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Neau, Steven H.; Bhandarkar, Satej V.; Hellmuth, Eckhard W.

doi:10.1023/a:1012148910975

Cited by 129 publications

(94 citation statements)

References 8 publications

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“…The regression coefficients of equation (5) are presented in table 3 together with solid and melt heat capacity of paracetamol [9]. Considerable sublimation prior to fusion unfortunately limited the upper range of the measurements and significant evaporation upon fusion prevented heat capacity data of the melt to be determined for the investigated compounds.…”

Section: Methodsmentioning

confidence: 99%

Determination of the activity of a molecular solute in saturated solution

Nordström

Rasmuson

2008

The Journal of Chemical Thermodynamics

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Section: Methodsmentioning

confidence: 99%

Determination of the activity of a molecular solute in saturated solution

Nordström

Rasmuson

2008

The Journal of Chemical Thermodynamics

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“…which still fulfils the restrictions of equation (9). Possibly, equation (10) will provide a comparatively better description of the temperature dependence of the activity coefficient at low temperatures for solutions approximating athermal behaviour -cases involving very large, flexible solute molecules in solutions of smaller solvent molecules.…”

Section: Theorymentioning

confidence: 98%

“…by assuming a linear temperature dependence of ΔCp [8], can allow for the integration to be performed. However, heat capacity data is frequently unavailable, and often, ΔCp is either neglected completely or approximated with a constant value such as the entropy of fusion at Tm [9]. There is a growing awareness of the fact that the temperature dependence of ΔCp can be significant, and Nordström and Rasmuson [8] have described a method allowing ΔCp to be estimated using solubility data in multiple solvents.…”

Section: Theorymentioning

confidence: 99%

(Solid+liquid) solubility of organic compounds in organic solvents – Correlation and extrapolation

Svärd

Rasmuson

2014

The Journal of Chemical Thermodynamics

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A semi-empirical model is developed for the regression of solid-liquid solubility data with temperature. The model fulfils the required boundary conditions, allowing for robust extrapolation to higher and lower temperatures. The model combines a representation of the solid-state activity which accommodates a temperature-dependent heat capacity difference contribution with a scaled three-parameter Weibull function representing the temperature dependence of the solution activity coefficient at equilibrium. Evaluation of the model is based on previously published experimental calorimetric and solubility data of four organic compounds, fenoxycarb, fenofibrate, risperidone and butyl paraben, in five common organic solvents, methanol, ethyl acetate, acetone, acetonitrile, and toluene. The temperature dependence of the van't Hoff enthalpy of solution and its components is analysed and discussed. Among the four compounds the influence of temperature on the enthalpy of fusion varies from moderate to substantial. Based on the semi-empirical model, a new equation containing three adjustable parameters is proposed for regression and extrapolation of solubility data for cases when only melting data and solubility data is available. The equation is shown to provide good accuracy and robustness when evaluated against the full semiempirical model as well as against commonly used, more simple empirical equations. It is shown how such a model can be used to obtain an estimate of the heat capacity difference for cases where accurate solubility data is available in multiple solvents.2

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“…It has been suggested [10] that, for the purpose of estimating the activity of the solid, ΔCp could be approximated by the entropy change upon melting. In the case of risperidone, ΔfusS (T m ) as calculated from experimental melting data is 99 J K -1 mol -1 , which is quite far below the corresponding heat capacity value obtained experimentally and clearly would lead to an underestimation of the influence of ΔCp on the thermodynamics of fusion and the activity of the solid.…”

Section: Analysis and Discussionmentioning

confidence: 99%

Thermodynamics of risperidone and solubility in pure organic solvents

Mealey

Svärd

Rasmuson

2014

Fluid Phase Equilibria

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The solid-liquid solubility of the thermodynamically stable form I of the drug risperidone has been determined by a gravimetric method in nine pure organic solvents in the temperature range 278.15-323.15 K. The melting temperature and associated enthalpy of fusion of risperidone form I has been determined by differential scanning calorimetry (DSC) to be 442.38 K and 43.94 kJ mol -1 , respectively. The heat capacity of the solid form I and the melt have been determined over a range of temperatures by temperature-modulated DSC, and extrapolated data has been used to calculate the Gibbs energy, enthalpy and entropy of fusion from ambient temperature up to the melting point. The ideal solubility within a Raoult's law framework is obtained from the Gibbs energy of fusion, and the solution activity coefficient at equilibrium in the nine solvents quantified. Solutions in all solvents exhibit positive deviation from Raoult's law, with the highest solubility (closest to ideality) in toluene, an aprotic apolar solvent. The solubility curves plotted in a van't Hoff graph show non-linear behaviour and are well-approximated by a second order polynomial.

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Abstract: For the compounds studied, delta Cp was not negligible and was closer to delta Sf than to zero. However, neither of the two assumptions was valid for accurately estimating the ideal solubility as given by the full equation.

Cited by 129 publications

References 8 publications

Determination of the activity of a molecular solute in saturated solution

Determination of the activity of a molecular solute in saturated solution

(Solid+liquid) solubility of organic compounds in organic solvents – Correlation and extrapolation

Thermodynamics of risperidone and solubility in pure organic solvents

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