Thermochemistry of paracetamol

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 ( \textC ₈ \textH ₉ \textO ₂ \textN,\text cr I ) = - ( 4 10.4 ±1. 3)\text kJ  \textmol ^{- 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 ( \textC ₈ \textH ₉ \textO ₂ \textN,\text g ) = - ( 2 80.5 ±1. 9)\text kJ  \textmol ^{- 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 ( \textC ₈ \textH ₉ \textO ₂ \textN,\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 ( \textC ₈ \textH ₉ \textO ₂ \textN,\text crII ) = - ( 40 8.4 ±1. 3)\text kJ  \textmol ^{- 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 ( \textC ₈ \textH ₉ \textO ₂ \textN,\text crIII ) = - ( 40 7.4 ±1. 3)\text kJ  \textmol ^{- 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 ( \textC ₈ \textH ₉ \textO ₂ \textN,\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 ( \textC ₈ \textH ₉ \textON,\text g ) = - ( 10 9. 2 ± 2. 2)\text kJ  \textmol ^{- 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}} (C₈H₉O₂N, 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.     

Determination of thermodynamic properties of YRhO3(s) by solid-state electrochemical cell and differential scanning calorimeter

The standard molar Gibbs free energy of formation of YRhO₃(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: ( - )\textPt - Rh/{ \textY₂\textO_\text3( \texts ) + \textYRh\textO₃( \texts ) + \textRh( \texts ) }//\textCSZ//\textO₂( p( \textO₂ ) = 21.21  \textkPa )/\textPt - 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 YRhO₃(s) from elements in their standard state using this electrochemical cell has been calculated and can be represented by: D_\textfG^\texto{ \textYRh\textO₃( \texts ) }/\textkJ  \textmo\textl ^{- 1}( ±1.61 ) = - 1,147.4 + 0.2815  T  ( \textK ) {\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 C^o_p,m C^{o}_{{p,m}} (T) of YRhO₃(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 YRhO₃(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.     

Studies on electron transfer reactions: reduction of heteropoly 10-tungstodivanadophosphate by <Emphasis Type="SmallCaps">l</Emphasis>-cysteine in aqueous acid medium

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, [PV^IVV^IVW₁₀O₄₀]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

Vanadium(V)-substituted Keggin-type heteropolyoxotungstophosphates as electron transfer and antimicrobial agents: oxidation of glutathione and sensitization of MRSA towards β-lactam antibiotics

Glutathione (GSH) undergoes facile electron transfer with vanadium(V)-substituted Keggin-type heteropolyoxometalates, [ \textPV^\textV \textW _{1 1} \textO _{4 0} ] ^{4 -} [ {\text{PV}}^{\text{V}} {\text{W}}_{ 1 1} {\text{O}}_{ 4 0} ]^{{ 4 { - }}} (HPA1) and [ \textPV^\textV \textV^\textV \textW _{1 0} \textO _{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, [ \textPV^\textIV \textW _{1 1} \textO 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 [ \textPV^\textIV \textV^\textIV \textW ₁₀ \textO 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 [ \textPV^\textV \textV^\textV \textV^\textV \textW ₉ \textO _{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.     

Catenated Gallium Compounds Supported by a<Emphasis Type="Italic"> Tris</Emphasis>(pyrazolyl)hydroborato Ligand

[ \textTp^\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 [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→GaI₃, [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]GaGaI₂GaI₂( \textHpz^\textMe₂ {\text{Hpz}}^{{{\text{Me}}_{2} }} ) and [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga(GaI₂)₂Ga[ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ], in addition to the cationic, mononuclear Ga(III) complex {[ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]₂Ga}⁺. Likewise, [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]M (M = K, Tl) reacts with (HGaCl₂) ₂ and Ga[GaCl₄] to give [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→GaCl₃, {[ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]₂Ga}[GaCl₄], and {[ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]GaGa[ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]}[GaCl₄]₂. The adduct [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→B(C₆F₅)₃ may be obtained via treatment of [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]K with “GaI” followed by addition of B(C₆F₅)₃. Comparison of the deviation from planarity of the GaY₃ ligands in [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→GaY₃ (Y = Cl, I) and [ \textTm^{\textBu\textt} {\text{Tm}}^{{{\text{Bu}}^{\text{t}} }} ]Ga→GaY₃, as evaluated by the sum of the Y–Ga–Y bond angles, Σ(Y–Ga–Y), indicates that the [ \textTm^{\textBu\textt} {\text{Tm}}^{{{\text{Bu}}^{\text{t}} }} ]Ga moiety is a marginally better donor than [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga. In contrast, the displacement from planarity for the B(C₆F₅)₃ ligand of [ \textTp^\textMe₂ {\text{Tp}}^{{{\text{Me}}_{2} }} ]Ga→B(C₆F₅)₃ is greater than that of [ \textTm^{\textBu\textt} {\text{Tm}}^{{{\text{Bu}}^{\text{t}} }} ]Ga→B(C₆F₅)₃, an observation that is interpreted in terms of interligand steric interactions in the former complex compressing the C–B–C bond angles.     

Kinetics and mechanism of oxidation of aquaethylenediaminetetraacetatocobaltate(II) by <Emphasis Type="Italic">N</Emphasis>-bromosuccinimide in aqueous acidic solution

The oxidation of aquaethylenediaminetetraacetatocobaltate(II) [Co(EDTA)(H₂O)]⁻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:

Large Carbon Cluster Anions Generated by Laser Ablation of Graphene

The formation of large even-numbered carbon cluster anions, \textC_\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 \textC₁₂₅ ^- {\text{C}}_{{125}}^{ - } to \textC₂₁₁ ^- {\text{C}}_{{211}}^{ - } , doubly charged anions from \textC₇₀^{2 -} {\text{C}}_{{70}}^{{2 - }} to \textC₂₃₀^{2 -} {\text{C}}_{{230}}^{{2 - }} and triply charged cluster anions from \textC₈₀^{3 -} {\text{C}}_{{80}}^{{3 - }} to \textC₂₂₄^{3 -} {\text{C}}_{{224}}^{{3 - }} can be observed. Tandem MS was applied to some selected cluster anions. Though no fragment anions larger than \textC₂₀ ^- {\text{C}}_{{20}}^{ - } can be observed by the process of collisional activation with N₂ gas for most cluster ions, several cluster anions can lose units of C₂, C₄, C₆ or C₈ in their collision process. The differences in their dissociation kinetics and structures require further calculations and experimental studies.     

Solvent extraction of microamounts of cesium into nitrobenzene using ammonium and thallium dicarbollylcobaltates in the presence of 2,3-naphtho-15-crown-5

Extraction of microamounts of cesium by a nitrobenzene solution of ammonium dicarbollylcobaltate ( \textNH ₄ ⁺ \textB ^- ) ( {{\text{NH}}_{ 4}^{ + } {\text{B}}^{ - } }) and thallium dicarbollylcobaltate ( \textTl ⁺ \textB ^- ) ( {{\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 \textML ⁺ {\text{ML}}^{ + } and \textML ₂ ⁺ {\text{ML}}_{ 2}^{ + } ( \textM ⁺ = \textNH₄ ⁺ ,\textTl ⁺ ,\textCs ⁺ ) ( {{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } ,{\text{Cs}}^{ + } } ) are present in the organic phase. The stability constants of the \textML ⁺ {\text{ML}}^{ + } and \textML₂ ⁺ {\text{ML}}_{2}^{ + } species ( \textM ⁺ = \textNH₄ ⁺ ,\textTl ⁺ ) ( {{\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 \textML ⁺ {\text{ML}}^{ + } and \textML₂ ⁺ {\text{ML}}_{2}^{ + } (\textM ⁺ = \textNH₄ ⁺ ,\textTl ⁺ ,\textCs ⁺ ;  \textL = \textN15\textC5) ({{\text{M}}^{ + } = {\text{NH}}_{4}^{ + } ,{\text{Tl}}^{ + } ,{\text{Cs}}^{ + } ;\;{\text{L}} = {\text{N}}15{\text{C}}5}) in the mentioned medium increases in the \textCs ⁺   <  \textNH₄ ⁺   <  \textTl ⁺ {\text{Cs}}^{ + }\,<\, {\text{NH}}_{4}^{ + }\,<\,{\text{Tl}}^{ + } order.     

Effect of the cathode structure on the electrochemical performance of anode-supported solid oxide fuel cells

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 ( \textLa_0.74 \textBi_0.10 \textSr_0.16 )\textMnO_{3 - 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 ( \textLa_0.74 \textBi_0.10 \textSr_0.16 )\textMnO_{3 - d} - ( \textBi_0.7 \textEr_0.3 \textO_1.5 ) \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 cm² 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 cm² 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.     

Natural Bond Orbital (NBO) Population Study of Some Para-Substituted N-Methyl-N-nitrosobenzenesulfonamide Biological Molecules in MeCN Solution

A theoretical study of several para-substituted N-methyl-N-nitrosobenzenesulfonamide biological molecules in MeCN solution has been performed using quantum computational ab initio RHF and density functional B3LYP and B3PW91 methods with the 6-311++G(d,p) basis set. Geometries obtained from DFT calculations were used to perform natural bond orbital analysis. The results show that an intramolecular hydrogen bond exists in the selected molecules, which is confirmed by the NBO analysis. The p characters of the two nitrogen natural hybrid orbitals $ \sigma_{{{\text{N}}3 - {\text{N}}2}} $ increase with increasing $ \sigma_{p} $ values of the para-substituent group on the benzene ring, which results in a lengthening of the N₃–N₂ bond. It is noted that the weakness of the N–N bond is due to $ n_{{{\text{O}}1}} \to \sigma_{{{\text{N}}3 - {\text{N}}2}}^{*} $ delocalization and is responsible for the longer N₃–N₂ bond. In addition, there is a direct correlation between hyperconjugation $ n_{{{\text{O}}1}} \to \sigma_{{{\text{N}}3 - {\text{N}}2}}^{*} $ and the bond dissociation energy in the system, which is confirmed by comparison with isoelectronic isomers.     

On the catalytic mechanism of Pt 4+/? in the oxygen transport activation of N2O by CO

The two-state reaction mechanism of the Pt₄^+/− with N₂O (CO) on the quartet and doublet potential energy surfaces has been investigated at the B3LYP level. The effect of Pt₄ ⁻ anion assistance is analyzed using the activation strain model in which the activation energy (ΔΕ ^≠) 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 Pt₄ ⁻ 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 N₂O 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 Pt₄ ⁻ anion system, it has very significant back-bonding interaction (N₂O negative charge of 0.79e), HOMO has 81.5% π* LUMO(N₂O) 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 N₂O molecule, the N–O bond weakening, and an O⁻(²P) dissociation without surface crossing. For the Pt₄ ⁺ cation system, the strength of the charge transfer is weaker, which leads to the diabatic (spin conserving) dissociation of N₂O: N₂O(¹∑⁺) → N₂(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.     

Thermochemical study on ternary complex of dysprosium <Emphasis Type="Italic">m</Emphasis>-nitrobenzoic acid with <Emphasis Type="Italic">o</Emphasis>-phenanthroline

A ternary binuclear complex of dysprosium chloride hexahydrate with m-nitrobenzoic acid and 1,10-phenanthroline, [Dy(m-NBA)₃phen]₂·4H₂O (m-NBA: m-nitrobenzoate; phen: 1,10-phenanthroline) was synthesized. The dissolution enthalpies of [2phen·H₂O(s)], [6m-HNBA(s)], [2DyCl₃·6H₂O(s)], and [Dy(m-NBA)₃phen]₂·4H₂O(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_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2phen·H₂O(s), 298.15 K] = 21.7367 ± 0.3150 kJ·mol⁻¹, \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [6m-HNBA(s), 298.15 K] = 15.3635 ± 0.2235 kJ·mol⁻¹, \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2DyCl₃·6H₂O(s), 298.15 K] = −203.5331 ± 0.2200 kJ·mol⁻¹, and \Updelta_\texts H_\textm^q \Updelta_{\text{s}} H_{\text{m}}^{\theta } [[Dy(m-NBA)₃phen]₂·4H₂O(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_\textm^q = 3 6 9. 4 9 ±0. 5 6   \textkJ·\textmol ^{- 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]₂·4H₂O(s) was estimated to be \Updelta_\textf H_\textm^q \Updelta_{\text{f}} H_{\text{m}}^{\theta } [[Dy(m-NBA)₃phen]₂·4H₂O(s), 298.15 K] = −5525 ± 6 kJ·mol⁻¹.     

A novel method for the determination of membrane hydration numbers of cations in conducting polymers

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:

Dissolution properties of hexanitrohexaazaisowurtzitane (CL-20) in ethyl acetate and acetone

The enthalpies of dissolution in ethyl acetate and acetone of hexanitrohexaazaisowurtzitane (CL-20) were measured by means of a RD496-2000 Calvet microcalorimeter at 298.15 K, respectively. Empirical formulae for the calculation of the enthalpy of dissolution (Δ_diss H), relative partial molar enthalpy (Δ_diss H _partial), relative apparent molar enthalpy (Δ_diss H _apparent), and the enthalpy of dilution (Δ_dil H _1,2) of each process were obtained from the experimental data of the enthalpy of dissolution of CL-20. The corresponding kinetic equations describing the two dissolution processes were \frac\textda\textdt = 1.60 ×10 ^{- 2} (1 - a)^0.84 {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = 1.60 \times 10^{ - 2} (1 - \alpha )^{0.84} for dissolution process of CL-20 in ethyl acetate, and \frac\textda\textdt = 2.15 ×10 ^{- 2} (1 - a)^0.89 {\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = 2.15 \times 10^{ - 2} (1 - \alpha )^{0.89} for dissolution process of CL-20 in acetone.     

Differentiation of α- or β-Aspartic Isomers in the Heptapeptides by the Fragments of [M + Na]<Superscript>+</Superscript> Using Ion Trap Tandem Mass Spectrometry

Electrospray ionization coupled with low energy collision induced dissociation (CID) in an ion trap mass spectrometer was used to examine the fragmentation patterns of the [M + Na]⁺ of eight pairs of heptapeptides containing α- or β-Asp residues in second and sixth amino acid positions, respectively. Selective cleavages at the peptide backbone C-terminal to two Asp residues were observed, which generated a series of C-terminal y₅ ions and N-terminal b₆ ions. Two typical ions: [ \texty₅ + \textNa-\textH ] ⁺ {\left[ {{{\text{y}}_{{5}}} + {\text{Na}}-{\text{H}}} \right]^{ + }} and [ \textb₆ + \textNa + \textOH ] ⁺ {\left[ {{{\text{b}}_{{6}}} + {\text{Na}} + {\text{OH}}} \right]^{ + }} , produced by α-Asp containing peptides were noted to be much more abundant than those of the peptides with β-Asp, which could be used for distinction of the isomers in Asp2 and Asp6, respectively. In addition, a series of internal ions generated by simultaneous cleavages at Asp residues were detected. Competitive reactions of carboxylic groups occurred between Asp6 side chain and C-terminus. Formation mechanisms of most product ions are proposed. The results obtained in this work are significant since low energy CID has been demonstrated to be effective for the distinction of Asp isomers.     

Mixed-Valence 24-Vanadophosphate Decorated with Six RuII(dmso)3 Groups: [{RuII3(dmso)9PVV11VIVRuIIIO37(OH)3}2]8?

The mixed-valence 24-vanadophosphate (1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal X-ray analysis was carried out on (Na-1), which crystallizes in the triclinic system, space group , with a = 17.168(3) ?, b = 18.1971(14) ?, c = 20.1422(13) ?, α = 114.753(3)°, β = 99.390(4)°, γ = 95.124(4)°, and Z = 2. Polyanion 1 has an unusual, open structure composed of 2 Ru^IIIO₆ octahedra, 2 V^IVO₆ octahedra, 14 V^VO₅ square-pyramids, 8 V^VO₄ tetrahedra, and 2 PO₄ tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six Ru^II(dmso)₃ groups. XPS studies on Na-1 confirm the presence of 2 Ru^III and 6 Ru^II as well as 22 V^V and 2 V^IV centers. Magnetic susceptibility data on Na-1 show that the V^IV–Ru^III pairs are coupled antiferromagnetically, with J ₁ = −13 K and J ₂ ∼ −3 K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. In Memoriam Prof. F. A. Cotton     

Thermal properties of Na2TeO4(s) and TiTe3O8(s)

Molar heat capacity measurement on Na₂TeO₄(s) and TiTe₃O₈(s) were carried out using differential scanning calorimeter. The molar heat capacity values were least squares analyzed and the dependence of molar heat capacity with temperature for Na₂TeO₄(s) and TiTe₃O₈(s) can be given as, $$ \begin{gathered} {\text{C}}^{\text{o}}_{{{\text{p}},{\text{m}}}} \left\{ {{\text{Na}}_{ 2} {\text{TeO}}_{ 4} \left( {\text{s}} \right)} \right\} \,={159}.17 { } + 1.2\,\times\,10^{-4}T-{55}.34\,\times\,10^{5}/T^{2};\hfill \\ C^{\text{o}}_{{{\text{p}},{\text{m}}}} \left\{ {{\text{TiTe}}_{ 3} {\text{O}}_{ 8} \left( {\text{s}} \right)} \right\}\,=\,{ 275}.22{ }+{4}.0\,\times\, 10^{-5}T-{58}.28\,\times\,10^{5}/T^{2};\hfill \\ \end{gathered} $$ From this data, other thermodynamic functions were evaluated.     

Accessing reaction rate constants in on-column reaction chromatography: an extended unified equation for reaction educts and products with different response factors

An extension of the unified equation of chromatography to directly access reaction rate constants k ₁ of first-order reaction in on-column chromatography is presented. This extended equation reflects different response factors in the detection of the reaction educt and product which arise from structural changes by elimination or addition, e.g., under pseudo-first-order reaction conditions. The reaction rate constants k ₁ and Gibbs activation energies DG ¹ \Delta G^{ \ne } of first-order reactions taking place in a chromatographic system can be directly calculated from the chromatographic parameters, i.e., retention times of the educt E and product P ( t_\textR^\textA t_{\text{R}}^{\text{A}} and t_\textR^\textB t_{\text{R}}^{\text{B}} ), peak widths at half height (w _A and w _B), the relative plateau height (h _p) of the conversion profile, and the individual response factors f _A and f _B. The evaluation of on-column reaction gas chromatographic experiments is exemplified by the evaluation of elution profiles obtained by ring-closing metathesis reaction of N,N-diallytrifluoroacetamide in presence of Grubbs second-generation catalyst, dissolved in polydimethylsiloxane (GE SE 30).      

Mechanisms for the formation of layered A<Subscript>4</Subscript>B<Subscript>3</Subscript>O<Subscript>12</Subscript> compounds from coprecipitated hydroxocarbonate and hydroxide systems

We have established and analyzed the sequences of phase transitions in synthesis of layered compounds in the A_nB_n–1O_3n family ( \textA₃^\textII\textLnB₃^\textV\textO₁₂ {\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 La₄Ti₃O₁₂ with n = 4) from coprecipitated hydroxocarbonate and hydroxide systems, including steps involving the formation, solid-phase reaction, or structural rearrangement of intermediates.