Although sharing a common phenylamine
substructure, these four compounds can be further divided into two subgroups--with acetochlor and alachlor in one group sharing the larger 2-chloro-N-(2,6-dimethylpheny1)-N-(methoxy-methyl)-acetamide core, and chlorambucil and melphalan in the other group, sharing the larger N, N-bis(2-chloroethyl) aniline core.
The method was based on precolumn derivatization of hydantoin-5-acetic acid with phenylamine and complete separation of enantiomers has been achieved on a CHI-DMB analytical column (250x4.
To study the Pi-Pi interactions between a chiral selector and the enantiomers of an analyte, a Pi- acidic or Pi-basic group would be contained in the molecules of the derivatives of hydantoin-5-acetic acid, so the aromatic amines such as phenylamine, 4methylaniline, 3,5-dimethylaniline and 3-nitroaniline were chosen as derivatization reagents.
As shown in Table-1, the retention and resolution of the phenylamine, 4-methylaniline and 3,5-dimethylaniline derivatives of hydantoin-5-acetic acid on the CHI-DMB column were approximate agreement, and the phenylamine derivative of hydantoin-5-acetic acid would be chosen as a typical sample.
1: the 3-nitroaniline derivative of hydantoin-5-acetic acid, 2: the phenylamine derivative of hydantoin-5-acetic acid, 3: the 4-methylaniline derivative of hydantoin-5-acetic acid, 4: the 3,5-dimethylaniline derivative of hydantoin-5-acetic acid; mobile phase composition on the CHI-DMB column: n-hexane 80%; mobile phase composition on the Chiralcel OD-H column: n-hexane 85%; t 1 : retention time of the first enantiomer; t 2 : retention time of the second enantiomer; Alpha: separation factor; R s : resolution; flow rate: 1.