On the morphology of caprolactam

Geertman, R.M.; Heijden, A.E.D.M. van der

doi:10.1016/0022-0248(92)90349-n

Cited by 21 publications

(19 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A number of authors [41][42][43] have shown, however, that solutions of polar solvents are more likely to contain solute molecules as monomers rather then dimers as is the case for the system studied here. Hence in these calculations, it was assumed that the aspirin molecules in solution are dispersed as monomeric species reflecting the polar solvent environment and dock accordingly.…”

Section: Morphology Prediction and Calculation Of Surface Energymentioning

confidence: 84%

A Structural−Kinetic Approach to Model Face-Specific Solution/Crystal Surface Energy Associated with the Crystallization of Acetyl Salicylic Acid from Supersaturated Aqueous/Ethanol Solution

Hammond

Pencheva

Roberts

2006

Crystal Growth & Design

View full text Add to dashboard Cite

Classical homogeneous nucleation theory has been integrated with molecular modeling techniques to model the effects of cluster shape-anisotropy associated with nucleation from solution. In this approach, the geometric shape of a crystal nucleus is modeled assuming it equates to the predicted growth morphology of the resultant macroscopic crystal with the later simulated via an attachment energy model using empirical intermolecular force calculations adopting the atom-atom approximation. A new coupled model integrating nucleation theory, morphological simulation and solvent binding calculations, has been developed and combined with experimental nucleation data for the case example of acetyl salicylic acid (aspirin) crystallizing from an aqueous/ ethanol solution. Nucleation parameters, such as critical nucleus size and specific surface energy, have been calculated and compared for the cases of both isotropic (spherical) and anisotropic (polyhedral) nucleus models. A comparison between nucleation data modeled on the basis of both shaped polyhedral and spherical clusters reveals a larger critical nucleus size for the anisotropic (D equivalent ) 16.54 Å at 40°C) compared to the isotropic (D ) 13.07 Å at 40°C) shape model. Theoretical molecular modeling calculations of the specific surface energy anisotropy in solution show the specific surface energy for the habit planes of aspirin to vary from 3.65 mJ/m 2 for the dominant {100} facet to 113 mJ/m 2 for the minor {1 h11} facet. A comparison between the dominant crystal habit planes, notably, the hydrophilic {100} and hydrophobic {002}, reveals them to be more differentiated in terms of their specific surface energy in solution (3.65 and 10.90 mJ/m 2 ) than in a vacuum (829 and 904 mJ/m 2 ), respectively, in good agreement with their known surface chemistry. The total, specific surface energy (41.9 mJ/m 2 ) in solution calculated via molecular modeling for the polyhedral-shaped clusters was found to be somewhat larger, but still in pleasing general agreement with that calculated from experimental nucleation data as determined using induction time measurements assuming a spherical nucleus (3.99 mJ/m 2 ). The potential for the further development of this overall modeling approach is reviewed.

show abstract

Section: Morphology Prediction and Calculation Of Surface Energymentioning

confidence: 84%

A Structural−Kinetic Approach to Model Face-Specific Solution/Crystal Surface Energy Associated with the Crystallization of Acetyl Salicylic Acid from Supersaturated Aqueous/Ethanol Solution

Hammond

Pencheva

Roberts

2006

Crystal Growth & Design

View full text Add to dashboard Cite

show abstract

“…Several researchers have discussed pre-condensation in the solution phase, and the need to account for Ž this effect in morphological modeling Geert-man and van . der Heijden, 1992;Grimbergen and Bennema, 1996 . Ž .…”

Section: Discussionmentioning

confidence: 99%

Modeling crystal shapes of organic materials grown from solution

2000

View full text Add to dashboard Cite

The shape of a crystalline organic solid has a major impact on its downstream processing and on its end-product quality, issues that are becoming increasingly important in the specialty and fine chemical, as well as the pharmaceutical and life science, industries. Though it is widely known that impro®ed crystal shapes can be achie®ed by ®ary-( ) ing the conditions of crystallization such as sol®ent type and impurity le®els , there is far less understanding of how to effect such a change. Until recently, most methods for predicting crystal shapes were based exclusi®ely on the internal crystal structure, and hence could not account for sol®ent or impurity effects. New approaches, howe®er, offer the possibility of accurately predicting the effects of sol®ents. Models for predicting crystal shape are re®iewed, as well as their utility for process and product design. IntroductionIn the chemical process industries, numerous organic ma-Ž terials are purified by solid-liquid separation such as adipic . acid, ibuprofen, and bisphenol A . Many of them, in particular specialty chemicals such as pharmaceuticals, are crystallized from solution. As with other separation techniques, the product purity is the primary measure of product quality. However, unlike other separations, solution crystallization produces materials with specific crystal shapes and size distributions, variables that have a substantial impact on downstream processing and product performance.The effects of crystal size and shape on solids processes are far reaching. They influence the rate at which material Ž . can be processed such as filtering, washing, and drying , as well as physical properties such as bulk density, mechanical strength, and wettability. Storage and handling characteristics, the ease with which solids flow, and the extent of dust formation are all, to some extent, a function of crystal morphology; so is the dispersibility and stability of crystals in suspension, which is important for materials, such as pigments, that are eventually formulated as colloids.Crystal morphology also plays a role in the quality and efficacy of solid dose pharmaceuticals. Crystals of different Ž shapes have different bioa®ailabilities rate and extent of adsorption in the human bodyᎏthis is often determined by the . dissolution rates of different crystal faces , in which case Correspondence concerning this article should be addressed to M. F. Doherty.shape must be controlled for both medical and regulatory Ž . purposes Romero et al., 1991 . Crystal morphology also affects the ease with which the drug is compressed into tablets Ž . Gordon and Amin, 1984 . Both are key factors in the pro-Ž cess efficiency and product quality of pharmaceuticals York, . .The significant impact that crystal size and shape have on crystallization processes requires that they, along with product purity, be tightly controlled. To handle composition and size distribution, there is a plethora of modeling and design Ž . techniques Tavare, 1995;Bermingham et al., 2000 . The phase behavior ...

show abstract

“…In crystallizations of -caprolactam employing cyclohexane as a solvent rather than in its presence as a trace impurity, an additional factor would be a statistical one in that the concentration of solute is much less than that of the solvent so substantially increasing the solvent's effectiveness in disrupting growth on the (200) surface. In essence, this is the mechanism for controlling the morphology of caprolactam crystallized from alkanes that was previously suggested, qualitatively, by van der Heijden et al 30 In consideration of the modified morphology calculated for caprolactam crystals in the presence of cyclohexane, illustrated in Figure 5, it is important to remember that this prediction, based on the modified attachment energies for the faces E′′ att , does not take into account any destabilizing effects that may occur within the individual growth slices due to the presence of the impurity. Essentially, E′′ att is a measure of the growth rate normal to the crystal surface expedited by the presence of an impurity molecule at a lattice site in the surface on which growth a Values are given for the initial, geometrically fitted position and the position of global minimum in lattice energy.…”

Section: Segregation Of Synthesis Impurities In Solid E-caprolactam Amentioning

confidence: 81%

Molecular and Solid-State Modeling of the Crystal Purity and Morphology of ε-Caprolactam in the Presence of Synthesis Impurities and the Imino-Tautomeric Species Caprolactim

2003

View full text Add to dashboard Cite

A study of impurity incorporation into host crystal surfaces, using molecular modeling techniques, is presented for -caprolactam, illustrating a rapid method for predicting the effects of additives on the purity and shape of particles formed through crystallization. Optimum positions, in terms of calculated lattice energy, were located for the impurity molecules within the host crystal lattice. Differential binding energies and modified attachment energies were calculated using the program HABIT95 (Clydesdale, G.; Roberts, K. J; Docherty, R. Quantum Chemistry Program Exchange 1996, 16, 1) for each impurity molecule for all the important growth forms. From the differential binding energies, values were calculated for the equilibrium segregation coefficients. The impact of the impurities cyclohexane, cyclohexanol, cyclohexanone, and the imino-tautomeric form of -caprolactam (or caprolactim) was considered in the study. Excellent agreement was found between calculated equilibrium segregation coefficients for the impurity cyclohexanone in the {110} and {111 h} forms of -caprolactam and reported experimental values for crystals grown from the melt in the presence of a wide range of cyclohexanone impurity concentrations, 0.1-30 mol %, for supersaturations of the melt, 2 × 10 -3 to 6 × 10 -3 (van den Berg, E. P. G.; Bögels, G.; Arkenbout, G. J. J. Cryst. Growth 1998, 191, 169-177). It was calculated that the incorporation of cyclohexanol into -caprolactam would be most significant for the {110} form and that the extent of partitioning of cyclohexane into the most important growth forms is 10-100 times smaller than those in the cases of cyclohexanol and cyclohexanone. The effect of impurity incorporation on the habit of -caprolactam crystals was calculated from the modified attachment energies.

show abstract

On the morphology of caprolactam

Cited by 21 publications

References 11 publications

A Structural−Kinetic Approach to Model Face-Specific Solution/Crystal Surface Energy Associated with the Crystallization of Acetyl Salicylic Acid from Supersaturated Aqueous/Ethanol Solution

A Structural−Kinetic Approach to Model Face-Specific Solution/Crystal Surface Energy Associated with the Crystallization of Acetyl Salicylic Acid from Supersaturated Aqueous/Ethanol Solution

Modeling crystal shapes of organic materials grown from solution

Molecular and Solid-State Modeling of the Crystal Purity and Morphology of ε-Caprolactam in the Presence of Synthesis Impurities and the Imino-Tautomeric Species Caprolactim

Contact Info

Product

Resources

About