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Neighboring Effect in Fragmentation Pathways of Cage Guanylhydrazones in the Gas Phase
journal contribution
posted on 2013-03-14, 00:00 authored by Marina Šekutor, Zoran Glasovac, Kata Mlinarić-MajerskiESI–MS/MS investigation of
the mono- and bis(guanylhydrazone)
derivatives 1–5 based on adamantane
and pentacycloundecane (PCU) skeleton was described. Elimination of
neutral guanidine is the most abundant reaction channel in the case
of 2,4-adamantyl and PCU derivatives 4 and 5, while the elimination of CH2N2 fragment is
preferred for other compounds. This was attributed to the cage opening
of adamantane or PCU skeletons in the former case leading to the formation
of the cyclohexyl- or cyclopropylcarbinyl carbocation stabilized by
the conjugation with the guanylhydrazone subunit. The main fragmentation
pathways observed experimentally were analyzed by using DFT calculations.
All investigated bis(guanylhydrazone)s formed dications and their
abundances were found to be proportional to the interguanidine distance
in the considered ions. Calculation of the first and the second proton
affinities supported qualitative interpretation of the dication abundance.
Close contact of two guanidine subunits is thus confirmed to be crucial
in determining preferential fragmentation pathway and to suppress
formation of the dication.
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Keywords
PCU derivatives 4guanylhydrazone subunitcage openingcyclopropylcarbinyl carbocationfragmentation pathwaydication abundanceinterguanidine distanceCage GuanylhydrazonesNeighboring EffectFragmentation PathwaysDFT calculationsPCU skeletonsCH 2N fragmentformationguanidine subunitsreaction channelfragmentation pathwaysproton affinitiesadamantane
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