Stereochemical effects in mass spectrometry. 7. Determination of absolute configuration of some organic molecules by reaction mass spectrometry

Hybrid density functional theory study of fragment ions generated during mass spectrometry of 1,3-dioxane derivatives

It was recently reported that the cis,cis and trans,trans diastereoisomers of four 2(r)-R-2,4(R),6(S)-trimethyl-1,3-dioxane derivatives show distinct electron ionization mass spectra. As a possible explanation for this finding, the authors suggested that the ions generated during the mass spectrometry of these compounds could follow different fragmentation patterns that initiate from different ion conformations. In this report, hybrid density functional theory methods have been used to investigate the conformational preference of three ions involved in the mass spectrometry of some 1,3-dioxane derivatives. We found that there is indeed more than one stable ion conformation for each of the investigated ions. Energy profiles along the torsional coordinates connecting the conformers are presented, and factors influencing the relative stability of ion conformations are discussed.

Chiral recognition of zinc(II) ion complexes composed of bicyclo[3.3.0] octane-2,6-diol and s-naproxen probed by collisional-induced dissociation

Chiral recognition of racemic bicyclo[3.3.0] octane-2,6-diol(B) was achieved in the gas phase using s-Naproxen(A) as reference, using the kinetics of competitive unimolecule dissociation of tetrameric zinc(II)-bound complexes by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer(ESI-FTMS). As undergoing a mild competitive collision-induced dissociation(CID) experiment with a constant pressure argon gas introduced by leak valve, the tetrameric cluster ion [A(2)B(2)Z(n)(II)-H](+) forms only two trimeric ions and R(chiral) is subsequently obtained in the kinetic method. Further studies obtained the difference of Gibbs free energy of [ABZ(n)(II)-H](+)(Delta Delta G(ABZn(II)-H](+))) by dissociating [A(2)BZ(n)(II)-H](+), resulting two fragment ions [ABZ(n)(II)-H](+) and [A(2)Z(n)(II)-H](+), which can be established to a linear relationship between Delta Delta G([ABZn(II)-H](+)) and R(chiral)' basing on the kinetic method. The value of R(chiral)' suggested that Delta Delta G([ABZn(II)-H](+)) could be regarded as zero. Meanwhile, dissociation of [AB(2)Z(n)(II)-H](+) generated only one daughter ion [ABZ(n)(II)-H](+) in a stable pressure. Thus, a linear relationship was established between the difference of Gibbs free energy of [AB(2)Z(n)(II)-H](+)(Delta Delta G([AB(2)Zn(II)-H](+))) and R(chiral)" if the Delta Delta G([ABZn(II)-H](+)) can be negligible. Because there is also a linear relationship of R(chiral) in the tetrameric ion [A(2)B(2)Z(n)(II)-H](+) and the Gibbs energy difference of trimeric cluster ion [A(2)BZ(n)(+)(II)-H](Delta Delta G([A(2)BZn(II)-H](+))) plus that of [AB(2)Z(n)(II)-H](+), Delta Delta G([A(2)BZ(n)(II)-H]+]) is easy to be calculated in the dissociation process of tetrameric ion. Stable of R(chiral), R(chiral)' and R(chiral)" under different pressures show T(eff) does not affect the chiral recognition of cluster ions in the condition selected. If an only-one-daughter-ion fragment process of [A(2)BZ(n)(II)-H](+) was existed, R(chiral)''' relating to this dissociation would be calculated just like R(chiral)" of [AB(2)Z(n)(II)-H](+) does. Conclusion was obtained that [A(2)BZ(n)(II)-H](+) makes more contribution to chiral recognition of tetrameric ion measured by kinetic method than [AB(2)Z(n)(II)-H](+) does as R(chiral)''' and R(chiral)" were applied as index to evaluate the Gibbs free energy difference of these two trimeric cluster ions. Further discussion shows that steric interactions and pi-pi stacking interactions are the major factors responsible for the observed efficient chiral recognition in this system.

Chiral recognition detected by fast atom bombardment mass spectrometry

Detection of chiral recognition in various intermolecular interaction systems using mass spectrometry has become important for the modern fields of analytical chemistry, organic chemistry, and biochemistry due to the characteristic nature of the rapid method and the trace amount needed. This review presents the various methods for detecting and evaluating chiral recognition used primarily in fast atom bombardment mass spectrometry. Emphasis is put on fundamentals and applications of these methods for variously existing enantioselective intermolecular interaction systems.