Abstract
In the APCI mass spectra of optically active methyl mandelate [M], a difference, which reflects molecular chirality, in the relative intensity of MH+ and diastereomeric adduct ion [M+XH]+ was observed when an optically active 1-phenylethylamine [X] was used as reagent gas. To investigate whether this difference is caused by enantio-selective ion-molecular reaction occuring in the gas phase, X-ray crystallography and MNDO-PM3 were performed to estimate the structure of both adduct ions. The estimated structures showed a difference of 2.2 kcal/mol in terms of heat of formation and the tendency agreed with the result of mass spectra. The energetic difference was due to the differene of hydrogen bonding force formed adduct ion and is caused by steric effects.
