Ab Initio Calculations of the Structure and Transition States of Molecular cations (emslj1)
EMSL Project ID
2202
Abstract
The structure of the ion and the internal energy content play the most important role in the fragmentation of ions from a wide variety of molecules. Since ion's structure may not be the same as its neutral precursor and its dissociations may proceed via a number of competing pathways involving a number of transition state(s), minor changes in the ion structure sometimes result in uniquely distinct dissociation behaviors. One of the most common example is the so called ortho effect in substituted aromatic nitro compounds containing alpha hydrogen(s) ortho to the nitro group resulting in the loss of an OH radical via transfer of an hydrogen atom to the oxygen in the nitro group. Furthermore, fragmentations via direct bond cleavage and nitro-nitrite rearrangement are also affected by the nature of the substituent group and its position with respect to the nitro group. These processes are only qualitatively understood since mass spectrometry alone cannot directly provide necessary information to explain these and other changes in the ionic dissociation behavior. It is therefore essential to use ab initio calculations to determine the geometry of the parent and any intermediate ions that can be correlated to changes in the dissociation behavior with the substituent groups.
Project Details
Project type
Exploratory Research
Start Date
2001-05-03
End Date
2001-10-01
Status
Closed
Released Data Link
Team
Principal Investigator