A computationally inspired investigation of the solid forms of (R)-1-phenylethylammonium-(S)-2-phenylbutyrate.
Following the computation of a lattice energy landscape which predicted that there should be more stable, denser forms of (R)-1-phenylethylammonium-(S)-2-phenylbutyrate, crystallizations from a range of solvents were performed to search for other polymorphs and investigate the possibility that the known P4(1) structure could be a hydrate. Extensive crystallization experiments from a wide range of solvents gave fine needles or microcrystalline samples. A redetermination of the P4(1) structure by powder X-ray diffraction located all protons, and in conjunction with other experimental and computational evidence showed that the structure was anhydrous. Evidence for two additional forms was found as mixtures with form I. These include an orthorhombic form, possibly a Z' = 3 polymorph, and another as yet unidentified form obtained as a minor component from dichloromethane solution. However, both these forms appear to be metastable with respect to form I (P4(1)), which is therefore probably the most thermodynamically stable form that can be crystallized from solution under ambient conditions. This determination of the solid state behavior of the less readily crystallized member of the diastereomeric salt system (R)-1-phenylethylammonium-(R/S)-2-phenylbutyrate provides a challenge to the theoretical modeling to explain its ideal resolution behavior.
Antoniadis
Constantinos D
CD
Department of Chemical Engineering, University College London, Torrington Place, London, United Kingdom.
D'Oria
Emiliana
E
Karamertzanis
Panagiotis G
PG
Tocher
Derek A
DA
Florence
Alastair J
AJ
Price
Sarah L
SL
Jones
Alan G
AG
D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D006860:Hydrogen Bonding; D008752:Methylene Chloride / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008962:Models, Theoretical; D008968:Molecular Conformation; D010654:Phenylbutyrates / Q000737:chemistry*; D012984:Software; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
C550381:1-phenylethylammonium-2-phenylbutyrate; D010654:Phenylbutyrates; D012997:Solvents; D014867:Water; D008752:Methylene Chloride