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1.
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
2.
Glutathione (GSH) undergoes facile electron transfer with vanadium(V)-substituted Keggin-type heteropolyoxometalates,
[ \text PV\textV \text W 1 1 \text O 4 0 ] 4 - [ {\text{PV}}^{\text{V}} {\text{W}}_{ 1 1} {\text{O}}_{ 4 0} ]^{{ 4 { - }}} (HPA1) and
[ \text PV\textV \text V\textV \text W 1 0 \text O 4 0 ] 5 - [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} ]^{{ 5 { - }}} (HPA2). The kinetics of these reactions have been investigated in phthalate buffers spectrophotometrically at 25 °C in aqueous
medium. One mole of HPA1 consumes one mole of GSH and the product is the one-electron reduced heteropoly blue,
[ \text PV\textIV \text W 1 1 \text O 40 ] 5- [ {\text{PV}}^{\text{IV}} {\text{W}}_{ 1 1} {\text{O}}_{ 40} ]^{ 5- } . But in the GSH-HPA2 reaction, one mole of HPA2 consumes two moles of GSH and gives the two-electron reduced heteropoly blue
[ \text PV\textIV \text V\textIV \text W 10 \text O 40 ] 7- [ {\text{PV}}^{\text{IV}} {\text{V}}^{\text{IV}} {\text{W}}_{ 10} {\text{O}}_{ 40} ]^{ 7- } . Both reactions show overall third-order kinetics. At constant pH, the order with respect to both [HPA] species is one and
order with respect to [GSH] is two. At constant [GSH], the rate shows inverse dependence on [H +], suggesting participation of the deprotonated thiol group of GSH in the reaction. A suitable mechanism has been proposed
and a rate law for the title reaction is derived. The antimicrobial activities of HPA1, HPA2 and
[ \text PV\textV \text V\textV \text V\textV \text W 9 \text O 4 0 ] 6 - [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 9} {\text{O}}_{ 4 0} ]^{{ 6 { - }}} (HPA3) against MRSA were tested in vitro in combination with vancomycin and penicillin G. The HPAs sensitize MRSA towards
penicillin G. 相似文献
3.
[
\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
4.
The standard molar Gibbs free energy of formation of YRhO 3(s) has been determined using a solid-state electrochemical cell wherein calcia-stabilized zirconia was used as an electrolyte.
The cell can be represented by:
( - )\text Pt - Rh/{ \text Y2\text O\text3( \text s ) + \text YRh\text O3( \text s ) + \text Rh( \text s ) }//\text CSZ//\text O2( p( \text O2 ) = 21.21 \text kPa )/\text Pt - Rh( + ) \left( - \right){\text{Pt - Rh/}}\left\{ {{{\text{Y}}_2}{{\text{O}}_{\text{3}}}\left( {\text{s}} \right) + {\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right) + {\text{Rh}}\left( {\text{s}} \right)} \right\}//{\text{CSZ//}}{{\text{O}}_2}\left( {p\left( {{{\text{O}}_2}} \right) = 21.21\;{\text{kPa}}} \right)/{\text{Pt - Rh}}\left( + \right) . The electromotive force was measured in the temperature range from 920.0 to 1,197.3 K. The standard molar Gibbs energy of
the formation of YRhO 3(s) from elements in their standard state using this electrochemical cell has been calculated and can be represented by:
D \textfG\texto{ \text YRh\text O3( \text s ) }/\text kJ \text mo\text l - 1( ±1.61 ) = - 1,147.4 + 0.2815 T ( \text K ) {\Delta_{\text{f}}}{G^{\text{o}}}\left\{ {{\text{YRh}}{{\text{O}}_3}\left( {\text{s}} \right)} \right\}/{\text{kJ}}\;{\text{mo}}{{\text{l}}^{ - 1}}\left( {\pm 1.61} \right) = - 1,147.4 + 0.2815\;T\;\left( {\text{K}} \right) . Standard molar heat capacity Cop,m C^{o}_{{p,m}} ( T) of YRhO 3(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges from 127 to
299 K and 305 to 646 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can
be represented by: $ {*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ $ \begin{array}{*{20}{c}} {\mathop C\nolimits_{p,m}^{\text{o}} \left( {{\text{YRh}}{{\text{O}}_3},{\text{s,}}T} \right)\left( {{\text{J}}\;{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}} \right)} & { = 109.838 + 23.318 \times {{10}^{ - 3}}T\left( {\text{K}} \right)} & { - 12.5964 \times {{10}^5}/{T^2}\left( {\text{K}} \right).} \\ {} & {\left( {305 \leqslant T\left( {\text{K}} \right) \leqslant 646} \right)} & {} \\ \end{array} The heat capacity of YRhO 3(s) was used along with the data obtained from the electrochemical cell to calculate the standard enthalpy and entropy of
formation of the compound at 298.15 K. 相似文献
5.
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
6.
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
7.
Extraction of microamounts of cesium by a nitrobenzene solution of ammonium dicarbollylcobaltate
( \text NH 4 + \text B - ) ( {{\text{NH}}_{ 4}^{ + } {\text{B}}^{ - } }) and thallium dicarbollylcobaltate
( \text Tl + \text B - ) ( {{\text{Tl}}^{ + } {\text{B}}^{ - } }) in the presence of 2,3-naphtho-15-crown-5 (N15C5, L) has been investigated. The equilibrium data have been explained assuming
that the complexes
\text ML + {\text{ML}}^{ + } and
\text ML 2 + {\text{ML}}_{ 2}^{ + }
( \text M + = \text NH4 + ,\text Tl + ,\text Cs + ) ( {{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } ,{\text{Cs}}^{ + } } ) are present in the organic phase. The stability constants of the
\text ML + {\text{ML}}^{ + } and
\text ML2 + {\text{ML}}_{2}^{ + } species
( \text M + = \text NH4 + ,\text Tl + ) ( {{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } }) in nitrobenzene saturated with water have been determined. It was found that the stability of the complex cations
\text ML + {\text{ML}}^{ + } and
\text ML2 + {\text{ML}}_{2}^{ + }
(\text M + = \text NH4 + ,\text Tl + ,\text Cs + ; \text L = \text N15\text C5) ({{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } ,{\text{Cs}}^{ + } ;\;{\text{L}} = {\text{N}}15{\text{C}}5}) in the mentioned medium increases in the
\text Cs + < \text NH4 + < \text Tl + {\text{Cs}}^{ + }\,<\, {\text{NH}}_{4}^{ + }\,<\,{\text{Tl}}^{ + } order. 相似文献
8.
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
9.
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
10.
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
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.
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
13.
In the present work temperature dependence of heat capacity of rubidium niobium tungsten oxide has been measured first in
the range from 7 to 395 K and then between 390 and 650 K, respectively, by precision adiabatic vacuum and dynamic calorimetry.
The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity
^ (T), C_{\text{p}}^{\text{o}} (T), enthalpy
H\texto (T) - H\texto (0) H^{\text{o}} ({\rm T}) - H^{\text{o}} (0) , entropy
S\texto ( T) - S\texto ( 0 ) S^{\text{o}} (T) - S^{\text{o}} \left( 0 \right) , and Gibbs function
G\texto (T) - H\texto (0) G^{{^{\text{o}} }} ({\rm T}) - H^{{^{\text{o}} }} (0) , for the range from T→0 to 650 K. The high-temperature X-ray diffraction and the differential scanning calorimetry were used for the determination
of temperature and decomposition products of RbNbWO 6. 相似文献
14.
Theoretical study of several para-substituted O-nitrosyl carboxylate compounds has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries obtained from DFT calculation were used to perform natural bond orbital analysis. It is noted that weakness in the O 3–N 2 sigma bond is due to $ n_{{{\text{O}}_{1} }} \to \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} Theoretical study of several para-substituted O-nitrosyl carboxylate compounds has been performed using density functional B3LYP method with 6-31G(d,p) basis set. Geometries
obtained from DFT calculation were used to perform natural bond orbital analysis. It is noted that weakness in the O3–N2 sigma bond is due to
n\textO1 ? s\textO3 - \textN2 * n_{{{\text{O}}_{1} }} \to \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} delocalization and is responsible for the longer O3–N2 bond lengths in para-substituted O-nitrosyl carboxylate compounds. It is also noted that decreased occupancy of the localized
s\textO3 -\textN2 \sigma_{{{\text{O}}_{3} --{\text{N}}_{2} }} orbital in the idealized Lewis structure, or increased occupancy of
s\textO3 - \textN2 * \sigma_{{{\text{O}}_{3} - {\text{N}}_{2} }}^{*} of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are related with
the resulting p character of the corresponding sulfur natural hybrid orbital of
s\textO3 -\textN2 \sigma_{{{\text{O}}_{3} --{\text{N}}_{2} }} bond orbital. In addition, the charge transfer energy decreases with the increase of the Hammett constants of substituent
groups and the partial charges distribution on the skeletal atoms may approve anticipating that the electrostatic repulsion
or attraction between atoms can give a significant contribution to the intra- and intermolecular interaction. 相似文献
15.
The formation of large even-numbered carbon cluster anions,
\text C\textn - {\text{C}}_{\text{n}}^{ - } , with n up to 500 were observed in the mass spectra generated by laser ablation of graphene and graphene oxide, and the signal
intensity of the latter is much weaker than that of the former. The cluster distributions generated from graphene can be readily
altered by changing the laser energy and the accumulation period in the FT - ICR cell. By choosing suitable experimental conditions,
weak signals of odd-numbered anions from
\text C125 - {\text{C}}_{{125}}^{ - } to
\text C211 - {\text{C}}_{{211}}^{ - } , doubly charged anions from
\text C702 - {\text{C}}_{{70}}^{{2 - }} to
\text C2302 - {\text{C}}_{{230}}^{{2 - }} and triply charged cluster anions from
\text C803 - {\text{C}}_{{80}}^{{3 - }} to
\text C2243 - {\text{C}}_{{224}}^{{3 - }} can be observed. Tandem MS was applied to some selected cluster anions. Though no fragment anions larger than
\text C20 - {\text{C}}_{{20}}^{ - } can be observed by the process of collisional activation with N 2 gas for most cluster ions, several cluster anions can lose units of C 2, C 4, C 6 or C 8 in their collision process. The differences in their dissociation kinetics and structures require further calculations and
experimental studies. 相似文献
16.
Abstract From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium
\text M2 + ( \text aq ) + 1 ·\text Sr2 + ( \text nb ) \rightleftarrows 1 ·\text M2 + ( \text nb ) + \text Sr2 + ( \text aq ) {\text{M}}^{2 + } \left( {\text{aq}} \right) + {\mathbf{1}} \cdot {\text{Sr}}^{2 + } \left( {\text{nb}} \right) \rightleftarrows {\mathbf{1}} \cdot {\text{M}}^{2 + } \left( {\text{nb}} \right) + {\text{Sr}}^{2 + } \left( {\text{aq}} \right) taking place in the two-phase water–nitrobenzene system (M 2+ = Ca 2+, Ba 2+, Cu 2+, Zn 2+, Cd 2+, Pb 2+, UO 2
2+, Mn 2+, Co 2+, Ni 2+; 1 = tetraphenyl p- tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants
of the 1 · M 2+ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the cation order Ba 2+, Mn 2+ < Co 2+ < Cu 2+, Ni 2+ < Zn 2+, Cd 2+, UO 2
2+ < Ca 2+ < Pb 2+. 相似文献
17.
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
18.
We have established and analyzed the sequences of phase transitions in synthesis of layered compounds in the A nB n–1O 3n family (
\text A3\textII\text LnB3\textV\text O12 {\text{A}}_3^{\text{II}}{\text{LnB}}_3^{\text{V}}{{\text{O}}_{{12}}} (A II = Ba, Sr, Ln = La, Nd, B V = Nb, Ta) and La 4Ti 3O 12 with n = 4) from coprecipitated hydroxocarbonate and hydroxide systems, including steps involving the formation, solid-phase
reaction, or structural rearrangement of intermediates. 相似文献
19.
Twelve surfactant Schiff base ligands were synthesized from salicylaldehyde and its chloro-, bromo- and methoxy- derivatives
by condensation with long-chain aliphatic primary amines, and a number of mixed ligand cobalt(III) surfactant Schiff base
coordination complexes of the type [Co(trien)A] 2+ were synthesized from the corresponding dihalogeno complexes by ligand substitution. The Schiff bases and their complexes
were characterized by physico-chemical and spectroscopic methods. The complexes form foams in aqueous solution upon shaking.
The critical micelle concentration (CMC) values of the complexes in aqueous solution were obtained from conductance measurements.
Specific conductivity data (at 303–323 K) served for the evaluation of the thermodynamics of micellization (
\Updelta G\textm0 \Updelta G_{\text{m}}^{0} ,
\Updelta H\textm0 \Updelta H_{\text{m}}^{0} ,
\Updelta S\textm0 \Updelta S_{\text{m}}^{0} ). The complexes were tested for its antimicrobial activity. 相似文献
20.
Polypyrrole polymer films doped with the large, immobile dodecylbenzene sulfonate anions operating in alkali halide aqueous
electrolytes has been used as a novel physico-chemical environment to develop a more direct way of obtaining reliable values
for the hydration numbers of cations. Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance technique
was used to determine the amount of charge inserted and the total mass change during the reduction process in a polypyrrole
film. From these values, the number of water molecules accompanying each cation was evaluated. The number of water molecules
entering the polymer during the initial part of the first reduction was found to be constant and independent of the concentration
of the electrolyte below ∼1 M. This well-defined value can be considered as the primary membrane hydration number of the cation
involved in the reduction process. The goal was to investigate both the effects of cation size and of cation charge. The membrane
hydration number values obtained by this simple and direct method for a number of cations are:
\textL\texti + : 5.5 - 5.3;\text N\texta + : 4.5 - 4.3; \textK + : 2.3 - 2.5;\text R\textb + : 0.9 - 0.8 ;\text C\texts + : ~ 0;\text M\textg2 + :10.4 - 10.6;\textC\texta2 + :7.9 - 8.1;\textS\textr2 + :5.7 - 6.1;\textB\texta2 + :3.0 - 3.1;\textY3 + :13.6 - 13.8 ;\textL\texta3 + :9.0 - 9.1. {\text{L}}{{\text{i}}^{ + }}:{ 5}.{5} - {5}.{3};{\text{ N}}{{\text{a}}^{ + }}:{ 4}.{5} - {4}.{3};{ }{{\text{K}}^{ + }}:{ 2}.{3} - {2}.{5};{\text{ R}}{{\text{b}}^{ + }}:{ }0.{9} - 0.{8 };{\text{ C}}{{\text{s}}^{ + }}:{ }\sim 0;{\text{ M}}{{\text{g}}^{{{2} + }}}:{1}0.{4} - {1}0.{6};{\text{C}}{{\text{a}}^{{{2} + }}}:{7}.{9} - {8}.{1};{\text{S}}{{\text{r}}^{{{2} + }}}:{5}.{7} - {6}.{1};{\text{B}}{{\text{a}}^{{{2} + }}}:{3}.0 - {3}.{1};{{\text{Y}}^{{{3} + }}}:{13}.{6 } - { 13}.{8 };{\text{L}}{{\text{a}}^{{{3} + }}}:{9}.0 - {9}.{1}. 相似文献
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