Revising Complex Supramolecular Polymerization under Kinetic and Thermodynamic Control

Pathway complexity, hierarchical organization, out of equilibrium, and metastable or kinetically trapped species are common terms widely used in recent, high‐quality publications in the field of supramolecular polymers. Often, the terminologies used to describe the different self‐assembly pathways, the species involved, as well as their relationship and relative stability are not trivial. Different terms and classifications are commonly found in the literature, however, in many cases, without clear definitions or guidelines on how to use them and how to determine them experimentally. The aim of this Minireview is to classify, differentiate, and correlate the existing concepts with the help of recent literature reports to provide the reader with a general insight into thermodynamic and kinetic aspects of complex supramolecular polymerization processes. A good comprehension of these terms and concepts should contribute to the development of new complex, functional materials.     

Hydrogen Spillover Through the Gas Phase. Some Kinetic Aspects

The deactivation kinetics of spillover hydrogen in the gas phase was investigated by systematic variation of the distance between catalyst and reaction compartment. It turned out to be a first-order reaction. Glass surfaces strongly accelerate the deactivation.     

A Thermodynamic Model for Gas Adsorption Isotherms

In this paper based on the principle of solution thermodynamics for gas–solid equilibrium, a relation is developed to express gas adsorption isotherms. An activity coefficient model based on weight fraction of sorbate in the solid phase has been derived that well describes the behavior of various gases on different types of adsorbents. The proposed model has been evaluated and compared with four other models commonly used for gas adsorption isotherms in the literature. For 12 different systems at various isotherms for the temperature range −128 to 100°C and the pressure range 0.02 to 1219 kPa for 689 data points, the proposed model predicts equilibrium pressure with an average deviation of 5.3%, which is about half of the error obtained from other methods. The proposed model clearly outperforms other available methods such as the vacancy solution theory, the ideal adsorption solution model, and other various modified forms of the Langmuir isotherm. Unique features of the proposed model are its simplicity, generality, and accuracy over the entire pressure and temperature ranges.     

Kinetic Relationships between Reactions in the Gas Phase and in Solution

Some recent examples of reactions proceeding both in the gas phase and in solution have been investigated to determine their kinetics and mechanisms. The ratio of the corresponding rate constants, k_G and k_L, of the elementary processes studied has been found to be about unity for unimolecular reactions and between 1 and 10 for bimolecular reactions. The mechanisms, overall rates, rate constants, and activation energies have been determined for the homogeneous gas reaction NOCl + Cl₂O = NO₂Cl + Cl₂ and the reaction NOCl + N₂O₅ = NO₂Cl + 2 NO₂, carried out in C₂F₃Cl₃.     

Thermodynamic Functions of Yttrium Trifluoride and Its Dimer in the Gas Phase

New calculations of the functions for YF₃ and Y₂F₆ in the gas phase using quantum-chemical calculations by MP2 and CCSD(T) methods are performed in connection with the ongoing work on obtaining reliable thermodynamic data of yttrium halides. The obtained values are entered in the database of the IVTANTERMO software complex. Equations approximating the temperature dependence of the reduced Gibbs energy in the Т = 298.15–6000 K range of temperatures are presented.     

Anisotropically Polarizable Dispersions. Basic Thermodynamic Equations and Kinetic Coefficients

Dispersion media formed by anisotropically polarizable particles suspended in nonconducting viscous fluid are considered. The particle anisotropy is set by a freezing-in unit vector; the particle shape is assumed to be close to spherical. A complete hydrodynamic model of such a medium is constructed. The expression for the free energy of a system is derived, and the laws governing the polarization of a dispersion medium and the relaxation of its anisotropy are revealed. The dependence of the effective viscosity of dispersion medium on the strength of an electric field during the flow in plane capillaries is determined.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 293–298.Original Russian Text Copyright © 2005 by Vasil’eva, Cherney.     

A Validated Direct Thin-Layer Chromatographic Separation and Enantioselective Determination of Racemic Centrally Acting Drugs Using Ion-Pair and Ligand-Exchange Chiral Selectors: A Thermodynamic Study of Complexation

JPC – Journal of Planar Chromatography – Modern TLC - A rapid, inexpensive, and stereoselective densitometric—thin-layer chromatographic (TLC) method using l-(+)-tartaric acid and...     

气相二茂铁双电荷离子的动能谱研究

The unimolecular charge separation reactions of the doubly charged ions FeC_(10)H_(10)~(2+)、FeC_(10)H_9~(2+)、FeC_(10)H_8~(2+) produced in the ion source by electron impact from ferrocene have been studied using Mass analyzed Ion Kinetic Energy Spectrometry (MIKES) technique. From the values of the kinetic energy releases (T), the intercharge distances (R) of the exploding doubly charged ions in their transition structures have been estimated and some structural informations about the transition states can be obtained. The collision induced reactions of the FeC_(10)H_(10)~(2+) ion with Ar have been studied using MIKES, we postulate a new type of continuing reaction which may be "collisional charge separation induced dissociation".     

Thermodynamic and Kinetic Foundations of the Micellization Theory: 5. Hierarchy of Kinetic Times

The characteristic kinetic times of micellization in the solution of a nonionic surfactant: the times of establishment of quasi-equilibrium concentrations of molecular aggregates in micellar, subcritical, and overcritical regions, times of establishment of quasi-equilibrium concentrations of molecular aggregates in the near-critical region of their sizes, the average time between two successive acts of emission of surfactant monomers by a micelle, the average value of micelle lifetime, the time of establishment of quasi-stationary mode of matter exchange between the solution and molecular aggregate, as well as the times of fast and slow relaxation in a solution were analyzed. The hierarchy of these times disclosing complex multistage kinetic process of micelle formation and decomposition and the establishment of equilibrium in the micellar solution was revealed. It was shown that this hierarchy is provided by the small parameters of the kinetic theory. The inverse problem of micellization kinetics was discussed; this problem allows us to find the characteristics of the formation work for micellar aggregate from the experimental data on the relaxation time of micellar solution.     

Supramolecular Adducts of Cucurbit[7]uril and Amino Acids in the Gas Phase

The complexation of the macrocyclic cavitand cucurbit[7]uril (Q7) with a series of amino acids (AA) with different side chains (Asp, Asn, Gln, Ser, Ala, Val, and Ile) is investigated by ESI-MS techniques. The 1:1 [Q7 + AA + 2H]²⁺ adducts are observed as the base peak when equimolar Q7:AA solutions are electrosprayed, whereas the 1:2 [Q7 + 2AA + 2H]²⁺ dications are dominant when an excess of the amino acid is used. A combination of ion mobility mass spectrometry (IM-MS) and DFT calculations of the 1:1 [Q7 + AA + 2H]²⁺ (AA = Tyr, Val, and Ser) adducts is also reported and proven to be unsuccessful at discriminating between exclusion or inclusion-type conformations in the gas phase. Collision induced dissociation (CID) revealed that the preferred dissociation pathways of the 1:1 [Q7 + AA + 2H]²⁺ dications are strongly influenced by the identity of the amino acid side chain, whereas ion molecule reactions towards N-butylmethylamine displayed a common reactivity pattern comprising AA displacement. Special emphasis is given on the differences between the gas-phase behavior of the supramolecular adducts with amino acids (AA = Asp, Asn, Gln, Ser, Ala, Val, and Ile) and those featuring basic (Lys and Arg) and aromatic (Tyr and Phe) side chains.

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Kinetic and Thermodynamic Study on the Liquid Phase Adsorption by Starchy Materials in the Alcohol-Water System

Improving adsorptive processes demands a constant search for new adsorbents. In the case of alcohol-water separation, zeolites are widely used. The use of new adsorbents as a substitute for zeolites, mainly starch, has been proposed recently. This work is a thermodynamic and kinetic study of liquid phase adsorption of water from methanol, ethanol, propanol and butanol-water mixtures using starch as the adsorbent. The thermodynamic data were obtained by means of the static method at three different temperatures (25, 40 and 50°C), and were correlated by the Langmuir isotherm. The kinetic data were obtained in a finite liquid bath cell. The influence of temperature and molecular chain length of the alcohol on the capacity and adsorption rate were determined.     

关于弯曲界面气液两相相平衡化学势相等热力学判据的讨论

Thermodynamic criterion of equal chemical potential for phase equilibrium between gas and liquid in curved interface has been introduced in many textbooks and papers. In this paper, the process of the derivation of the criterion is proved to be wrong with analysis. In order to solve the problem, a proof procedure for the thermodynamic criterion of equal chemical potential is provided based on the definition of chemical potential. At the same time, a new thermodynamic criterion of two-phase equilibrium in curved interface is established using Gibbs interface thermodynamics and a new method for derivation of Kelvin equation is put forward based on the thermodynamic criterion of two-phase equilibrium. The new criterion which is derived directly from the second law of thermodynamics has a specific thermodynamic significance and clear physical model.     

直接乙醇燃料电池中乙醇电氧化过程的热力学和动力学考虑

从热力学和动力学角度讨论了质子交换膜燃料电池中的乙醇电氧化过程.理论计算得出直接乙醇燃料电池比乙醇重整质子交换膜燃料电池具有较高的有效能效率.从热力学分析可知,温度低于100℃时乙醇完全氧化的最大转化率仅为14%.从动力学角度考虑,PtSn/C催化剂对乙醇电氧化具有较高的催化活性,但仍不能使乙醇发生完全电氧化.热力学和动力学分析表明,操作温度是影响直接乙醇燃料电池性能的关键因素,它对开发新型催化剂和电解质膜材料提出了新的要求.     

A Combined Kinetic and Thermodynamic Approach for the Interpretation of Continuous‐Flow Heterogeneous Catalytic Processes

The heterogeneous proline‐catalyzed aldol reaction was investigated under continuous‐flow conditions by means of a packed‐bed microreactor. Reaction‐progress kinetic analysis (RPKA) was used in combination with nonlinear chromatography for the interpretation, under synthetically relevant conditions, of important mechanistic aspects of the heterogeneous catalytic process at a molecular level. The information gathered by RPKA and nonlinear chromatography proved to be highly complementary and allowed for the assessment of optimal operating variables. In particular, the determination of the rate‐determining step was pivotal for optimizing the feed composition. On the other hand, the competitive product inhibition was responsible for the unexpected decrease in the reaction yield following an apparently obvious variation in the feed composition. The study was facilitated by a suitable 2D instrumental arrangement for simultaneous flow reaction and online flow‐injection analysis.     

Antiplasmodial Drugs in the Gas Phase: A CID and DFT Study of Quinolon-4(1H)-Imine Derivatives

The gas-phase behavior of 12 quinolon-4(1H)-imine derivatives with antiplasmodial activity was investigated using electrospray ionization tandem mass spectrometry together with collision induced dissociation and density functional theory (DFT) calculations. The most probable protonation site was predicted by calculating the proton affinity (PA) values for each possible protonation site and it was found to be the imine nitrogen for all compounds under study. Fragmentation pathways of the protonated molecules were proposed and the assignment of product ion structures was performed taking into account theoretical calculations. The nature of the quinoline substituent was found to influence the gas-phase behavior of the compounds under study. The data acquired allowed to bracket the proton affinity of the quinolin-4-imine scaffold, which can be a useful starting point to choose appropriate references for determining PA values of this scaffold. Figure

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Halogen‐Bonded Supramolecular Capsules in the Solid State,in Solution,and in the Gas Phase

Supramolecular capsules were assembled by neutral halogen bonding (XB) and studied in the solid state, in solution, and in the gas phase. The geometry of the highly organized capsules is shown by an X‐ray crystal structure which features the assembly of two XB hemispheres, geometrically rigidified by H‐bonding to eight MeOH molecules and encapsulation of two benzene guests. To enhance capsular association strength, tuning the XB donor is more efficient than tuning the XB acceptor, due to desolvation penalties in protic solvents, as shown for a tetraquinuclidine XB acceptor hemisphere. With a tetra(iodoethynyl) XB donor and a tetralutidine XB acceptor, the association in deuterated benzene/acetone/methanol 70:30:1 at 283 K reaches K _a=(2.11±0.39)×10⁵ m ⁻¹ (ΔG =−6.9±0.1 kcal mol⁻¹). The stability of the XB capsules in the gas phase was confirmed by electrospray ionization mass spectrometry (ESI‐MS). A new guest binding site was uncovered within the elongated iodoethynyl capsule.