首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Densities, ??, and viscosities, ??, of binary mixtures of 2-methyl-2-propanol with acetone (AC), ethyl methyl ketone (EMK) and acetophenone (AP), including those of the pure liquids, were measured over the entire composition range at 298.15, 303.15 and 308.15?K. From these experimental data, the excess molar volume $V_{\mathrm{m}}^{\mathrm{E}}$ , deviation in viscosity ????, partial and apparent molar volumes ( $\overline{V}_{\mathrm{m},1}^{\,\circ }$ , $\overline{V}_{\mathrm{m},2}^{\,\circ }$ , $\overline{V}_{\phi ,1}^{\,\circ}$ and $\overline{V}_{\phi,2}^{\,\circ} $ ), and their excess values ( $\overline{V}_{\mathrm{m},1}^{\,\circ \mathrm{E}}$ , $\overline{V}_{\mathrm{m,2}}^{\,\circ \mathrm{ E}}$ , $\overline {V}_{\phi \mathrm{,1}}^{\,\circ \mathrm{ E}}$ and $\overline{V}_{\phi \mathrm{,2}}^{\,\circ \mathrm{ E}}$ ) of the components at infinite dilution were calculated. The interaction between the component molecules follows the order of AP > AC > EMK.  相似文献   

2.
The densities, ρ, of binary mixtures of butyl acrylate with 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol, including those of the pure liquids, were measured over the entire composition range at temperatures of (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K and atmospheric pressure. From the experimental data, the excess molar volume $ V_{\text{m}}^{\text{E}} $ V m E , partial molar volumes $ \overline{V}_{\text{m,1}} $ V ¯ m,1 and $ \overline{V}_{\text{m,2}} $ V ¯ m,2 , and excess partial molar volumes $ \overline{V}_{\text{m,1}}^{\text{E}} $ V ¯ m,1 E and $ \overline{V}_{\text{m,2}}^{\text{E}} $ V ¯ m,2 E , were calculated over the whole composition range as were the partial molar volumes $ \overline{V}_{\text{m,1}}^{^\circ } $ V ¯ m,1 ° and $ \overline{V}_{\text{m,2}}^{^\circ } $ V ¯ m,2 ° , and excess partial molar volumes $ \overline{V}_{\text{m,1}}^{{^\circ {\text{E}}}} $ V ¯ m,1 ° E and $ \overline{V}_{\text{m,2}}^{{^\circ {\text{E}}}} $ V ¯ m,2 ° E , at infinite dilution,. The $ V_{\text{m}}^{\text{E}} $ V m E values were found to be positive over the whole composition range for all the mixtures and at each temperature studied, indicating the presence of weak (non-specific) interactions between butyl acrylate and alkanol molecules. The deviations in $ V_{\text{m}}^{\text{E}} $ V m E values follow the order: 1-butanol < 2-butanol < 2-methyl-1-propanol < 2-methyl-2-propanol. It is observed that the $ V_{\text{m}}^{\text{E}} $ V m E values depend upon the position of alkyl groups in alkanol molecules and the interactions between butyl acrylate and isomeric butanols decrease with increase in the number of alkyl groups at α-carbon atom in the alkanol molecules.  相似文献   

3.
Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B?) in the presence of bis(diphenylphosphino)methane dioxide (DPPMDO, L) has been investigated. The equilibrium data have been explained assuming that the species $ {\text{HL}}^{ + } $ , $ {\text{HL}}_{2}^{ + } $ , $ {\text{ML}}_{2}^{3 + } $ , $ {\text{ML}}_{3}^{3 + } $ and $ {\text{ML}}_{4}^{3 + } $ (M3+ = Eu3+, Am3+) 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 the stability constants of the corresponding complexes $ {\text{EuL}}_{n}^{3 + } $ and $ {\text{AmL}}_{n}^{3 + } $ , where n = 2, 3 and L is DPPMDO, in water–saturated nitrobenzene are comparable, whereas in this medium the stability of the cationic species $ {\text{AmL}}_{4}^{3 + } $ (L = DPPMDO) is somewhat higher than that of $ {\text{EuL}}_{4}^{3 + } $ with the same ligand L.  相似文献   

4.
A quantitative method including peak-fitting for determination of the content of short chain branching (SCB) in ethylene/??-olefin copolymers based on differential scanning calorimetry is described. After stepwise isothermal crystallization, the fractions with similar SCB and lamellar thickness are sorted into groups. The content of each group is determined using the peak-fitting area. The statistical terms, the arithmetic mean SCB content $ \overline{C}_{\text{n}} $ , the weighted mean SCB content $ \overline{C}_{\text{w}} $ and the branching broadness index $ I = \overline{C}_{\text{w}} /\overline{C}_{\text{n}} $ are calculated. Through comparing with the SCB contents measured by 13CNMR analysis, the results show that this method can quantitatively characterize the content of SCB in ethylene/??-olefin copolymers with a high degree of accuracy.  相似文献   

5.
Different tetraalkylammonium, viz. N+(CH3)4, N+(C2H5)4, N+(C3H7)4, N+(C4H9)4 along with simple ammonium salts of bis (2-ethylhexyl) sulfosuccinic acid have been prepared by ion-exchange technique. The critical micelle concentration of surfactants with varied counterions have been determined by measuring surface tension and conductivity within the temperature range 283–313 K. Counterion ionization constant, α, and thermodynamic parameters for micellization process viz., $\Delta G_m^{\text{0}} $ , $\Delta H_m^{\text{0}} $ , and $\Delta S_m^{\text{0}} $ and also the surface parameters, Γmax and Amin, in aqueous solution have been determined. Large negative $\Delta G_m^{\text{0}} $ of micellization for all the above counterions supports the spontaneity of micellization. The value of standard free energy, $\Delta G_m^{\text{0}} $ , for different counterions followed the order $${\text{N}}^{\text{ + }} \left( {{\text{CH}}_{\text{3}} } \right)_4 >{\text{NH}}_{\text{4}}^{\text{ + }} >{\text{Na}}^{\text{ + }} >{\text{N}}^{\text{ + }} \left( {{\text{C}}_{\text{2}} {\text{H}}_5 } \right)_{\text{4}} {\text{ $>$ N}}^{\text{ + }} \left( {{\text{C}}_{\text{3}} {\text{H}}_{\text{7}} } \right)_4 >{\text{N}}^{\text{ + }} \left( {{\text{C}}_{\text{4}} {\text{H}}_{\text{9}} } \right)_4 $$ , at a given temperature. This result can be well explained in terms of bulkiness and nature of hydration of the counterion together with hydrophobic and electrostatic interactions.  相似文献   

6.
The equilibrium constants and thermodynamic parameters for complex formation of 18-crown-6(18C6) with Zn2+, Tl+, Hg2+ and $ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $ cations have been determined by conductivity measurements in acetonitrile(AN)-dimethylformamide(DMF) binary solutions. 18-crown-6 forms 1:1 complexes [M:L] with Zn2+, Hg2+ and $ {\text{UO}}^{{{\text{2 + }}}}_{{\text{2}}} $ cations, but in the case of Tl+ cation, a 1:2 [M:L2] complex is formed in most binary solutions. The thermodynamic parameters ( $ \Delta {\text{H}}^{ \circ }_{{\text{c}}} $ and $ \Delta {\text{S}}^{ \circ }_{{\text{c}}} $ ) which were obtained from temperature dependence of the equilibrium constants show that in most cases, the complexes are enthalpy destabilized but entropy stabilized and a non-monotonic behaviour is observed for variations of standard enthalpy and entropy changes versus the composition of AN/DMF binary mixed solvents. The obtained results show that the order of selectivity of 18C6 ligand for these cations changes with the composition of the mixed solvent. A non-linear relationship was observed between the stability constants (logKf) of these complexes with the composition of AN/DMF binary solutions. The influence of the $ {\text{ClO}}^{ - }_{{\text{4}}} $ , $ {\text{NO}}^{ - }_{{\text{3}}} $ and $ {\text{Cl}}^{ - } $ anions on the stability constant of (18C6-Na+) complex in methanol (MeOH) solutions was also studied by potentiometry method. The results show that the stability of (18C6-Na+) complex in the presence of the anions increases in order: $ {\text{ClO}}^{ - }_{{\text{4}}} $  >  $ {\text{NO}}^{ - }_{{\text{3}}} $  >  $ {\text{Cl}}^{ - } $ .  相似文献   

7.
The reaction quotient Q can be expressed in partial pressures as $\hbox {Q}_\mathrm{P}$ or in mole fractions as $\hbox {Q}_{\mathrm{x}}$ . $\hbox {Q}_\mathrm{P}$ is ostensibly more useful than $\hbox {Q}_{\mathrm{x}}$ because the related $\hbox {K}_{\mathrm{x}}$ is a constant for a chemical equilibrium in which T and P are kept constant while $\hbox {K}_{\mathrm{P}}$ is an equilibrium constant under more general conditions in which only T is constant. However, as demonstrated in this work, $\hbox {Q}_{\mathrm{x}}$ is in fact more important both theoretically and technically. The relationships between $\hbox {Q}_{\mathrm{x}}$ , $\hbox {Q}_\mathrm{P}$ , and $\hbox {Q}_{\mathrm{C}}$ are discussed. Four examples of applications are given in detail.  相似文献   

8.
Measurement of the transport of water with respect to the second solvent component in a binary aqueous mixture gives the Washburn number, $ w_{\text{W}} = (n_{\text{W}} )_{ + } t_{ + } - (n_{\text{W}} )_{ - } t_{ - } $ , in a transport number determination, where the ions move in opposite directions, and give the Erdey–Grúz number, $ \Upsigma n_{\text{W}} = (n_{\text{W}} )_{ + } + (n_{\text{W}} )_{ - } $ , in a diffusion experiment, where the ions move in the same direction. Here n W and t are the number of water molecules and transport number, respectively, of the anion or cation. Combination of the results of these two experiments allows unambiguous determination of values for the solvent transport numbers, $ n_{\text{W}} $ , of the individual ions. While the values of $ n_{\text{W}} $ depend on the cosolvent, at high dilutions of the second component the highest value of $ n_{\text{W}} $ found, $ N_{\text{W}} $ , should approach the number of water molecules transported by the ion in pure water, $ N_{\text{W}}^{0} $ . New data for alkali-metal, alkaline-earth metal, hydrogen and halide ions in dilute mixtures of t-butyl alcohol with water are presented. Values of $ N_{\text{W}} $ rounded to whole numbers thus found are: 12 (Li+), 10 (Na+), 6 (K+), 5 (Rb+), 5 (Cs+), 1 (H+), 13 (Ca2+), 16 (Sr2+) and 15 (Ba2+). Factors influencing preferential solvation are briefly discussed. Detailed recalculations of $ n_{\text{W}} $ in the raffinose–water system from literature data also allows resolution of a problem with the Onsager Relations.  相似文献   

9.
Sound speeds have been measured for aqueous solutions of the nucleoside thymidine at T = 298.15 K and at the pressures p = (10, 20, 40, 60, 80, and 100) MPa. The partial molar volumes at infinite dilution, $ V_{2}^{\text{o}} $ , the partial molar isentropic compressions at infinite dilution, $ K_{S,2}^{\text{o}} $ , and the partial molar isothermal compressions at infinite dilution, $ K_{T,2}^{\text{o}} $ $ \{ K_{T,2}^{\text{o}} = - (\partial V_{2}^{\text{o}} /\partial p)_{T} \} $ , have been derived from the sound speeds at elevated pressures using methods described in our previous work. The $ V_{2}^{\text{o}} $ and $ K_{T,2}^{\text{o}} $ results were rationalized in terms of the likely interactions between thymidine and the aqueous solvent. The $ V_{2}^{\text{o}} $ results were also compared with those calculated using the revised Helgeson–Kirkham–Flowers (HKF) equation of state.  相似文献   

10.
The stability constants of 1:1 (M:L) complexes of benzo-15-crown-5 (B15C5) with Li+, Na+, K+ and NH4 + cations, the Gibbs standard free energies ( $ \Updelta {\text{G}}_{\text{c}}^{ \circ } $ ), the standard enthalpy changes ( $ \Updelta {\text{H}}_{\text{c}}^{ \circ } $ ) and standard entropy changes ( $ \Updelta {\text{S}}_{\text{c}}^{ \circ } $ ) for formation of these complexes in acetonitrile–methanol (AN–MeOH) binary mixtures have been determined conductometrically. The conductance data show that the stoichiometry of the complexes formed between the macrocyclic ligand and the studied cations is 1:1 (M:L). In most cases, addition of B15C5 to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The results show that the selectivity order of B15C5 for the metal cations changes with the nature and composition of the binary mixed solvent. The values of standard enthalpy changes ( $ \Updelta {\text{H}}_{\text{c}}^{ \circ } $ ) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard entropy ( $ \Updelta {\text{S}}_{\text{c}}^{ \circ } $ ) were calculated from the relationship $ \Updelta {\text{G}}_{{{\text{c}},298.15}}^{ \circ } = \Updelta {\text{H}}_{\text{c}}^{ \circ } - 298.15\Updelta {\text{S}}_{\text{c}}^{ \circ } $ . A non-linear behavior was observed between the stability constants (log Kf) of the complexes and the composition of the acetonitrile–methanol (AN–MeOH) binary solution. The results obtained in this study, show that in most cases, the complexes formed between B15C5 and Li+, Na+, K+ and NH4 + cations are both enthalpy and entropy stabilized and the values of these thermodynamic quantities change with the composition of the binary solution.  相似文献   

11.
The densities, ρ 123, and speeds of sound, u 123, of ternary o-toluidine (OT, 1) + tetrahydropyran (THP, 2) + pyridine (Py) or benzene or toluene (3) mixtures have been measured as a function of composition at 298.15, 303.15 and 308.15 K. Values of the excess molar volumes, $ V_{123}^{\text{E}} , $ and excess isentropic compressibilities, $ (\kappa_{\text{S}}^{\text{E}} )_{123} , $ of the studied mixtures have been determined by employing the measured experimental data. The observed thermodynamic properties were fitted with the Redlich–Kister equation to determine adjustable ternary parameters and standard deviations. The $ V_{123}^{\text{E}} $ and $ (\kappa_{\text{S}}^{\text{E}} )_{123} $ values were also analyzed in terms of Graph theory. It was observed that Graph theory correctly predicts the sign as well as magnitude of $ V_{123}^{\text{E}} $ and $ (\kappa_{\text{S}}^{\text{E}} )_{123} $ values of the investigated mixtures. Analysis of the data suggests strong interactions and a more close packed arrangement in OT (1) + THP (2) + Py (3) mixtures as compared to those of the OT (1) + THP (2) + benzene (3) or toluene (3) mixtures. This may be due to the presence of a nitrogen atom in Py which results in stronger interactions for the OT:THP molecular entity as compared to those with benzene or toluene.  相似文献   

12.
The crystal structure of n-undecylammonium bromide monohydrate was determined by X-ray crystallography. The crystal system of the compound is monoclinic, and the space group is P21/c. Molar enthalpies of dissolution of the compound at different concentrations m/(mol·kg?1) were measured with an isoperibol solution–reaction calorimeter at T = 298.15 K. According to the Pitzer’s electrolyte solution model, the molar enthalpy of dissolution of the compound at infinite dilution ( $ \Updelta_{\text{sol}} H_{\text{m}}^{\infty } $ ) and Pitzer parameters ( $ \beta_{\text{MX}}^{(0)L} $ and $ \beta_{\text{MX}}^{(1)L} $ ) were obtained. Values of the apparent relative molar enthalpies ( $ {}^{\Upphi }L $ ) of the title compound and relative partial molar enthalpies ( $ \bar{L}_{2} $ and $ \bar{L}_{1} $ ) of the solute and the solvent at different concentrations were derived from experimental values of the enthalpies of dissolution.  相似文献   

13.
The thermodynamics of the stepwise complexation reaction of Cm(III) with propionate was studied by time resolved laser fluorescence spectroscopy (TRLFS) and UV/Vis absorption spectroscopy as a function of the ligand concentration, the ionic strength and temperature (20–90 °C). The molar fractions of the 1:1 and 1:2 complexes were quantified by peak deconvolution of the emission spectra at each temperature, yielding the log10 $ K_{n}^{\prime } $ values. Using the specific ion interaction theory (SIT), the thermodynamic stability constants log10 $ K_{n}^{0} (T) $ were determined. The log10 $ K_{n}^{0} (T) $ values show a distinct increase by 0.15 (n = 1) and 1.0 (n = 2) orders of magnitude in the studied temperature range, respectively. The temperature dependency of the log10 $ K_{n}^{0} (T) $ values is well described by the integrated van’t Hoff equation, assuming a constant enthalpy of reaction and $ \Updelta_{\text{r}} C^\circ_{{p,{\text{m}}}} = 0, $ yielding the thermodynamic standard state $ \left( {\Updelta_{\text{r}} H^\circ_{\text{m}} ,\Updelta_{\text{r}} S^\circ_{\text{m}} ,\Updelta_{\text{r}} G^\circ_{\text{m}} } \right) $ values for the formation of the $ {\text{Cm(Prop)}}_{n}^{3 - n} $ , n = (1, 2) species.  相似文献   

14.
The density functional theory (DFT) calculations within the framework of generalized gradient approximation have been employed to systematically investigate the geometrical structures, stabilities, and electronic properties of Pd n Si q (n = 1–7 and q = 0, +1, ?1) clusters and compared them with the pure ${\text{Pd}}_{n + 1}^{q}$ (n = 1–7 and q = 0, +1, ?1) clusters for illustrating the effect of doping Si atom into palladium nanoclusters. The most stable configurations adopt a three-dimensional structure for both pure and Si-doped palladium clusters at n = 3–7. As a result of doping, the Pd n Si clusters adopt different geometries as compared to that of Pd n+1. A careful analysis of the binding energies per atom, fragmentation energies, second-order difference of energies, and HOMO–LUMO energy gaps as a function of cluster size shows that the clusters ${\text{Pd}}_{4}^{ + }$ , ${\text{Pd}}_{4}$ , ${\text{Pd}}_{8}^{ - }$ , ${\text{Pd}}_{5} {\text{Si}}^{0, + , - }$ , and ${\text{Pd}}_{7} {\text{Si}}^{0, + , - }$ possess relatively higher stability. There is enhancement in the stabilities of palladium frameworks due to doping with an impurity atom. In addition, the charge transfer has been analyzed to understand the effect of doped atom and compared further.  相似文献   

15.
The structure and the stability of pentazolide compounds $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 6-{\it n}}^{\it q}$ (A = B, Al, Si, P, and S; n= 1–3; q = +1, 0, ?1, ?2, and ?3), as high energy-density materials (HEDMs), have been investigated at the B3LYP/6-311+G* level of theory. The natural bond orbital analysis shows that the charge transfer plays an important role when the $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 6-{\it n}}^{\it q}$ species are decomposed to $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 5-{\it n}}\hbox{N}_3^{\it q}$ and N2. The more negative charges are transferred from the N2 molecule after breaking the N5 ring, the more stable the systems are with respect to the decomposition. Moreover, the conclusion can be drawn that ${\hbox{Al}(\hbox{N}_5)_5^{2-}}$ and ${\hbox{Al}_2(\hbox{N}_5)_4^{2-}}$ are predicted to be suitable as potential HEDMs.  相似文献   

16.
Standard transfer Gibbs energies, $ \Updelta_{\text{tr}} G^{^\circ } $ , of a series of homologues α-amino acids have been evaluated by determining the solubility of glycine, alanine, amino butyric acid and norvaline gravimetrically at 298.15 K. Standard entropies of transfer, $ \Updelta_{\text{tr}} S^{^\circ } $ , of the amino acids have also been evaluated by extending the solubility measurement to five equidistant temperatures ranging from 288.15 to 308.15 K. The chemical contributions $ \Updelta_{\text{tr,ch}} G^{^\circ } (i) $ of α-amino acids, as obtained by subtracting theoretically computed contributions to $ \Updelta_{\text{tr}} G^{ \circ } $ due to cavity and dipole–dipole interaction effects from the corresponding experimental $ \Updelta_{\text{tr}} G^{ \circ } $ , are indicative of the superimposed effect of increased basicity and dispersion and decreased hydrophobic hydration (hbh) in DMF–water solvent mixtures as compared to those in water, while, in addition, $ T\Updelta_{\text{tr,ch}} S^{^\circ } (i) $ is guided by structural effects. The computed chemical transfer energies of the –CH2– group, $ \Updelta_{\text{tr,ch}} P^{^\circ } $ (–CH2–) [P = G or S] as obtained by subtracting the value of lower homologue from that of immediately higher homologue, are found to change with composition indicating involvement of several opposing factors in the calculation of the chemical interactions. The $ \Updelta_{\text{tr,ch}} G^{^\circ } $ (–CH2–) values are found to be guided by the decreased hydrophobic effect in DMF–water mixtures, and are indicative of the nature of the three dimensional structure of the aquo-organic solvent system around each solute.  相似文献   

17.
The densities, ρ 12, and speeds of sound, u 12, of 1-ethyl-3-methylimidazolium tetrafluoroborate (1) + N-methylformamide or N,N-dimethylformamide (2) binary mixtures at (293.15. 298.15. 303.15, 308.15 K), and excess molar enthalpies, $ H_{12}^{\text{E}} $ H 12 E , of the same mixtures at 298.15 K have been measured over the entire mole fraction range using a density and sound analyzer (Anton Paar DSA-5000) and a 2-drop microcalorimeter, respectively. Excess molar volume, $ V_{12}^{\text{E}} $ V 12 E , and excess isentropic compressibility, $ \left( {\kappa_{S}^{\text{E}} } \right)_{12} $ ( κ S E ) 12 , values have been calculated by utilizing the measured density and speed of sound data. The observed data have been analyzed in terms of: (i) Graph theory and (ii) the Prigogine–Flory–Patterson theory. Analysis of the $ V_{12}^{\text{E}} $ V 12 E data in terms of Graph theory suggest that: (i) in pure 1-ethyl-3-methylimidazolium tetrafluoroborate, the tetrafluoroborate anion is positioned over the imidazoliun ring and there are interactions between the hydrogen atom of (C–H{edge}) and proton of the –CH3 group (imidazolium ring) with fluorine atoms of tetrafluoroborate anion, and (ii) (1 + 2) mixtures are characterized by ion–dipole interactions to form a 1:1 molecular complex. Further, the $ V_{12}^{\text{E}} $ V 12 E , $ H_{12}^{\text{E}} $ H 12 E and $ \left( {\kappa_{S}^{\text{E}} } \right)_{12} $ ( κ S E ) 12 values determined from Graph theory compare well with their measured experimental data.  相似文献   

18.
The standard (p° = 0.1 MPa) molar enthalpies of formation in the crystalline state of the 2-, 3- and 4-hydroxymethylphenols, $ {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} ( {\text{cr)}} = \, - ( 3 7 7. 7 \pm 1. 4)\,{\text{kJ}}\,{\text{mol}}^{ - 1} $ , $ {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} ( {\text{cr) }} = - (383.0 \pm 1.4) \, \,{\text{kJ}}\,{\text{mol}}^{ - 1} $ and $ {{\Updelta}}_{\text{f}} H_{\text{m}}^{\text{o}} ( {\text{cr)}} = - (382.7 \pm 1.4)\,{\text{kJ}}\,{\text{mol}}^{ - 1} $ , respectively, were derived from the standard molar energies of combustion, in oxygen, to yield CO2(g) and H2O(l), at T = 298.15 K, measured by static bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to measure the dependence of the vapour pressure of the solid isomers of hydroxymethylphenol with the temperature, from which the standard molar enthalpies of sublimation were derived using the Clausius–Clapeyron equation. The results were as follows: $ \Updelta_{\rm cr}^{\rm g} H_{\rm m}^{\rm o} = (99.5 \pm 1.5)\,{\text{kJ}}\,{\text{mol}}^{ - 1} $ , $ \Updelta_{\rm cr}^{\rm g} H_{\rm m}^{\rm o} = (116.0 \pm 3.7) \,{\text{kJ}}\,{\text{mol}}^{ - 1} $ and $ \Updelta_{\rm cr}^{\rm g} H_{\rm m}^{\rm o} = (129.3 \pm 4.7)\,{\text{ kJ mol}}^{ - 1} $ , for 2-, 3- and 4-hydroxymethylphenol, respectively. From these values, the standard molar enthalpies of formation of the title compounds in their gaseous phases, at T = 298.15 K, were derived and interpreted in terms of molecular structure. Moreover, using estimated values for the heat capacity differences between the gas and the crystal phases, the standard (p° = 0.1 MPa) molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, were derived for the three hydroxymethylphenols.  相似文献   

19.
The interaction of oxatomide (OXA), azacyclonol (AZA) and chloropheniramine (ClPA) antihistamine drugs with iodine was studied spectrophotometrically in different solvents and at three different temperatures. The electronic, FT-IR, far-IR, and mass spectra of the resulting charge-transfer (CT) complexes were recorded, in addition to thermal analysis. The results obtained show that the stoichiometries of the reactions are all 1:1. The observed time dependence of the CT band and subsequent formation of $ {\text{I}}_{3}^{ - } $ in solution were related to the slow transformation of the initially formed 1:1 (donor: I2) outer complex to an inner complex (electron donor?Cacceptor), followed by a fast reaction of the inner complex with iodine to form a triiodide ion. The characteristic strong absorptions of $ {\text{I}}_{3}^{ - } $ are observed around 360?nm. The CT-complexes have the formulae [(OXA)I]+ $ {\text{I}}_{3}^{ - } $ , [(AZA)I]+ $ {\text{I}}_{3}^{ - } $ and [(ClPA)I]+ $ {\text{I}}_{3}^{ - } $ . The formation constants (K), molar absorption coefficients (?? CT), and thermodynamic parameters ??H #, ??S # and ??G # of these interaction have been determined and discussed.  相似文献   

20.
The acid?Cbase behavior of $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ was investigated by measuring the formal potentials of the $\mathrm{Fe}(\mathrm{CN})_{6}^{3-}$ / $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ couple over a wide range of acidic and neutral solution compositions. The experimental data were fitted to a model taking into account the protonated forms of $\mathrm{Fe}(\mathrm{CN})_{6}^{4-}$ and using values of the activities of species in solution, calculated with a simple solution model and a series of binary data available in the literature. The fitting needed to take account of the protonated species $\mathrm{HFe}(\mathrm{CN})_{6}^{3-}$ and $\mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-}$ , already described in the literature, but also the species $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}$ (associated with the acid?Cbase equilibrium $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}\rightleftharpoons \mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-} + \mathrm{H}^{+}$ ). The acidic dissociation constants of $\mathrm{HFe}(\mathrm{CN})_{6}^{3-}$ , $\mathrm{H}_{2}\mathrm{Fe}(\mathrm{CN})_{6}^{2-}$ and $\mathrm{H}_{3}\mathrm{Fe}(\mathrm{CN})_{6}^{-}$ were found to be $\mathrm{p}K^{\mathrm{II}}_{1}= 3.9\pm0.1$ , $\mathrm{p}K^{\mathrm{II}}_{2} = 2.0\pm0.1$ , and $\mathrm{p}K^{\mathrm{II}}_{3} = 0.0\pm0.1$ , respectively. These constants were determined by taking into account that the activities of the species are independent of the ionic strength.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号