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Open AccessArticle

Improved Resolution of 4-Chloromandelic Acid and the Effect of Chlorine Interactions Using (R)-(+)-Benzyl-1-Phenylethylamine as a Resolving Agent

1
School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
2
Department of Chemical and Biochemical Engineering, Western University, London, ON N6A 5B9, Canada
3
Department of Engineering, Faculty of Agriculture, Dalhousie University, Truro, NS B2N 5E3, Canada
*
Author to whom correspondence should be addressed.
Molecules 2018, 23(12), 3354; https://doi.org/10.3390/molecules23123354
Received: 1 December 2018 / Revised: 16 December 2018 / Accepted: 17 December 2018 / Published: 18 December 2018
In order to avoid the disadvantage of commonly used resolving agent 1-phenylethylamine (hereafter: PEA), which is soluble in water, (R)-(+)-benzyl-1-phenylethylamine ((R)-(+)-BPA) was used to resolve 4-chloromandelic acid (4-ClMA) in this study. The optimal resolution conditions were determined: absolute ethanol as a solvent, the molar ratio of 4-ClMA to (R)-(+)-BPA as 1:1, the filtration temperature as 15 °C, and the amount of solvent as 1.6 mL/1 mmol 4-ClMA. Thermophysical properties, such as melting point, heat of fusion, and solubility, exhibited significant differences between the less and more soluble salts. The single crystals for the pair of diastereomeric salts were cultivated and their crystal structures were examined thoroughly. In addition to commonly observed interactions like hydrogen bonding and CH/π interactions. The chlorine…chlorine interaction was observed in the less soluble salt presenting as Cl…Cl between adjacent hydrogen network columns, while the Cl/π interaction was observed in the more soluble salt. It was found that halogen interactions played an important role in chiral recognition of 4-ClMA by (R)-(+)-BPA. View Full-Text
Keywords: chlorine interactions; 4-chloromandelic acid; benzyl-1-phenylethylamine; chiral discrimination; resolution chlorine interactions; 4-chloromandelic acid; benzyl-1-phenylethylamine; chiral discrimination; resolution
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MDPI and ACS Style

Peng, Y.; Feng, C.; Rohani, S.; He, Q. Improved Resolution of 4-Chloromandelic Acid and the Effect of Chlorine Interactions Using (R)-(+)-Benzyl-1-Phenylethylamine as a Resolving Agent. Molecules 2018, 23, 3354.

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