Lattice energy calculations by semiempirical and quantum mechanical methods have been carried out on 17 crystals of phenoxypropionic acids (PPAs), including 5 pairs of racemic and homochiral partners. Racemic crystals always consist of centrosymmetric cyclic hydrogen-bonded dimers, while homochiral crystals invariably include chain ("catemer") motifs of O-H···O hydrogen bonds, except for one case having a pseudo-2-fold axis dimer with two molecules in the asymmetric unit. Energy differences between homochiral and racemic crystals are small, without a consistent trend of higher stability of either state. Partitioned molecule-molecule energy calculations show that hydrogen bonds compete with diffuse dispersive factors or local electrostatic interactions. Monte Carlo methods with empirical atom-atom potentials were also applied to simulate the structural and energetic equilibrium properties of some racemic and homochiral liquids. The latter are very nearly isoenergetic, apparently irrespective of molecular size, shape, and chemical constitution, and do not display significant differences in internal structure with respect to type, number, or persistency of hydrogen-bonded pairs. However, major changes in molecular conformation are predicted for PPAs upon crystallization. On the basis of these results, the roles of thermodynamics and kinetics are discussed in the context of understanding spontaneous resolution.
Theoretical Study of Chiral Carboxylic Acids : Structural and Energetic Aspects of Crystalline and Liquid States / A. Gavezzotti, L. Lo Presti. - In: CRYSTAL GROWTH & DESIGN. - ISSN 1528-7483. - 15:8(2015 Aug), pp. 3792-3803.
Theoretical Study of Chiral Carboxylic Acids : Structural and Energetic Aspects of Crystalline and Liquid States
A. GavezzottiPrimo
;L. Lo Presti
2015
Abstract
Lattice energy calculations by semiempirical and quantum mechanical methods have been carried out on 17 crystals of phenoxypropionic acids (PPAs), including 5 pairs of racemic and homochiral partners. Racemic crystals always consist of centrosymmetric cyclic hydrogen-bonded dimers, while homochiral crystals invariably include chain ("catemer") motifs of O-H···O hydrogen bonds, except for one case having a pseudo-2-fold axis dimer with two molecules in the asymmetric unit. Energy differences between homochiral and racemic crystals are small, without a consistent trend of higher stability of either state. Partitioned molecule-molecule energy calculations show that hydrogen bonds compete with diffuse dispersive factors or local electrostatic interactions. Monte Carlo methods with empirical atom-atom potentials were also applied to simulate the structural and energetic equilibrium properties of some racemic and homochiral liquids. The latter are very nearly isoenergetic, apparently irrespective of molecular size, shape, and chemical constitution, and do not display significant differences in internal structure with respect to type, number, or persistency of hydrogen-bonded pairs. However, major changes in molecular conformation are predicted for PPAs upon crystallization. On the basis of these results, the roles of thermodynamics and kinetics are discussed in the context of understanding spontaneous resolution.File | Dimensione | Formato | |
---|---|---|---|
Gavezzotti_Lo-Presti_revised.pdf
accesso aperto
Tipologia:
Post-print, accepted manuscript ecc. (versione accettata dall'editore)
Dimensione
6.99 MB
Formato
Adobe PDF
|
6.99 MB | Adobe PDF | Visualizza/Apri |
Gavezzotti_Lo-Presti_Crystal_Growth__and_Design_2015_10.1021acs.cgd.5b00442.pdf
accesso riservato
Tipologia:
Publisher's version/PDF
Dimensione
553.54 kB
Formato
Adobe PDF
|
553.54 kB | Adobe PDF | Visualizza/Apri Richiedi una copia |
Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.