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1.
G. Duplâtre L. M. Al-Shukri A. Haessler 《Journal of Radioanalytical and Nuclear Chemistry》1980,55(2):199-211
The rate constants for the reactions of positronium with halogen molecules and with halide ions in methanol (I2, Br2, Cl−, Br−) and in dimethylsulphoxide (I2, Cl−) have been measured. The variations of the ortho-positronium lifetime in mixtures of these solutes have been used for quantitative
determination of the formation constants of the corresponding polyhalides. These were found to be 2.9 and 5.4 M−1, respectively, for I2Cl− and I2Br− in methanol and 2.0 M−1 for I2Cl− in dimethylsulphoxide. Experiments on acidified AgClO4 solutions confirmed the formation, at molar concentrations, of the Ag2 ClO
4
+
species, very probably a triplet ion association. 相似文献
2.
Ashraf A. Mohamed 《Monatshefte für Chemie / Chemical Monthly》2001,132(8):919-928
Summary. A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The
method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H2O2. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of
H2O2. The optimum reaction conditions are TFP (0.4 × 10−3
M), H2SO4 (1.0M), H3PO4 (2.0M), and H2O2 (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm−3 and a detection limit of 0.04 ng ċ cm−3, based on the 3 Sb criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as
0.2, 1.0, 2.0, and 4.0 ng ċ cm−3 of I−, IO3
-, or IO4
- in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food
samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide
determination.
Received January 19, 2001. Accepted (revised) March 12, 2001 相似文献
3.
Süheyla Pura 《Journal of solution chemistry》2008,37(3):351-364
The equivalent conductivities of tris-(ethylenediamine)chromium complexes, [Cr(en)3]X3 (where X−= Cl−, Br−, I−; en = ethylenediamine) were measured as functions of temperature (278.15 to 328.15 K) and concentration [(1.948 ×10−4 to 10.728 ×10−4 mol⋅dm−3) and (2.282 ×10−4 to 11.246 ×10−4 mol⋅dm−3)] in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAC), respectively. Equivalent conductivity values for [Cr(en)3]X3 in DMF were found to be higher than those in DMAC. The conductivity data were analyzed with the Robinson-Stokes equations.
For [Cr(en)3]X3, the limiting equivalent ionic conductivities of [Cr(en)3]3+ and the ion-association constants (K
A) of the ion-pair between [Cr(en)3]3+ and the monovalent halide anions were determined in DMF and DMAC. The values of K
A for three complex salts in DMF were higher than those in DMAC. This can be ascribed to an increase of the ion-association
constants with a decrease of the relative permittivity of the solvents. The values of K
A at 298.15 K decreased in the order Cl−> Br−> I− in DMF and Cl−> I−> Br− in DMAC. The K
A
values for [Cr(en)3]Cl3 increased with increasing temperature in both DMF and DMAC. For [Cr(en)3]X3(X−= Br−, I−) in both solvents, this indicates increasing disorder occurs with increasing temperature.
Thermodynamic parameters (standard Gibbs energy, enthalpy and entropy changes) were determined from the temperature dependence
of K
A in DMF and DMAC. These parameters were inter-compared in their dependences on temperature and solvent. 相似文献
4.
Ashraf A. Mohamed 《Monatshefte für Chemie / Chemical Monthly》2001,56(2):919-928
A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H2O2. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of H2O2. The optimum reaction conditions are TFP (0.4 × 10−3 M), H2SO4 (1.0M), H3PO4 (2.0M), and H2O2 (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm−3 and a detection limit of 0.04 ng ċ cm−3, based on the 3 Sb criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as 0.2, 1.0, 2.0, and 4.0 ng ċ cm−3 of I−, IO3 -, or IO4 - in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide determination. 相似文献
5.
Kallol K. Ghosh Sancheeta Kolay Sunita Bal Manmohan L. Satnami Pierluigi Quagliotto P. R. Dafonte 《Colloid and polymer science》2008,286(3):293-303
The kinetics of the hydrolysis of p-nitrophenyl acetate (PNPA) and p-nitrophenyl diphenyl phosphate (PNPDPP) by hydroxamate ions mediated by gemini surfactants with quaternary ammonium bromide
(16-n-16,2Br−, n = 3, 4, 6, 12) and pyridinium chloride (12py-n-py12,2Cl−, n = 3, 4) head group have been investigated at 27 °C. The gemini surfactant with the pyridinium head group, 12-py-4-py12,2Cl− (tetramethylene-1,4 bis dodecylpyridinium chloride) shows a large rate acceleration effect than that with an ammonium head group, 16-12-16,2Br−, relative to those in water. The apparent pK
a of the hydroxamic acids have been determined in the presence of gemini surfactants. Catalytic system N-phenylbenzohydroxamate/12py-4-py12,2Cl− demonstrated over ~1,590-fold and ~255-fold rate enhancement in the hydrolysis of PNPA and PNPDPP, respectively, for the
identical reaction performed in buffer aqueous media at 27 °C. The second order rate constant and binding constants for reactions
were determined employing pseudophase model for micellar catalysis. 相似文献
6.
The adsorption of Cl−, Br−, and I− ions on the renewable liquid In-Ga and Tl-Ga electrodes from 0.1 M solutions in dimethyl formamide (DMF) is investigated
by using the method of differential capacitance measurements. The results are compared with similar data obtained on Hg and
Ga electrodes in DMF and with the corresponding data obtained in acetonitrile (AN). It is shown that, in DMF, the adsorption
parameters and the series of surface activity of halide ions (Hal−) significantly depend on the metal nature. In contrast to Hg electrode, on which the surface activity of halide ions increases
in the series: Cl− < Br− < I−, on In-Ga, as well as on the Ga electrode, it varies in the reverse order: I− < Br− < Cl−, whereas on the Tl-Ga electrode, partially reversed series of surface activity is observed: Br− < I− < Cl−. The results are explained within the framework of Andersen-Bockris model. An analysis of experimental results leads to the
following qualitative conclusions: (1) on the In-Ga and Tl-Ga electrodes, as well as on Ga electrode, free energy of metal-Hal− interaction (
$
\Delta G_{_{M - Hal^ - } }
$
\Delta G_{_{M - Hal^ - } }
) increases in series I− < Br− < Cl−; (2) for Cl−, Br−, and I−,
$
\Delta G_{_{M - Hal^ - } }
$
\Delta G_{_{M - Hal^ - } }
) grows in series Tl-Ga < In-Ga < Ga; (3) an absolute magnitude of $
\Delta G_{_{M - Hal_1^ - } } - \Delta G_{_{M - Hal_2^ - } }
$
\Delta G_{_{M - Hal_1^ - } } - \Delta G_{_{M - Hal_2^ - } }
(Hal1−, and Hal2− are any ions of Cl−, Br−, and I−) increases in series Hg < Tl-Ga < In-Ga < Ga; (4) the metal-DMF chemisorption interaction is much stronger than the metal-AN
interaction and increases in series Tl-Ga < In-Ga < Ga. 相似文献
7.
Adsorption of Cl−, Br−, and I− (Hal−) ions from their 0.1 M solutions in N-methylformamide, a solvent with the highest permittivity (182.4 at 25°C), at liquid
Ga-, (In-Ga)-, and (Tl-Ga)-electrodes with refreshable surface was studied by the measuring of differential capacitance and
by using an open-circuit jet electrode. It is shown that the adsorption parameters and the surface activity series depend
significantly on the metal nature. For the (In-Ga)- and (Tl-Ga)-electrodes, like for Hg-electrode, the halogenide-ion surface
activity increases in the following series: Cl− < Br− < I−; for the Ga-electrode, it varies in the opposite sequence: I− < Br− < Cl−. By example of the Ga-electrode in N-methylformamide, it is shown for the first time that the phenomenon of the surface activity
series reversal can be observed not only in aprotic solvents but also in protonic ones. The data obtained in N-methylformamide
is compared with that obtained in dimethyl formamide and acetonitrile. The halogenide-ion adsorption at the Ga-, (In-Ga)-,
and (Tl-Ga)-electrodes decreases in the series N-methylformamide < dimethyl formamide < acetonitrile. The results in aggregate
are explained in terms of the Andersen-Bockris model. The data obtained in N-methylformamide, dimethyl formamide, and acetonitrile
evidence the increase of ΔG
M-Hal
−in the series (Tl-Ga) < (In-Ga) < Ga, that is, with the increasing of the metal work function. This points out the donor-acceptor
nature of the metal-halogenide-ion interaction, in which the halogenide-ions are donors of electron pair with respect to the
metals. 相似文献
8.
R. S. Lokhande S. A. Parab 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(5):771-774
Ion exchange equilibrium constant (K) for Cl−/Br− and Cl−/C2O42− system was studied at different temperatures from 30 to 45°C. For both uni-univalent and uni-bivalent exchange systems, the
value of K increases with rise in temperature i.e., from 1.16 at 30°C to 2.95 at 45°C for Cl−/Br− system and 19.5 at 30°C to 30.0 at 45°C for Cl−/C2O42− system indicating the endothermic ion exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution.
The article is published in the original. 相似文献
9.
A novel dicalix[4]pyrrolyl-substituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye I with an absorption peak at approximately 670 nm and an emission peak at about 690 nm was prepared. As an anion receptor,
I displayed a red shift in absorption spectra and fluorescence quenching in varying degrees in the presence of F−, AcO−, H2PO4−, or Cl−. Compared with the parent calix[4]pyrrole, a representative anion receptor, I exhibited a stronger affinity to these anions due to the formation of a sandwich complex through multiple hydrogen-bonding
interactions. 相似文献
10.
The electrode characteristics and selectivities of PVC-based thiocyanate selective polymeric membrane electrode (PME) incorporating
the newly synthesized zinc complex of 6,7:14,15-Bzo2-10,11-(4-methylbenzene)-[15]-6,8,12,14-tetraene-9,12-N2-1,5-O2 (I
1
) and zinc complex of 6,7:14,15-Bzo2-10,11-(4-methylbenzene)-[15]-6,14-diene-9,12-dimethylacrylate-9,12-N2-1,5-O2 (I
2
) are reported here. The best response was observed with the membrane having a composition of I2:PVC:o-NPOE:HTAB in the ratio of 6:33:59:2 (w/w; milligram). This electrode exhibited Nernstian slope for thiocyanate ions over working concentration range of 4.4 × 10−7 to 1.0 × 10−2 mol L−1 with detection limit of 2.2 × 10−7 mol L−1. The performance of this electrode was compared with coated graphite electrode (CGE), which showed better response characteristics
w.r.t Nernstian slope 59.0 ± 0.2 mV decade−1 activity, wide concentration range of 8.9 × 10−8 to 1.0 × 10−2 mol L−1 and detection limit of 6.7 × 10−8 mol L−1. The response time for CGE and PME was found to be 8 and 10 s, respectively. The proposed electrode (CGE) was successfully
applied to direct determination of thiocyanate in biological and environmental samples and also as indicator electrode in
potentiometric titration of SCN− ion. 相似文献
11.
Electrochemical investigations of the reaction mechanism and kinetics between riboflavin immobilised on zirconium phosphate
(ZPRib) in carbon paste and NADH showed results yielding reliable information about aspects on the mechanism of the electron
transfer reaction between the flavin and NADH. The formal potential (E°′) of the adsorbed riboflavin was −220 mV versus SCE at pH 7.0. A shift about 250 mV towards a more positive potential compared
with its value in solution was assigned to the interaction between the basic nitrogen of riboflavin and the acid groups of
ZP. The invariance of the E°′ with the pH of the contacting solution and the effect of different buffer constituents were attributed to the protection
effect of ZP over the riboflavin. The electrocatalytic oxidation of NADH at the electrode was investigated using cyclic voltammetry
and rotating disk electrode methodology using a potential of −50 mV versus SCE. The heterogeneous electron transfer rate constant,
k
obs, was 816 M−1 s−1 and the Michaelis-Menten constant, K
M, was 1.8 mM (confirming a charge transfer complex intermediate in the reaction) for an electrode with a riboflavin coverage
of 6.8 × 10−10 mol cm−2. This drastic increase in the reaction rate between NADH and the immobilised riboflavin was assigned to the shift of the
E°′. A surprising effect with addition of calcium or magnesium ion to the solution was also observed. The E°′ was shifted to −150 mV versus SCE and the reaction rate for NADH oxidation increased drastically.
Received: 22 February 1999 / Accepted: 10 March 1999 相似文献
12.
S. Lokhande S. A. Parab 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(13):2346-2349
Determination of ion-exchange equilibrium constant (K) for Cl−/I− and Cl−/C2O42− system was studied at different temperatures from 25 to 45°C and by varying concentration of iodide and oxalate ion solution.
For both uni-univalent and uni-bivalent exchange systems, using 0.5 g of ion-exchange resin DUOLITE A-116 (in chloride form),
the value of K increases with rise in temperature i.e., from 13.0 at 25°C to 19.05 at 45°C for Cl−/I− system and 33.0 at 25°C to 63.0 at 45°C for Cl−/C2O42− system indicating the endothermic ion-exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution. 相似文献
13.
G. Duplatre L. M. Al-Shukri A. G. Maddock 《Journal of Radioanalytical and Nuclear Chemistry》1980,60(1):159-172
The rate constants for the reactions of positronium with I
3
−
, Br−, and I− in dimethylsulphoxide (DMSO) and for I
3
−
in water have been determined, and the orthopositronium lifetime variations have been used for studying polyhalide formation
in the (I2+Br−)/DMSO system. It is found that the formation of more than one polyhalide is needed to account for the data. On basis of this
new evidence, previous results in methanol and in DMSO are re-examined. Besides the primary I2X− (X−: halide), I2X
2
2−
complexes have to be invoked. Trial absorption measurements confirm the presence of solvolysis equilibria for I2 in DMSO. Taking these facts into account, much higher, albeit poorly defined, values than previously reported are found for
the I2X− formation constants. The reliable Kc values deduced are 28M−1, 0.57M−1 and 2.5M−1 respectively for I2Cl−, I2Cl
2
2
and I2Br
2
2−
in methanol, and 1.4M−1 and 0.8M−1, respectively for I2Cl
2
2−
and I2Br
2
2−
in DMSO. 相似文献
14.
The adsorption of Cl−, Br−, and I− ions from their 0.1 M solutions in dimethyl formamide at renewable liquid Hg- and Ga-electrodes was studied under similar
experimental conditions by the differential-capacitance and jet-electrode methods. The data obtained points out to a strong
effect of the metal nature on adsorption parameters and the halogenide-ion surface activity series. The halogenide-ion surface
activity at the Hg-electrode increased in the following sequence: Cl− < Br− < I−; at the Ga-electrode, in the reverse sequence: I− < Br− < Cl−. The results are explained qualitatively in terms of the Andersen-Bockris model. It follows from the obtained data that (1)
the free energy of the metal-halogenide-ion interaction increases in the following sequence: I− < Br− < Cl−; (2) the free energy of the Ga-halogenide-ion interaction exceeds that of the Hg−halogenide-ion interaction; and (3) the difference of the Cl−, Br−, and I− ions interaction with the metals increased significantly when passing from Hg− to Ga-electrode. 相似文献
15.
R. S. Lokhande P. U. Singare M. H. Dole 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(13):2313-2317
The study on thermodynamics of ion exchange equilibrium for uni-univalent Cl−/I−, Cl−/Br−, and uni-divalent Cl−/SO42−, Cl−/C2O42− reaction systems was carried out using ion-exchange resin Duolite A-113. The equilibrium constant K was calculated by taking into account the activity coefficient of ions both in solution as well as in the resin phase. The
K values calculated for uni-univalent and uni-divalent anion exchange reaction systems were observed to increase with rise
in temperature, indicating the endothermic exchange reactions having enthalpy values of 17.21, 36.60, 19.50, 18.43 kJ/mol
respectively. 相似文献
16.
Nilesh M. Vaghela Nandhibatla V. Sastry Vinod K. Aswal 《Colloid and polymer science》2011,289(3):309-322
The surface active and aggregation behavior of ionic liquids of type [C
n
mim][X] (1-alkyl-3-methylimidazolium (mim) halides), where n = 4, 6, 8 and [X] = Cl−, Br− and I− was investigated by using three techniques: surface tension, 1H nuclear magnetic resonance (NMR) spectroscopy, small-angle neutron scattering (SANS). A series of parameters including critical
aggregation concentrations (CAC), surface active parameters and thermodynamic parameters of aggregation were calculated. The
1H NMR chemical shifts and SANS measurements reveal no evidence of aggregates for the short-chain 1-butylmim halides in water
and however small oblate ellipsoidal shaped aggregates are formed by ionic liquids with 1-hexyl and 1-octyl chains. Analysis
of SANS data analysis at higher concentrations of [C8mim][Cl] showed that the microstructures consist of cubically packed molecules probably through π–π and hydrogen bond interactions. 相似文献
17.
Najoua Katif Rachel A. Harries Andrew M. Kelly John S. Fossey Tony D. James Frank Marken 《Journal of Solid State Electrochemistry》2009,13(10):1475-1482
The transfer of the α-hydroxy-carboxylates of glycolic, lactic, mandelic and gluconic acid from the aqueous electrolyte phase
into an organic 4-(3-phenylpropyl)-pyridine (PPP) phase is studied at a triple-phase boundary electrode system. The tetraphenylporphyrinato
complex MnTPP dissolved in PPP is employed to drive the anion transfer reaction and naphthalene-2-boronic acid (NBA) is employed
as a facilitator. In the absence of a facilitator, the ability of α-hydroxy-carboxylates to transfer into the organic phase
improves, consistent with hydrophobicity considerations giving relative transfer potentials (for aqueous 0.1 M solution) of
gluconate>glycolate>lactate>mandelate. In the presence of NBA, a shift of the reversible transfer potential to more negative
values is indicating fast reversible binding (the mechanism for the electrode process is EICrev) and the binding constants are determined as K
glycolate = 2 M−1, K
mandelate = 60 M−1, K
lactate = 130 M−1 and K
gluconate = 2,000 M−1. The surprisingly strong interaction for gluconate is rationalised based on secondary interactions between the gluconate
anion and NBA. 相似文献
18.
Functionalized polypyrrole films were prepared by incorporation of Fe(CN)6
3− as doping anion during the electropolymerization of pyrrole at a glassy carbon electrode from aqueous solution. The electrochemical
behavior of the Fe(CN)6
3−/Fe(CN)6
4− redox couple in polypyrrole was studied by cyclic voltammetry. An obvious surface redox reaction was observed and dependence
of this reaction on the solution pH was illustrated. The electrocatalytic ability of polypyrrole film with ferrocyanide incorporated
was demonstrated by oxidation of ascorbic acid at the optimized pH of 4 in a glycine buffer. The catalytic effect for mediated
oxidation of ascorbic acid was 300 mV and the bimolecular rate constant determined for surface coverage of 4.5 × 10−8 M cm−2 using rotating disk electrode voltammetry was 86 M−1 s−1. Furthermore, the catalytic oxidation current was linearly dependent on ascorbic acid concentration in the range 5 × 10−4–1.6 × 10−2 M with a correlation coefficient of 0.996. The plot of i
p versus v
1/2 confirms the diffusion nature of the peak current i
p.
Received: 12 April 1999 / Accepted: 25 May 1999 相似文献
19.
Xue-Fang Shang Xiu-Fang Xu Hai Lin Jie Shao Hua-Kuan Lin 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):275-281
A novel artificial receptor, (3′-nitrobenzo)[2,3-d]-(3′′-nitrobenzo)[9,10-d]-1,4,8,11-tetraazacyclotetradecane-5,7,12,14-tetraone,
has been synthesized and shows high selective and recognitive ability for F- among F−, Cl−, Br−, AcO−, H2PO4− by UV-vis and 1H NMR titration experiments. Theoretical investigations suggest that the fluoride selectivity among various anions comes from
the fact that the fluoride approaches much closer to the amide protons than other anions located above the cavity. The interaction
energies support the large binding ability difference between F− and Cl−/Br−/AcO−/H2PO4−. 相似文献
20.
Two multiamide calix[4]arenes (5, 6) were synthesized and characterized by NMR, MS and elemental analysis. The binding properties
of receptors with some anions (π-O2NPhOPO32−, π-O2NPhO−, H2PO4−, Ac−, Cl−, Br− and I−) were studied by UV-Vis spectra. The results indicate that the tetraamide calix[4]arenes (5, 6) have a good selectivity to
the anions containing aromatic ring (π-O2NPhOPO3
2−, π-O2NPhO−). The 1 : 1 complexes between host and guest were formed through multiple hydrogen bonding and π-π interactions. The hosts
5 and 6 also show a definite binding ability for the anions (H2PO4−, Ac−, Cl−) that have no ultraviolet absorption, which provides a simple method of spectrum detection for these anions. 相似文献