Nitronium Cation Research Articles

Quasi-RRHO approximation and DFT study for understanding the mechanism and kinetics of nitration reaction of benzonitrile with nitronium ion

The nitration reaction of benzonitrile with nitronium cation, NO2+, has been studied within the Molecular Electron Density Theory at the MN15-L/aug-cc-pVTZ level of theory. For this electrophilic aromatic substitution (EAS) reaction, three regioisomeric reaction paths have been studied. Quasi-RRHO approximation was applied to consider the vibrational contribution to entropy and correct the Gibbs free energy profile of the reaction in the solvent phase. Benzonitrile is less nucleophilically activated than benzene due to the presence of the electron-withdrawing CN group the meta position is the more favorable reaction path of this EAS reaction. The analysis of ELF and AIM demonstrates that binding of cyanide group to the aromatics ring (CC bond) is strong due to the transfer of electron densities of CN bond and N-atom to the disynaptic basin of this bond.

Nitrated Graphene Oxide Derived from Graphite Oxide: A Promising Energetic Two-Dimensional Material.

In order to synthesize a novel two-dimensional energetic material, nitrated graphene oxide (NGO) was prepared by the nitrification of graphite oxide to make a functional modification. Based on the morphological characterization, the NGO has a greater degree of curl and more wrinkles on the surface. The structure characterization and density functional theory calculation prove that epoxy and hydroxyl groups on the edge of graphite oxide have reacted with nitronium cation (NO2+) to produce nitro and nitrate groups. Hydrophobicity of NGO implied higher stability in storage than graphene oxide. Synchronous simultaneous analysis was used to explore the decomposition mechanism of NGO preliminarily. The decomposition enthalpy of NGO is 662.0 J·g−1 and the activation energy is 166.5 kJ·mol−1. The thermal stability is similar to that of general nitrate energetic materials. The hygroscopicity, thermal stability and flammability of NGO prove that it is a novel two-dimensional material with potential applications as energetic additives in the catalyst, electrode materials and energetic devices.

Rapid and scalable synthesis of chiral porphyrin cage compounds

An improved and scalable synthetic route to chiral porphyrin cage compounds, which will be used as catalytic machines for the encoding of information into polymers, has been developed. The porphyrin cage was made chiral by introducing one or two nitro groups on its xylylene sidewalls. This nitration was performed with fuming nitric acid at low temperature and occurred in a highly regioselective fashion. The latter was thought to be the result of the binding of a nitronium cation inside the cavity of the cage compound, directing the reaction to the sidewalls. However, 1H NMR titrations of the porphyrin cage compound with either nitric acid or the nitronium salt [NO2][BF4] revealed that the effect of the host-guest binding of the nitronium ion on the selectivity of the reaction is negligible. Instead, protonation of the porphyrin plays an essential role as it prevents the ring from being oxidized, allowing the nitration to be directed to the sidewalls.

Oxysulfonation of coke coal by nitrosylsulfuric acid

The interaction of coke coal with nitrosylsulfuric acid NOHSO4 in acetonitrile at 20–25°C, times to 24 h, and the NOHSO4/coal ratio R ≤ 50 mmol/g was studied. The process leads to the formation of oxysulfonated coal accompanied by an increase in the weight (to 46%), a decrease (by a factor of 3.8–7.3) in the concentration of radicals, and the formation of the following O-, S-, and N-containing groups in the coal structure: carboxyl, phenol, sulfo groups (≤1.9 mmol/g), and nitroso groups (≤0.9 mmol/g). Changes in the characteristics of oxysulfonated coal under varying R and upon hydrolysis were established by IR and EPR spectroscopy and elemental analysis. The results were interpreted within the framework of a mechanism that included the formation of coal radical cations as a result of electron transfer from coal to the nitronium cation, the intercalation of the bisulfate anion into the coal structure, and the nitrosation and sulfonation of coal arenes. Side oxidation reactions occurred simultaneously with the formation of carboxyl, phenol, and quinoid groups.

Reactions of 2-methyleneadamantane and 2-benzylideneadamantane with acetyl nitrate

The reactions of 2-methylene- and 2-benzylideneadamantane with acetyl nitrate have been studied. In the case of 2-methyleneadamantane, the reaction proceeds via addition of nitronium cation at the double bond followed by stabilization of 2-nitromethyl-2-adamantyl carbocation. In the case of 2-benzylidenadamantane, ortho-substitution at the benzene ring occurred predominantly.

Complex formation and liquid–liquid extraction of anionic chelate of cobalt(II)-4-(2-thiazolylazo)resorcinol with 1,4-diphenyl-3-(phenylamino)-1H-1,2,4-triazole

The complex formation of anionic chelate of Co(II)–4-(2-thiazolylazo)resorcinol (TAR) with 1,4-diphenyl-3-(phenylamino)-1H-1,2,4-triazole (Nitron, Nt) in the liquid–liquid extraction system Co(II)–TAR–Nt–H2O–CHCl3 was studied. The optimum conditions for the formation of ternary ion-association complex Co–TAR–Nt were determined. The molar ratio of the reagents was determined by independent methods. Based on it, reaction scheme and general formula of the complex was suggested. The extraction equilibriums were investigated and quantitatively were characterized by the equilibrium constants and recovery factor with the aid of independent methods. The effect of various foreign ions and reagents on the complex formation between the anionic chelate Co(II)-TAR and the nitronium cation was studied. The validity of beer’s law was checked and some analytical characteristics were calculated.

The Electrophilic Substitution of Sydnones: the Reaction with 3-Aryl-4-Phenylsydnones, 3-Arylmethylsydnones and 3-Phenylethylsydnone

The electrophilic substitution of 3-aryl-4- phenylsydnones, 3-arylmethylsydnones and 3-phenylethyl- sydnone are studied in order to understand extend of dual nature of the sydnone ring. In the reaction, the nitronium cation is more reactive toward to the aryl ring attached at N(3). The presence of a methyl or methoxyl group on the benzene ring of the arylalkyl group or of methylene between the aryl and the sydnonyl ring causes the phenyl ring to become electrophilic.

Leghemoglobin green derivatives with nitrated hemes evidence production of highly reactive nitrogen species during aging of legume nodules

Globins constitute a superfamily of proteins widespread in all kingdoms of life, where they fulfill multiple functions, such as efficient O(2) transport and modulation of nitric oxide bioactivity. In plants, the most abundant Hbs are the symbiotic leghemoglobins (Lbs) that scavenge O(2) and facilitate its diffusion to the N(2)-fixing bacteroids in nodules. The biosynthesis of Lbs during nodule formation has been studied in detail, whereas little is known about the green derivatives of Lbs generated during nodule senescence. Here we characterize modified forms of Lbs, termed Lba(m), Lbc(m), and Lbd(m), of soybean nodules. These green Lbs have identical globins to the parent red Lbs but their hemes are nitrated. By combining UV-visible, MS, NMR, and resonance Raman spectroscopies with reconstitution experiments of the apoprotein with protoheme or mesoheme, we show that the nitro group is on the 4-vinyl. In vitro nitration of Lba with excess nitrite produced several isomers of nitrated heme, one of which is identical to those found in vivo. The use of antioxidants, metal chelators, and heme ligands reveals that nitration is contingent upon the binding of nitrite to heme Fe, and that the reactive nitrogen species involved derives from nitrous acid and is most probably the nitronium cation. The identification of these green Lbs provides conclusive evidence that highly oxidizing and nitrating species are produced in nodules leading to nitrosative stress. These findings are consistent with a previous report showing that the modified Lbs are more abundant in senescing nodules and have aberrant O(2) binding.

Mechanistic insight into alcohol oxidation mediated by an efficient green CuII-bipy catalyst with and without TEMPO by density functional methods

Density functional theory (DFT) calculations have been performed to investigate the alcohol oxidation to acetaldehyde catalyzed by the Cu-bipy (bipy = 2,2'-bipyridine) catalyst with and without TEMPO (TEMPO stands for 2,2,6,6-tetramethylpiperidinyloxy). In the presence of TEMPO, two mechanisms are proposed, which are (1) TEMPO and the alcohol coordinate to the Cu center and react in the coordination sphere, and (2) the formation of the nitronium cation. On the basis of our calculations, the nitronium cation mechanism can be ruled out. For the case without TEMPO, it is found that the change of the Cu oxidation states (Cu(II) <--> Cu(I)) plays an important role in assisting the catalytic reaction cycle, while the O(2) molecule assists the formation of the product acetaldehyde. In addition, the overall activation barrier with TEMPO is preferred over the pathway without TEMPO by 5.2 kcal mol(-1). This is consistent with the experimental observation that the Cu-bipy catalyst in the absence of TEMPO is less efficient when compared with that in the presence of TEMPO. The difference in mechanism is discussed tentatively based on the molecular orbitals.

SOLVENT EFFECT ON ELECTROPHILIC AND RADICAL SUBSTITUTION OF TOLUENE MONONITRATION REACTIONS

Two kinds of nitrating reagents, a nitronium cation [Formula: see text] and a nitro radical (· NO2), were used in the gaseous phase toluene mononitration reaction. The closed shell calculation for electrophilic substitution and open shell calculation for radical substitution were both performed in solventless, H2O -solvated, and CH3OH -solvated molecular reaction systems. In the series of electrophilic toluene nitration reactions, both ortho-nitro toluene (o-MNT) and para-nitro toluene (p-MNT) are more abundant products than meta-nitro toluene (m-MNT), no matter what solvent is used in the reaction system. The reaction energy barrier for obtaining each kind of mononitro toluene follows a stepwise decreasing trend when the reaction is carried out in the solventless, H2O -solvated, and CH3OH -solvated systems. In all radical toluene nitration reactions, solventless or solvated, m-MNT is the most abundant product. The energy barrier data also show that the nitration reaction is more feasible in a solvated than in a solventless system. H2O has a more obvious solvent effect than CH3OH in the · NO2radical substitution reaction, and the H2O -solvated system provides a lower activation energy reaction path.

Electrophilic aromatic substitution regioselectivity for benzene derivatives in terms of cationic localization energies from semiempirical quantum chemical computations

Cationic localization energies ( Λ +) for the interaction of monosubstituted benzenes with nitronium cation have been computed by the PM3 method. Yields ( Y) of nitration isomeric products correlate linearly with the Λ + values. The ln Y= a+ bΛ + expressions agree both with Arrhenius equation and with linear free energy relationships.

Unexpected regioselectivity in nitration of 3-aminoquinoxalin-2(1H )-ones †

Regioselective nitration takes place at position 8 of 6,7-disubstituted-3-aminoquinoxalin-2(1H)-ones 3a–d. The orientation is not disturbed by the electronic or steric effects of the substituents on the aromatic ring and on the amino group. The isomeric 5-nitro derivative 9 is formed only in a roundabout way from 3,6,7-trichloroquinoxalin-2(1H)-one 7. When position 8 is occupied, the 5-nitro derivatives appear only as a minor component. The isomers were identified by NMR techniques. Theoretical calculations (AM1, Hartree–Fock, B3LYP) and NMR investigations confirmed the presumed nitronium cation attack on the monoprotonated species 3ap.

Reactions of polyfluoroaromatic compounds with electrophilic agents. Part 20. Nitrofluorination of pentafluorophenoxydifluoromethane and decafluorodiphenyl ether

When nitrofluorinated with HNO 3 in anhydrous HF, the pentafluorophenol ethers C 6F 5OR (R=CHF 2, C 6F 5) add the nitronium cation to the para and ortho positions with respect to the substituent or eventually to form the corresponding 3-nitrocyclohexa-1,4-dienes. The formation of the diene with a CFOR fragment, arising from nitronium cation addition to the para position, has been shown to be reversible in the case of R=CHF 2, unlike that from reaction at the ortho position which afforded the diene containing a CF 2 ring fragment.

ChemInform Abstract: On the Nitration of Polyhaloalkenes by Mixtures of Nitric and Sulfuric Acids.

AbstractBei der Behandlung der Di‐ bzw. Trichloralkene (I) mit Nitriersäure erhält man die α‐Nitro‐carbonsäurechloride (II), die in Form der Ester (IV) isoliert werden.

Nitration of polyhaloalkenes by mixtures of nitric and sulfuric acids

The nitration of polyhaloalkenes was carried out under conditions for the complete conversion of nitric acid to the nitronium cation. Butyl esters of α-nitrocarboxylic acids were obtained by esterification of the nitration products.

Nitro derivatives of the thiophene series. 4. Nitration of thiophene derivatives with metal nitrates in acetic anhydride

The nitration of 2-formylthiophene, 2-acetothienone, and unsaturated ketones of the thiophene series with copper and aluminum nitrates in acetic anhydride at various temperatures was studied. At low temperatures 2-acetothienone gives a mixture of 4- and 5-nitro isomers, while 2-formylthipphene gives only a 5-nitro-substituted compound in the diacetate form; α,β-unsaturated ketones are not nitrated under these conditions. When the reaction is carried out at 70–90 °C, one can obtain mixtures of nitro ketones in the case of unsaturated ketones; 2-formylthiophene is oxidized to thiophene-2-carboxylic acid, while 2-acetothienone gives a substance, the structure of which could not be established. The reaction of copper and aluminum nitrates with acetic anhydride was investigated by means of thermal and x-ray diffraction analysis. It is shown that the reaction is accompanied by the formation of free nitric acid, and the nitrating agent in these mixtures is consequently the nitronium cation.

Nitration of pentaerythritol by HNO3-H2SO4-H2O system

It was shown experimentally that the nitrating agent in the O-nitration of pentaerythritol by HNO3-H2SO4-H2O nitrating mixtures is not the nitronium cation but evidently the free unionized nitric acid molecule.