Capillary Gas Chromatography
Analytical Chemistry and Spectroscopy
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Permethylated β-cyclodextrin (hereafter designated perMe-β-CD), dililuted or not in polysiloxane, is an efficient chiral discriminant for native, 3-methylated, and 1,3-dimethylated series of 5-methyl-5-(CnH2n + 1)hydantoins. From thermodynamic data obtained with pure perMe-β-CD and with the aid of molecular modeling, it is concluded that: (i) For native hydantoin derivatives having a carbon chain at the 5-position varying from ethyl to nonyl (2≤n≤9), the retention time is related to their H-bonding capability. The resolution is poor for derivatives with n≤4. For n≤5, the resolution is considerably improved and this increase in resolution is attributed to the long alkyl chain being capable of being buried inside the cyclodextrin cavity. (ii) For 1,3-dimethylhydantion derivatives having a carbon chain at the 5-position varying from ethyl to hexyl(2≤n≤6), the retention time is mainly determined by a steric fit between the solute and the inner volume of the macrocyclic cavity. For n = 2, a particular behavior is observed, consistent with a total inclusion of the solutes inside the cavity. By contrast with the native hydantoins, the selectively is high for light derivatives. Thus, the selectivity does not correlate with a strong docking energy (such as the presence of H-bonds postulated with native derivatives). (iii) For 3-methylhydantoin derivatives having a carbon chain at the 5-position varying from ethyl to octyl (2≤n≤8), as expected, retension time and selectivity are intermediate between that of native hydantoins and 1,3-dimethylhydantoins. For all three series, where n≤5, the increase in chain length (n) does not bring about substantial changes in the chromatographic results. Therefore, for these long alkyl chain derivatives, similar dominant interactions with perMe-β-CD are postulated.
Type of Medium: