Abnormal behavior of nitropyridines in substitution reactions with anions

The reactions of the anions of isonicotinamide and 2-amino-5-nitropyridine with 2-chloro-5-nitropyridine and 3-nitropyridine were observed to give rise to unexpected substitution products presumably via a radical anion mechanism.     

Photochemical reactions of allylphenoxide anions

Photochemical behaviour of sodium allylphenoxides 1a–3a was compared with that of corresponding neutral allylphenols 1b–3b, and a striking difference was found in reactivity as well as in course of the reaction. Remarkably higher photoreactivity of allylphenoxide anions, especially that of o-allylphenoxide 1a, is ascribed to the efficiency of electron transfer. The characteristic reaction products derived only from the anions were as follows: (a) intramolecular cyclization products, indanols 9, from 2a, (b) rearranged reduction products 10 from both 2a and 3a, and (c) degradative methanol-adduct 11 from 3a. Methanol-adducts 7 and photo-reduction products 6 were formed in either case. In addition cyclization products with the participation of O atom, 4 and 5, were obtained from 1a and 1b. Occurrence of the di-π-methane rearrangement was restricted to the reaction of neutral species 1b–3b. A mechanism based on electron transfer in the excited state is suggested for the course of the photoreaction.     

A potentiometric study of the reactions of some anions with 1,2,4,6-tetraphenylpyridinium acetate. II. Organic anions

Summary A new titrant, 1,2,4,6-tetraphenylpyridinium acetate, has been evaluated for the potentiometric precipitation titration of semimicro amounts of a series of organic anions. Emf's were monitored with a perchlorate ion-selective electrode and a double-junction reference electrode. The nitrate and fluoroborate ion-selective electrodes also responded to the various anions. The classes of compounds which can be determined are nitroform and some nitroform-yielding compounds, phenylborates, 2,4,6-trinitro compounds, some dinitrophenols and nitrophenols, some halogenated phenols and others.

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Zusammenfassung 1,2,4,6-Tetraphenyrpyridiniumacetat wurde für die potentiometrische Fällungstitration von Halbmikromengen einer Reihe organischer Anionen herangezogen. Die elektromotorische Kraft wurde mit einer ionenselektiven Perchloratelektrode und einer doppelt verbundenen Bezugselektrode gemessen. Auch ionenselektive Nitrat- und Fluoboratelektroden sprechen auf die verschiedenen Anionen an. Folgende Verbindungsgruppen können so bestimmt werden: Nitroform und dessen Verbindungen, Phenylborate, 2,4,6-Trinitroverbindungen, einige Dinitro- und Mononitrophenole, manche Halogenphenole und dgl.

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Parts of this paper were presented at the 9th Meeting of the JANNAF Propellant Characterization Subcommittee Meeting at the U. S. Air Force Academy, Colorado Springs, CO, June 6–8, 1978. — Work performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore Laboratory under contract number W-7405-ENG-48.     

The reactions of some 1,1,1-tribromo-alkyl systems with thiolate anions

Compounds containing a 1,1,1-tribromoethyl group are normally dehydrobrominated by reaction with sodium thiolates. If a 1,1,1-tribromobut-3-ene fragment is present cyclisation to a 2,2-dibromocyclopropylmethyl thioether or rearrangement are also observed.     

Ion-ion reactions in the gas phase: Proton transfer reactions of protonated pyridine with multiply charged oligonucleotide anions

Isolated triply and doubly charged anions of the single-stranded deoxynucleotide 5′-d(AAAA)-3′ were allowed to undergo ion-ion proton transfer reactions with protonated pyridine cations within a quadrupole ion trap mass spectrometer. Sufficiently high ion number densities and spatial overlap of the oppositely charged ion clouds could be achieved to yield readily measurable rates. Three general observations were made: (1) the ion-ion reaction rate constants were estimated to be 10^{? (7 ? 8)} cm³ ion^?1 s^?1; (2) the ion-ion reaction rates were found to be dependent on the reactant ion number density, which could be controlled by both the reactant ion number and the pseudopotential well depth, and (3) very little fragmentation, if any, was observed, as might normally be expected with highly exothermic proton transfer reactions.     

Thiophene-2-carbaldehyde and benzaldehyde thiosemicarbazones in reactions with propargyl bromide and 1,3-dibromopropyne

The reaction of thiophene-2-carbaldehyde and benzaldehyde thiosemicarbazones with propargylbromide in methanol provided S-(2-propyne)thiosemicarbazones hydrobromides of thiophene-2-carbaldehyde and benzaldehyde. Reaction products obtained from thiosemicarbazones and 1,3-dibromopropyne in methanol at heating were 2-thenilydene(benzylidene)azino-4-bromomethylidene-4,5-dihydrothiazol-3-ium bromides.     

Exploring intramolecular reactions in complex systems with metadynamics: the case of the malonate anions

We have determined the optimized structures, relative energies and intramolecular reactions for two anionic forms of malonic acid, anion malonate(-1) (HO(2)CCH(2)CO(2)(-)) and malonate(-2) ((-)O(2)CCH(2)CO(2)(-)). For this purpose we employed accurate quantum chemistry calculations using second-order M?ller-Plesset perturbation theory and Density Functional Theory with an aug'-cc-p-VTZ basis set to determine the structures and energies, and a novel metadynamics method based on Car-Parrinello molecular dynamics for the thermal reactions. For both malonates, we found new isomers (keto and enol structures) characterized by CO(2) rotations and intramolecular proton transfers. These proton transfers characterize the keto-enol tautomerism that takes place both in the monoanion and dianion. In all cases, the keto tautomer is the more stable configuration. The metadynamics method allows the system to explore the potential energy surface in a few picoseconds, crossing activation barriers of 20-50 kcal/mol.     

Collision-induced reactions of size-selected molecular cluster anions

Collision-induced reactions of size-selected cluster anions, (CO₂) _n ^? and (N₂O)_nO^? with He and Kr atoms were studied at collision energies from 0.1 to 2.0 eV (center-of mass) by means of a tandem mass-spectrometer equipped with a pair of octapole ion guides. The dominant process was evaporation of the constituent molecules from the parent cluster ion. The absolute cross section for the evaporation was measured as functions of the size of the parent cluster ion and the collision energy. The reaction was explained by collisional excitation of the parent cluster ion followed by its unimolecular dissociation. The observed cross sections which correspond to those for the collisional excitation agree with those calculated in terms of charge-induced dipole and induced dipole-induced dipole interactions between the parent cluster ion and the target atom. The distributions of the product ions resulting from the unimolecular dissociation were reproduced by a simple calculation based on RRK theory. In the collision of (CO₂) _n ^? , the cross sections for (CO₂) ₁₀ ^? and (CO₂) ₁₄ ^? were significantly small and their abundances in the product ion distributions were particularly large. These findings indicate that (CO₂) ₁₀ ^? and (CO₂) ₁₄ ^? are stable species. On the other hand, stable species in (N₂O)_nO^? was found to be (N₂O)₅O^?.     

Substitution reactions of some polynuclear carbonyl anions

The reactions of [FeCo₃(CO)₁₂]^- and [MnFe₂(CO)₁₂]^- with a number of monodentate phosphorus donor ligands (L) are reported, and complexes of the type [FeCo₃(CO)₁₁L]^- and [MnFe₂(CO)₁₁L]^- have been isolated and characterised. Only with Ph₂PCH₂CH₂PPh₂ (DPPE) was it possible to replace more than one CO group, the complex [FeCo₃(CO)₁₀(DPPE)]^- being obtained. Protonation of the ironcobalt anions leads to the neutral hydrido clusters and is accompanied by a large kinetic isotope effect, although not as large as for [FeCo₃(CO)₁₂]^- itself. The reaction of [FeCo₃(CO)₁₂]^- with Ph₂C₂ gives [FeCo₃(CO)₁₀(Ph₂C₂)]^-.     

How iodide anions inhibit the phase-transfer catalyzed reactions of carbanions

The inhibitory effect of iodide anions on the phase-transfer catalyzed reactions of carbanions generated in liquid-liquid two-phase systems by aqueous NaOH is due to preferential location of these anions in the interfacial region of the two-phase system—organic phase/concd aqueous NaOH. In such situation, the basic activity of NaOH in this region is decreased and the equilibrium of deprotonation of the carbanion precursors is disfavoured.     

Synthesis and some reactions of silicon phthalocyanine anions

The reactions of PcSi(OH)₂ or Me₃Si(OSiPc)_1–3 OSiMe₃ with Na or K afford anions of silicon mono-, di-, and triphthalocyanines (Pc_1–3) characterized by electronic absorption and EPR spectra. The reactions of the Pc_1–3 anions with proton donors (H₂O and CH₃COOH), Me₃SiCl, and O₂ are carried out. The Pc_1–3 anions in THF are reduced to the Pc ₁ ^3? monophthalocyanine trianion with the partial rearrangement of the phthalocyanine into corrole. In benzene the reactions of Pc_1–3 with Na or K occur only with an additive of crown ether (15C5): Na reduces Pc₁ to the Pc ₁ ^2? dianion, Pc₂ and Pc₃ do not react with Na, and potassium reduces Pc_1–3 to the P trianion.     

Dimerization and protonation reactions of nitrosonitrobenzenes radical anions

The electrochemical behavior of 2-, 3-, and 4-nitrosonitrobenzenes (NNB) in DMF (with Bu₄NClO₄ suppoting salt) in the presence and in the absence of different proton donors (water, phenol, benzoic, acetic, chloroacetic, and sulfuric acids) is studied by the methods of cyclic voltammetry, chronoamperometry and also by electrolysis at the controlled potential. The electrochemical reduction of these compounds is shown to preferentially afford either monomeric (N-nitrophenylhydroxylamines) or dimeric (azoxy compounds) products, which is determined by the interplay between reactions of protonation and dimerization of NNB radical anions. The dimerization reactions proceed fast and reversibly to afford the corresponding dimeric dianions with the basicity much higher as compared with NNB radical anions as the result of which the monomeric products are formed in the presence of “strong” proton donors and the dimeric products form in the presence of “weak” proton donors. Like the effective rate of formation of dimeric products, the basicity of radical anions increases in the row 4- < 3- < 2-NNB.     

Microwave-assisted Kumada-type cross-coupling reactions of iodinated carba-closo-dodecaborate anions

The microwave-assisted Pd-catalyzed Kumada-type cross-coupling reaction of iodinated carba-closo-dodecaborate anions requires smaller amounts of Grignard reagent and catalyst and results in higher yields in much shorter reaction times in comparison to a reaction with conventional heat transfer. 12-Ph(3)P-closo-1-CB(11)H(11) was identified as the side product of the cross-coupling reactions that use [PdCl(2)(PPh(3))(2)]. The inner salt, which is the first example for a {closo-1-CB(11)} cluster with a B-P bond, was selectively synthesized via a related microwave-assisted cross-coupling protocol and characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. In addition, the crystal structures of the tetraethyl ammonium salts of [12-Ph-closo-1-CB(11)H(11)](-), [12-(4-MeOC(6)H(4))-closo-1-CB(11)H(11)](-), and [12-(H(2)C═(Me)CC≡C)-closo-1-CB(11)H(11)](-) are described.     

The formation of iron carbonyl radical anions in the reactions of iron carbonyls with trimethylamine N-oxide

The interaction of iron carbonyls, Fe(CO)₅, Fe₂(CO)₉ and Fe₃(CO)₁₂ with Me₃NO occurs according to a one-electron redox-disproportionation scheme giving rise to iron carbonyl radical anions: Fe₂(CO)₈^·− (1), Fe₃(CO)₁₂^·− (2), Fe₃(CO)₁₁^·− (3) and Fe₄(CO)₁₃^·− (4). The role of Me₃NO, inducing CO-substitution, consists of the generation of reactive 17-electron species with a labile coordination sphere in which the substitution for other ligands occurs, resulting from fast ligand and electron exchange in the confines of the ETC-reaction.     

Complexing,exchange and reactions of tungsten hexafluoride with some simple anions

Complex formation is observed between WF₆ and many anions. Arrhenius activation energies for exchange between free and complexed WF₆ are given for WF₆N₃⁻ and WF₆CN⁻. It is shown that exchange occurs via a displacement mechanism. Bands in the vibrational spectra of N₃⁻, WF₆N₃⁻ and WF₅N₃ are presented.     

Photochemical reactions of disulphide radical anions in Frozen water-salt matrix

Photochemical reactions of disulphide radical anions CH₃SSCH ₃ ^– induced by light with =436, 405 and 365 nm in a watersalt matrix of 6M LiCl at 77 K have been studied. It has been shown that upon excitation disulphide radical anions may enter into electron photodetachment reaction and the S–S bond is cleft. Kinetical nonequivalence of disulphide radical anions in photochemical reactions has been shown to manifest itself in different mechanisms of their transformations.