for 11-aza-11-deoxy and 11-azaprostanoids are described. The key intermediate in both routes was 5-O-benzoyl-3C-carboxymethyl-2,3-γ-lactone)-3-deoxy-α-L-lyxo-furanose which is readily available from L-arabinose.     

Electrochemical Catalysis of the Reduction of 1,1,2-Trifluorotrichloroethane (Freon 113) by Outer-Sphere Electron Transfer Mediators

Cyclic voltammetry and preparative electrolysis in DMF were used to study the electrochemical catalytic reduction of 1,1,2-trifluorotrichloroethane with aromatic electron transfer mediators (p-dicyanobenzene, p-diacetylbenzene, fluoranthen, perylene, and (E)-azobenzene), leading to trichloroethylene in high yield. The results of a kinetic study of these systems indicate that the efficiency of other mediators of this class may be estimated relative to their redox properties. In comparison with direct electrochemical reduction of Freon 113, the use of aromatic electron transfer agents significantly raises the efficiency of Freon conversion and permits us to perform the reaction at less negative potentials.     

Integrated band intensities of 1,1,1-trichlorotrifluoroethane,CFC113a,and 1,1,2-trichlorotrifluoroethane,CFC113

The integrated band intensities of 1,1,2-trichlorotrifluoroethane, CFC113, and 1,1,1-trichlorotrifluoroethane, CFC113a, have been measured, the latter for the first time. The former are in reasonable agreement with the reported results of Varanasi and Chudamani [J. Geophys. Res. 93, 1666 (1988)]. The total integrated intensities in the range 1300 to 700 cm⁻¹ are, respectively, 3218 and 3138 atm⁻¹ cm⁻². Attention is drawn to possible significant sources of error deriving from choices of band shape.     

Simultaneous determination of CFC-11, CFC-12 and CFC-113 in seawater samples using a purge and trap gas-chromatographic system

We have optimized the analytical parameters of a homemade instrument for the simultaneous measurement of the chlorofluorocarbons CCl₂F₂ (CFC-12), CCl₃F (CFC-11) and C₂Cl₃F₃ (CFC-113) in seawater. Seawater samples are flame sealed into 60 ml glass ampoules avoiding any contact with the atmosphere and stored in cold, dark condition until analysis. In the laboratory, after cracking the ampoule in an enclosed chamber filled with ultra-pure nitrogen, the seawater sample is transferred to a stripping chamber, where ultra-pure nitrogen is used to purge the dissolved CFCs from the seawater. The extracted gases are then cryogenically trapped, subsequently the trap is isolated and heated and the CFCs are transferred by a carrier gas stream into a precolumn and then are separated on a gaschromatographic packed column. To separate adequately CFC-12 from N₂O, during the early part of the chromatographic run, the gas stream passes through a molecular sieve, which is then isolated and backflushed. The CFCs are detected on an electron capture detector (⁶³Ni ECD). After a careful choice of the experimental conditions, the performances of the system were evaluated. The detection limits for seawater samples are: 0.0081 pmol kg⁻¹ for CFC-12, 0.0073 pmol kg⁻¹ for CFC-11 and 0.0043 pmol kg⁻¹ for CFC-113. The reproducibility of replicate samples lies within 5% for the three CFCs. The system has been successfully employed for CFC measurements in seawater samples collected in the Ross Sea (Antarctica) in the framework of the Italian Antarctic research project.     

Spectral,Optical, and Photocatalytic Characteristics of Quantum-Sized Particles of CdTe

Methods were developed for the synthesis of quantum-sized particles of CdTe, stabilized in aqueous solutions of thioglycolic acid, using H₂Te or NaHTe produced in situ by electrochemical reduction of tellurium. The spectral and optical characteristics of the synthesized CdTe nanoparticles were studied. It was found that they have photocatalytic activity in the reduction of methylviologen with sodium sulfite.     

样条变换集成罚函数偏最小二乘方法用于光谱数据重构和定量分析

针对高维小样本光谱数据所显现的函数型数据(Functional data)特性、与性质参数的非线性关系及变量间存有的严重共线性,采用了样条变换集成罚函数偏最小二乘回归新技术.它首先以三次B基样条变换实现非线性光谱数据的线性化重构,随后将重构的新光谱矩阵交由罚函数偏最小二乘法(Penalized PLS)构建其与性质参变量间的校正模型,其中罚函数中的光滑因子由交叉验证优化确定以调控模型的拟合精度.最后,通过小麦样品水分含量的近红外光谱定量分析,结果显示该技术光谱数据重构稳健,去噪明显,并有效解决高维小样本的过拟合和变量间的共线性,而预测集的均方根误差(RMSEP)为0.1808%,方法的非线性校正模型预测能力得到了明显提高.     

Mass Spectral Characteristics of Pivalolactone and Polypivalolactone

The mass spectral characteristics of pivalolactone and its polymer have been determined. The monomeric lactone (MW 100) shows no molecular ion peak but does show peaks at 70 and 42 m/e associated with the loss of formaldehyde and then carbon monoxide and at 56 and 41 associated with the loss of isobutene and carbon dioxide. Only weak peaks, corresponding to the presence of traces of oligomers, are observed above m/e 71. The polymer, at volatilization temperatures of 250-350°C, gives fragments of up to 1242 m/e with a pattern recurring over intervals of 100 m/e units. The principal peaks occur at X42, X70, X83, and X01 m/e. Above 301, the X42 and X70 peaks are observable up to X = 12. The X70 fragment is assigned an acylium isobutyrate radical ion structure and the X42 fragment is assigned an isobutyl radical ion structure. The degradation products are accounted for as being formed from volatilized cyclic oligomers.     

具有双光子吸收的咔唑类分子的设计、合成及光谱特性

设计、合成了四个新的咔唑类具有较大双光子吸收截面的化合物,研究它们的光谱特性,对双光子吸收的构效关系进行初步探索.     

氟里昂134a的真空紫外光电离和光解离的同步辐射研究

利用同步辐射真空紫外光研究了氟里昂134a(CH₂FCF₃)的光电离和光解离过程,通过测量各离子的光电离效率曲线,得到了该分子的电离能(12.68±0.04)eV和所有碎片离子的出现势,运用Gaussian-03计算了母体和中性碎片及相应离子的电子态、对称性和能量.结合理论计算结果对离子出现势的理论值和实验值进行了比较,分析了母体离子可能的光解离通道.     

Destruction of Freon HFC-134a Using a Nozzleless Microwave Plasma Source

In this paper, results of the pyrolysis of Freon HFC-134a (tetrafluoroethane C₂H₂F₄) in an atmospheric pressure microwave plasma are presented. A waveguide-based nozzleless cylinder-type microwave plasma source (MPS) was used to produce plasma for the destruction of Freon HFC-134a. The processed gaseous Freon HFC-134a at a flow rate of 50–212 l min⁻¹ was introduced to the plasma by four gas ducts which formed a swirl flow in the plasma reactor (a quartz cylinder). The absorbed microwave power was 0.6–3 kW. The experimental results showed that the Freon was converted into carbon black, hydrogen and fluorine. The total conversion degree of HFC-134a was up to 84% with selectivity of 100% towards H₂, F₂ and C₂, which means that there was no conversion of HFC-134a into other hydrocarbons. The Freon destruction mass rate and corresponding energetic mass yield were up to 34.5 kg h⁻¹ and 34.4 kg per kWh of microwave energy absorbed by the plasma, respectively.     

Low-temperature EPR study of radical cations of vinyl ethers in a Freon matrix

Using low-temperature EPR the transformations of radical cations of aliphatic vinyl ethers radiolytically generated in a Freon matrix have been investigated. Three-line spectra found at 77 K [hfs constants of 1.5 mT (1H) and 2.2 mT (1H)] and at 95 K [1.9–2.1 mT (2H)] were attributed to the radical cation. A quartet was observed at 130 K, usually with binomial intensities [hfs constants of 1.3 mT (3H)] and a triplet [1.7–1.9 mT (2H)] was found after cooling samples back to 95 K. The conversion of the quartet to the triplet was found to be thermally reversible and both spectra are assigned to different states of a (distonic) dimer cation.     

Spectral Properties and Photochromic Characteristics of Spiropyran Dyes

IntroductionSince the last decade, a large number of workshave concentrated on the photochromic behavior of in-dolinospirobenzopyran dyes[1—4]. Interest in these com-pounds has been concerned with the reversibility of thetransformation between the colorl…     

偶氮苯双亲化合物的合成及在其DMF中的光谱特性

以4-氨基苯甲酸乙酯为原料,通过重氮化-偶合等反应,设计合成了4-（4-辛烷氧基苯偶氮）苯甲酸钾（AZO-a）和4-（4-十四烷氧基苯偶氮）苯甲酸钾（AZO-b）等偶氮苯双亲化合物,其结构经¹H NMR和FT-IR确证。采用UV-Vis考察合成产物在N, N-二甲基甲酰胺（DMF）溶剂中紫外吸收影响。      

31P NMR Spectral Evidence for the Hexacoordinated Phosphorus Intermediates in the Reaction of Oxyphosphorochloridate With Amino Acids

Abstract

The nucleophilic groups on the side chain of amino acid can attack phosphoryl to form high-coordinated phosphorus intermediate. which was similar to the active sits of the CAMP-enzyme system [1, 2]     

Transformations in the dibenzo[a,d]cycloheptene series

The synthesis of 5-aminomethyl-5-hydroxy-5H-dibenzo[a,d]cycloheptene derivatives 3 was accomplished by two separate routes. The first route involves the reaction of 4 with Corey's Reagent followed by reaction with either amines or hydrazines. The reaction products with hydrazines (e.g. 6 ) were hydrogenolyzed, either with hydrogen in the presence of platinum, or with hydrazine in the presence of Raney nickel to yield 3 . The second route to these compounds ( 3 ) proceeds by a Reformatsky reaction on 4 followed by acid-hydrazide formation and Curtius degradation of 8 to afford spirooxazolidones 9 . Compounds 9 can be alkylated on nitrogen ( 10 ), and either 9 or 10 hydrolyzed to give the target compounds 3 .