TY - JOUR
T1 - Stereochemical analysis of deuterated alkyl chains by charge-remote fragmentations of protonated parent ions
AU - Zhang, Kangling
AU - Bouchonnet, Stephane
AU - Serafin, Scott V.
AU - Morton, Thomas Hellman
N1 - Funding Information:
The authors are grateful to Henri Audier, in whose laboratory the GC/ion trap experiments were performed, and to Dr. Sophie Bourcier for communicating her ESI/triple quad results. This research was supported by the CNRS and by NSF grants CHE9983610 and CHE0078286.
PY - 2003/5/15
Y1 - 2003/5/15
N2 - MH+ ions from sec-alkyl m-dimethylamino ethers have been studied by MS/MS using chemical ionization (CI) and electrospray ionization (ESI). Collisionally activated dissociation (CAD) of MH+ from the vicinally perdeuterated 3-hexyl ether, CH3CD2CHOArCD2CH2CH3, shows that alkene expulsion is >96% regioselective, yielding m/z 139 and m/z 124 fragment ions. The fact that alkene elimination is not 100% regioselective (but gives about 3% m/z 138) is attributed to a small amount of ion-neutral complex formation. CAD of MH+ ions from vicinally monodeuterated ethers (the 3-hexyl-4-d1 ether (1) and the sec-butyl-3-d1 ether (2)) demonstrates that the erythro and threo diastereomers give significantly different m/z 139:m/z 138 fragment ion intensity ratios. These intensity ratios are sufficiently reproducible that they can be used to quantitate the proportions of erythro and threo in mixtures. DFT calculations show substantial differences between the 4-center transition states for charge-remote elimination vs. alkene elimination from a neutral precursor.
AB - MH+ ions from sec-alkyl m-dimethylamino ethers have been studied by MS/MS using chemical ionization (CI) and electrospray ionization (ESI). Collisionally activated dissociation (CAD) of MH+ from the vicinally perdeuterated 3-hexyl ether, CH3CD2CHOArCD2CH2CH3, shows that alkene expulsion is >96% regioselective, yielding m/z 139 and m/z 124 fragment ions. The fact that alkene elimination is not 100% regioselective (but gives about 3% m/z 138) is attributed to a small amount of ion-neutral complex formation. CAD of MH+ ions from vicinally monodeuterated ethers (the 3-hexyl-4-d1 ether (1) and the sec-butyl-3-d1 ether (2)) demonstrates that the erythro and threo diastereomers give significantly different m/z 139:m/z 138 fragment ion intensity ratios. These intensity ratios are sufficiently reproducible that they can be used to quantitate the proportions of erythro and threo in mixtures. DFT calculations show substantial differences between the 4-center transition states for charge-remote elimination vs. alkene elimination from a neutral precursor.
KW - 4-Center transition state
KW - Density functional theory
KW - Dissociative resonance structures
KW - Keto-enol tautomerization
KW - Vicinal elimination
KW - Zwitterion
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U2 - 10.1016/S1387-3806(03)00047-2
DO - 10.1016/S1387-3806(03)00047-2
M3 - Article
AN - SCOPUS:0242417163
SN - 1387-3806
VL - 227
SP - 175
EP - 189
JO - International Journal of Mass Spectrometry
JF - International Journal of Mass Spectrometry
IS - 1
ER -