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1.
The standard enthalpies of formation of alkaline metals thiolates in the crystalline state were determined by reaction-solution
calorimetry. The obtained results at 298.15 K were as follows:
\Updelta \textf H\textm\texto (\text MSR, \text cr) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} ({\text{MSR,}}\;{\text{cr}}) /kJ mol −1 = −259.0 ± 1.6 (LiSC 2H 5), −199.9 ± 1.8 (NaSC 2H 5), −254.9 ± 2.4 (NaSC 4H 9), −240.6 ± 1.9 (KSC 2H 5), −235.8 ± 2.0 (CsSC 2H 5). These results where compared with the literature values for the corresponding alkoxides and together with values for
\Updelta \textf H\textm\texto ( \text MSH, \text cr) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{MSH}},\;{\text{cr}}}\right) were used to derive a consistent set of lattice energies for MSR compounds based on the Kapustinskii equation. This allows
the estimation of the enthalpy of formation for some non-measured thiolates. 相似文献
2.
l-cysteine undergoes facile electron transfer with heteropoly 10-tungstodivanadophosphate,
[ \textPV\textV \textV\textV \textW 1 0 \textO 4 0 ]5 - , \left[ {{\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} } \right]^{5 - } , at ambient temperature in aqueous acid medium. The stoichiometric ratio of [cysteine]/[oxidant] is 2.0. The products of the
reaction are cystine and two electron-reduced heteropoly blue, [PVIVVIVW10O40]7−. The rates of the electron transfer reaction were measured spectrophotometrically in acetate–acetic acid buffers at 25 °C.
The orders of the reaction with respect to both [cysteine] and [oxidant] are unity, and the reaction exhibits simple second-order
kinetics at constant pH. The pH-rate profile indicates the participation of deprotonated cysteine in the reaction. The reaction
proceeds through an outer-sphere mechanism. For the dianion −SCH2CH(NH3
+)COO−, the rate constant for the cross electron transfer reaction is 96 M−1s−1 at 25 °C. The self-exchange rate constant for the
- \textSCH2 \textCH( \textNH3 + )\textCOO - \mathord | / |
\vphantom - \textSCH2 \textCH( \textNH3 + )\textCOO - ·\textSCH2 \textCH( \textNH3 + )\textCOO - ·\textSCH2 \textCH( \textNH3 + )\textCOO - {{{}^{ - }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } } \mathord{\left/ {\vphantom {{{}^{ - }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } } {{}^{ \bullet }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } }}} \right. \kern-\nulldelimiterspace} {{}^{ \bullet }{\text{SCH}}_{2} {\text{CH}}\left( {{{\text{NH}}_{3}}^{ + } } \right){\text{COO}}^{ - } }} couple was evaluated using the Rehm–Weller relationship. 相似文献
3.
Bis(2,4,6-tripyridyl 1,3,5-triazine)iron(II),
\text Fe(\text TPTZ) 2 2 + {\text{Fe(\text{TPTZ})}}_{ 2}^{{ 2 { + }}} reacts with 3-(2-pyridyl)-5,6-bis(4-phenyl-sulfonicacid)-1,2,4-triazine (PDTS) and 3-(4-(4-phenylsulfonicacid)-2-pyridyl)-5,6-bis(4-phenylsulfonic-acid)-1,2,4-triazine
(PPDTS) to give
\text Fe( PDTS) 3 4- {\text{Fe(PDTS)}}_{ 3}^{ 4- } and
\text Fe( PPDTS) 3 7- {\text{Fe(PPDTS)}}_{ 3}^{ 7- } respectively. Both of these substitution reactions are fast and their kinetics were monitored by stopped-flow spectrophotometry
in acetate buffers in the pH range of 3.6–5.6 at 25–45 °C. Both reactions are first order in
\text Fe( TPTZ) 2 2 + {\text{Fe(TPTZ)}}_{ 2}^{{ 2 { + }}} and triazine, and pH has negligible effect on the rate. The kinetic data suggest that these reactions occur in an associative
path and a mechanism is proposed considering both protonated and unprotonated forms of PDTS and PPDTS are very similar in
reactivity. The kinetic and activation parameters have been evaluated. 相似文献
4.
The substitution of bis(2,4,6-tripyridyl 1,3,5-triazine)iron(II),
\text Fe( TPTZ) 2 2 + {\text{Fe(TPTZ)}}_{ 2}^{{ 2 { + }}} by 2,2′,6,2″-terpyridine (terpy) occurs on a time scale of about 6 m. The kinetics of this reaction was followed by stopped-flow
spectrophotometry in the pH range of 3.6–5.6 in acetate buffer. The data indicate that the reaction occurs in two consecutive
steps: kinetic data for both steps were acquired simultaneously and analyzed independently. The first step is assigned to
the reaction between
\text Fe( TPTZ) 2 2 + {\text{Fe(TPTZ)}}_{ 2}^{{ 2 { + }}} and terpy to give Fe(TPTZ)(terpy) 2+, followed by its reaction with another terpy molecule to give the final product,
\text Fe( terpy) 2 2 + {\text{Fe(terpy)}}_{ 2}^{{ 2 { + }}} . The rate of the reaction increases with increases in [terpy] and pH. The kinetic and activation parameters determined for
both steps suggest that they involve both associative and dissociative paths. The ternary complex Fe(TPTZ)(terpy) 2+ has been prepared, and the kinetics of its reaction with terpy suggest that this reaction is identical with the second step
of the
\text Fe( TPTZ) 2 2 + {\text{Fe(TPTZ)}}_{ 2}^{{ 2 { + }}} -terpy system, supporting the proposed mechanism. 相似文献
5.
From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium
\text Cs + ( \text aq ) + \text A - ( \text aq ) + 1( \text nb )\underset \rightleftharpoons 1·\text Cs + ( \text nb ) + \text A - ( \text nb ) {\text{Cs}}^{ + } \left( {\text{aq}} \right) + {\text{A}}^{ - } \left( {\text{aq}} \right) + {\mathbf{1}}\left( {\text{nb}} \right)\underset {} \rightleftharpoons {\mathbf{1}}\cdot{\text{Cs}}^{ + } \left( {\text{nb}} \right) + {\text{A}}^{ - } \left( {\text{nb}} \right) taking place in the two-phase water-nitrobenzene system (A − = picrate, 1 = dibenzo-21-crown-7; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K
ex ( 1·Cs +, A −) = 4.4 ± 0.1. Further, the stability constant of the 1·Cs + complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β nb ( 1·Cs +) = 6.3 ± 0.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the resulting cationic
complex species 1·Cs + was solved. 相似文献
6.
A ternary binuclear complex of dysprosium chloride hexahydrate with m-nitrobenzoic acid and 1,10-phenanthroline, [Dy( m-NBA) 3phen] 2·4H 2O ( m-NBA: m-nitrobenzoate; phen: 1,10-phenanthroline) was synthesized. The dissolution enthalpies of [2phen·H 2O(s)], [6 m-HNBA(s)], [2DyCl 3·6H 2O(s)], and [Dy( m-NBA) 3phen] 2·4H 2O(s) in the calorimetric solvent (V DMSO:V MeOH = 3:2) were determined by the solution–reaction isoperibol calorimeter at 298.15 K to be
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2phen·H 2O(s), 298.15 K] = 21.7367 ± 0.3150 kJ·mol −1,
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [6 m-HNBA(s), 298.15 K] = 15.3635 ± 0.2235 kJ·mol −1,
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2DyCl 3·6H 2O(s), 298.15 K] = −203.5331 ± 0.2200 kJ·mol −1, and
\Updelta \texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [[Dy( m-NBA) 3phen] 2·4H 2O(s), 298.15 K] = 53.5965 ± 0.2367 kJ·mol −1, respectively. The enthalpy change of the reaction was determined to be
\Updelta \textr H\textmq = 3 6 9. 4 9 ±0. 5 6 \text kJ·\text mol - 1 . \Updelta_{\text{r}} H_{\text{m}}^{\theta } = 3 6 9. 4 9 \pm 0. 5 6 \;{\text{kJ}}\cdot {\text{mol}}^{ - 1} . According to the above results and the relevant data in the literature, through Hess’ law, the standard molar enthalpy of
formation of [Dy( m-NBA) 3phen] 2·4H 2O(s) was estimated to be
\Updelta \textf H\textmq \Updelta_{\text{f}} H_{\text{m}}^{\theta } [[Dy( m-NBA) 3phen] 2·4H 2O(s), 298.15 K] = −5525 ± 6 kJ·mol −1. 相似文献
7.
The oxidation of aquaethylenediaminetetraacetatocobaltate(II) [Co(EDTA)(H 2O)] −2 by N-bromosuccinimide (NBS) in aqueous solution has been studied spectrophotometrically over the pH 6.10–7.02 range at 25 °C.
The reaction is first-order with respect to complex and the oxidant, and it obeys the following rate law:
\textRate = k\textet K 2 K 3 [ \textCo\textII ( \textEDTA )( \textH 2 \textO ) - 2 ]\textT [\textNBS] \mathord | / |
\vphantom [\textNBS] ( [ \textH + ] + K 2 ) ( [ \textH + ] + K 2 ) {\text{Rate}} = k^{\text{et} } K_{ 2} K_{ 3} \left[ {{\text{Co}}^{\text{II}} \left( {\text{EDTA}} \right)\left( {{\text{H}}_{ 2} {\text{O}}} \right)^{ - 2} } \right]_{\text{T}} {{[{\text{NBS}}]} \mathord{\left/ {\vphantom {{[{\text{NBS}}]} {\left( {\left[ {{\text{H}}^{ + } } \right]{ + }K_{ 2} } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {\left[ {{\text{H}}^{ + } } \right]{ + }K_{ 2} } \right)}} 相似文献
8.
This article reports the values of the standard ( p
o = 0.1 MPa) molar enthalpies of formation, in the gaseous phase,
\Updelta \textf H\textm\texto ( \text g ), {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{g}} \right), at T = 298.15 K, of 2-acetyl-5-nitrothiophene and 5-nitro-2-thiophenecarboxaldehyde as −(48.8 ± 1.6) and (4.4 ± 1.3) kJ mol −1, respectively. These values were derived from experimental thermodynamic parameters, namely, the standard ( p
o = 0.1 MPa) molar enthalpies of formation, in the crystalline phase,
\Updelta \textf H\textm\texto ( \text cr ) , {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} \left( {\text{cr}} \right) , at T = 298.15 K, obtained from the standard molar enthalpies of combustion,
\Updelta \textc H\textm\texto , {{\Updelta}}_{\text{c}} H_{\text{m}}^{\text{o}} , measured by rotating bomb combustion calorimetry, and from the standard molar enthalpies of sublimation, at T = 298.15 K, determined from the temperature–vapour pressure dependence, obtained by the Knudsen mass loss effusion method.
The results are interpreted in terms of enthalpic increments and the enthalpic contribution of the nitro group in the substituted
thiophene ring is compared with the same contribution in other structurally similar compounds. 相似文献
9.
In the present work the uranyl hexacyanoferrate (K 2UO 2[Fe(CN) 6]) is deposited on the palladized aluminum (Pd-Al) electrode from a
\text UO22 + + \text Fe( \text CN ) 6 - 3 {\text{UO}}_{2}^{2 + } + {\text{Fe}}\left( {\text{CN}} \right)_{6}^{ - 3} solution. Then the anodic stripping chronopotentiometry (ASCP) was used to strip the K 2UO 2[Fe(CN) 6] from the Pd-Al surface. The operational conditions including: pH, K 3Fe(CN) 6 concentration, deposition potential, deposition time and stripping current were optimized. The ASCP calibration graph was
linear in concentration range 10–460 μM. of
\text UO22 + {\text{UO}}_{2}^{2 + } and the detection limit was 8.5 μM. The interference of some concomitant ions during the deposition process of K 2UO 2[Fe(CN) 6] was studied. The proposed method was successfully applied for analysis of some uranium mineral ores. 相似文献
10.
Combustion calorimetry, Calvet-drop sublimation calorimetry, and the Knudsen effusion method were used to determine the standard
( p
o = 0.1 MPa) molar enthalpies of formation of monoclinic (form I) and gaseous paracetamol, at T = 298.15 K:
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text cr I ) = - ( 4 10.4 ±1. 3)\text kJ \text mol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) = - ( 4 10.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text g ) = - ( 2 80.5 ±1. 9)\text kJ \text mol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) = - ( 2 80.5 \pm 1. 9){\text{ kJ}}\;{\text{mol}}^{ - 1} . From the obtained
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text cr I ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) value and published data, it was also possible to derive the standard molar enthalpies of formation of the two other known
polymorphs of paracetamol (forms II and III), at 298.15 K:
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text crII ) = - ( 40 8.4 ±1. 3)\text kJ \text mol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crII}}} \right) = - ( 40 8.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text crIII ) = - ( 40 7.4 ±1. 3)\text kJ \text mol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crIII}}} \right) = - ( 40 7.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} . The proposed
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text O 2 \text N,\text g ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) value, together with the experimental enthalpies of formation of acetophenone and 4′-hydroxyacetophenone, taken from the
literature, and a re-evaluated enthalpy of formation of acetanilide,
\Updelta \textf H\textm\texto ( \text C 8 \text H 9 \text ON,\text g ) = - ( 10 9. 2 ± 2. 2)\text kJ \text mol - 1 , \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{ON}},{\text{ g}}} \right) = - ( 10 9. 2\,\pm\,2. 2){\text{ kJ}}\;{\text{mol}}^{ - 1} , were used to assess the predictions of the B3LYP/cc-pVTZ and CBS-QB3 methods for the enthalpy of a isodesmic and isogyric
reaction involving those species. This test supported the reliability of the theoretical methods, and indicated a good thermodynamic
consistency between the
\Updelta \textf H\textm\texto \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} (C 8H 9O 2N, g) value obtained in this study and the remaining experimental data used in the
\Updelta \textr H\textm\texto \Updelta_{\text{r}} H_{\text{m}}^{\text{o}} calculation. It also led to the conclusion that the presently recommended enthalpy of formation of gaseous acetanilide in
Cox and Pilcher and Pedley’s compilations should be corrected by ~20 kJ mol −1. 相似文献
11.
Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H +B −) in the presence of polyethylene glycol PEG 1000 (L) has been investigated. The equilibrium data have been explained assuming
that the complexes
\text H 2 \text L2 + {\text{H}}_{ 2} {\text{L}}^{2 + } ,
\text ML 2+ {\text{ML}}^{ 2+ } and
\text MHL 3+ {\text{MHL}}^{ 3+ }
( \text M 2+ = \text Sr 2+ , \text Ba 2+ ) \left( {{\text{M}}^{ 2+ } = {\text{Sr}}^{ 2+ } ,\,\,{\text{Ba}}^{ 2+ } } \right) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated
with water have been determined. It was found that in water-saturated nitrobenzene the stability constant of the
\text BaL 2+ {\text{BaL}}^{ 2+ } cationic complex species is somewhat higher than that of the complex
\text SrL 2+ {\text{SrL}}^{ 2+ } . 相似文献
12.
Colloidal indigo is reduced to an aqueous solution of leuco-indigo in a mediated two-electron process converting the water-insoluble dye into the water-soluble leuco form. The colloidal dye does not interact directly with the electrode surface, and to employ an electrochemical process for this reduction, the redox mediator 1,8-dihydroxyanthraquinone (1,8-DHAQ) is used to transfer electrons from the electrode to the dye. The mediated reduction process is investigated at a (500-kHz ultrasound-assisted) rotating disc electrode, and the quantitative analysis of voltammetric data is attempted employing the Digisim numerical simulation software package. At the most effective temperature, 353 K, the diffusion coefficient for 1,8-DHAQ is (0.84±0.08)×10 −9 m 2 s −1, and it is shown that an apparently kinetically controlled reaction between the reduced form of the mediator and the colloidal indigo occurs within the diffusion layer at the electrode surface. The apparent bimolecular rate constant k
app=3 mol m −3 s −1 for the rate law
\frac d[ \text leuco - \text indigo ] dt = k\textapp ×[ \text mediator ] ×[ \text indigo ]\frac{{d{\left[ {{\text{leuco}} - {\text{indigo}}} \right]}}} {{dt}} = k_{{{\text{app}}}} \times {\left[ {{\text{mediator}}} \right]} \times {\left[ {{\text{indigo}}} \right]} is determined and attributed to a mediator diffusion controlled dissolution of the colloid particles. The average particle size and the number of molecules per particles are estimated from the apparent bimolecular rate constant and confirmed by scanning electron microscopy. 相似文献
13.
The assumption that potassium permanganate may serve as a kinetics standard in solid decomposition kinetics made a priori
on the basis of the mechanism of the congruent dissociative vaporization of KMnO 4 and its crystal structure was successfully supported experimentally. As expected, the decomposition rate of KMnO 4 does not depend on the kind of foreign gas (He, air, CO 2 and Ar) and on the measurement technique (isothermal or dynamic). Other requirements for KMnO 4 as an ideal kinetics standard are satisfied as well. The use of the third-law method for determining the molar enthalpy of
a reaction
( \Updelta \textr H\textT\texto / n ) \left( {\Updelta_{\text{r}} H_{\text{T}}^{\text{o}} / \nu } \right) provides an excellent reproducibility of results. The mean value of
\Updelta \textr H\textT\texto / n \Updelta_{\text{r}} H_{\text{T}}^{\text{o}} / \nu from 12 experiments in different gases is 138.3 ± 0.6 kJ mol −1, which coincides with the value of 138.1 kJ mol −1 calculated from the isothermal measurements in different gases by the second-law method. As predicted by theory, the random
errors of the second-law and Arrhenius plot methods are 10–20 times greater. In addition, the use of these methods in the
case of dynamic measurements is related to large systematic errors caused by an inaccurate selection of the geometrical (contraction)
model. The third-law method is practically free of these errors. 相似文献
14.
[
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]M (M = K, Tl) reacts with “GaI” to give a series of compounds that feature Ga–Ga bonds, namely [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→GaI 3, [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]GaGaI 2GaI 2(
\text Hpz\textMe2 {\text{Hpz}}^{{{\text{Me}}_{2} }} ) and [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga(GaI 2) 2Ga[
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ], in addition to the cationic, mononuclear Ga(III) complex {[
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ] 2Ga} +. Likewise, [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]M (M = K, Tl) reacts with (HGaCl 2)
2
and Ga[GaCl 4] to give [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→GaCl 3, {[
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ] 2Ga}[GaCl 4], and {[
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]GaGa[
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]}[GaCl 4] 2. The adduct [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→B(C 6F 5) 3 may be obtained via treatment of [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]K with “GaI” followed by addition of B(C 6F 5) 3. Comparison of the deviation from planarity of the GaY 3 ligands in [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→GaY 3 (Y = Cl, I) and [
\text Tm\textBu\textt {\text{Tm}}^{{{\text{Bu}}^{\text{t}} }} ]Ga→GaY 3, as evaluated by the sum of the Y–Ga–Y bond angles, Σ(Y–Ga–Y), indicates that the [
\text Tm\textBu\textt {\text{Tm}}^{{{\text{Bu}}^{\text{t}} }} ]Ga moiety is a marginally better donor than [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga. In contrast, the displacement from planarity for the B(C 6F 5) 3 ligand of [
\text Tp\textMe2 {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→B(C 6F 5) 3 is greater than that of [
\text Tm\textBu\textt {\text{Tm}}^{{{\text{Bu}}^{\text{t}} }} ]Ga→B(C 6F 5) 3, an observation that is interpreted in terms of interligand steric interactions in the former complex compressing the C–B–C
bond angles. 相似文献
15.
The study elementarily investigated the effect of the cathode structure on the electrochemical performance of anode-supported
solid oxide fuel cells. Four single cells were fabricated with different cathode structures, and the total cathode thickness
was 15, 55, 85, and 85 μm for cell-A, cell-B, cell-C, and cell-D, respectively. The cell-A, cell-B, and cell-D included only
one cathode layer, which was fabricated by
( \text La0.74 \text Bi0.10 \text Sr0.16 )\text MnO3 - d \left( {{\text{La}}_{0.74} {\text{Bi}}_{0.10} {\text{Sr}}_{0.16} } \right){\text{MnO}}_{{3 - \delta }} (LBSM) electrode material. The cathode of the cell-C was composed of a
( \text La0.74 \text Bi0.10 \text Sr0.16 )\text MnO3 - d - ( \text Bi0.7 \text Er0.3 \text O1.5 ) \left( {{\text{La}}_{0.74} {\text{Bi}}_{0.10} {\text{Sr}}_{0.16} } \right){\text{MnO}}_{{3 - \delta }} - \left( {{\text{Bi}}_{0.7} {\text{Er}}_{0.3} {\text{O}}_{1.5} } \right) (LBSM–ESB) cathode functional layer and a LBSM cathode layer. Different cathode structures leaded to dissimilar polarization
character for the four cells. At 750°C, the total polarization resistance ( R
p) of the cell-A was 1.11, 0.41 and 0.53 Ω cm 2 at the current of 0, 400, and 800 mA, respectively, and that of the cell-B was 1.10, 0.39, and 0.23 Ω cm 2 at the current of 0, 400, and 800 mA, respectively. For cell-C and cell-D, their polarization character was similar to that
of the cell-B and R
p also decreased with the increase of the current. The maximum power density was 0.81, 1.01, 0.79, and 0.43 W cm −2 at 750°C for cell-D, cell-C, cell-B, and cell-A, respectively. The results demonstrated that cathode structures evidently
influenced the electrochemical performance of anode-supported solid oxide fuel cells. 相似文献
16.
Extraction of microamounts of europium and americium by a phenyltrifluoromethyl sulfone (FS 13) solution of hydrogen dicarbollylcobaltate
(H +B −) in the presence of N,N,N′,N′-tetraethyl-2,6-dipicolinamide (TEtDPA, L) has been investigated. The equilibrium data have been explained assuming that the
species HL +,
\text HL 2 + , {\text{HL}}_{ 2}^{ + } ,
\text ML23 + {\text{ML}_{2}^{3 +}} and
\text ML 3 3+ {\text{ML}_{ 3}^{ 3+}} (M 3+ = Eu 3+, Am 3+) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species in
FS 13 saturated with water have been determined. It was found that the stability constants of the corresponding complexes
\text EuLn 3+ {\text{EuL}}_{n}^{ 3+ } and
\text AmLn 3+ {\text{AmL}}_{n}^{ 3+ }, where n = 2, 3 and L is TEtDPA, in the mentioned FS 13 medium are comparable. 相似文献
17.
The two-state reaction mechanism of the Pt 4+/− with N 2O (CO) on the quartet and doublet potential energy surfaces has been investigated at the B3LYP level. The effect of Pt 4
− anion assistance is analyzed using the activation strain model in which the activation energy (Δ Ε
≠) is decomposed into the distortion energies
(\Updelta E 1 \textdist ) (\Updelta E^{ \ne }_{\text{dist}} ) and the stabilizing transition state (TS) interaction energies
(\Updelta E 1 \textint ) (\Updelta E^{ \ne }_{\text{int}} ) , namely
\Updelta E 1 = \Updelta E 1 \textdist + \Updelta E 1 \textint \Updelta E^{ \ne } = \Updelta E^{ \ne }_{\text{dist}} + \Updelta E^{ \ne }_{\text{int}} . The lowering of activation barriers through Pt 4
− anion assistance is caused by the TS interaction
\Updelta E 1 \textint \Updelta E^{ \ne }_{\text{int}} (−90.7 to −95.6 kcal/mol) becoming more stabilizing. This is attributed to the N 2O π*-LUMO and Pt d HOMO back-donation interactions. However, the strength of the back-donation interactions has significantly
impact on the reaction mechanism. For the Pt 4
− anion system, it has very significant back-bonding interaction (N 2O negative charge of 0.79e), HOMO has 81.5% π* LUMO(N 2O) character, with 3d orbital contributions of 10.7% from Pt (3) and 7.7% from Pt (7) near the 4TS4 transition state. This facilitates the bending of the N 2O molecule, the N–O bond weakening, and an O −( 2P) dissociation without surface crossing. For the Pt 4
+ cation system, the strength of the charge transfer is weaker, which leads to the diabatic (spin conserving) dissociation
of N 2O: N 2O( 1∑ +) → N 2( 1∑ g+) + O( 1D). The quartet to doublet state transition should occur efficiently near the 4TS1 due to the larger SOC value calculated of 677.9 cm −1. Not only will the reaction overcome spin-change-induced barrier (ca. 7 kcal/mol) but also overcome adiabatic barrier (ca.
40.1 kcal/mol).Therefore, the lack of a thermodynamic driving force is an important factor contributing to the low efficiency
of the reaction system. 相似文献
18.
A carbon past electrode modified with [Mn(H 2O)(N 3)(NO 3)(pyterpy)],
( \text pyterpy = 4¢- ( 4 - \text pyridyl ) - 2,2¢:\text6¢,\text2¢¢- \text terpyridine ) \left( {{\text{pyterpy}} = 4\prime - \left( {4 - {\text{pyridyl}}} \right) - 2,2\prime:{\text{6}}\prime,{\text{2}}\prime\prime - {\text{terpyridine}}} \right) complex have been applied to the electrocatalytic oxidation of nitrite which reduced the overpotential by about 120 mV with
obviously increasing the current response. Relative standard deviations for nitrite determination was less than 2.0%, and
nitrite can be determined in the ranges of 5.00 × 10 −6 to 1.55 × 10 −2 mol L −1, with a detection limit of 8 × 10 −7 mol L −1. The treatment of the voltammetric data showed that it is a pure diffusion-controlled reaction, which involves one electron
in the rate-determining step. The rate constant k′, transfer coefficient α for the catalytic reaction, and diffusion coefficient of nitrite in the solution, D, were found to be 1.4 × 10 −2, 0.56× 10 −6, and 7.99 × 10 −6 cm 2 s −1, respectively. The mechanism for the interaction of nitrite with the Mn(II) complex modified carbon past electrode is proposed.
This work provides a simple and easy approach to detection of nitrite ion. The modified electrode indicated reproducible behavior,
anti-fouling properties, and stability during electrochemical experiments, making it particularly suitable for the analytical
purposes. 相似文献
19.
In various samples of marine organisms from the central Adriatic Sea 210Po was determined by alpha spectrometry and thirteen heavy metals (Mn, Fe, Co, Cr, V, Ni, Cu, Zn, Cd, As, Sn, Hg and Pb) by
energy dispersive, polarised X ray fluorescence spectrometry (EDPXRF). 210Po activity concentration ranged between 0.3 and 44.6 Bq kg −1 fresh weight. The data obtained depend upon the type of the marine organism; among the pelagic species, anchovy displayed
the highest polonium concentration. Typical concentration
( \upmu \text g·\text g(\textfresh) - 1 ) \left( {\upmu {\text{g}}\cdot{\text{g}}_{{({\text{fresh}})}}^{ - 1} } \right) ranges were as follows: Mn: <1.32–1.73; Fe: 4.11–94.27; Co < 0.13–0.23; Ni: <0.13–0.52; Cu: 0.37–145.31; Zn: 0.46–16.46;
Cd: <0.10–0.25; As: 0.36–60.52; Hg: <0.13–0.70; Pb: <0.13–0.35, Sn: <0.20–12.67; V and Cr were always <1.32. The data obtained
are also compared with those obtained by other authors for the same organism coming from other Italian seas. 相似文献
20.
The standard ( p
o = 0.1 MPa) molar enthalpies of formation
\Updelta \textf H\textm\texto ( \text l), {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} ( {\text{l),}} of the liquid 2-methylfuran, 5-methyl-2-acetylfuran and 5-methyl-2-furaldehyde were derived from the standard molar energies
of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The Calvet high temperature vacuum sublimation technique was
used to measure the enthalpies of vaporization of the three compounds. The standard ( p
o = 0.1 MPa) molar enthalpies of formation of the compounds, in the gaseous phase, at T = 298.15 K have been derived from the corresponding standard molar enthalpies of formation in the liquid phase and the standard
molar enthalpies of vaporization. The results obtained were −(76.4 ± 1.2), −(253.9 ± 1.9), and −(196.8 ± 1.8) kJ mol −1, for 2-methylfuran, 5-methyl-2-acetylfuran, and 5-methyl-2-furaldehyde, respectively. 相似文献
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