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1.
Quantum yields () for the generation of singlet oxygen sensitized by Pd(II) complexes of water-soluble porphyrins: meso-tetrakis(4-N-methylpyridyl)porphine [PdTMPyP]4+ ( = 0.9), meso-tetrakis(4-N,N,N-trimethylaminophenyl)porphine [PdTTMAPP]4+ ( = 0.8), meso-tetrakis(4-carboxyphenyl)porphine [PdTCPP]4– ( = 0.7), and meso-tetrakis(4-sulfonatophenyl)porphine [PdTSPP]4– ( = 0.5) were determined using a chemical method. It was found that the dimerization and aggregation of metalloporphyrins greatly influence the value. The quantum yields evaluated for the formation of singlet oxygen sensitized by metalloporphyrin monomeric and dimeric forms are , M 0.9 and , D 0.2, respectively, and do not depend on the porphyrin nature.  相似文献   

2.
Zusammenfassung Es wird über die indirekte und die direkte VUV-Photolyse von luftfreiem Methanol in flüssiger Phase bei 1236 Å berichtet. Bei der Bestrahlung von wäßr. 0,01m-Methanol wurden folgende Produkte und Ausbeuten erhalten: (H2)=1,00, (HCHO)=0,27, (CH2OH)2=0,12, (CH2OH·CHO)=0,04 und (HCOOH)=0,02. Die Photolyse von flüssigem Methanol lieferte die gleichen Produkte, jedoch mit höheren Ausbeuten: (H2)=1,50, (HCHO)=0,98, (CH2OH)2=0,28 und (CH2OH·CHO)=0,06. Unter Anwendung von Methanol als Radikalfänger konnte auch die Quantenausbeute der Wasserphotolyse bei 1236 Å, (H,OH)=1,025 verifiziert werden. Wahrscheinliche Reaktionsmechanismen werden diskutiert.
V.U.V.-Photolysis of methanol at 1236 Å
The indirect and the direct v.u.v.-photolysis of air free methanol in liquid phase at 1236 Å is reported. After irradiation of aqueous 0.01M-methanol the following products were obtained: (H2)=1.00, (HCHO)=0.27, (CH2OH)2=0.12, (CH2OH·CHO)=0.04 and (HCOOH)=0.02. The photolysis of liquid methanol yielded the same compounds, however with higher amount as follows: (H2)=1.50, (HCHO)=0.98, (CH2OH)2=0.28 and (CH2OH·CHO)=0.06. Using methanol as a scavenger for the H and OH radicals the quantum yield of the water photolysis at 1236 Å could be verified to be (H,OH)=1.025. Probable reaction mechanisms are discussed.


Mit 3 Abbildungen

Herrn Prof. Dr.E. Broda zum 60. Geburtstag gewidmet.  相似文献   

3.
Zusammenfassung Das photochemische Verhalten von wässerigem Methanol, gesättigt mit Argon, CO bzw. O2 wurde bei 1470 Å als Funktion der VUV-Dosis und der Methanolkonzentration untersucht. Als Reaktionsprodukte wurden Wasserstoff, Formaldehyd, Glykolaldehyd, Glykol, Ameisensäure und in Gegenwart von Sauerstoff auch Peroxyd nachgewiesen. In 10–2 m-Methanol, gesättigt mit Argon, betrug (H2)=0,69 und (HCHO)=0,22, in Gegenwart von 7·10–4 m-CO war (H2)=0,10 und (HCHO)=0,29, während bei Sättigung mit O2 (10–3 mO2) (H2)=0,01, (HCHO)=0,33, (HCOOH)=0,20 und (H2O2)=0,22 gefunden wurde. Die -Werte der übrigen Produkte, die unter den angegebenen Bedingungen erhalten wurden, waren <0,07. Durch Erhöhung der Methanolkonzentration bis zu reinem Methanol, gesättigt mit Argon, stieg die Ausbeute von H2, HCHO und (CH2OH)2 entsprechend an, während die von HCOOH und CH2OHCHO sich praktisch nicht änderte. Bei reinem, mit Argon gesättigtem Methanol war (H2)=0,89 und (HCHO)=0,73. Das Glykol erreichte bei etwa 2m-Methanol eine Höchstausbeute von =0,38. Reaktionsmechanismen werden diskutiert.
Photochemical carbonylation and oxidation of aqueous methanol at 1470 Å
The photochemical behaviour of aqueous methanol saturated with argon, CO and O2, resp., has been investigated at 1470 Å as a function of the v.u.v. dose and the methanol concentration. Hydrogen, formaldehyde, glycolaldehyde, glycol, formic acid and, in the presence of oxygen, also peroxide were detected. In 10–2 M-CH3OH saturated with argon (H2)=0,69 and (HCHO)=0,22 were found; in the presence of 7·10–4 M-CO the yields are (H2)=0,10 and (HCHO)=0,29, whereas under saturation with oxygen (10–3 M O2) (H2)=0,01, (HCHO)=0,33, (HCOOH)=0,20 and (H2O2)=0,22. The quantum yields of all other products obtained under the conditions mentioned above are <0.07. With increasing methanol concentration up to pure argon saturated methanol, the quantum yields of H2, HCHO and (CH2OH)2 increase correspondingly, whereas the yields of HCOOH and CH2OHCHO remain practically unchanged. When irradiating pure, argon saturated methanol, (H2)=0,89 and (HCHO)=0,73 were found. A maximum yield of (CH2OH)2=0,38 was achieved using 2M-CH3OH. Reaction mechanisms are discussed.
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4.
The apparent equivalent volume V, expansibility E, and compressibility K of an artificial seawater solution containing10 ionic components (Na+, Mg2+, Ca2+, K+, Sr2+, Cl, SO 4 2– , HCO 3 , Br, and F) and one nonionic component (H3BO3) has been determined from0 to40°C (in5° intervals) and from0.1 to0.8 m ionic strength at1 atm. The concentration dependence (Iv=volume ionic strength) of the V's, E's, and K's have been examined by using a Masson-type equation, = ° +S'I V 1/2, and a Redlich-type equation, = ° +SI V 1/2 +BI V, where ° is the infinite-dilution value, S is the empirical Masson slope, S is the theoretical Debye-Hückel slope, and B is an empirical deviation constant. By using Young's rule, = Ei(i), the apparent equivalent volumes, expansibilities, and compressibilities for sea salt have been estimated from the ionic and nonionic components making up the mixture. The estimated apparent molal quantities agree very well with the directly measured values providing the concentration terms, S i and Bi, are weighted according to the methods of Wood and Reilly.Contribution Number 1599 from the University of Miami.  相似文献   

5.
Summary The following chromatographic variables are totally optimized based on the recently developed information theory of optimization: mobile phase composition, column length, flow rate, wavelength, and the amount of internal standard. The optimal internal standard is selected from among six candidates. Two types of optimal conditions (- and -optimals) are proposed: the -optimal is defined as the most precise analysis (the maximal ) while the -optimal is the most efficient (rapid) analysis (the maximal ). The observation times for the determination of an antipyretics mixture (three components) in liquid chromatography are ca. 50 s for the -optimal and ca. 8 min for the -optimal. The reliability of the - and -optimals is verified by experiments.  相似文献   

6.
A variational method is proposed which results in an approximate wave function for an excited state which has the maximum overlap with the true excited state eigenfunction. The method involves the calculation of the quantities E=¦H¦ and =¦(H-E)2¦, but is free of the constraint that the trial function must remain orthogonal to all states of the same symmetry which lie beneath it. One must know, however, an approximation to the true eigenvalue. A discussion is given on how one might gain the latter information, lacking knowledge of the spectrum, from the repeated application of the method.
Zusammenfassung Es wird eine Variationsmethode vorgeschlagen, die auf eins genäherte Wellenfunktion für einen angeregten Zustand führt, welche sich maximal mit der wahren Eigenfunktion des angeregten Zustandes überlappt. Die Methode ermöglicht die Berechnung der Größen: E=¦H¦ und =¦(H-E)2¦, ist aber frei von der Nebenbedingung, daß die Versuchsfunktion orthogonal zu allen benachbarten Zuständen mit derselben Symmetrie bleiben muß. — Man will jedoch eine Näherung des wahren Eigenwertes wissen. — Eine Diskussion darüber, wie man durch wiederholte Anwendung der Methode letztere Information gewinnen kann, ohne Kenntnisse über das Spektrum zu besitzen, wird durchgeführt.

Résumé Méthode variationnelle pour la détermination d'une fonction d'onde d'un état excité présentant le recouvrement maximum avec la fonction d'onde exacte. La méthode implique le calcul de E=¦H¦ et =¦(H-E)2¦ mais ne comporte pas la contrainte d'orthogonalité de la fonction d'essai à tous les états inférieurs de même symétrie. On doit cependant connaître une valeur approchée de la valeur propre exacte. Discussion sur la manière dont on peut obtenir cette valeur approchée sans connaître le spectre, par application répétée de la méthode.
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7.
The catalytic rearrangement of the cyclopentasiloxanes mD5-m, where represents a 3, 3, 3-trifluoropropyl(methyl)siloxane link and D a dimethylsiloxane link, and m=2–5 has been studied by the method described previously [1]. The rate of rearrangement and the rate of formation of a linear polysiloxane rise with an increase in m from 2 to 4. The equilibrium concentration of the linear polysiloxane formed from mD5-m and from mD4-m (m=0–4) [1] is inversely proportional to the molar fraction of links in the ring and rises with an increase in the total concentration of siloxane links in solution. Results have been obtained on the kinetics of the formation of the cyclosiloxanes mDn (where m=0–5, n=0–5, and m+n=3-6) during the rearrangement of the cyclopentasiloxanes mD5-m. It has been established that at equilibrium a mixture of cyclosiloxanes mDn containing practically constant ratios of tetramers, pentamers, and hexamers (m+n=4, 5, and 6) is obtained, regardless of the composition and structure of the initial cyclosiloxane and of the conditions of rearrangement (polymerization). The cyclopentasiloxanes mD5-m are less active in the process of rearrangement than the cyclotetrasiloxanes mD4-m. The activity of the cyclosiloxanes in rearrangement in the presence of a base rises in the sequence D4D3 2D3<3D2<4D < 2D2 < 3D.For part II, see [1].  相似文献   

8.
Ge K-edge and Mn K-edge EXAFS spectroscopy was used to study changes in the local environment of germanium and manganese atoms during radiolysis of the Ph3GeMn(CO)5 complex. On exposure to X-radiation, the metal complex undergoes a number of transformations depending on the radiant exposure (). It was shown that at = (6–8) × 106 J/m2, the initial metal complex decomposes into the [Ph3Ge] and [Mn(CO) n ] fragments with partial detachment of the CO groups from Mn atoms. When = 1.3 × 107 J/m2, Mn atoms lose completely the CO groups to form finely dispersed metal nanoparticles, which interact with the surrounding atoms (carbon or nitrogen). With further increase in , the local environment of the Mn atoms no longer changes. The Ge atoms remain coordinated to the Ph groups as increases up to 2 × 107 J/m2, but starting with = 1.6 × 107 J/m2, metal–metal bonds are formed; subsequently, the amount of this phase increases and when = 2.6 × 108 J/m2, it becomes predominant. Since manganese and germanium atoms lose their ligands at different values, one can conclude that germanium and manganese nanoparticles are the final products in the radiolysis of Ph3GeMn(CO)5.  相似文献   

9.
The ansatz = (1+1/2r12)+ with the bare nuclear (or screened nuclear) wave function and expanded in products of one-electron functions is explored for second-order perturbation theory and for variational calculations of the ground state of Helium-like ions.The energy increments E l (2) corresponding to the partial wave expansion of go asymptotically as l–8, while conventional partial wave increments go as l–4. is coupled to by a residual interaction U12 that has no singularity for r12=0. With the present ansatz it is sufficient to include l-values up to 5 in order to get the second-order energy accurate to one microhartree. For the same accuracy l4 is sufficient in a CI with correlated reference function while in conventional CI one must go to l50. The surprisingly faster convergence of the variational approach as compared to second-order perturbation theory is explained. The slow convergence of the traditional partial wave expansion is entirely due to the attempt to represent the quantity 1=¦r12r12 –1¦ by its partial wave expansion. The best reference function shows very little shielding and resembles closely the eigenstate of the bare nuclear Hamiltonian. The generalization to arbitrary systems is discussed and it is pointed out that the calculation of difficult integrals can be avoided without a significant loss in accuracy.  相似文献   

10.
Summary A chromatographic system set at an operating condition takes its own precision and efficiency which are numerically described by the information called FUMI and the information flow , respectively. Optimization for a variable such as mobile phase composition draws a line in the - space. This paper demonstrates that optimization of different variables displays different patterns of lines in the - space. The variables examined here are mobile phase composition, column length, flow rate (velocity) and detection wavelength (or the amount of internal standard). Clear difference in the analytical roles of the variables can be known from the - plots.  相似文献   

11.
In current textbooks fugacity is introduced according to its differential or integral mathematical formulation. In this article an alternative method of explanation is offered. It is suggested that the real state of a pure gas can be described by comparing it to a hypothetical idealized state. The differences between these two states can then be expressed in terms of a function, , defined as (T,P) = real(T,P) - ideal(T,P) where real and ideal are the chemical potentials of the gas in its real and ideal states, respectively. The function is a molar excess quantity and is expressed as (T,P) = RT1n where is the fugacity coefficient. This approach introduces fugacity deductively through the function, which leads to , the fugacity coefficient. This method is also appropriate for introducing the activity of solution components and the fugacity of a real gas in gaseous mixtures.  相似文献   

12.
Mathematical formalism of the low rank perturbation method (LRP) is applied to the vibrational isotope effect in the harmonic approximation. A pair of two n-atom isotopic molecules A and B which are identical except for isotopic substitutions at atomic sites is considered. Relations which express vibrational frequencies k and normal modes k of the perturbed isotopic molecule B in terms of the vibrational frequencies i and normal modes i of the unperturbed molecule A are derived. In these relations complete specification of the unperturbed normal modes i is not required. Only amplitudes | i of normal modes i at sites affected by the isotopic substitution are needed.  相似文献   

13.
The influence of the number of 3, 3, 3-trifluoropropyl(methyl)siloxane links (/) in the cyclotetrasiloxanes mD4-m, where D represents the dimethylsiloxane link and m=0–4, on the rearrangement of these compounds in acetone solution under the action of sodium siloxanolate has been studied. The rearrangement takes place with the formation of a linear polysiloxane the degradation of which yields, in addition to the initial ring, cyclosiloxanes with a different structure. The rate of rearrangement of mD4-m and of the formation of a linear polysiloxane rises with an increase in m from 0 to 3. The equilibrium concentration of the linear polysiloxane formed from mD4-m is inversely proportional to m. Results have been obtained on the kinetics of the formation of the cyclosiloxanes mDn, where m=0–5, n=0–5, and m+n=3–6, in the rearrangement of the rings D3, 2D2, 3D, and 4. The reactivity of the siloxane links rises in the sequence (CH3)2Si-O-Si(CH3)2 < (CF3CH2CH2)-(CH3) Si-O-Si(CH3)2 <(CF3CH2CH2) (CH3)Si-O-Si(CH3) (CH2CH2CF3) . Because of the negative inductive effect transferred through the siloxane links, the 3, 3, 3-trifluoropropyl groups strongly activate the siloxane ring with respect to nucleophiiic reagents.For part I, see [3].  相似文献   

14.
X-ray emission and EXAFS spectroscopies were used to examine changes in the nearest environment of manganese atoms upon radiolysis of [EtC5H4Mn(CO)2NO]+(PF6) at different energy exposures (). It was found that the initial complex loses the CO and NO ligands at = 4.5 × 106 J/m2. An increase in to 7.5 × 106 J/m2 gives rise to Mn–Mn bonds with lengths characteristic of Mn dimers. At = 9.0 × 106 J/m2, Mn nanoparticles are formed; they interact with the carbon atoms of EtC5H4 and the fluorine atoms of PF6 anions. Further increase in = 2.6 × 107 J/m2 yields manganese-containing nanoparticles structured like metallic Mn; their surface atoms interact with carbon atoms formed in the disintegration of the EtC5H4 ligands. The formation of manganese carbides and fluorides at = 2.6 × 108 J/m2 reduces the content of the metal constituent in nanoparticles; this content is zero at = 4.4 × 108 J/m2. The final radiolysis products are manganese carbides and fluorides (or fluorocarbides).  相似文献   

15.
A 2p STO may be replaced by a linear combination of 1s and 2s orbitals, = (1sA-1sf) + (2sA-2sB). Such a should improve LCAO-MO-SCF calculations in minimal STO basis set with simpler programs.  相似文献   

16.
Summary The role of the volume of the sample and the sample vial in equilibrium headspace-gas chromatography is discussed. A new term, thesample phase fraction (S) is introduced. It is shown that if the value of S is kept constant, the vial's volume has no influence on the sensitivity of the headspace analysis (which is proportional to the concentration of the analyte in the headspace). In a given headspace sampling system, concentration of the compound of interest in the headspace (c G * ) at equilibrium is related to the value of S: a higher S will increase c G * . However, the influence is important only in the case of low distribution coefficients: in the case of higher distribution coefficients this influence is negligible. This conclusion is also true for small changes in the sample volume in duplicate analyses: exact reproducibility of the sample volume is important only in the case of low distribution coefficient values.  相似文献   

17.
The quantum yields of formation of chloride ions were determined in photolysis (=254 nm) of watercarbon tetrachloride organic phase of CCl4(Cl)=0.89±0.04 water-chlorobenzene (PhCl(Cl)=0.137± ±0.005) two-phase systems and saturated aqueous solutions of carbon tetrachloride (CCl4(Cl)=18.9±5.6 and chlorobenzene PhCl(Cl)=0.56±0.03. The quantum yields of chloride ions obtained from these systems are compared with partial radiation yields in the same systems. A mechanism for formation of Cl ions is proposed.  相似文献   

18.
The temperature dependence of limiting apparent molal volumes ° in water for some alcohols (methanol, ethanol, 1-propanol, 2-butanol, 3-pentanol, 3-hexanol, 2,5-hexanediol, cyclopentanol, cyclohexanol, cycloheptanol, and 1,4-cyclohexanediol) and ethers (trimethylene oxide, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxepane, 1,3,5-trioxane, dimethoxymethane, 1,2-dimethoxyethane, diethoxymethane, and diethyl ether) has been studied in the temperature range 10–50°C by means of an automatic digital-readout dilatometer. Values of the thermal expansion coefficient * = (1/°)(°/T)p have been obtained at several temperatures and discussed together with literature data on expansibilities of related compounds. The data show a wide spectrum of values of * at low temperatures which is narrowed at the higher ones. The expansibilities of monofunctional alcohols increase with increasing temperature; the opposite effect is observed for polyhydric alcohols. The *'s of ethers are very slightly temperature dependent and are much higher, at low temperature, than those of alcohols having the same ratio ofn o/nc. These results are discussed in terms of solutewater interactions, and a possible interpretation is put forward.  相似文献   

19.
Density, heat capacity and surface tension measurements of sodium decylsulfate (NaDeS)-dodecyldimethylamine oxide (DDAO)-water mixtures were carried out as functions of the surfactants total molality mt at fixed stoichiometric mixture compositions XNaDeS. From the surface tension data, the critical micelle concentration of NaDeS-DDAO mixtures as a function of XNaDeS were obtained. From density and heat capacity data, the apparent molar volume V,2 and heat capacity C,2 of NaDeS-DDAO mixtures in water were calculated, respectively. At a given mole fraction, V,2 and C,2 monotonically increases and decreases, respectively, with increasing mt. However, anomalies were observed at XNaDeS=0.1 and 0.3 for both V,2 and C,2 vs. mt curves. The nonideal contributions to the thermodynamic properties for the formation of surfactant-surfactant mixed micelles in water by mixing aqueous solutions of pure NaDeS and DDAO micelles were calculated at 0.3 mol-kg–1 for the micellized surfactants mixture. The excess volume Vexc and heat capacity as functions of XNaDeS are concave and S-shaped curves, respectively. All the properties are compared to those for sodium dodecylsulfate-DDAO mixture. In addition, to clarify the effect of the change in the hydrophobicity of the surfactants mixtures Vexc for the dodecyltrimethylammonium bromide-decyltrimethylammonium bromide mixture were calculated from literature data.  相似文献   

20.
Inductively coupled, radiofrequency-induced plasmas of allyl amine, operated at low values of electrical power P/ monomer flow rate (P/), have been investigated using mass spectrometry (MS) and deposition rate measurements. The solid, plasma deposit products were obtained as films and analyzed by X-ray photoelectron spectroscopy (XPS) and grazing angle infra-red (IR). The positiveion MS data indicate that species of the general types (nM – H)+, (nM+H)+, and nM+, where M represents a unit of the starting material (monomer), are present in the plasma. The relative abundance of these was monitored as a function of the electrical power supplied to the plasma. Mass spectrometry of the plasma neutrals revealed that only M and its fragments are present in the plasma: no neutral oligomeric species were detected. XPS analysis revealed that the plasma deposits contain at least three different nitrogen functional groups. The relative proportions of these were only marginally affected by plasma power. The deposition rate increased with P/. The observation of three classes of species in the plasma-phase sets allyl amine apart from other compounds previously studied. We believe that the plasma-phase chemistry accounts for the low retention of amine in the solid-phase plasma product and for the weak dependence of deposit chemistry on P/.  相似文献   

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