The present study aimed at screening conglomerate derivatives of racemic chlocyphos (4-(2chlorophenyl)-5, 5-dimethyl-2-hydroxy-1, 3, 2-dioxaphosphorinane 2-oxide) and to perform enantiomeric separation by preferential crystallization. A list of more than twenty chlocyphos salt derivatives were characterized by various techniques (SHG, DSC and X-ray powder diffraction). A family of salts formed with various alkyl amines crystallize as conglomerates is evidenced. The first attempts to resolve these conglomerates by preferential crystallization at small scale were successful. The mitigated performances of these entrainments are discussed.
We
established that ethylammonium chlocyphos also belongs to a
family of conglomerate-forming systems composed of chlocyphos and
alkyl amine. The pure enantiomer and racemic mixture exhibit very
close X-ray powder diffraction patterns but with some peak shifts.
This led to consider that ethylammonium chlocyphos could crystallize
as a conglomerate but with partial solid solutions close to the pure
enantiomer. The crystal structures of the pure (S)- and (R)-ethylammonium chlocyphos were solved
using single-crystal data. The temperature–composition binary
phase diagram between the two enantiomers of ethylammonium chlocyphos
system was investigated to determine the limit of the solid solutions.
This was confirmed by a Tammann plot related to the eutectic invariant
characterizing the melting of the conglomerate. The limit of the composition
range of the partial solid solutions was confirmed by X-ray powder
diffraction measurements on different enantiomeric compositions.
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