Investigation of azoles and azines. 76. Mass spectra of 5- and 6-substituted uracils

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.See [1] for Communication 75.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 520–531, April, 1990.     

Research in the pyrimidine series XXVI. Calculation of the in-plane normal vibrations of the “enol” forms of barbituric acids

The frequencies and forms of the in-plane normal vibrations of the “enol” forms of barbituric and 5-chloro- and 2-thiobarbituric acids and their deutero derivatives were calculated for the C_s symmetry point group. On the basis of an analysis of the forms of the normal vibrations, the principal frequencies observed in the IR spectra of 5-substituted (methyl, chloro, and bromo) and 2-thiobarbituric acids were assigned with respect to the types of vibrations. The force constants were also determined. The results of the calculations also confirm and refine the previously proposed interpretation of the IR spectra of crystalline samples of the investigated compounds and make it possible to form a judgment regarding the presence of tautomers in the crystalline state and in solutions from the IR spectra.     

High-resolution NMR spectrum of deuterated and undeuterated poly(propene sulfone)

100 MHz spectra have been obtained for DMSO-d₆ solutions of poly(propene sulfone) made from propene (I), propene-1,1,3,3,3-d₅ (II), propene-cis-1,2-d₂ (III) and propene-2-d₁ (IV) by copolymerization with sulfur dioxide; also by oxidation of poly-(propene-2-d₁ sulfide)s of different tacticities. The following chemical shifts and coupling constants were determined: τ_A = 6.06, 6.12, 6.19; τ_B = 6.43, 6.51; τ_C = 6.05; τ_CH3 = 8.44; J = 6.5 Hz; J_AB = 14.0 Hz. Both the A and B protons are sensitive to tacticity, giving rise to five lines in the methylene spectrum of III and ten lines, consisting of four overlapping AB quartets, in the methylene spectrum of IV. From a consideration of the relative intensities of the peaks in the spectra of poly(propene-2-d₁ sulfone)s of different tacticities the following assignment to triad structures has been made: τ_A: 6.06 h_i, 6.12 i and s, 6.19 h_s; τB: 6.43 h_i and i, 6.51 s and h_s. The proportions of the four triad-structures correspond to a single-parameter model for chain growth in which the probability of an isotactic placement σ is 0.50 for the free-radical copolymerization of propene and sulfur dioxide, 0.55 for the ZnCO₃-initiated polymerization of propene sulfide and 0.64 for the CdCO₃-initiated polymerization of propene sulfide. The spectrum of III shows that for polymer made at ?90°C, one mode of addition is preferred. By analogy with other systems it is assumed that this is trans addition. For polymer made at 60°C, both trans and cis addition occur in nearly equal proportions. Assuming that cis addition occurs via the inversion of the intermediate alkyl radical, the activation energy for inversion is found to exceed that for addition of sulfur dioxide by 2.7 kcal/mole (11 kJ/mole). This appears to be the first reported case of a preferred mode of addition to an ethylenic bond in a free radically initiated polymerization.     

Sensitizing gaseous detonations for hydrogen/ethylene-air mixtures using ozone and H2O2 as dopants for application in rotating detonation engines

The effect of ozone and hydrogen peroxide as dopants on hydrogen-air and ethylene-air detonations was investigated with one-dimensional ZND calculations. Also, the effects of dopants were studied numerically with argon and helium as diluents with an aim to reduce the temperature of detonation products while maintaining a detonation wave of sufficient strength such that its propagation is stable near its propagation limits. The primary goal of the present investigation is to isolate the chemical kinetic effects from fluid and gas dynamic effects by altering the ignition chemistry of an unburned mixture without significantly changing its thermodynamic and physical properties. The ZND calculations demonstrate that the addition of O₃ and H₂O₂ in small quantities will substantially reduce the induction length (Δ_i) and time (τ_i), even with higher diluent percentages of argon and helium, making it a viable solution for reducing the operating temperatures of rotating detonation engines (RDEs). The effects of O₃ and H₂O₂ are also studied numerically at lower equivalence ratios for H₂/C₂H₄-air detonations with an aim to reduce the post-detonation temperatures below 2000 K for its application in practical engine cycles. Also, the efficacy of CF₃I, as an ignition promoter at small quantities, is studied numerically for hydrogen-air detonations, and its performance is compared with O₃ and H₂O₂.     

Unsaturated 4H-1,3-oxazines (review)

Data on the methods of production, chemical properties, and biological activity of unsaturated 4H-1,3-oxazines are generalized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 291–308, March, 1994.     

Unsaturated hydantoin derivatives. 18. Alkaline hydrolysis of 2-thioxo-5-arylidenehydantoins and some of their derivatives

The alkaline hydrolysis of 2-thioxo-5-arylidenehydantoins (R = p-NO₂, p-Br, H, p-Me, and p-OMe) and their mono- and dialkyl derivatives proceeds with the formation of arylpyruvic acids, which undergo subsequent decomposition in the presence of oxygen in alkali solutions. 2-Thioxohydantoin, thioparabanic acid, and thiourea were not detected among the reaction products. Side processes involving the oxidation of the thioxohydantoins also take place under these conditions. The rate of hydrolysis of 2-thioxo-5- arylidenehydantoins varies as the concentration of alkali in solution changes, and the log k = f (C_KOH) dependence is S-shaped. The hydrolysis of nonionized hydantoins and their monoanions is a bimolecular reaction and is first-order in substrate and hydroxide ion. The rate-determining step in the hydrolysis is the addition of hydroxide ion to the carbon atom of the C₄=O group.See [1] for communication 17.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 406–412, March, 1979.     

Unsaturated hydantoin derivatives. 19. Effect of temperature on the rate of alkaline hydrolysis of 2-thioxo-5-arylidenehydantoins and some of their derivatives

The effect of temperature on the rate of alkaline hydrolysis of the monoanions of 2-thioxo-5-arylidenehydantoins was studied. The investigated series obeys an isokinetic law with isokinetic temperature =321±10°K. The kinetic data obtained constitute evidence that the mechanisms of the hydrolysis of 2-thioxo-5-arylidenehydantoins and their oxygen analogs are identical. A change in the solvation of the starting and transition states is the principal reason for the change in the reactivities of 5-arylidene-2-thioxohydantoins under the influence of the substituent and the temperature as compared with 5-arylidenehydantoins, the N- and Smethyl derivatives, and 4-thioxo-5-benzylidenehydantoin.See [1] for communication 18.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 813–820, June, 1979.     

A new synthesis of 1,3-thiazines and their transformation into 1-substituted-6-alkyluracils by extrusion of carbonyl sulfide

A simple synthesis of 5-acyl-4-hydroxy-3,6-dihydro-2H-1,3-thiazine-2,6-diones from malonic acid, potassium thiocyanate and acid anhydrides is described. A new, general, regioselective method for the synthesis of 1-substituted-6-alkyluracils by the reaction of these thiazines with primary alkyl and arylamines is reported.     

Studies on the series of azoles and azines. 66. Synthesis,spectra and structure of 5-arylazo- and 5-arylideneamino-2,4,6-triaminopyrimidines and their 6-hydroxy analogs

5-Arylazo and 5-arylideneamino-2,4,6-triaminopyrimidines and their 6-hydroxy analogs were obtained by azo coupling of 2,4,6-triamino- and 2,4-diamino-6-hydroxypyrimidines with aryldiazonium salts, and also by the reaction of benzaldehydes with 2,4,5,6-tetraamino- and 2,4,5-triamino-6-hydroxypyrimidines, respectively. According to spectral data, in solvents with different polarity, these compounds exist preferentially in the triamino- or diaminohydroxy form. The main paths of the mass spectrometric fragmentation of the compounds studied have been determined.See [1] for Communication 65.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 659–667, May, 1988.