caa a22 4500 467992738 CHVBK 20180323112549.0 cr unu---uuuuu 170328e19900401xx s 000 0 eng 10.1007/BF00497220 doi (NATIONALLICENCE)springer-10.1007/BF00497220 Investigation of azoles and azines. 76. Mass spectra of 5- and 6-substituted uracils [Elektronische Daten] [V. Mirzoyan, R. Melik-Ogandzhanyan, T. Rusavskaya, E. Studentsov, B. Ivin] Peaks of molecular ions that generally have the maximum intensity are observed in the mass spectra of most of the investigated 5- and 6-substituted uracils and 5-substituted orotic acids and their deutero analogs and methylated derivatives. The principal pathway of the fragmentation of the molecular ions is retrodiene fragmentation with the formation of [O=C(4)C(5)R5C(6)R(6)N(1)R1]+ (F1) ions. The stabilities of the latter depend on the nature and position of the substituents attached to the C(5) and C(6) atoms. The fragmentation of the F1 ions can be realized via four principal pathways (B-E) with the detachment of N-CR6 (B), O=C=CR5 (C), CO (D), and R6 (E) fragments. The most general pathway for the fragmentation of 5-substituted uracils is pathway C, whereas the most general pathway for 6-substituted uracils is pathway E. In the spectra of 5-substituted orotic acids the intensities of the molecular-ion peaks are high (∼100%) only in the case of electron-donor R5 and decrease sharply with an increase in the electron-acceptor strength of the substituent. The principal pathways of fragmentation of the molecular ions are decarboxylation (F) and retrodiene fragmentation (A), the contribution of which is appreciably smaller. The M-CO2 ions formed after decarboxylation undergo fragmentation via a scheme similar to that observed for 5-substituted uracils. Plenum Publishing Corporation, 1990 Mirzoyan V. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut Melik-Ogandzhanyan R. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut Rusavskaya T. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut Studentsov E. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut Ivin B. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut Chemistry of Heterocyclic Compounds Kluwer Academic Publishers-Plenum Publishers 26/4(1990-04-01), 446-455 0009-3122 26:4<446 1990 26 10593 https://doi.org/10.1007/BF00497220 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00497220 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Mirzoyan V. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut NATIONALLICENCE 700 1- Melik-Ogandzhanyan R. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut NATIONALLICENCE 700 1- Rusavskaya T. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut NATIONALLICENCE 700 1- Studentsov E. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut NATIONALLICENCE 700 1- Ivin B. Leningrad Institute of Pharmaceutical Chemistry, 197022, Leningrad aut NATIONALLICENCE 773 0- Chemistry of Heterocyclic Compounds Kluwer Academic Publishers-Plenum Publishers 26/4(1990-04-01), 446-455 0009-3122 26:4<446 1990 26 10593 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer