Neat Ethanol Research Articles

H-bonding interaction study for binary mixtures of methyl cellosolve and ethanol: a dielectric, FTIR spectroscopic and volumetric approach

The dielectric measurement of neat ethylene glycol monomethyl ether (EGMME), neat ethanol and their binary mixtures have been carried out using time domain technique in frequency range of 10 MHz to 50 GHz at the temperature range from 10 °C to 25 °C with a difference of 5 °C. The frequency domain technique within the frequency range of 20 Hz to 2 MHz is used to obtain complex dielectric permittivity ε*(ω), electrical modulus M*(ω), complex electrical conductivity σ*(ω) and loss tangent (tan δ) at 25 °C. The dielectric spectra obtained using TDR technique are fitted in Cole-Davidson model to extract the dielectric parameters such as static dielectric permittivity (ε s), relaxation time (τ) and asymmetric distribution parameter (β). These relaxation parameter values are used to predict intermolecular hydrogen bonding between EGMME and ethanol molecules. Furthermore, the inter-molecular interactions through H-bonding between EGMME and ethanol molecules have been confirmed and discussed using Kirkwood correlation factor, excess permittivity, thermodynamic parameter, Bruggeman factor, excess molar volume, excess dielectric permittivity at high frequency and Fourier transform infrared (FTIR) spectra.

Laminar flame speed measurements of ethanol, iso-octane, and their binary blends at temperatures up to 1020 K behind reflected shock waves

A shock tube augmented with a laser-spark ignition system was used to measure the atmospheric-pressure (1 atm ±2%) laminar flame speeds of neat ethanol and iso-octane as well as ethanol/iso-octane blends in a 21% O2-79% Ar (so-called “airgon”) oxidizer. Low-temperature (453 K–524 K) validation experiments of atmospheric-pressure, stoichiometric ethanol/air were first performed for comparison with literature. Two fuel blends with 50% and 85% ethanol (by volume) in iso-octane (E50 and E85, respectively) were then studied in airgon at high unburned-gas temperatures (637 K–1020 K) and at various equivalence ratios (0.75, 1, and 1.2). The low-temperature ethanol/air measurements showed good agreement with literature data, confirming the accuracy of flame speeds measured using a shock tube. High-temperature fuel/airgon flame speeds were simulated with various kinetic models, and significant model disagreement was found, highlighting the value of the new flame speed data in the high-temperature regime. To make the present fuel/airgon measurements compatible with practical engineering applications using air as the oxidizer, the ratio of fuel/airgon and fuel/air flame speeds was calculated using 1D simulations for each experiment, then subsequently used to perform mixture-scaling for the fuel/airgon data to obtain equivalent fuel/air flame speeds. Fuel/air laminar flame speed correlations as a function of the unburned-gas temperature were determined for the studied fuel blends and equivalence ratios. Finally, flame speed sensitivity analyses conducted for high-temperature ethanol/airgon and iso-octane/airgon flames revealed three key governing reactions. Assigning common rate expressions to these reactions across different kinetic models improved the agreement between model-predicted and experimentally measured ethanol flame speeds, but did not have a similar effect for iso-octane, suggesting the need for further exploration of iso-octane-specific reaction rates to facilitate better model agreement.

Prediction of combustion, performance, and emission parameters of ethanol powered spark ignition engine using ensemble Least Squares boosting machine learning algorithms

This research concentrates on the application of machine learning techniques to predict combustion, performance, and emission parameters in a dual-fuel spark ignition (SI) engine powered by neat gasoline and E20 ethanol dual fuel. The goal is to overcome the limitations posed by repeated engine experiments and nonlinear test results. In order to optimise engine parameters, the research seeks to develop efficient machine learning models with high generalizability and employ an optimisation strategy to determine the optimal engine settings. Input for training and evaluating machine learning algorithms, such as Artificial Neural Networks (ANN), and Ensemble LS Boosting was derived from experimental data from a combustion test engine, which includes Neat gasoline, and Ethanol dual fuel blend E20 at various load conditions. The dataset includes engine combustion, performance, and emission indices such as brake thermal efficiency (BTE), Exhaust Gas Temperature (EGT), Hydrocarbons (HC), Carbon monoxide (CO), Carbon dioxide (CO2), and Nitrogen oxides (NOx), under various operating conditions. Load and brake-specific fuel consumption (BSFC) were training input attributes. Using a comprehensive experimental database of input-output engine parameters, the Artificial Neural Network (ANN) and Ensemble LS Boosting were constructed. The training data points were resampled to generate multiple training datasets for training different models. 50 test samples were used to evaluate the generalisation capability of the machine learning models, while BTE, EGT, CO, CO2, HC and NOx, were the primary parameters subject to prediction. The optimal machine learning method was determined by comparing R-squared (R2) values, root mean square error (RMSE), mean square error (MSE), and mean absolute error (MAE). Using multiple hyperparameter tuning iterations, the agreement between actual and predicted values for diverse Ensemble LS Boost algorithms was evaluated. The Ensemble LS Boost model exhibits the maximum level of agreement between predicted and experimental engine parameters across all datasets when compared to the other ANN models. This finding was corroborated by additional research based on test datasets, specifically the test sample interpolation data, which measures generalisation ability. The study also focuses on developing and applying two unique, interactive Simulink models for the Spark Ignition (SI) engine that are tailored for Neat Gasoline and Ethanol E20 test fuels under all loads. The key component of the model-based development technique in MATLAB and Simulink was the incorporation of sophisticated machine learning algorithms, i.e., Ensemble Least-Squares (LS) Boosting, to the model-based development workflow which produced reliable results. Implementing an Ensemble LS Boost machine learning framework is therefore highly recommended as an efficient method for predicting and optimising the combustion, performance, and emission characteristics of dual-fuel gasoline engines utilising Ethanol-based dual-fuel blends.

How Pulse Width Affects Laser Ablation of Organic Liquids.

Laser synthesis in liquids is often carried out in organic solvents to prevent oxidation of metals during nanoparticle generation and to produce tailored carbon-based nanomaterials. This work investigates laser ablation of neat organic liquids acetone, ethanol, n-hexane, and toluene with pulse widths ranging from 30 fs to 4 ps through measurements of reaction kinetics and characterization of the ablation products with optical spectroscopy and mass spectrometry. Increasing the pulse width from 30 fs to 4 ps impacts both the reaction kinetics and product distributions, suppressing the formation of solvent molecule dimers and oxidized molecules while enhancing the yields of gaseous molecules, sp-hybridized carbons, and fluorescent carbon dots. The observed trends are explained in the context of established ionization mechanisms and cavitation bubble dynamical processes that occur during ultrashort pulsed laser ablation of liquid media. The results of this work have important implications both for controlling the formation of carbon shells around metal nanoparticles during the ablation of solid targets in liquid and producing carbon nanomaterials directly from the ablation of organic liquids without a solid target.

Solubility of Salicylic Acid in Some (Ethanol + Water) Mixtures at Different Temperatures: Determination, Correlation, Thermodynamics and Preferential Solvation

Equilibrium mole fraction solubility of salicylic acid in nine aqueous-ethanolic mixtures, as well as in neat water and neat ethanol, was determined at seven temperatures from T = (293.15 to 323.15) K. Salicylic acid solubility in these mixtures was adequately correlated with well-known correlation/prediction methods based on Jouyban-Acree model. Apparent thermodynamic quantities, i.e. Gibbs energy, enthalpy, and entropy, for the dissolution and mixing processes, were computed by means of the van’t Hoff and Gibbs equations. The enthalpy–entropy compensation plot of enthalpy vs. Gibbs energy of dissolution was not linear exhibiting positive slopes from neat water to the mixture of w1 = 0.30 and from the mixture of w1 = 0.50 to neat ethanol indicating enthalpy-driven drug transfer processes but negative in the interval of 0.30 < w1 < 0.50 indicating entropy-driven drug transfer processes from more polar to less polar solvent systems. Moreover, by using the inverse Kirkwood–Buff integrals it is observed that salicylic acid is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in those mixtures of 0.24 < x1 < 1.00.

Understanding the effect of Intake temperature on the ϕ-sensitivity of toluene-ethanol reference fuels and neat ethanol

The low-temperature combustion (LTC) is an attractive concept that enables the modem combustion engines to move toward sustainability mainly by increasing the efficiency and decreasing the emissions. The modern combustion engines which are working based on the LTC concept have specific fuel requirements. Fuel ϕ-sensitivity is a key factor to be considered for tailoring fuels for these engines. Fuel with a high ϕ-sensitivity are more responsive to thermal or fuel stratifications; the auto-ignition properties of different air-fuel mixtures of these fuels, with different equivalence ratio (ϕ), are more diverse. This diversity provide a smoother heat release rate in stratified condition. In this study 11 different toluene–ethanol reference fuels (TERFs) in three research octane number (RON) groups of 63, 84, and 105 together with neat ethanol are evaluated. The Lund ϕ-sensitivity method is used to evaluate these fuels in a cooperative fuel research (CFR) engine. The effect of variation of intake temperature on pressure sensitivity of fuel at a constant combustion phasing is evaluated. This evaluation is performed at two intake temperature of 373 and 423 K, and the results are compared with the outcome of the Lund ϕ-sensitivity number with the intake temperature of 323 K. This study shows that the CR sensitivity response of different blends to the intake charge temperature variation depends on the fuel composition. Accumulated low temperature heat release and latent heat of vaporization. It proves that the fuel ϕ-sensitivity will vary under different thermodynamic conditions. There was a clear link between the accumulated heat released during the early reaction and CR sensitivity of the blends at different intake temperature of 373 and 423 K but the link with the latent heat of vaporization (HoV) found to be inexplicit.

Beating neat fuels by dedicated blending: Performance analysis of bio-hybrid fuel blends on a spark-ignition engine for passenger car applications

The alcohol fuel ethanol is well known for its favorable engine performance in terms of both high net indicated efficiency and low nitrogen oxide emissions. Other alternative neat fuels such as 2-butanone were not able to outperform ethanol in its engine performance. In addition, ethanol has lower production costs compared to 2-butanone, which makes ethanol even more attractive. To compete with neat fuels, model-based fuel design was introduced to tailor fuels by means of dedicated blending of neat alternative components. First, a blend consisting of ethanol, 2-butanone, cyclopentane, and cyclopentanone (EBCC) was defined. Second, a ketone–ester–alcohol–alkane (KEAA) blend consisting of methyl isopropyl ketone, methyl acetate, ethyl acetate, ethanol, methanol, and pentane was developed. Both blends were optimized regarding their production costs while simultaneously considering fuel properties such as the octane number, the oxygen content, and the enthalpy of vaporization. Although both blends showed promising fuel properties, their performance in an internal combustion engine was not evaluated in the fuel design process. This study presents investigations of both blends on a thermodynamic spark-ignition single-cylinder engine for passenger car applications with a compression ratio of 16.4. In particular, a variation of the engine load at an engine speed of 2000 1/min and two variations of the relative air/fuel ratio at the same engine speed and net indicated mean effective pressures of 6 bar and 15 bar were performed. The combustion behavior of the two blends was compared to that of neat ethanol, neat 2-butanone, and conventional gasoline pump fuel. In addition, 0D/1D simulations were performed to evaluate the efficiency losses during the combustion. EBCC achieved a maximum net indicated efficiency of 46.9% at a net indicated mean effective pressure of 15 bar and a relative air/fuel ratio of 1.7, exceeding ethanol’s maximum net indicated efficiency of 46.0% in the same operating point. KEAA achieved a lower net indicated efficiency than ethanol and was on the same level as neat 2-butanone, resulting in a maximum net indicated efficiency of 45.0% in the same operating point. This work shows that the combustion performance in an internal combustion engine should be considered in the fuel design process to better predict promising fuel candidates from an engine perspective.

Maximizing net fuel economy improvement from fusel alcohol blends in gasoline using multivariate optimization

Fusel alcohol mixtures containing ethanol, isobutanol, isopentanol, and 2-phenylethanol have been shown to be a promising means to maximize renewable fuel yield from various biomass feedstocks and waste streams. We hypothesized that use of these fusel alcohol mixtures as a blending agent with gasoline can significantly lower the greenhouse gas emissions from the light-duty fleet. Since the composition of fusel alcohol mixtures derived from fermentation is dependent on a variety of factors such as biocatalyst selection and feedstock composition, multi-objective optimization was performed to identify optimal fusel alcohol blends in gasoline that simultaneously maximize thermodynamic efficiency gain and energy density. Pareto front analysis combined with fuel property predictions and a Merit Score-based metric led to prediction of optimal fusel alcohol-gasoline blends over a range of blending volumes. The optimal fusel blends were analyzed based on a Net Fuel Economy Improvement Potential metric for volumetric blending in a gasoline base fuel. The results demonstrate that various fusel alcohol blends provide the ability to maximize efficiency improvement while minimizing increases to blending vapor pressure and decreases to energy density compared to an ethanol-only bioblendstock. Fusel blends exhibit predicted Net Fuel Economy Improvement Potential comparable to neat ethanol when blended with gasoline in all scenarios, with increased improvement over ethanol at moderate to high bio-blendstock blending levels. The optimal fusel blend that was identified was a mixture of 90% v/v isobutanol and 10% v/v 2-phenylethanol, blended at 45% v/v with gasoline, yielding a predicted 4.67% increase in Net Fuel Economy Improvement Potential. These findings suggest that incorporation of fusel alcohols as a gasoline bioblendstock can improve both fuel performance and the net fuel yield of the bioethanol industry.

Solubility of meloxicam in ethylene glycol-water and propylene glycol-ethanol mixtures: Experimental determination and thermodynamic analysis

The solubility profile of meloxicam in ethylene glycol (EG)-water and propylene glycol (PG)–ethanol mixtures at five temperatures in the range of 288.15–308.15 K under atmospheric pressure are determined and related by means of the Jouyban-Acree model. Experimental results show that solubility always increases as temperature increases; and, when the composition of ethylene glycol increased in the first mixture, while in the second one is maximum, in the region 0.4 < XPG < 0.8. The thermodynamic parameters (Gibbs energy, enthalpy and entropy) of meloxicam in both systems are also calculated by using vańt Hoff and Gibbs equations. Both Gibbs energy and enthalpy of solution are positive in the mixture under analysis. As far as, dissolution entropy is negative in all proportion of EG except for neat ethanol; in PG mixture is positive when 0.1 > XPG and the range 0.4 < XPG < 0.6. For ethylene glycol–water mixtures, enthalpy-driving is the main contributing force to the Gibbs energy. Conversely, in propylene glycol systems, the entropic contribution is higher.

Comparative Chiral Separation of Thalidomide Class of Drugs Using Polysaccharide-Type Stationary Phases with Emphasis on Elution Order and Hysteresis in Polar Organic Mode

The enantioseparation of four phthalimide derivatives (thalidomide, pomalidomide, lenalidomide and apremilast) was investigated on five different polysaccharide-type stationary phases (Chiralpak AD, Chiralpak AS, Lux Amylose-2, Chiralcel OD and Chiralcel OJ-H) using neat methanol (MeOH), ethanol (EtOH), 1-propanol (PROP), 2-propanol (IPA) and acetonitrile (ACN) as polar organic mobile phases and also in combination. Along with the separation capacity of the applied systems, our study also focuses on the elution sequences, the effect of mobile phase mixtures and the hysteresis of retention and selectivity. Although on several cases extremely high resolutions (Rs > 10) were observed for certain compounds, among the tested conditions only Chiralcel OJ-H column with MeOH was successful for baseline-separation of all investigated drugs. Chiral selector- and mobile-phase-dependent reversals of elution order were observed. Reversal of elution order and hysteresis of retention and enantioselectivity were further investigated using different eluent mixtures on Chiralpak AD, Chiralcel OD and Lux Amylose-2 column. In an IPA/MeOH mixture, enantiomer elution-order reversal was observed depending on the eluent composition. Furthermore, in eluent mixtures, enantioselectivity depends on the direction from which the composition of the eluent is approached, regardless of the eluent pair used on amylose-based columns. Using a mixture of polar alcohols not only the selectivities but the enantiomer elution order can also be fine-tuned on Chiralpak AD column, which opens up the possibility of a new type of chiral screening strategy.

Comparative analysis of ternary blends of renewable Diesel, diesel and ethanol with diesel

Renewable diesel is the alternative fuel, produced using hydroprocessing. Renewable diesel can replace diesel fuel without any modifications to existing CI engines. Alongwith renewable diesel, ethanol is also environmently friendly with better cold flow properties than diesel. In present work, various blends of diesel, renewable diesel, and ethanol were prepared, which is rarely researched. Physicochemical properties of all blends were investigated to do a comparative analysis with diesel. The percentage of ethanol was kept at 5%, 10% and 15%, renewable diesel at 20%, 30% and 40% and rest was diesel. It was observed that viscosity, density, and calorific value of neat ethanol (1.076 cSt, 764.1 gm/cm3, and 26.8 MJ/kg) was lower compared to diesel (2.42cSt, 837gm/cm3, and 42.57 MJ/kg) and renewable diesel (2.75cSt, 819gm/cm3, and 41.8 MJ/kg). This was overcome with higher proportion of renewable diesel in each blend. Cold filter plugging point of both ethanol (−51 °C) and renewable diesel (−14 °C) helped improve cold flow properties of all blends. There was an improvement in cetane index of various blends because of renewable diesel’s high cetane index (66.3). It is suggested to use ethanol up to 10% and renewable diesel up to 30% as such blends’ have physio-chemical properties at par with diesel.

Chiral separation of oxazolidinone analogues by liquid chromatography on polysaccharide stationary phases using polar organic mode

The enantioseparation of four oxazolidinone and one biosimilar thiazolidine derivatives was performed on seven different polysaccharide-type chiral stationary phases (Lux Amylose-1, Lux i-Amylose-1, Lux Amylose-2, Lux Cellulose-1, Lux Cellulose-2, Lux Cellulose-3, Lux Cellulose-4) differing in backbone (cellulose or amylose), substituent or the immobilization technologies (coated or immobilized). Polar organic mode was employed using neat methanol (MeOH), ethanol (EtOH), 2-propanol (IPA) and acetonitrile (ACN) either alone or in combinations as mobile phases. Amylose-based columns with ACN provided the highest enantioselectivities for the studied compounds. The replacement of an oxygen with a sulfur atom in the backbone of the studied analytes significantly alters the enantiomer recognition mechanism. Chiral selector-, mobile-phase-, and interestingly immobilization-dependent enantiomer elution order reversal was also observed. Reversal of elution order and hysteresis of retention and enantioselectivity was further investigated using different mixtures of IPA:MeOH and ACN:MeOH on amylose-type chiral stationary phases. Hysteresis of retention and enantioselectivity was observed on all investigated amylose-type columns and binary eluent mixtures, which can be further utilized for fine-tuning chiral separation performance of the studied columns.

Selective Chloride-Mediated Neat Ethanol Oxidation to 1,1-Diethoxyethane via an Electrochemically Generated Ethyl Hypochlorite Intermediate

Selective primary alcohol oxidation to form aldehydes products without overoxidation to carboxylic acids remains a key chemistry challenge. Using simple alkylammonium chloride as the electrolyte with a glassy carbon working electrode in neat ethanol solvent, 1,1-diethoxyethane (DEE) was prepared with >95% faradaic efficiency (FE). DEE serves as a storage platform protecting acetaldehyde from overoxidation and volatilization. UV-vis spectroscopy shows that the reaction proceeds through an ethyl hypochlorite intermediate as the sole chloride oxidation product, and that this intermediate decomposes unimolecularly (rate constant k = (6.896 ± 0.516) × 10-4 s-1) to form HCl catalyst and acetaldehyde, which undergoes rapid nucleophilic attack by ethanol solvent to form the DEE product. This indirect oxidation mechanism enables ethanol oxidation at much less positive potentials due to the fast kinetics for chloride anion oxidation.

Equilibrium solubility of vanillin in some (ethanol + water) mixtures: determination, correlation, thermodynamics and preferential solvation

Equilibrium mole fraction solubility of vanillin in nine aqueous-ethanolic mixtures, as well as in neat water and neat ethanol, was determined at seven temperatures from T = 293.15 to T = 323.15 K. Vanillin solubility in these mixtures was adequately correlated with several well-known correlation models with the mean percentage deviations of 5.9 to 18.3%. Respective apparent thermodynamic functions, i.e. Gibbs energy, enthalpy, and entropy, for the dissolution, mixing and solvation processes, were computed using the van’t Hoff and Gibbs equations. The enthalpy–entropy relationship for vanillin was non-linear in the plot of enthalpy vs. Gibbs energy of dissolution with positive slopes from neat water to the mixture of w1 = 0.10 and the interval 0.50 < w1 < 0.90 but negative in the interval 0.10 < w1 < 0.50 and from w1 = 0.90 to neat ethanol. Accordingly, in the first cases the vanillin transfer from more polar to less polar solvent systems is enthalpy-driven but entropy-driven for the last ones. Moreover, by means of the inverse Kirkwood-Buff integrals is observed that vanillin is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in mixtures of 0.23 < x1 < 1.00.

Viscosity Investigations on the Binary Systems of (1 ChCl:2 Ethylene Glycol) DES and Methanol or Ethanol

In this study, the viscosity behavior of two mixtures of Ethaline (1 ChCl:2 ethylene glycol) with either methanol or ethanol were investigated over the temperature range of 283.15–333.15 K at atmospheric pressure. The measured viscosities of neat Ethaline, methanol, and ethanol showed reliable agreement with the corresponding reported literature values. The mixture viscosities were modeled by an Arrhenius-like model to determine the behavior of viscosity with respect to temperature. The data were also modeled by the four well-known mixture viscosity models of Grunberg–Nissan, Jouyban–Acree, McAllister, and Preferential Solvation. All of the model results were reliable, with the Jouyban–Acree and Preferential Solvation models showing the most accurate agreement with the experimental measurements. The Jones–Dole viscosity model was also investigated for the measured viscosities, and by analyzing the results of this model, strong interactions among Ethaline and the alcohol molecules were proposed for both systems. As a final analysis, viscosity deviations of the investigated systems were calculated to study the deviations of the viscosity behaviors with respect to ideal behavior. Both systems showed negative viscosity deviations at all of the investigated temperatures, with the negative values tending towards zero, and hence more ideal behavior, with increasing temperatures. Moreover, in order to correlate the calculated viscosity deviations, the Redlich–Kister model was successfully used for both systems and at each investigated temperature.

Development of a laminar burning velocity empirical correlation for combustion of iso-octane/ethanol blends in air

This study presents the first demonstration of Marshall and Hinton’s empirical correlation for laminar burning velocity (LBV) applied to iso-octane/ethanol blends. The “Oxford” correlation is first validated for neat iso-octane and ethanol combustion against the outputs of three different chemical kinetics mechanisms and experimental data from the literature. The effects of three different mixing rules, simple energy fraction, modified Le Châtelier, and modified version of the more complex mixing law of Hirasawa, on the predicted LBVs of iso-octane/ethanol blends are evaluated. The modified Le Châtelier mixing law is used with the Oxford correlation to predict blend LBVs at various temperature and pressure conditions. The results are validated against previously unpublished data for iso-octane/ethanol binary fuels at elevated temperature and pressure (up to 10 bar) both from this group, and from the earlier experimental studies of Varea et al. (CORIA) and Broustail et al. (PRISME). The Oxford correlation is shown to perform well across a wide range of temperature and pressure conditions (respectively 298–640 K and 1–10 bar) for the single component fuels. Used in conjunction with a modified Le Châtelier mixing law, the LBVs predicted by the correlation provide an excellent match to the available experimental data across the full range of ethanol concentrations examined (25, 50, and 75% v/v).

Comprehensive insight into solubility, dissolution properties and solvation behaviour of dapsone in co-solvent solutions

This research was mainly committed to the solubility profile, dissolution properties and solvation behavior for the systems formed by dapsone in aqueous solutions of ethanol/acetone/methanol (1) and non-aqueous solution of ethyl acetate (1) + ethanol (2) accompanied by numerous computational methodology. All experiments for solubility were conducted by using a shake-flask method at pressure p = 101.2 kPa and temperatures from 278.15 to 323.15 K. For each solvent solution system, the equilibrium solubility in magnitude of dapsone was recorded as highest in neat ethanol/ethyl acetate/methanol/acetone (1) at 323.15 K; and lowest in neat ethanol (2) or water (2) at 278.15 K. The three-dimensional Hansen solubility parameter was utilized here to investigate solubility performance. Numerous common relationships including modified van’t Hoff Jouyban–Acree model, mixture response surface model, Jouyban–Acree model, and modified Wilson model provided acceptable correlation consequences for the solubility magnitudes obtained with relative average deviations of < 12.33 %. The solubility magnitude at temperature of 298.15 K was also studied by the extended Hildebrand solubility approach, gaining RAD of < 3.24 %. By consideration of some accessible solution properties, the preferential solvation of dapsone was further examined through quantitation by employing the inverse Kirkwood–Buff integrals way. The positive parameters of preferential solvation in ethanol/acetone/methanol-rich and intermediate composition solutions indicates that the drug dapsone is preferentially solvated by ethanol/acetone/methanol. It can be speculated that dapsone performs as Lewis acid behavior with ethanol/acetone/methanol molecules in above composition regions. Nevertheless preferential solvation of dapsone is made neither by ethanol nor by ethyl acetate in the ethyl acetate + ethanol solution. The dissolution of dapsone in all studied systems was endothermic and entropy-driven process.

Solubility of coumarin in (ethanol + water) mixtures: Determination, correlation, thermodynamics and preferential solvation

Equilibrium mole fraction solubility of coumarin in nine aqueous-ethanolic mixtures, as well as in neat water and neat ethanol, was determined at seven temperatures from (293.15 to 323.15) K. Coumarin solubility in was adequately correlated with several well-known correlation models with the mean percentage deviations of 5.1–10.8%. The respective apparent thermodynamic functions (Gibbs energy, enthalpy, and entropy) for the dissolution, mixing and solvation processes were computed using the van’t Hoff and Gibbs equations. The enthalpy-entropy relationship for coumarin was non-linear in the plot of enthalpy vs. Gibbs energy of dissolution with negative slope from neat water to the mixture of w1 = 0.10 but positive from this mixture to neat ethanol. Accordingly, in the first case the coumarin transfer from neat water to the mixture of w1 = 0.10 is entropy-driven, which could be attributed to water molecules release originally bounded as “icebergs” around the non-polar groups of this drug. Otherwise, in mixtures of w1 ≥ 0.10 the driving mechanism for the transfer of coumarin from the more polar solvent systems to those less polar is the enthalpy, probably owing the better drug solvation. Moreover, by means of the inverse Kirkwood-Buff integrals is observed that apparently coumarin is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in mixtures of 0.23 < x1 < 1.00.

Solubility and dissolution thermodynamics of 5-fluorouracil in (ethanol + water) mixtures

Equilibrium mole fraction solubility of 5-fluorouracil (5-FU) in 19 aqueous-ethanolic mixtures, as well as in neat water and neat ethanol, was determined at seven temperatures from (293.15 to 323.15) K. 5-FU solubility in these mixtures was adequately correlated with several well-known correlation models. The respective apparent thermodynamic functions (Gibbs energy, enthalpy, and entropy) for the dissolution, mixing and solvation processes were computed using the van’t Hoff and Gibbs equations. The enthalpy–entropy relationship for 5-FU was non-linear in the plot of enthalpy vs. Gibbs energy of solution with variant but positive slope in almost all the composition regions. Thus, the driving mechanism for 5-FU transfer processes was the enthalpy. In addition, by means of the inverse Kirkwood-Buff integrals is observed that apparently 5-FU is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in ethanol-rich mixtures.

Solubility Behavior of Ethyl l-Thiazolidine-4-carboxylate Hydrochloride in 15 Neat Solvents and Ethanol + Methyl Acetate Binary Solvent from 283.15 to 323.15 K

The solubility (mole fraction) of ethyl l-thiazolidine-4-carboxylate hydrochloride in 15 individual solvents including water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-...