Specific Interaction Enthalpies Research Articles

Calculation of the formation enthalpies of charge-transfer complexes with iodine from the binding constants at 298.15 K

There is a continuing interest in charge-transfer complex chemistry, particularly in their formation thermodynamics. Nowadays, the binding constants and Gibbs energies of formation are available for many complexes. However, the experimental determination of the complexation enthalpies is a more difficult procedure, as it usually requires the establishment of the temperature dependence of the binding constant. Our recent studies of the compensation relationship in the thermodynamics of solvation in hydrogen-bonded systems opened the way to the calculation of the enthalpies of specific (i.e., localized donor-acceptor) interactions (Δint(sp)H) directly from the Gibbs energies at 298.15 K (Δint(sp)G). The calculation procedure is based on the following equation: Δint(sp)G/(kJ·mol−1) = 0.66·Δint(sp)H/(kJ·mol−1) + 2.5n (n corresponds to the coordination number of a solute).In the present work, we checked whether the above relation can be applied to the complex formation between halogens (primarily iodine) and organic electron donors. For 152 complexes with aromatics, nitrogen, oxygen, sulfur, selenium, and phosphor-containing compounds, the formation enthalpies were estimated using the data on equilibrium constants at 298.15 K. In most cases, agreement with the experimental binding enthalpies within the expected measurement error was observed (RMS = 1.4 kJ·mol−1, AD = –0.4 kJ·mol−1).

Intermolecular interactions and thermochemical properties for aliphatic alcohols in 2-methyltetrahydrofuran: “structure–property” relations

Many traditional solvents used in industrial synthesis have significant ecological impacts. To address this, 2-methyltetrahydrofuran has been proposed as a “green” alternative to solvents like dichloromethane, tetrahydrofuran, and 1,4-dioxane. However, simply switching to a green solvent without considering its economic and environmental impact can lead to lower product yield, increased waste, and higher energy costs. Therefore, we aim to systematically analyze the heats of solution of hydrocarbons and alcohols with 2-methyltetrahydrofuran. Additionally, we develop “structure–property” relationships for calculation of the enthalpy of solvation of aliphatic alcohols in 2-methyltetrahydrofuran. We also determine the enthalpies of specific interactions in the “alcohol-2-methyltetrahydrofuran” systems to better understand intermolecular interactions in solutions of 2-methyltetrahydrofuran. This work will provide valuable insights into the properties and energies of these interactions and facilitate the transition to more environmentally friendly media.

The hydrogen bonding enthalpies of water and methanol in ionic liquids

The thermochemical study of hydrogen bonding of water with different proton acceptor ionic liquids was carried out. Along with the available experimental data, the solution enthalpies of water in [BMIM][TfO], [BMIM][BF4] and [BMIM][PF6] were measured. The hydrogen bonding enthalpies of water with various ionic liquids were determined by using previously developed method of solvation enthalpy separation into the nonspecific solvation enthalpy and the specific solute-solvent interaction enthalpy (hydrogen bonding). The findings indicate the formation of a complex, where one molecule of water is bound to two molecules of ionic liquids. Similarly, hydrogen bonding enthalpies of methanol with the same proton acceptor ionic liquids were determined.

Thermodynamics of hydrogen bonding of weak bases in alcohol solutions: Calorimetry of solution, IR-spectroscopy and vapor pressure analysis

Abstract The properties of solutes and their reactivity in aliphatic alcohols significantly depend on the formation of hydrogen bonds. In this work, calorimetric, FTIR-spectroscopic and gas chromatographic vapor pressure studies of hydrogen bonds of weak bases in solution of aliphatic alcohols were carried out. Enthalpies of solutions at infinite dilution of ketones, nitriles and acetates in methanol and octan-1-ol were measured. Obtained from the calorimetric data, the enthalpies of specific interaction of weak bases in aliphatic alcohols unexpectedly found to be positive. IR spectra of solutions of ketones in aliphatic alcohols at infinite dilution were measured at different temperatures. Enthalpies of specific interaction in studied systems obtained from the spectroscopic data confirmed the endothermic process and are in good agreement with calorimetric results. Gibbs energies and entropies of specific interaction of weak bases in aliphatic alcohols were determined. Obtained results show, that the hydrogen bonding process of weak bases in aliphatic alcohols differs substantially from the formation of complexes 1:1 ROH⋯B (B – weak proton acceptor) in aprotic media. The complicated process of hydrogen bonding of weak bases in aliphatic alcohols apparently is controlled by the entropy factor, because these values are above zero.

Enthalpy of cooperative hydrogen bonding in complexes of tertiary amines with aliphatic alcohols: Calorimetric study

The work is devoted to the investigation of thermodynamics of specific interaction of the tertiary aliphatic and aromatic amines with associated solvents as which aliphatic alcohols were taken. Solution enthalpies of aliphatic alcohols in amines (tri- n-propylamine, 2-methylpyridine, 3-methylpyridine, N-methylimidazole) as well as amines in alcohols were measured at infinite dilution. The enthalpies of specific interaction (H-bonding) in systems studied were determined based on experimental data. The enthalpies of specific interaction of amines in aliphatic alcohols significantly lower than the enthalpies of hydrogen bonding in complexes amine–alcohol of 1:1 composition determined in base media due to the reorganization of aliphatic alcohols as solvents. The determination of solvent reorganization contribution makes possible to define the hydrogen bonding enthalpies of amines with clusters of alcohols. Obtained enthalpies of hydrogen bonding in multi-particle complexes are sensitive to the influence of cooperative effect. It was shown, that hydrogen bond cooperativity factors in multi-particle complexes of alcohols with amines are approximately equal for all alcohols when pyridines and N-methylimidazole as solutes are used. At the same time, H-bonding cooperativity factors in complexes of trialkylamines with associative species of alcohols decrease with increasing of alkyl radical length in alcohol and amine molecules. This work shows that the thermodynamic functions of specific interaction of solutes with associated solvents cannot be described using the H-bond parameters for the complexes of 1:1 composition.

Enthalpy of cooperative hydrogen bonding in the complexes of triethyl- and tri-n-butylamines with alcohols: Effect of the alkyl chain length

The measurements of enthalpies of triethylamine and tri-n-butylamine dissolution in aliphatic alcohols and, vice versa, of aliphatic alcohols in amines were carried out. Enthalpies of specific interactions in the studied systems were calculated. The enthalpy of specific interaction determined in the alcohol medium, are significantly less than those obtained at dissolving alcohols in amines. The mechanism of specific interaction of amines with alcohols is discussed. Enthalpies of cooperative hydrogen bonds of tertiary amines with alcohol clusters are calculated. The dependences between the enthalpies of hydrogen bond and the spatial structure of interacting molecules are revealed.

Enthalpies of specific interaction of heteroatom derivatives of three-coordinate phosphorus with chloroform

The nature of hydrogen bonds formed by chloroform with three-coordinate phosphorus derivatives containing sulfur, silicon, and chlorine atoms and their carbon analogs was revealed by analysis of the experimental enthalpies of specific interactions. The main donor centers in the examined compounds were found to be oxygen atoms and π-electron systems of aromatic rings. Sulfur atoms give rise to weaker complexes as compared to oxygen. Phosphorus, chlorine, and silicon atoms are not involved directly in specific interactions with the solvent.

Electronic effects on the enthalpy of specific interaction of three-coordinate phosphorus compounds and acetals with chloroform

The effect of electronic factors in five- and six-membered cyclic three-coordinate phosphorus compounds and acetals on the enthalpy of their specific interaction with chloroform was estimated.

Solution calorimetry of organic nonelectrolytes as a tool for investigation of intermolecular interactions

AbstractThe paper is mainly the review and generalization of the previous publications of the authors. It demonstrates that solution calorimetry method gives the opportunities of more detailed understanding of various aspects of intermolecular interactions in solution. We are assured that prerequisite to such an understanding is the successive analysis of various solute–solvent systems from the simplest ones which include alkanes as a solute or as a solvent to the most complex systems with solvent self‐association via hydrogen bonding. Particular findings discussed in this paper are (i) an inconspicuous contribution of electrostatic solute–solvent interaction to the solvation enthalpy and, accordingly, the dominating contribution of dispersion interactions for nonspecifically solvated solutes; (ii) new, very general method for the extraction of specific interaction enthalpy from the enthalpy of solvation; (iii) new method of determination of self‐association enthalpies for the solvents associated via hydrogen bonding; (iv) new method for determination of cooperative hydrogen bonding enthalpies of proton acceptors with associated species of alcohols; (v) the unique method of experimental determination of the hydrophobic effect enthalpy. Copyright © 2007 John Wiley & Sons, Ltd.

Determination of solvation and specific interaction enthalpies of adamantane derivatives in aprotic solvents

Solution and solvation enthalpies at infinite dilution of 1-bromoadamantane, 1-adamantanol, and 2-adamantanone are reported at 298.15 K in a set of 14 aprotic solvents. The specific interaction enthalpies of the solid solutes are calculated using a methodology recently published by other authors. 1-Adamantanol’s specific interaction enthalpies show a good correlation with the Kamlet–Taft β scale.

Calorimetric determination of the enthalpy of specific interaction of chloroform with a number of proton-acceptor compounds

Calorimetry was used to measure the enthalpies of solution of chloroform in various proton-acceptor solvents and, vice versa, proton-acceptors in chloroform. Based on a previously proposed equation, the enthalpies of specific interaction were calculated and compared with the published data on the enthalpy of hydrogen bonding of chloroform with various proton-acceptor solvents. The composition of the H-bonded complexes mainly formed during the dissolution of proton-acceptor solutes in chloroform was established. It was demonstrated that the dissolution of ethers in chloroform is predominantly accompanied by the formation of 1: 1 complexes, while the dissolution of acetone, dimethylformamide, and dimethyl sulfoxide in chloroform gives rise to more complex associates.

Quantitative Description of the Hydrophobic Effect: the Enthalpic Contribution

A new method of experimental determination of the hydrophobic effect enthalpy is proposed. The method is based on regarding the hydration enthalpy as the sum of the nonspecific hydration enthalpy, specific hydration enthalpy, and the hydrophobic effect enthalpy. The hydrophobic effect enthalpies of noble and simple substance gases, alkanes, arenes, and normal aliphatic alcohols are determined. For the noble gases and alkanes, the hydrophobic effect enthalpy is found to be negative and independent of the size of molecule. For aromatic hydrocarbons, it is positive and grows up with the size of the hydrocarbon. The hydrophobic effect enthalpies of normal aliphatic alcohols are determined by assuming that the specific interaction enthalpies of alcohols in water and in methanol are equal. The hydrophobic effect enthalpy values for the aliphatic alcohols (-10.0 +/- 0.9 kJ.mol(-1)) were found to be close to the alkanes hydrophobic effect enthalpies (-10.7 +/- 1.5 kJ.mol(-1)).

Calorimetric determination of hydrogen‐bonding enthalpy for neat aliphatic alcohols

AbstractHydrogen bonding in pure aliphatic alcohols is investigated using a novel calorimetric approach. Average enthalpies of hydrogen bonding were determined for methanol, ethanol, propan‐1‐ol, propan‐2‐ol, butan‐1‐ol, hexan‐1‐ol and octan‐1‐ol. For all the studied alcohols except methanol the average hydrogen‐bonding enthalpies fall in the range from −16.9 to −17.7 kJ mol−1. A slightly smaller value of −15.1 kJ mol−1 was observed for methanol. From the enthalpies of the specific interactions of the alcohols and chloroform (as proton donors) formed with the alcohols and diethyl ether (as proton acceptors), the dimerization enthalpies were determined for the investigated alcohols: −8.6 ± 0.7 kJ mol−1. The specific interaction and dimerization enthalpies obtained are concurrent with the Badger–Bauer rule and the hydrogen‐bond cooperativity effects. The calorimetric data obtained are supported by literature Fourier transform infrared data on dimer and multimer formation for ethanol and octan‐1‐ol in tetrachloromethane solution. Copyright © 2005 John Wiley & Sons, Ltd.

An investigation into surface energetics of rice hull ash particles using Inverse Gas Chromatography (IGC)

Silanol groups that are present on the surface of rice hull ash or silica ash fillers can positively influence the reinforcing character of the filler. However, being hydrophilic, they present the problem of aggregation and moisture absorption. Physicochemical contributions to reinforcement, provided by silanol groups, influence the filler-polymer and filler-filler interactions. In this study, we investigated the surface energetics of silica ash particles and the effect of chemical surface modification on the free surface energy of silica ash particles was studied. Inverse Gas Chromatography (IGC), a successful evaluation technique for the surface energy of solids, has been used at infinite dilution to determine the nature of surface interaction of various probes with a silica ash surface. The Gibbs free energies and enthalpies of specific interactions were also determined to estimate the acid-base characteristics of the surface of silica ash particles. The influence of heat treatment and surface modification upon the physicochemical parameters was also investigated. It was found that the silica ash surface is acidic in nature. Modification of the surface, by hydrophobization using silane agents, reduces the specific component of surface energy and could be expected to positively affect the reinforcing character. Surface modification reduced the specific component of surface energy by 80% and positively affects the filler-matrix interaction.

A new method for the extraction of specific interaction enthalpy from the enthalpy of solvation

AbstractA new, simple method for the extraction of specific interaction enthalpy from the enthalpy of solvation is proposed. It is based on empirical but very general relationships describing the non‐specific solvation enthalpy. The specific interaction enthalpy is calculated from the solution enthalpies in the solvent under consideration, cyclohexane and tetrachloromethane. The solution enthalpy of at least one linear alkane in the solvent must also be available. The solution enthalpies of a ‘model compound’ or homomorph are not required. This method is applicable not only for proton‐donor solutes but also for acceptor solutes such as iodine. It can be used also for solvents associated by hydrogen bonding (e.g. alcohols). The enthalpies of specific interaction for 280 solute–solvent systems were calculated. Solution enthalpy data were mainly obtained from the literature and partially measured by the authors. The results were compared with literature data on complexation enthalpy. Copyright © 2004 John Wiley & Sons, Ltd.

A Simple Method for Determining the Enthalpy of Specific Solute-Solvent Interaction

An equation correlating a parameter that described the enthalpy of nonspecific solvation of nonelectrolytes with a quantity characterizing intermolecular solute-solvent interaction was found. A simple and versatile method based on this equation was suggested for calculating the enthalpy of nonspecific solvation and the enthalpy of specific solute-solvent interaction.

Molecular Complexes of Crown Ethers in Crystals and Solutions

A review of the experimental and theoretical studies of the crown ether complexes with polar molecules in their crystals, solutions, and in a gas phase is given. The type of the molecular bonds in the complexes, their stoichiometry, and the change in the macrocycle conformation during complex formation are considered, as well as the effect of the macrocycle structure and the nature of the medium on the efficiency of the molecular bonding. New data are given on the enthalpies of transfer of the crown ethers from tetrachloromethane into solvents capable of forming hydrogen bonds. The enthalpies of specific interactions of macrocycles with the molecules of the solvents in the medium of the same solvents are characterized. The conformations of the crown ethers in the media under study are discussed.

The Hydroxyl Group-Solvent and Carbonyl Group-Solvent Specific Interactions for Some Selected Solutes Including Positional Isomers in Acetonitrile/Water Mixed Solvents Monitored by HPLC

We have evaluated the specific hydroxyl group-solvent and carbonyl group-solvent interactions by using an Alltima C18 stationary phase and by measuring the retention data of carefully selected solutes in 60/40, 70/30, and 80/20(v/v%) acetonitrile/water eluents at 25, 30, 35, 40, 45, and 50 oC. The selected solutes are phenol, acetophenone, alkylbenznes(benzene to hexylbenznene), 4 positional isomers of phenylbutanol, 5-phenyl-1-pentanol, 3 positional isomers of alkylarylketone derived from butylbenzene, and 1-phenyl-2-hexanone. The magnitudes of hydroxyl group-acetonitrile/water specific interaction enthalpies are larger than those of carbonyl group-acetonitrile/water specific interaction enthalpies in general while the magnitudes of carbonyl group-methanol/water specific interaction enthalpies are larger than those of hydroxyl group-methanol/water specific interactions. We observed clear discrepancies in functional group-solvent specific interaction among positional isomers. The variation trends of solute transfer enthalpies and entropies with mobile phase composition in the acetonitrile/water system are much different from those in the methanol/water system. The well-known pocket formation of acetonitrile in aqueous acetonitrile mixtures has proven to be useful to explain such phenomena.

Multiparameter Correlations for Describing Thermodynamic Parameters of Solvation: II. Enthalpy of Specific Interaction

The applicability of the approach based on the linear solvation energy relationship to describing the enthalpies of specific solvent-solute interactions was examined. In associated solvents, this approach reflects the contribution of specific interaction incorrectly. Although the enthalpies of solvation as a whole are described well, this is an “occasional” result and is due to averaging over different compounds and redistribu- tion of contributions from other types of interactions. A modification of this approach was suggested to take into account the effect of reorganization of an associated solvent.

Molecular Complexes of Crown Ethers in Crystals and Solutions

A review of the experimental and theoretical studies of the crown ether complexes with polar molecules in their crystals, solutions, and in a gas phase is given. The type of the molecular bonds in the complexes, their stoichiometry, and the change in the macrocycle conformation during complex formation are considered, as well as the effect of the macrocycle structure and the nature of the medium on the efficiency of the molecular bonding. New data are given on the enthalpies of transfer of the crown ethers from tetrachloromethane into solvents capable of forming hydrogen bonds. The enthalpies of specific interactions of macrocycles with the molecules of the solvents in the medium of the same solvents are characterized. The conformations of the crown ethers in the media under study are discussed.