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1.
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
2.
The molar enthalpies of solution of 2-aminopyridine at various molalities were measured at T=298.15 K in double-distilled water by means of an isoperibol solution-reaction calorimeter. According to Pitzer’s theory,
the molar enthalpy of solution of the title compound at infinite dilution was calculated to be D solHm¥ = 14.34 kJ·mol -1\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\infty} = 14.34~\mbox{kJ}\cdot\mbox{mol}^{-1}, and Pitzer’s ion interaction parameters b MX(0)L, b MX(1)L\beta_{\mathrm{MX}}^{(0)L}, \beta_{\mathrm{MX}}^{(1)L}, and CMXfLC_{\mathrm{MX}}^{\phi L} were obtained. Values of the relative apparent molar enthalpies (
φ
L) and relative partial molar enthalpies of the compound ([`( L)] 2)\bar{L}_{2}) were derived from the experimental enthalpies of solution of the compound. The standard molar enthalpy of formation of the
cation C 5H 7N 2 +\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{ +} in aqueous solution was calculated to be D fHmo(C 5H 7N 2+,aq)=-(2.096±0.801) kJ·mol -1\Delta_{\mathrm{f}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{C}_{5}\mathrm{H}_{7}\mathrm{N}_{2}^{+},\mbox{aq})=-(2.096\pm 0.801)~\mbox{kJ}\cdot\mbox{mol}^{-1}. 相似文献
3.
The curing kinetics of a bi-component system about o-cresol-formaldehyde epoxy resin ( o-CFER) modified by liquid crystalline p-phenylene di[4-(2,3-epoxypropyl) benzoate] ( p-PEPB), with 3-methyl-tetrahydrophthalic anhydride (MeTHPA) as a curing agent, were studied by non-isothermal differential
scanning calorimetry (DSC) method. The relationship between apparent activation energy E
a and the conversion α was obtained by the isoconversional method of Ozawa. The reaction molecular mechanism was proposed. The results show that
the values of E
a in the initial stage are higher than other time, and E
a tend to decrease slightly with the reaction processing. There is a phase separation in the cure process with LC phase formation.
These curing reactions can be described by the Šesták–Berggren (S–B) equation, the kinetic equation of cure reaction as follows:
\frac\text da\text dt = Aexp( - \frac E\texta RT )a m ( 1 - a ) n {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = A\exp \left( { - {\frac{{E_{\text{a}} }}{RT}}} \right)\alpha^{m} \left( {1 - a} \right)^{n} . 相似文献
4.
The molar conductivities ( Λ) of solutions of bis(2,2′-bipyridine) bis(thiocyanate)chromium(III) triiodide [Cr III(bipy) 2(SCN) 2]I 3 (where bipy denotes 2,2′-bipyridine, C 10H 8N 2), [
_3^-\mathrm{A}^{+}\mathrm{I}_{3}^{-}
], were measured in acetonitrile (ACN) at the temperatures 294.15, 299.15, and 305.15 K. In addition, cyclic voltammograms
(CVs) of [
A +I 3-\mathrm{A}^{+}\mathrm{I}_{3}^{-}
] were recorded on platinum, gold, and glassy carbon working electrodes in ACN, using n-tetrabutylammonium hexafluorophosphate (NBu 4PF 6) as the supporting electrolyte, at scan rates ( v) ranging from 0.05 to 0.12 V⋅s −1. Furthermore, electrochemical impedance spectroscopic (EIS) measurements were carried out in the frequency range 50 Hz< f<50 kHz using these three working electrodes. The measured molar conductivities ( Λ) demonstrate that [
A +I 3-\mathrm{A}^{+}\mathrm{I}_{3}^{-}
] behaves as uni-univalent electrolyte in ACN over the investigated temperature range. The Λ values were analyzed by means of the Lee-Wheaton conductivity equation in order to estimate the limiting molar conductivities ( Λ
o), as well as the thermodynamic association constants ( K
A), at each experimental temperature for formation of [A +
I 3-\mathrm{I}_{3}^{-}
] ion-pairs. The limiting ionic conductivities (
l ±o\lambda_{\pm}^{\mathrm{o}}
), the diffusion coefficients at infinite dilution ( D
±), as well as the Stokes’ radii ( r
St) were determined for both A + and
I 3-\mathrm{I}_{3}^{-}
ions. The thermodynamic parameters for the ionic association process, i.e. the Gibbs energy (
D GAo\Delta G_{\mathrm{A}}^{\mathrm{o}}
), enthalpy (
D HAo\Delta H_{\mathrm{A}}^{\mathrm{o}}
), and entropy (
D SAo\Delta S_{\mathrm{A}}^{\mathrm{o}}
), were also determined. The mobility and diffusivity of the A + ion increase linearly with increasing temperature because the solvent medium becomes less viscous as the temperature increases.
The K
A values indicate that significant ion association occurs that is not influenced by temperature changes. The ion-pair formation
process is exothermic (
D HAo < 0\Delta H_{\mathrm{A}}^{\mathrm{o}}<0
), leading to the generation of additional entropy (
$\Delta S_{\mathrm{A}}^{\mathrm{o}}>0$\Delta S_{\mathrm{A}}^{\mathrm{o}}>0
). As a result, the Gibbs energy
D GAo\Delta G_{\mathrm{A}}^{\mathrm{o}}
is negative (
D GAo < 0\Delta G_{\mathrm{A}}^{\mathrm{o}}<0
) and the formation of
[A +I 3-][\mathrm{A}^{+}\mathrm{I}_{3}^{-}]
becomes favorable. CV studies on
[A +I 3-][\mathrm{A}^{+}\mathrm{I}_{3}^{-}]
solutions indicated that the redox pair Cr 3+/2+ appears to be quasi-reversible on a glassy carbon electrode but is completely irreversible on platinum and gold electrodes.
EIS experiments confirm that, among these three electrodes, the glassy carbon working electrode has the smallest resistance
to electron transfer. 相似文献
5.
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
6.
[
\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
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.
Apparent molar volumes ( V
2,φ
) and heat capacities ( C
p2,φ
) of glycine in known concentrations (1.0, 2.0, 4.0, 6.0, and 8.0 mol⋅kg −1) of aqueous formamide (FM), acetamide (AM), and N, N-dimethylacetamide (DMA) solutions at T=298.15 K have been calculated from relative density and specific heat capacity measurements. These measurements were completed
using a vibrating-tube flow densimeter and a Picker flow microcalorimeter, respectively. The concentration dependences of
the apparent molar data have been used to calculate standard partial molar properties. The latter values have been combined
with previously published standard partial molar volumes and heat capacities for glycine in water to calculate volumes and
heat capacities associated with the transfer of glycine from water to the investigated aqueous amide solutions, D[`( V)] 2,tro\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`( C)] p2,tro\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} respectively. Calculated values for D[`( V)] 2,tro\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`( C)] p2,tro\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} are positive for all investigated concentrations of aqueous FM and AM solutions. However, values for D[`( C)] p2,tro\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} associated with aqueous DMA solutions are found to be negative. The reported transfer properties increase with increasing
co-solute (amide) concentration. This observation is discussed in terms of solute + co-solute interactions. The transfer properties
have also been used to estimate interaction coefficients. 相似文献
9.
To understand the thermodynamic characteristics of cationic surfactants in binary mixtures, the aggregation behavior of hexadecyltrimethylammonium
chloride (CTAC) has been investigated in ethylene glycol (EG) + water solvent mixtures at different temperatures and EG to
water ratios. The critical micelle concentration (CMC) and degree of counter ion bonding ( β) were calculated from electrical conductivity measurements. An equilibrium model for micelle formation was applied to obtain
the thermodynamic parameters for micellization, including the standard Gibbs energies of micellization (D Gmico)\Delta G_{\mathrm{mic}}^{\mathrm{o}}), standard enthalpies of micelle formation (D Hmico)\Delta H_{\mathrm{mic}}^{\mathrm{o}}) and standard entropies of micellization (D Smico)\Delta S_{\mathrm{mic}}^{\mathrm{o}}). Our results show that D Gmico\Delta G_{\mathrm{mic}}^{\mathrm{o}} is always negative and slightly dependent on temperature. The process of micellization is entropy driven in pure water, whereas
in EG + water mixtures the micellization is enthalpy driven. 相似文献
10.
The molar enthalpies of solution of an alanine-based ionic liquid (IL) [C 4mim][Ala], 1-butyl-3-methylimidazolium alanine, containing various amount of water and various molalities Δ sol
H
m(wc), were measured with a solution-reaction isoperibol calorimeter at (298.15±0.01) K, where wc denotes water content. According
to Archer’s method, the standard molar enthalpies of solution of [C 4mim][Ala] containing known amounts of water,
D solHmo(wc)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{wc})
, were obtained. In order to eliminate the effect of the small amount of residual water in the source [C 4mim][Ala], a linear fitting of
D solHmo(wc)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{wc})
against water content was carried out, yielding a good straight line where the intercept is the standard molar enthalpy of
solution of anhydrous [C 4mim][Ala],
D solHmo(pure IL)=-(61.42±0.08)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{pure}\ \mathrm{IL})=-(61.42\pm 0.08)
kJ⋅mol −1. The hydration enthalpy of the alanine anion [Ala] − was estimated using Glasser’s lattice energy theory. 相似文献
11.
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M + (aq) + NaL + (nb) ⇔ ML + (nb) + Na + (aq) taking place in the two-phase water–nitrobenzene system (M + = H 3O +,
\text NH4+ {\text{NH}}_{4}{}^{+} , Ag +, Tl +; L = hexaethyl p- tert-butylcalix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants
of the ML + complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following order:
\text Ag + < NH 4 + < \text H 3 \text O + < \text Na + < \text Tl + . {\text{Ag}}^{ + } \, < \,\hbox{NH}_{4}{}^{ + } \, < \,{\text{H}}_{ 3} {\text{O}}^{ + } \, < \,{\text{Na}}^{ + } \, < \,{\text{Tl}}^{ + }. 相似文献
12.
The mer-[Ru(pic) 3] isomer, where pic is 2-pyridinecarboxylic acid, undergoes base hydrolysis at pH > 12. The reaction was monitored spectrophotometrically
within the UV–Vis spectral range. The product of the reaction, the [Ru(pic) 2(OH) 2] − ion, is formed via a consecutive two-stage process. The chelate ring opening is proceeded by the nucleophilic attack of OH − ion at the carbon atom of the carboxylic group and the deprotonation of the attached hydroxo group. In the second stage,
the fast deprotonation of the coordinated OH − ligand leads to liberation of the monodentato bonded picolinate. The dependence of the observed pseudo-first-order rate constant
on [OH −] is given by
k\textobs1 = \frac k + k1 [\text OH - ] + k + k2 K1 [\text OH - ] 2 k - + k1 + ( k + + k2 K1 )[\text OH - ] + k + K1 [\text OH - ] 2 k_{{{\text{obs}}1}} = \frac{{k_{ + } k_{1} [{\text{OH}}^{ - } ] + k_{ + } k_{2} K_{1} [{\text{OH}}^{ - } ]^{2} }}{{k_{ - } + k_{1} + \left( {k_{ + } + k_{2} K_{1} } \right)[{\text{OH}}^{ - } ] + k{}_{ + }K_{1} [{\text{OH}}^{ - } ]^{2} }} and
( k\textobs2 = \frac kca + kcb K2 [\text OH - ]1 + K2 [\text OH - ] ) \left( {k_{{{\text{obs}}2}} = \frac{{k_{ca} + k_{cb} K_{2} [{\text{OH}}^{ - } ]}}{{1 + K_{2} [{\text{OH}}^{ - } ]}}} \right) for the first and the second stage, respectively, where k
1, k
2, k
-, k
ca
, k
cb
are the first-order rate constants and k
+ is the second-order one, K
1 and K
2 are the protolytic equilibria constants. 相似文献
13.
Densities, viscosities and ultrasonic speeds of sound for binary mixtures of 1,2-dimethoxyethane (DME) with benzene, toluene,
chlorobenzene, benzyl chloride, benzaldehyde, nitrobenzene, and aniline are reported over the entire composition range at
ambient pressure and temperature (i.e., T=298.15 K and p=1.01×10 5 Pa). These experimental data were utilized to derive the excess molar volumes ( VmEV_{\mathrm{m}}^{\mathrm{E}}), excess viscosities ( η
E), and various acoustic parameters including the deviation in isentropic compressibility (Δ κ
S
), internal pressure ( π
I), and excess enthalpy ( H
E). From the excess molar volumes ( VmEV_{\mathrm{m}}^{\mathrm{E}}), the excess partial molar volumes ([`( V)] m,1E\overline{V}_{\mathrm{m},1}^{\mathrm{E}} and [`( V)] m,2E\overline{V}_{\mathrm{m},2}^{\mathrm{E}}) and excess partial molar volumes at infinite dilution ([`( V)] m,10,E\overline{V}_{\mathrm{m},1}^{0,\mathrm{E}} and [`( V)] m,20,E\overline{V}_{\mathrm{m},2}^{0,\mathrm{E}}) were derived and discussed for each liquid component in the mixtures. The excess/deviation properties were found to be either
negative or positive, depending on the molecular interactions and the nature of the liquid mixtures. 相似文献
14.
Speeds of sound have been measured in dipropylene glycol monopropyl ether mixtures with methanol, 1-propanol, 1-pentanol,
and 1-heptanol as a function of composition at 288.15, 298.15, and 308.15 K and atmospheric pressure. Measurements of viscosity
at 298.15 K and atmospheric pressure have also been made for the same mixtures over the whole composition range. The speeds
of sound were combined with our previous densitity results to obtain the isentropic compressibility κ
S
. The molar volumes were multiplied by the isentropic compressibilities to obtain estimates of K
S,m
and its excess counterparts KS,mEK_{S,m}^{\mathrm{E}}. The KS,mEK_{S,m}^{\mathrm{E}} values are negative over the entire range of composition for all mixtures. Deviations in viscosity η from the mixing relation ∑ x
i
ln η
i
and excess Gibbs energies of activation for viscous flow Δ G
∗E have been derived for all of these systems. Also, from the speed of sound results, the apparent molar compressibilities [`( K)] f,i0\overline{K}_{\phi ,i}^{0} of the components have been calculated at infinite dilution. The variations of these properties with the composition, temperature
and the number of carbon atoms in the alcohol molecule are discussed in terms of molecular interactions. The experimental
results have also been discussed on the basis of IR measurements. 相似文献
15.
The 17O-NMR spin-lattice relaxation times ( T
1) of water molecules in aqueous solutions of n-alkylsulfonate (C 1 to C 6) and arylsulfonic anions were determined as a function of concentration at 298 K. Values of the dynamic hydration number,
(S -) = nh - (t c- /t c0 - 1)(\mathrm{S}^{-}) = n_{\mathrm{h}}^{ -} (\tau_{\mathrm{c}}^{-} /\tau_{\mathrm{c}}^{0} - 1), were determined from the concentration dependence of T
1. The ratios (t c -/t c0\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0}) of the rotational correlation times (t c -\tau_{\mathrm{c}}^{ -} ) of the water molecules around each sulfonate anion in the aqueous solutions to the rotational correlation time of pure water
(t c0\tau_{\mathrm{c}}^{0}) were obtained from the n
DHN(S −) and the hydration number ( nh -n_{\mathrm{h}}^{ -} ) results, which was calculated from the water accessible surface area (ASA) of the solute molecule. The t c -/t c0\tau_{\mathrm{c}}^{ -}/\tau_{\mathrm{c}}^{0} values for alkylsulfonate anions increase with increasing ASA in the homologous-series range of C 1 to C 4, but then become approximately constant. This result shows that the water structures of hydrophobic hydration near large
size alkyl groups are less ordered. The rotational motions of water molecules around an aromatic group are faster than those
around an n-alkyl group with the same ASA. That is, the number of water–water hydrogen bonds in the hydration water of aromatic groups
is smaller in comparison with the hydration water of an n-alkyl group having the same ASA. Hydrophobic hydration is strongly disturbed by a sulfonate group, which acts as a water
structure breaker. The disturbance effect decreases in the following order: $\mbox{--} \mathrm{SO}_{3}^{-} > \mbox{--} \mathrm{NH}_{3}^{ +} > \mathrm{OH}> \mathrm{NH}_{2}$\mbox{--} \mathrm{SO}_{3}^{-} > \mbox{--} \mathrm{NH}_{3}^{ +} > \mathrm{OH}> \mathrm{NH}_{2}. The partial molar volumes and viscosity B
V
coefficients for alkylsulfonate anions are linearly dependent on their n
DHN(S −) values. 相似文献
16.
In neutral zinc the 4 p
2 configuration lies above the 3 d
104 s ionization limit and its levels become perturbers in the continuum. Lines have been identified in the Zn I spectrum for the
multiplet, whereas no lines have been found for transitions to 4 p
2 1
D or 1
S. In this paper, cross sections for photoionization from 4 s4 p levels are reported that reveal the positions and widths of the 4 p
2 resonances. Calculations were performed using the multiconfiguration Hartree-Fock (MCHF) and B-spline R-matrix (BSR) method. Results from Breit–Pauli calculations that ignore the background continua are also presented. Included
in the latter are energies for the levels and transition data (transition energies, line strengths, f-values, and A-rates) for all E1 transitions between these
levels. Transition energies and the agreement in the length and velocity values, particularly for allowed transitions, indicate
the accuracy of the computational model. Line widths are compared with other estimates.
Contribution to the Serafin Fraga Memorial Issue. 相似文献
17.
Densities, ρ, and speeds of sound, u, of 2-heptanone + aniline + N-methylaniline or + pyridine systems have been measured at (293.15, 298.15 and 303.15) K and atmospheric pressure using a
vibrating tube densimeter and sound analyzer. The ρ and u values were used to calculate excess molar volumes, V
E, and the excess functions at 298.15 K for the speed of sound, u
E, the thermal expansion coefficient, a pE\alpha_{p}^{\mathrm{E}}, and for the isentropic compressibility, k SE\kappa_{\mathrm{S}}^{\mathrm{E}}. V
E and k SE\kappa_{\mathrm{S}}^{\mathrm{E}} are both negative and increase in the sequence: aniline < N-methylaniline < pyridine. In contrast, u
E is positive and changes in the opposite way. The data suggest the existence of interactions between unlike molecules, which
are much weaker in the pyridine solution. Aromatic amine–alkanone interactions are stronger in mixtures with acetone. The
linear dependence of Rao’s constant with concentration reveals that there is no complex formation in the investigated systems. 相似文献
18.
Results of solubility experiments involving crystalline nickel oxide (bunsenite) in aqueous solutions are reported as functions
of temperature (0 to 350 °C) and pH at pressures slightly exceeding (with one exception) saturation vapor pressure. These
experiments were carried out in either flow-through reactors or a hydrogen-electrode concentration cell for mildly acidic
to near neutral pH solutions. The results were treated successfully with a thermodynamic model incorporating only the unhydrolyzed
aqueous nickel species (viz., Ni 2+) and the neutrally charged hydrolyzed species (viz., Ni(OH) 20)\mathrm{Ni(OH)}_{2}^{0}). The thermodynamic quantities obtained at 25 °C and infinite dilution are, with 2 σ uncertainties:
log 10Ks0o = (12.40 ±0.29),\varDelta rGmo = -(70. 8 ±1.7)\log_{10}K_{\mathrm{s0}}^{\mathrm{o}} = (12.40 \pm 0.29),\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = -(70. 8 \pm 1.7) kJ⋅mol −1;
\varDelta rHmo = -(105.6 ±1.3)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = -(105.6 \pm 1.3) kJ⋅mol −1;
\varDelta rSmo = -(116.6 ±3.2)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} =-(116.6 \pm 3.2) J⋅K −1⋅mol −1;
\varDelta rCp,mo = (0 ±13)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = (0 \pm 13) J⋅K −1⋅mol −1; and log 10Ks2o = -(8.76 ±0.15)\log_{10}K_{\mathrm{s2}}^{\mathrm{o}} = -(8.76 \pm 0.15);
\varDelta rGmo = (50.0 ±1.7)\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = (50.0 \pm 1.7) kJ⋅mol −1;
\varDelta rHmo = (17.7 ±1.7)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = (17.7 \pm 1.7) kJ⋅mol −1;
\varDelta rSmo = -(108±7)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} = -(108\pm 7) J⋅K −1⋅mol −1;
\varDelta rCp,mo = -(108 ±3)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = -(108 \pm 3) J⋅K −1⋅mol −1. These results are internally consistent, but the latter set differs from those gleaned from previous studies recorded in
the literature. The corresponding thermodynamic quantities for the formation of Ni 2+ and Ni(OH) 20\mathrm{Ni(OH)}_{2}^{0} are also estimated. Moreover, the Ni(OH) 3 -\mathrm{Ni(OH)}_{3}^{ -} anion was never observed, even in relatively strong basic solutions ( mOH - = 0.1m_{\mathrm{OH}^{ -}} = 0.1 mol⋅kg −1), contrary to the conclusions drawn from all but one previous study. 相似文献
19.
Sound velocity and density measurements of aqueous solutions of the anionic surfactant SDS (sodium dodecyl sulfate) and the
cationic surfactant CTAB (cetyltrimethylammonium bromide) with the drug furosemide (0.002 and 0.02 mol⋅dm −3) have been carried out in the temperature range 20–40 °C. From these measurements, the compressibility coefficient ( β), apparent molar volume ( φ
v
) and apparent molar compressibility ( φ
κ
) have been computed. From electrical conductivity measurements, the critical micelle concentrations (CMCs) of SDS and CTAB
has been determined in the above aqueous furosemide solutions. From the CMC values as a function of temperature, various thermodynamic
parameters have been evaluated: the standard enthalpy change (D Hmo\Delta H_{\mathrm{m}}^{\mathrm{o}}), standard entropy change (D Smo\Delta S_{\mathrm{m}}^{\mathrm{o}}), and standard Gibbs energy change (D Gmo\Delta G_{\mathrm{m}}^{\mathrm{o}}) for micellization. This work also included viscosity studies of aqueous solutions of SDS and CTAB with the drug in order
to determine the relative viscosity ( η
r). UV-Vis studies have also been carried for the ternary drug/surfactant/water system having SDS in the concentration range
0.002–0.014 mol⋅dm −3. All of these parameters are discussed in terms of drug–drug, drug–solvent and drug–surfactant interactions resulting from
of various electrostatic and hydrophobic interactions. 相似文献
20.
The molar enthalpies of solution of VOSO 4⋅3.52H 2O(s) at various molalities in water and in aqueous sulfuric acid (0.1 mol⋅kg −1), Δ sol
H
m, were measured by a solution-reaction isoperibol calorimeter at 298.15±0.01 K. An improved Archer’s method to estimate the
standard molar enthalpy of solution, D solH0m\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}, was put forward. In terms of the improved method, the values of D solH0m=-24.12±0.03 kJ·mol -1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-24.12\pm 0.03~\mbox{kJ}{\cdot}\mbox{mol}^{-1} of VOSO 4⋅3.52H 2O(s) in water and D solH0m=-15.38±0.06 kJ·mol -1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-15.38\pm 0.06~\mbox{kJ}{\cdot}\mbox{mol}^{-1} in aqueous sulfuric acid were obtained, respectively. The data indicates that the energy state of VOSO 4 in aqueous H 2SO 4 is higher than that in pure water. 相似文献
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