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Unimolecular Reactivity of Uracil–Cu 2+ Complexes in the Gas Phase
Author(s) -
Lamsabhi Al Mokhtar,
Alcamí Manuel,
Mó Otilia,
Yáñez Manuel,
Tortajada Jeanine,
Salpin JeanYves
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600399
Subject(s) - chemistry , uracil , fragmentation (computing) , ion , mass spectrometry , copper , mass spectrum , reactivity (psychology) , spectral line , gas phase , analytical chemistry (journal) , organic chemistry , physics , medicine , dna , biochemistry , alternative medicine , chromatography , pathology , astronomy , computer science , operating system
The gas‐phase interaction of copper(II) ions with uracil are studied by means of mass spectrometry and B3LYP/6‐311+G(2df,2p)//B3LYP/6‐31G(d) calculations. Positive‐ion electrospray spectra show that the reaction of uracil with copper(II) gives rise to singly charged species, whereby the [Cu(uracilH)] + complex is the most intense ion in the spectra at low concentration. Mass spectrometry/mass spectrometry (MS/MS) experiments show that the loss of HNCO and NCO are the dominant fragmentation processes, accompanied by a minor loss of CO. A systematic study of the spectra obtained with different labeled species, namely, 2‐ 13 C‐ ( m / z 175), 2‐ 13 C,1,3‐ 15 N 2 ‐ ( m / z 177) and 3‐ 15 N‐uracil ( m / z 175), concludes unambiguously that both the loss of HNCO and NCO involve exclusively C2 and N3, whereas only C4 is involved in the loss of CO. Suitable mechanisms for these fragmentation processes are proposed through a theoretical survey of the corresponding potential energy surface. In these mechanisms, π complexes, which lie high in energy with respect to the global minimum, play a significant role in the loss of NCO; this explains why both products, HNCO and NCO involve the same atoms of the ring.