The ethylene radical cation: Twisted or planar?

Ab initio molecular-orbital calculations are used to examine the structure of the ethylene radical cation. The results point to a twisted equilibrium geometry, in agreement with experiment. Very large basis sets and highly correlated wavefunctions are necessary to describe even qualitatively the torsional potential function of this ion.     

Reaction path calculations for the interaction of the ethylene radical cation with triplet oxygen

UMNDO reaction path calculations for trapping of the ethylene-cation radical with ground state oxygen suggest that formation of a dioxetane radical cation proceeds through the intermediacy of a peroxycation radical. The predicted enthalpy of activation (ΔH? = 13.8 kcal/mol) is consistent with rapid trapping of olefinic cation radicals by triplet oxygen at room temperature.     

Reactions of aliphatic,aromatic, and heterocyclic aminothiols with diacetylene

Reactions of aliphatic, aromatic, and heterocyclic aminothiols with diacetylene in liquid ammonia or methanol furnished the corresponding aminoorganylsulfanylbutenynes of predominantly Z-configuration.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 11, 2004, pp. 1725–1727.Original Russian Text Copyright © 2004 by Volkov, Volkova.     

Reactions of 4-chlorothiopyrylium cation with nucleophiles

Reactions of 4-chlorothiopyrylium cation (1) with a variety of nucleophiles have been investigated. Thiophenol, aniline, N-methylaniline, sodium phenoxide and sodium methoxide reacted with 1 to give 4-substituted products. On the other hand, Grignard reagents and alkyl amines afforded ring-opened products by nucleophilic attack at the 2-position. The difference in reaction position according to the kind of nucleophile can be reasonably intrepreted in terms of the principle of hard and soft acids and bases. The “aromatic character” of thiopyrylium cation is discussed on the basis of the relative reactivities in nucleophilic substitution of 1, N-methyl-4-chloropyridinium (2) and 4-chloropyrylium (8) cations.     

Tetramethylcyclobutadiene radical cation

The tetramethylcyclobutadiene radical cation has been generated photochemically in solutions of aluminum halide σ complexes of tetramethylcyclobutadiene. It decays thermally to a “dimeric” radical cation.     

Reactions of N-heterocyclic carbenes (NHCs) with one-electron oxidants: possible formation of a carbene cation radical

One-electron oxidation of N-heterocyclic carbenes (NHCs) has been carried out using oxidising agents such as tetracyanoethylene (TCNE) and ferrocenium [Cp(2)Fe](+); the formation of carbene radical cations is postulated.     

The structure of the radical cation of ethylene oxide (oxirane) in low-temperature matrices

Based on analysis of ESR spectra, it is suggested that the initial species formed by electron loss from oxirane (¹³C) in CFCl₃ at 77 K is the ring-closed o(n) radical, rather than the ring-opened “allylic” radical.     

Reactions of actinide ions with ethylene oxide

Naked and oxo-ligated actinide (An) monopositive ions were reacted with ethylene oxide, cyclo-C(2)H(4)O (EtO). Along with An = U, Np, Pu and Am, ions of two lanthanide (Ln) elements, Ln = Tb and Tm, were studied for comparison. Metal and metal oxide ions, M(+), MO(+) and MO(2)(+), were generated by laser ablation and immediately reacted with EtO. Unreacted and product ions were detected by time-of-flight mass spectrometry. It was apparent that the overall reaction cross-sections decreased in the order U(+) > or = Np(+) > Pu(+) > Am(+). A primary reaction channel for each studied metal was the formation of MO(+) from M(+), in accord with the expected exothermicity of oxygen abstraction from EtO. For U, Np and Pu, the dioxides were also major products, indicating OAn(+)--O dissociation energies of at least 350 kJ mol(-1), the energy required for O-atom abstraction from EtO. For Am, Tb and Tm, the dioxides were only very minor products, reflecting the stabilities of the trivalent states and resistance to oxidation to higher valence states; the structures/bonding in these MO(2)(+) are intriguing given that the formal pentavalent bonding state is effectively unattainable. It was demonstrated that EtO, unlike more thermochemically favorable but kinetically restricted O-donors, is effective at achieving facile oxidation of actinide metal ions to the monoxide, and to the dioxide if the second O-abstraction reaction is exothermic. Several intriguing minor products were also identified, most of which incorporate metal--oxygen bonding and are attributed to the oxophilicity of the f-block elements; the contrast to the behavior of first-row d-block transition elements is striking in this regard. Particularly noteworthy was the formation of MH(4)(+) (and MOH(4)(+)), evidently via abstraction of all four H atoms from a single C(2)H(4)O molecule; the structures/bonding in these novel 'hydride' species are indeterminate and warrant further attention.     

1,1′-Diphenyl-bis-germatrane with persistent radical cation

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Methyl propionate radical cation

Examination of the reactions of the long-lived (>0.5-s) radical cations of CD₃CH₂COOCH₃ and CH₃CH₂COOCD₃ indicates that the long-lived, nondecomposing methyl propionate radical cation CH₃CH₂C(O)OCH ₃ ^+· isomerizes to its enol form CH₃CH=C(OH)OCH ₃ ^+· (ΔH _{isomerization} ? ?32 kcal/mol) via two different pathways in the gas phase in a Fourier-transform ion cyclotron resonance mass spectrometer. A 1,4-shift of a β-hydrogen of the acid moiety to the carbonyl oxygen yields the distonic ion ^·CH₂CH₂C⁺ (OH)OCH₃ that then rearranges to CH₃CH=C(OH)OCH ₃ ^+· probably by consecutive 1,5- and 1,4-hydrogen shifts. This process is in competition with a 1,4-hydrogen transfer from the alcohol moiety to form another distonic ion, CH₃CH₂C⁺(OH)OCH ₂ ^· , that can undergo a 1,4-hydrogen shift to form CH₃CH=C(OH)OCH ₃ ^+· . Ab initio molecular orbital calculations carried out at the UMP2/6-31G** + ZPVE level of theory show that the two distonic ions lie more than 16 kcal/mol lower in energy than CH₃CH₂C(O)OCH ₃ ^+· . Hence, the first step of both rearrangement processes has a great driving force. The 1,4-hydrogen shift that involves the acid moiety is 3 kcal/mol more exothermic (ΔH _{isomerization}=?16 kcal/mol) and is associated with a 4-kcal/mol lower barrier (10 kcal/mol) than the shift that involves the alcohol moiety. Indeed, experimental findings suggest that the hydrogen shift from the acid moiety is likely to be the favored channel.     

Reactivity of vinylamine radical cation with neutral dienes

The gas-phase ion—molecule reactions between ionized vinylamine ([CH₂ ? CHNH₂]^+.) as a set of conjugated and unconjugated dienes were studied by Fourier transform is observed. Conjugated dienes lead to the elimination of NH₃ or of an hydrocarbon radical from the adduct [M + CH₂ ? CHNH₂]^+.. In the case of unconjugated dienes a regiospecific cyclobutanation-cycloreversion process is observed. Reaction mechanisms are proposed to explain these experimental findings.     

Reactions of (cyclopentadienyl)nitrosyldicarbonylmanganese cation with amines

The [(XC₅H₄)Mn(CO)(NO)L]⁺ complexes react with primary alkylamines to give carboxamido complexes, where X = H, CH₃; L = CO, P(C₆H₅)₃. In the case of L = CO, the carboxamido complexes may be isolated, whereas with L = P(C₆H₅)₃ the reversibility of the reactions permits the isolation only of the starting materials when the solutions are evaporated to dryness. This diminished tendency to form carboxamido complexes is related to the decreased electron density on the carbonyl carbon going from L = CO to L = P(C₆H₅)₃. The presence of the coordinated NO group does not change the reactivity of the cationic complexes towards amines.     

A stable radical-substituted radical cation with strongly ferromagnetic interaction: nitronyl nitroxide-substituted 5,10-diphenyl-5,10-dihydrophenazine radical cation

A stable radical-substituted radical ion with strongly ferromagnetic intramolecular interaction (J) between the radical and radical ion sites is an attractive spin building block of organic magnets. We prepared 2-nitronyl nitroxide-substituted 5,10-diphenyl-5,10-dihydrophenazine radical cation, 1+. The 1+ salt was stable under aerated conditions at room temperature and had a large J/kB value (>/=+700 K).     

A nonelectrocyclic path from the cyclobutene cation radical to the 1,3-butadiene cation radical

The conversion of the cyclobutene cation radical to the 1,3-butadiene cation radical has been studied using MINDO /3 and ab initio SCF MO methods. Not only smooth electrocyclic but also stepwise, non-electrocyclic routes were considered. Both calculational methods agree that the preferred reaction path is a novel nonelectrocyclic one proceeding through an intermediate “cyclopropylcarbinyl cation radical.” The quantitative agreement in the activation parameters calculated by the two methods is excellent. The proposed intermediate also provides an attractive explanation for the mass spectrometric fragmentation patterns of the cyclobutene and butadiene cation radicals.     

Reactions of the 1-ferrocenyl-1,3-diphenylallyl cation with nucleophiles

Conclusion The reactions of 1-ferrocenyl-1,3-diphenylallyl cation with nucleophiles have been studied. In most cases they take place at the secondary carbon cation center; products of reaction at the tertiary center are found only in the case of small nucleophiles (MeO^–, OH^–). The data are evidence for the importance of steric factors, and also show that the ratio of reaction products at the -and -positions does not directly reflect charge distribution in the 1-ferrocenylallyl system.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2769–2776, December, 1986.     

High pressure radical polymerization of ethylene with nitrogen

The radical polymerization of ethylene has been performed in the presence of nitrogen. The structural characteristics of polymers prepared with 0–25 weight % of nitrogen at 1,200 atm were determined by usual solution methods (viscometry, GPC) and by infrared spectroscopy. The experimental results show that, when the demixing in two phases appears, long chain branching decreases and unsaturation increases.