title: Neighboring effect in fragmentation pathways of cage guanylhydrazones in the gas phase.
abstract: ESI-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.
authors: Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička c. 54, P.O. Box 180, 10 002 Zagreb, Croatia.
authors: Marina
authors: M
authors: Šekutor
authors: Zoran
authors: Z
authors: Glasovac
authors: Kata
authors: K
authors: Mlinarić-Majerski
mesh_terms: D000218:Adamantane / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D019791:Guanidine / Q000737:chemistry*; D006835:Hydrazones / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D011522:Protons; D011789:Quantum Theory; D021241:Spectrometry, Mass, Electrospray Ionization; D013816:Thermodynamics
chemical_list: D005740:Gases; D006835:Hydrazones; D011522:Protons; D019791:Guanidine; D000218:Adamantane