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Experiments were performed to examine the reaction of peroxynitrite with excess of CO2 in the presence of HCO2-, H2O2, methanol, 2-propanol and diethylenetriaminepentaacetic acid using the stopped-flow technique. Thirty to 33% of peroxynitrate was formed in aerated solutions containing organic and inorganic solutes. A direct association between the amount of peroxynitrite and peroxynitrate yield was observed.

Isotopic shifts and agreement with density functional theory frequency calculations revealed that laser-ablated scandium atoms react with nitrogen to form ScN, Sc(N2) and (ScN)2 and their N2 ligated counterparts. It was noted that annealed argon matrix samples with 2% N2 and nitrogen matrix samples give almost the same absorptions for the ligated complexes (NN)xScN and (ScN)2(NN)x. The reaction of a second Sc atom with an intermediate ScN2 species yields the rhombic (ScN)2 species, providing a nitrogen fixation approach with naked metal atoms.

A study was conducted to analyze 14NO-14NO and its isotopomers, 13NO-15NO and 15NO-15NO, in argon matrix using near and far-infrared spectroscopy. The frequency of the nonactive mode was determined from combination bands. The available frequencies of the three isotopic species were also computed. Results identified the frequencies of five infrared-active modes of cis-ON-NO. Findings also suggested that random shifts correlated with solid-state effects.

A study relating to research on nitrogen cations such as NO2+ and NO+ and the identification of related, halogen-free, highly energetic cations was conducted, using ab initio methods, to probe the feasibility of using the bicyclic NO4+ cation. Results of the study indicate that the bicyclic D2d NO4+ cation is a highly energetic species with an estimated decomposition energy of 137 kcal/mol and gas phase heat of formation of 370 kcal/mol. Its low decomposition barrier and high vertical electron affinity, however, make its experimental observation problematic and severely limit its potential usefulness.

The heterogeneous reactions of nitryl halides with aqueous salt solutions as a model substrate for atmospheric sea salt aerosol were investigated. The reaction of Br2 with nitrite solution was found to be a convenient approach to the synthesis of BrNO2. The heterogeneous reactions result in the formation and loss of BrNO2 on salt solutions. The temperature-dependent lifetime of BrNO2 in a quartz cell was measured and the activation energy for the unimolecular decay at atmospheric pressure was obtained.

The equilibrium for the gas-phase clustering reactions N2H+(H2)(sub n-1) + H2 = N2H+(H2)(sub n) with n = 1-13 was investigated using a pulsed-electron beam mass spectrometer. Experimental results revealed anomalous changes of binding energies in the cluster ion N2H+(H2)(sub n) as indicated in the increase in the bond energies of N2H+(H2)(sub n) with n = 2 -> 5. It was found that the charge transfer occurs in the cluster ion N2H+(H2)(sub n) from the H2 ligands to the N2H+ moiety. The increase in n results in the self-tightening of the bonds in the cluster ions.

A new pathway was studied for the degradation of 4-nitrotoluene (4-NT) by a Mycobacterium strain which was isolated from a mixed soil sample from the Stuttgart area. Resting cells of the Mycobacterium strain metabolized 4-NT with concomitant release of small amounts of ammonia under aerobic conditions. Under anaerobic conditions, 4-NT was completely converted to 6-amino-m-cresol. Cell extracts converted 4-hydroxylaminotoluene to 6-amino-m-cresol and could be confirmed as the initial metabolite in the pathway.

An example of a side-on bound zirconium dinitrogen complex,(((Pr(super i)(sub 2)PCH2SiMe2)2N)Zr(O-2,6-Me2C6H3))2(mu-eta2:eta2-N2), is presented. Data from solid state structural analysis show that the dinitrogen unit is bound in a side-on mode of coordination, with the N-N bond distance at 1.528(7) angstrom. The Zr2(mu-eta2:eta2-N2) core has a flattened butterfly shape instead of a completely planar structure like in other related systems. Results underscore the importance of the use of Zr as the metal center and the choice of the ancillary ligand in this mode of bonding.

Research was conducted to examine the general utility of facile Overman rearrangement reactions which makes the reaction more important for the syntheses of complex nitrogen-containing natural products. Results indicate that lower temperature during preparation of the imidate was indispensable to prevent elimination and led to remarkable improvements of the yield. The addition of K2CO3 had a minor effect and modifications did not improve the rearrangement.

Nitroaromatic compounds (NACs) proved useful in the characterization of predominant reductants such as Fe(II) in an anaerobic leachate-contaminated aquifer. The NACs were transformed into aromatic amines within 2-70 days in the leachate plume as well as in microbially active and microbially deactivated experiments. Results revealed that Fe(II) associated with ferric iron minerals can be used as a highly reactive reductant in anaerobic aquifers.

A study was conducted to characterize the synthesis of aminomethyl-substituted o-nitroanilines based from 6-bromo-5-methyl-8-nitro-1,4-dihydrobenzo(d)(1,3)-oxazin-2-one. A proposed mechanism involving azaquinodimethane intermediates was considered in the study. Results suggested that the generation of aquinodimethane intermediates can have a significant impact on organic synthesis associated with the synthesis of substituted nitrogen heterocycles.

A study was conducted to examine the influence of pressure on the decomposition rates of a couple of acidic nitroalkanes, namely nitromethane and 2-nitropropane. A piston-in-cylinder assembly was utilized to carry out high pressure experimental work. Results indicated that the decomposition pathways of nitroalkanes in aprotic solvents were influenced by the availability of alpha hydrogen. Findings also showed that the dominant reaction channel changed with pressure.

A study was conducted to investigate the effects of thermal decomposition and pressure on six-membered cyclic nitramines and nitrosamines in dilute solution (THF). The activation volume profiles of hexahydro-1,3,5-trinitro-1,3,5-triazine were determined in THF solvent at 130 and 145 degrees C. Results indicated that the decomposition pathway of nitramines and nitrosamines directly correlated with structural properties and reaction conditions.

Electron spin echo envelope modulation (ESEEM) spectroscopy was used to determine the ESEEM of -amine, -imine and isothiocyanate coordinated oxovanadium complexes. The high frequency current parameter of the nitrogen in the isothiocyanate substituent is higher compared to those of the nitrogen atoms from both the amine and imine substituents. This extends the correlation rule to a novel type of nitrogen.

Cycloaddition process occurs in the reaction between 4,6-dinitrobenzofuroxan (DNBF) with ethyl vinyl ether forming the diastereomeric dihydrooxazine N-oxide cycloadducts. Further addition of the enol reagent to the mixture results in a second cycloaddition that yields a bis(diydrooxazine N-oxide) product. It was observed that these reactions occur through inverse electron demand Diels-Alder cycloaddition processes. Findings suggest a low aromatic character for the DNBF molecule.

Sodium hexanitrocobaltate(III) (Na3Co(NO2)6) has been investigated as a new reagent for the nitrosation of various substrates containing an amino functionality. Reaction of hydrazide with Na3Co(NO2)6 was expected to obtain the carboxylic acid as a final product in aqueous solution. Hydrogen-ion concentration of the reaction mixture remained in the 4.3-5 range. High yields of 1,3-diaryltriazenes were due to the treatment of aromatic amines with Na3Co(NO2)6. It was found that nitrosation of aliphatic amines did not succeed due to complex formation with the reagent.

Lower-limit concentration of active N atoms stored in a cryomatrix has been found using Fourier transform infrared (FTIR) spectroscopic measurements. Bombardment of the matrix by N and N(sub.2) neutrals with energies estimated to be 20 - 120 eV gives a concentration of N(sub.3) radicals proportional to the beam flux in a linear fashion.

Thermally stable but light sensitive diazides were synthesized and subsequently subjected to photolysis to yield quininoidal dinitrenes. The dinitrenes were characterized by electron spin resonance spectrometry (ESR) and the molecules were found to exhibit triplet ESR. Such observation was proposed to be due to their excited states. The dinitrenes also had large zero field splitting (zfs) values which were found to be in accordance with spin polarization models. These findings would be valuable for further studies on the exchange interaction between unpaired electrons.

The tandem carbenoid cyclization-dipolar cycloaddition-Mannich cyclization reaction of diazo imides can be used for the construction of polyheterocyclic ring systems. This three-step procedure starts with the Rh(II)-catalyzed cyclization of an alpha-diazo imide to produce an isomunchnone 1,3-dipole. This is followed by an intramolecular 1,3-dipolar cycloaddition. N-Acyliminium is initiated by exposure of the cycloadduct to a Lewis acid. The annulation is completed by Mannich cyclization of a tethered pi-bond onto the cationic intermediate.

The Cs symmetry of the ground state of the P(NMe2)3 molecule, with its planar and pyramidal geometries at the nitrogen atoms, is an inherent structural property of compounds containing the P(NR2)3 skeleton and related E(NR2)3 units. This was proven by the good agreement between ab initio calculations and single-crystal x-ray diffraction experiments concerning the crystal structures of P(NMe2)3 and H2C=P(NMe2)3 and the gas-phase structure of H2C=P(NMe2)3.

Oximes were oxidized to the corresponding halonitro products and ketones in aqueous solutions in the presence of halide ions, hydrogen peroxide and chloroperoxidase hemoprotein isolated from the fungus Caldaromyces fumago (CPO). Experimental observations of the conversion, which were performed in aqueous solutions, underscored the direct and limited participation of the enzyme in the reaction and the presence of a competitive nonenzymatic oxime oxidation/halogenation pathway.

The Houk transition state model is applicable to cycloadducts of an exo and endo transition state arising from the 1,3-dipolar cycloaddition of nitrones to (E)-gamma-oxygenated alpha,beta-unsaturated esters. While it may describe the steric course of the reaction leading to endo adducts when 1,2-disubstituted electron-deficient olefins are used, the possibility of intramolecular hydrogen bonding should always be considered when using allylic alcohols.

The kinetics underlying (p-nitrophenoxy)pentaimidazolylcyclotriphosphazene formation via the reaction of p-nitrophenolate (PNP-) and hexaimidazolylcyclotriphosphazene in aqueous THF was observed at 24 degrees Celsius and at pH values between 5.5 and 7.5. The reaction, which proceeded via nucleophilic monosubstitution of imidazole by PNP-, was found to exhibit a bell-shaped pH-rate profile, with hexaimidazolylcyclotriphosphazene having a pKa = 5.4.

Polynitrogen molecules were examined systematically at high levels of ab initio and density functional theory. Besides N2, the thermodynamically most stable Nn molecules, located with the aid of a newly developed energy increment system, are all based on pentazole units. The geometric, energetic, and magnetic criteria establish pentazole (2) and its anion (3) to be as aromatic as their isoelectronic analogues. The bond lengths in 2 and 3 are equalized.

The chemistry underlying the flash vacuum pyrolysis of 4-nitro-3-phenylisoxazole was investigated to develop a synthetic pathway to 4-nitro-2-phenyloxazole. The resulting route, which appears to be based on the acid-catalyzed thermal isomerization of 4-nitro-3-phenylisoxazole, affords products that act as a dienophile and dipolarophile in (2 + 4) cycloaddition reactions with several dienes.

A survey of literature published between the 1970s and 1990s on the use of metal-catalyzed reductive carbonylation of aromatic nitrogen compounds in the synthesis of isocyanates, aromatic armines, carbamates and urea is presented. The review, which highlight the ease of accessibility, low cost and applicability of carbon monoxide as a reducing agent, showed that the catalyst has been optimized for the different reactions with respect to the metal complex, ligand, counterion and cocatalyst.

The 4-methoxy, 4-phenyl and 4-cyano substituted N-tert-butyl-(2-acetylphenyl) nitrenium ions were considered. Specifically, laser flash photolysis and photothermal beam deflection were employed to examine the electronic and steric effects of ring substituents on the lifetimes and reaction rates of arylnitrenium ions in its reactions with nucleophiles. The results demonstrated the CN group's ability to destabilize the arylnitrenium ions.

Ab initio molecular orbital computations were employed to examine the mechanisms underlying the decomposition of 5-nitro-2,4-dihydro-3H-1,2,4-triazolone (NTO). Specifically, the energetics for the tautomerism, ionization and bond dissociations of the explosive and nitromethane were compared. The results suggested several decomposition pathways, namely, hydrogen atom transfer, C-NO2 bond homolysis and N-OH bond homolysis.

The reaction between tert-BuNHLi and TeCl4 in a 4:1 ratio yields thermally stable Te-N compounds. The tellurium diimide dimer, Te2(Ntert-Bu)4, is bonded through an exocyclic nitrogen atom to LiTe(Ntert-Bu)2(NHtert-Bu), to form the most important centrosymmetric complex. The complexes have an ability to dimerize due to the presence of Te-N multiple bonds. The variable temperature 1H- and 7Li-NMR spectra and X-ray crystallography reveal some weak Te-N bonds since rapid proton shifts are observed. The mechanisms for the fluxional processes in these complexes is also discussed.

Oxidation potentials of nitrogen bases in dimethyl sulfoxide (DMSO) and the acidity values of corresponding acids provide the solution-phase homolytic bond dissociation energies (BDE) of H-N+ bonds. The proton affinity values and adiabatic ionization potentials enable the determination of gas-phase BDE values of H-B+ bonds. Acetonitrile (AN) may be used instead of or along with DMSO. Equations used for the calculations and the BDE values are given.

The two-step reduction of allylic alcohols to homoallylic nitro compounds was employed to prepare aristeromycin. The procedure, which yields regio- and stereospecific products in good yields, involves the palladium-catalyzed nitromethylation of pi-allylpalladium complexes synthesized from allylic ethyl carbonates in the presence of nitromethane. The nitromethylation, which is preceded by ionization and decarboxylation, affords nitroalkenes.

High concentrations of natural organic nitrogen compounds cause disinfection interferences in wastewaters. This was the experience of a wastewater treatment plant in Hampton Roads, VA, which handles sizable amounts of brewery waste. To confirm that the compounds are responsible for the interferences, brewery effluent was mixed with different wastewaters to form mixtures with differing chemical features. After chlorination at uniform levels, fecal coliform levels were measured. Mixtures with high ratios of total organic nitrogen to ammonia (TON/NH3) were poorly disinfected by aqueous chlorine. The disinfection ate also tended to decline with increasing TON/NH3 ratios.

The nitrogen superacid (CF3SO2)2NH and its conjugate anion in (Mg H2O 6)(CF3SO2 2N)2.2H2O is structurally characterized by single-crystal X-ray diffraction. The molecular structure of (CF3SO2)2NH has a two-fold crystallographic axis cutting through the N-H bonds in the center. The anion (CF3SO 2N)- undergoes electron delocalization from the planar, sp2-hybridized nitrogen into the 3d orbitals of sulfur. This results to the shortening of the S-N bonds by about 0.07 angstroms on deprotonation.

The intermolecular NH...H(Ir)...HN interactions of IrH(2-thiazolidinethione)4(PCy3) (BF4)2 were examined in both the solution and crystalline states. The results showed a novel four-membering ring formed by the hydrogen bonds between the NH groups and a fluorine of BF(sub 4)(super -). Intramolecular NH...Ir interactions have also been observed in the complexes Ir(H)2(PCy3)2(L)2 (BF4) for L = 2-thiazolidinethione and 2-benzothiazolethione.

The Staudinger reaction of azides with acyl derivatives has been investigated by NMR and other spectometric methods. A mechanism has been proposed for the reaction. This involves the formation of the triazaphosphadiene, reactions of the triazaphosphadiene and reactions via the iminophosphorane. The kinetic parameters for these reactions are presented.

The second-order kinetics for the aminolysis of phenyl acetates with poly(ethyleneimine) were investigated. Linear Bronsted-type plots were obtained for less reactive esters 2-nitrophenyl acetate, 4-acetoxy-3-chlorobenzoic acid and 4-acetoxybenzenesulfonates. The results showed that the intermolecular acid or base catalyses in the aminolysis reactions are less important than the uncatalyzed decomposition of the tetrahedral intermediate to the products.

A novel scheme for the synthesis of amines is described. The method involves the exposure of amidocuprates to oxygen at low temperature. The amidocuprates were prepared from organocopper reagents and lithium amides. The mechanism for the reaction involves the intramolecular coupling of aminyl radicals with the ligands on Cu in the intermediate amidocuprate. The method can be also applied to the preparation of N-substituted hydrazines.

The red methanoic solution of 1,3,5-trinitrobenzene and methioxide iodide has been treated with aqueous sodium hypochlorite. Analysis showed 3,5-dichloro-2,4,6-trimethoxynitrobenzene as the major isolated product and 1,3,5-trichloro-2,4,6-trimethoxybezeneas as a minor isolated product. The dominant reaction was the total degradation of the aromatic ring by reaction with hyphochlorite ion to form chloropicrin, Cl3CNO2 and carbon dioxide.

A novel method for the introduction of substituents on the carbon backbone of azamacrocycles via a Weinreb amide attached to the periphery of a single macrocyclic intermediate. This method has been applied to the synthesis of the anti-HIV agent (+/-)JM22936. The scheme involves connecting the 1,4,8,11-tetraazacyclotetradecane ring system at the carbon rather than the nitrogen position.

The preparation and characterization of C-perfluoroalkylated nitrogen bases are described. The synthesis involves the indirect electrochemical reduction of perfluoroalkyl halides in the presence of imidazole, purine and pyrimidine anions following the SRN1 substitution mechanism. The aromatic nucleophilic substitution reactions of fluorinated aryl halides 1-iodo-2-(trifluoromethyl)benzene and 1-(4'-iodo-tetrafluorophenyl)imidazole were also investigated.

The dynamic NMR analysis of the 13C spectra of an isomeric bicyclic amine, 2-methyl-2-azabicyclo(2.2.1)heptane, is described. The results showed that the endo isomer of the compound is more stable than the exo isomer by 0.3kcal mol-1. The inversion barrier of 7.2 kcal mol-1 is lower when compared to model acyclic amines although its internal CNC bond angles is less than the tetrahedral angel of 109.47 degrees. Analysis showed the influence of torsional (eclipsing) strain and angle strain in determining the inversion barrier.

The preparation and characterization of N,N'-diaryl-2,5-dioxopiperazines are described. The stereoselective synthesis involves the self-coupling of 2-bromopropananilides. The reaction can be controlled to favor cis-(R,R) or cis-(S,S)/trans-(R,S) isomers by starting either from a single enantiomer or racemate and by the promoter, aryl substituent and solvent. The six diastereomeric couples have been characterized by 1H NMR spectroscopy and X-ray crystallography.

The synthesis and characterization of 1-aminopyrroles are described. The scheme involves the condensation of 2-(trimethylsilyl)ethyl hydrazide with 1,4-dicarbonyl compounds and subsequent deprotection under mild conditions. The reaction conditions for the syntheses are presented. These 1-aminopyrroles can be used in the preparation of unsymmetrical 1,1'-bispyrroles and in reductive amination reactions.

The energies and activation of the neutral, charged and N-allyl ketenimine 3 aza-Cope reactions have been investigated. The results of MP4/6-31G*//MP2/6-31G* ab initio calculations showed that the activation energies of these rearrangement reactions were consistent with the experimental observations. The N-allyl ketenimine rearrangement was found to have the least amount of bond breaking and bond making among the three archetypal aliphatic 3-aza-Cope reactions.

The epoxide opening reactions with nitrogen heterocycles such as indoles, pyrroles, imidazoles and pyrazoles under both high-pressure and silica gel-catalyzed conditions have been investigated. The results showed that the reactions are effective for the alkylation of these heterocycles. The stereoselectivity of the reaction has been demonstrated with the epoxide ring opening reaction of (R)-(+)-styrene oxide with indole.

The stereoselective radical cyclization to the enamide double bond can be applied in the synthesis of alkaloids and related nitrogen heterocyclic compounds. Complete facial selectivity has been observed for type A reactions where the nitrogen is contained in an annelated pyrrolidine or piperidine ring to form bis-annelated five- and six-membered cations. The reaction mechanisms for the radical cyclizations of chiral enamides are presented.

The general synthesis of arylpyrroles, -indoles, and -imidazoles is described. The scheme involves a one-step electrochemically induced S(sub RN)1 in liquid ammonia from a nitrogen heterocyclic anion and an aromatic chloride activated by an electron-withdrawing group or by a heteroatom. The investigated heterocycles included pyrrole, 2,5-dimethylpyrrole, 2-,5-di-tert-butylpyrrole, indole, imidazole, 2-methylimidazole and 4(5)-methylimidazole.

The conformational enantiomers arising from the presence of a stereogenic naphthyl-nitrogen chiral axis in N-naphthylimines were examined. The results showed significant twisting in the planes that contain the naphthyl and imino moieties for imines the bear the 1-naphthyl substituent bonded to the C=N nitrogen atom. The E,Z exchange was shown to occur via inversion of the trigonal nitrogen atom based on the results of R,S enantiomerization and E,Z interconversion studies.