TY - JOUR
T1 - Computational modeling of capillary electrophoretic behavior of primary amines using dual system of 18-crown-6 and β-cyclodextrin
AU - Elbashir, Abdalla A.
AU - Suliman, Fakhr Eldin O.
PY - 2011/8/5
Y1 - 2011/8/5
N2 - Using capillary electrophoresis (CE) three chiral primary amine compounds 1-aminoindan (AI), 1-(1-naphthyl)ethylamine (NEA) and 1,2,3,4-tetrahydro-1-naphthylamine (THAN), exhibited only partial or no separation when β-cyclodextrin (βCD) was used as chiral selector. The use of 18-crown-6 (18C6) as a second additive with βCD resulted in an enhanced separation. A molecular modeling study, using molecular mechanics and the semiempirical PM6 calculations, was used to help explaining the mechanism of the enantiodifferentiation and to predict the separation process. Optimization of the structures of the complexes by the PM6 method indicate that the poor separation obtained in the presence of the βCD chiral selector alone is due to the small binding energy differences (ΔΔE) of 4.7, 1.1 and 1.2kcalmol-1 for AI, NEA and THAN, respectively. In the presence of 18C6 it was suggested that a sandwich compound between 18C6, amine and βCD is formed. Theoretical calculations show that a significant increase in the binding energy is obtained for the sandwich compounds indicating strong hydrophobic and van der Waals interactions that show enhanced enantiodifferentiation.
AB - Using capillary electrophoresis (CE) three chiral primary amine compounds 1-aminoindan (AI), 1-(1-naphthyl)ethylamine (NEA) and 1,2,3,4-tetrahydro-1-naphthylamine (THAN), exhibited only partial or no separation when β-cyclodextrin (βCD) was used as chiral selector. The use of 18-crown-6 (18C6) as a second additive with βCD resulted in an enhanced separation. A molecular modeling study, using molecular mechanics and the semiempirical PM6 calculations, was used to help explaining the mechanism of the enantiodifferentiation and to predict the separation process. Optimization of the structures of the complexes by the PM6 method indicate that the poor separation obtained in the presence of the βCD chiral selector alone is due to the small binding energy differences (ΔΔE) of 4.7, 1.1 and 1.2kcalmol-1 for AI, NEA and THAN, respectively. In the presence of 18C6 it was suggested that a sandwich compound between 18C6, amine and βCD is formed. Theoretical calculations show that a significant increase in the binding energy is obtained for the sandwich compounds indicating strong hydrophobic and van der Waals interactions that show enhanced enantiodifferentiation.
KW - CE
KW - Chiral separation
KW - Crown ether
KW - Cyclodextrin
KW - Primary amines
KW - Sandwich compounds
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U2 - 10.1016/j.chroma.2011.06.030
DO - 10.1016/j.chroma.2011.06.030
M3 - Article
C2 - 21726870
AN - SCOPUS:79960121935
SN - 0021-9673
VL - 1218
SP - 5344
EP - 5351
JO - Journal of Chromatography A
JF - Journal of Chromatography A
IS - 31
ER -