Formation Of Hydrazine Research Articles

Understanding the Nitrogen Reduction Reaction Mechanism on CuFeO2Photocathodes.

This study investigates the reaction pathways for the conversion of N2to NH3on CuFeO2(CFO) by employing density functional theory (DFT) calculations. Concentrating on the most stable (012) surface orientation, two systems were examined: the pristine (012) surface and the corresponding oxygen defective surface. To find the thermodynamic stable pathway, the associative Heyrovskýmechanism was considered, containing four different reaction pathways. The reaction intermediates predominantly interact with the iron sites on the surface, following the distal alternating reaction pathway via the formation of hydrazine. Introducing oxygen defects changes the reaction mechanism to a Mars-van-Krevelen-type mechanism, avoiding the formation of hydrazine, while the Gibbs free energy of the first hydrogenation step is lowered by 1.17 eV (from 2.17 to 1.00 eV). Analyzing the charge density distribution reveals that oxygen defective surface enables CFO to facilitate a π-backdonation between iron sites and the NRR intermediates, increasing the intermediate-surface interaction. This indicates an enhanced catalytic activity for the nitrogen reduction reaction (NRR) by generating oxygen lattice defects in CFO.

Bisgermylene-Stabilized Stannylone: Catalytic Reduction of Nitrous Oxide and Nitro Compounds via Element-Ligand Cooperativity.

This study describes the synthesis, structural characterization, and catalytic application of a bis(germylene)-stabilized stannylone (2). The reduction of digermylated stannylene (1) with 2.2 equiv of potassium graphite (KC8) leads to the formation of stannylone 2 as a green solid in 78% yield. Computational studies showed that stannylone 2 possesses a formal Sn(0) center and a delocalized 3-c-2-e π-bond in the Ge2Sn core, which arises from back-donation of the p-type lone pair electrons on the Sn atom to the vacant orbitals of the Ge atoms. Stannylone 2 can serve as an efficient precatalyst for the selective reduction of nitrous oxide (N2O) and nitroarenes (ArNO2) with the formation of dinitrogen (N2) and hydrazines (ArNH-NHAr), respectively. Exposure of 2 with N2O (1 atm) resulted in the insertion of two oxygen atoms into the Ge-Ge and Ge-Sn bonds, yielding the germyl(oxyl)stannylene (3). Moreover, the stoichiometric reaction of 2 with 1-chloro-4-nitrobenzene afforded an amido(oxyl)stannylene (4) through the complete scission of the N-O bonds of the nitroarene. Stannylenes 3 and 4 serve as catalytically active species for the catalytic reduction of nitrous oxide and nitroarenes, respectively. Mechanistic studies reveal that the cooperation of the low-valent Ge and Sn centers allows for multiple electron transfers to cleave the N-O bonds of N2O and ArNO2. This approach presents a new strategy for catalyzing the deoxygenation of N2O and ArNO2 using a zerovalent tin compound.

Degradation of NTO induced by superoxide and hydroperoxyl radicals: a comprehensive DFT study.

Reactive oxygen species, produced in the aquatic environment under sunlight irradiation, actively take part in degradation of environmental pollutants. NTO (5-nitro-1,2,4-triazol-3-one), being a primary ingredient in a suite of insensitive munitions formulations, may be released into training range soils after incomplete detonations and dissolved in surface water and groundwater due to good water solubility. A detailed investigation of a possible mechanism for NTO decomposition in water induced by superoxide and hydroperoxyl radicals as one of the pathways for NTO environmental degradation was performed with a computational study at the PCM(Pauling)/M06-2X/6-311++G(d,p) level. Superoxide causes rapid deprotonation of NTO. Decomposition of NTO induced by hydroperoxyl radicals was found to be a multistep process leading to mineralization of the nitrocompound. The reaction process may begin with hydroperoxyl radical attachment to carbon atom of the CN double bond of NTO, then proceeds through rupture of C-N bonds and addition of water molecules leading to the formation of nitrous acid, ammonia, nitrogen gas, hydrazine, and carbon(IV) oxide. The obtained results indicate that the anionic form of NTO shows a higher reactivity towards hydroperoxyl radicals than its neutral form. Excitation of NTO by sunlight enables complete mineralization of NTO induced by superoxide. The calculated activation energies and exergonicity of the studied processes support the contribution of hydroperoxyl radicals and superoxide to the degradation of NTO in the environment into low-weight inorganic compounds.

Beyond the triple bond: unlocking dinitrogen activation with tailored superbase phosphines.

Activating atmospheric dinitrogen (N2), a molecule with a remarkably strong triple bond, remains a major challenge in chemistry. This theoretical study explores the potential of superbase phosphines, specifically those decorated with imidazolin-2-imine ((ImN)3P) and imidazolin-2-methylidene ((ImCH)3P) to facilitate N2 activation and subsequent hydrazine (H2NNH2) formation. Using density functional theory (DFT) at the M06L/6-311++G(d,p) level, we investigated the interactions between these phosphines and N2. Mono-phosphine-N2 complexes exhibit weak, noncovalent interactions (-0.6 to -7.1 kcal mol-1). Notably, two superbasic phosphines also form high-energy hypervalent complexes with N2, albeit at significantly higher energies. The superbasic nature and potential for the hypervalency of these phosphines lead to substantial N2 activation in bis-phosphine-N2 complexes, where N2 is "sandwiched" between two phosphine moieties through hypervalent P-N bonds. Among the phosphines studied, only (ImN)3P forms an exothermic sandwich complex with N2, stabilized by hydrogen bonding between the ImN substituents and the central N2 molecule. A two-step, exothermic hydrogen transfer pathway from (ImN)3P to N2 results in the formation of a bis-phosphine-diimine (HNNH) sandwich complex. Subsequent hydrogen transfer leads to the formation of a bis-phosphine-hydrazine (H2NNH2) complex, a process that, although endothermic, exhibits surmountable activation barriers. The relatively low energy requirements for this overall transformation suggest its potential feasibility under the optimized conditions. This theoretical exploration highlights the promise of superbase phosphines as a strategy for metal-free N2 activation, opening doors for the development of more efficient and sustainable nitrogen fixation and utilization methods.

Crystallization of isoniazid in choline-based ionic liquids: Physicochemical properties and anti-tuberculosis activity

Crystallization of isoniazid in choline-based ionic liquids: Physicochemical properties and anti-tuberculosis activity

N–N Bond Formation by a Small-Ring Phosphine Catalyst via the PIII/PV Cycle: Mechanistic Study and Guidelines to Obtain a Good Catalyst

The mechanism of the N–N cross-coupling of nitroarene and aniline catalyzed by 1,2,2,3,4,4-hexamethylphosphetane oxide (1PO) as well as the prediction of a better catalyst was theoretically investigated using DFT and DLPNO-CCSD(T) calculations. An active species 1P is generated through deoxygenation of 1PO by diphenylsilane. Then, 1P extracts one oxygen atom from nitroarene to produce nitrosoarene. In this deoxygenation step, the [3 + 1] cheletropic addition is a rate-determining step with the ΔG0≠ and ΔG0 values of 28.8 and −7.3 kcal/mol, respectively. Next, nitrosoarene exclusively undergoes a dehydrative condensation reaction with aniline to form an azo-cation intermediate, which is the origin of the high selectivity in this cross-coupling reaction. In this step, 2,4,6-trimethylbenzoic acid plays an essential role to significantly reduce the ΔG0≠ value from 41.1 to 14.8 kcal/mol. Subsequently, 1P reacts with the azo cation to form a stable hydrazinylphosphonium species through the nucleophilic attack of the phosphorus atom to the cationic nitrogen atom. The phosphonium center preferably accepts a hydroxyl group from water to ensure the formation of hydrazine in the subsequent step. In the [3 + 1] cheletropic addition step, the highest occupied molecular orbital (HOMO) of 1P plays an important role. The small-ring scaffold of 1P raises the HOMO energy compared to acyclic phosphorus compounds to achieve high activity of 1P. Substitution of a dimethylamino group for the methyl group in 1P was theoretically predicted to improve the activity by further increasing the HOMO energy.

Light Alters the NH3 vs N2H4 Product Profile in Iron‐catalyzed Nitrogen Reduction via Dual Reactivity from an Iron Hydrazido (Fe=NNH2) Intermediate

AbstractWhereas synthetically catalyzed nitrogen reduction (N2R) to produce ammonia is widely studied, catalysis to instead produce hydrazine (N2H4) has received less attention despite its considerable mechanistic interest. Herein, we disclose that irradiation of a tris(phosphine)borane (P3B) Fe catalyst, P3BFe+, significantly alters its product profile to increase N2H4 versus NH3; P3BFe+ is otherwise known to be highly selective for NH3. We posit a key terminal hydrazido intermediate, P3BFe=NNH2, as selectivity‐determining. Whereas its singlet ground state undergoes protonation to liberate NH3, a low‐lying triplet excited state leads to reactivity at Nα and formation of N2H4. Associated electrochemical and spectroscopic studies establish that N2H4 lies along a unique product pathway; NH3 is not produced from N2H4. Our findings are distinct from the canonical mechanism for hydrazine formation, which proceeds via a diazene (HN=NH) intermediate and showcase light as a tool to tailor selectivity.

Light Alters the NH3 vs N2 H4 Product Profile in Iron-catalyzed Nitrogen Reduction via Dual Reactivity from an Iron Hydrazido (Fe=NNH2 ) Intermediate.

Whereas synthetically catalyzed nitrogen reduction (N2 R) to produce ammonia is widely studied, catalysis to instead produce hydrazine (N2 H4 ) has received less attention despite its considerable mechanistic interest. Herein, we disclose that irradiation of a tris(phosphine)borane (P3 B ) Fe catalyst, P3 B Fe+ , significantly alters its product profile to increase N2 H4 versus NH3 ; P3 B Fe+ is otherwise known to be highly selective for NH3 . We posit a key terminal hydrazido intermediate, P3 B Fe=NNH2 , as selectivity-determining. Whereas its singlet ground state undergoes protonation to liberate NH3 , a low-lying triplet excited state leads to reactivity at Nα and formation of N2 H4 . Associated electrochemical and spectroscopic studies establish that N2 H4 lies along a unique product pathway; NH3 is not produced from N2 H4 . Our findings are distinct from the canonical mechanism for hydrazine formation, which proceeds via a diazene (HN=NH) intermediate and showcase light as a tool to tailor selectivity.

Metallic MoO2 as a Highly Selective Catalyst for Electrochemical Nitrogen Fixation to Ammonia under Ambient Conditions

AbstractThe development of earth‐abundant and non‐noble based metal catalysts for electrochemical nitrogen reduction towards sustainable ammonia production from N2 and H2O in the ambient atmosphere holds immense potential in realizing an alternate route to energy‐intensive Haber‐Bosch process. Herein, we have employed highly conductive MoO2 synthesized by hydrothermal route as an electrocatalyst for ammonia generation. The MoO2 catalyst was employed for electrochemical nitrogen reduction in N2 saturated 0.1 m HCl electrolyte in a two‐compartment cell. Ammonia yield rate of 2.30 μg h−1 mg−1cat and 2.40 % Faradaic efficiency has been obtained at a potential of −0.3 V vs. RHE. The MoO2 catalyst is selective for ammonia generation without any hydrazine formation. The metallic nature of MoO2 catalyst assists in achieving comparable activity for the electrochemical nitrogen reduction. The above catalyst has the potential for providing better ammonia yield rate by combining or doping with other active elements.

Beyond the thermodynamic volcano picture in the nitrogen reduction reaction over transition-metal oxides: Implications for materials screening

Electrocatalytic production of ammonia from dinitrogen is considered as a sustainable alternative to the energy-demanding and pollutive Haber-Bosch process. A promising class of materials for selective nitrogen reduction (NRR) corresponds to transition-metal oxides given that these electrodes do not show a high activity toward the competing hydrogen evolution reaction. So far, density functional theory calculations have been used to comprehend trends in a class of materials by using the concept of scaling relations and volcano plots. This thermodynamic theory pinpoints that either the formation of the *NNH adsorbate or the formation of ammonia are reconciled with the potential-determining reaction steps. Thus, the development of NRR catalyst has largely focused on the optimization of these two elementary processes. In the present contribution, overpotential and kinetic effects are factored into the volcano plot for the NRR over transition-metal oxides by making use of the recently introduced activity descriptor G max ( η ). It is illustrated that the thermodynamic volcano picture is too simplistic as the limiting reaction step may alter close to the volcano apex: there, particularly surface reactions may govern the reaction rate. In addition, it is demonstrated how to include the formation of hydrazine as a competing side reaction into the volcano plot, which is of importance for weak binding *NNH catalysts where the formation of hydrazine may compete with the formation of ammonia. Given that the outlined methodology in this manuscript is universal and not restricted to the class of transition-metal oxides, the presented kinetic volcano picture may contribute to the development of NRR catalysts for nitrogen fixation. Application of the activity descriptor G max ( η ) allows deriving a kinetic volcano plot to study electrocatalytic nitrogen reduction reaction in a class of materials, thereby moving beyond the thermodynamic volcano picture and the potential-determining step.

Catalytic Reduction of Dinitrogen to Ammonia and Hydrazine Using Iron–Dinitrogen Complexes Bearing Anionic Benzene-Based PCP-Type Pincer Ligands

Abstract Among synthetic models of nitrogenases, iron–dinitrogen complexes with an Fe–C bond have attracted increasing attention in recent years. Here we report the synthesis of square-planar iron(I)–dinitrogen complexes supported by anionic benzene-based PCP- and POCOP-type pincer ligands as carbon donors. These complexes catalyze the formation of ammonia and hydrazine from the reaction of dinitrogen (1 atm) with a reductant and a proton source at −78 °C, producing up to 252 equiv of ammonia and 68 equiv of hydrazine (388 equiv of fixed N atom) based on the iron atom of the catalyst. Anionic iron(0)–dinitrogen complexes, considered an essential reactive species in the catalytic reaction, are newly isolated from the reduction of the corresponding iron(I)–dinitrogen complexes. This study examines their reactivity using experiments and DFT calculations.

A Parent Iron Amido Complex in Catalysis of Ammonia Oxidation.

Parent amido complexes are crucial intermediates in ammonia-based transformations. We report a well-defined ferric ammine system [Cp*Fe(1,2-Ph2PC6H4NH)(NH3)]+ ([1-NH3]+), which processes electrocatalytic ammonia oxidation to N2 and H2 at a mild potential. Through establishing elementary e-/H+ conversions with the ferric ammine, a formal Fe(IV)-amido species, [1-NH2]+, together with its conjugated Lewis acid, [1-NH3]2+, was isolated and structurally characterized for the first time. Mechanism studies indicated that further oxidation of [1-NH2]+ induces the reaction of the parent amido unit with NH3. The formation of hydrazine is realized by the non-innocent nature of the phenylamido ligand that facilitates the concerted transfer of one proton and two electrons.

Hierarchical CoS2/MoS2 flower-like heterostructured arrays derived from polyoxometalates for efficient electrocatalytic nitrogen reduction under ambient conditions

Electrochemical nitrogen reduction reaction (NRR) has been identified as a prospective alternative for sustainable ammonia production. Developing cost-effective and highly efficient electrocatalysts is critical for NRR under ambient conditions. Herein, the hierarchical cobalt-molybdenum bimetallic sulfide (CoS2/MoS2) flower-like heterostructure assembled from well-aligned nanosheets has been easily fabricated through a one-step strategy. The efficient synergy between different components and the formation of heterostructure in CoS2/MoS2 nanosheets with abundant active sites makes the non-noble metal catalyst CoS2/MoS2 highly effective in NRR, with a high NH3 yield rate (38.61μgh-1mgcat.-1), Faradaic efficiency (34.66%), high selectivity (no formation of hydrazine) and excellent long-term stability in 1.0mol L-1 K2SO4 electrolyte (pH=3.5) at -0.25V versus the reversible hydrogen electrode (vs. RHE) under ambient conditions, exceeding much recently reported cobalt- and molybdenum-based materials, even catch up with some noble-metal-based catalyst. Density functional theory (DFT) calculation indicates that the formation of N2H* species on CoS2(200)/MoS2(002) is the rate-determining step via both the alternating and distal pathways with the maximum ΔG values (1.35eV). These results open up opportunities for the development of efficient non-precious bimetal-based catalysts for NRR.

N-Amino-1,8-Naphthalimide is a Regenerated Protecting Group for Selective Synthesis of Mono-N-Substituted Hydrazines and Hydrazides.

A new route to synthesis of various mono-N-substituted hydrazines and hydrazides by involving in a new C-N bond formation by using N-amino-1,8-naphthalimide as a regenerated precursor was invented. Aniline and phenylhydrazines are reproduced upon reacting these individually with 1,8-naphthalic anhydride followed by hydrazinolysis. The practicality and simplicity of this C-N dihalo alkanes; developed a synthon for bond formation protocol was exemplified to various hydrazines and hydrazides. N-amino-1,8-naphthalimide is suitable synthon for transformation for selective formation of mono-substituted hydrazine and hydrazide derivatives. Those are selective mono-amidation of hydrazine with acid halides; mono-N-substituted hydrazones from aldehydes; synthesis of N-aminoazacycloalkanes from acetohydrazide scaffold and inserted to hydroxy derivatives; distinct synthesis of N,N-dibenzylhydrazines and N-benzylhydrazines from benzyl halides; synthesis of N-amino-amino acids from α-halo esters. Ecofriendly reagent N-amino-1,8-naphthalimide was regenerated with good yields by the hydrazinolysis in all procedures.

Impact of storage conditions on a new child-friendly dispersible tablet for treating Tuberculosis in pediatrics.

Background: In 2020 the composition and procedure to elaborate a new formulation containing Isoniazid, Pyrazinamide and Rifampicin to treat tuberculosis in pediatric patients was published. The temperature and relative humidity in Tuberculosis-endemic countries are high, > 30ºC and > 70% respectively and thus these meteorological conditions required a new dosage form. The objective of this work is to register changes in tablet quality and stability over time when exposed to different storage conditions according to ICH. Method: Tablets were subjected to accelerated, long term and low relative humidity conditions. The effect of light was also tested. Quality was measured by evaluating weight changes tensile strength, disintegration time, and drug content. Hydrazine formation was also evaluated as it is considered a mutagenic degradation product. Results: Tablets stored at low relative humidity showed the best stability. There was no statistically significant difference between tablets exposed to or protected from light. Moreover, the formation of Hydrazine was not detected during stability studies. Conclusion: This new dosage form for treating Tuberculosis is stable and able to maintain its quality when appropriate storage conditions are used.

Hydrazine Formation via Coupling of a Nickel(III)–NH2 Radical

AbstractM(NHx) intermediates involved in N−N bond formation are central to ammonia oxidation (AO) catalysis, an enabling technology to ultimately exploit ammonia (NH3) as an alternative fuel source. While homocoupling of a terminal amide species (M‐NH2) to form hydrazine (N2H4) has been proposed, well‐defined examples are without precedent. Herein, we discuss the generation and electronic structure of a NiIII‐NH2 species that undergoes bimolecular coupling to generate a NiII2(N2H4) complex. This hydrazine adduct can be further oxidized to a structurally unusual Ni2(N2H2) species; this releases N2 in the presence of NH3, thus establishing a synthetic cycle for Ni‐mediated AO. Distribution of the redox load for H2N‐NH2 formation via NH2 coupling between two metal centers presents an attractive strategy for AO catalysis using Earth‐abundant, late first‐row metals.

Hydrazine Formation via Coupling of a Nickel(III)-NH2 Radical.

M(NHx ) intermediates involved in N-N bond formation are central to ammonia oxidation (AO) catalysis, an enabling technology to ultimately exploit ammonia (NH3 ) as an alternative fuel source. While homocoupling of a terminal amide species (M-NH2 ) to form hydrazine (N2 H4 ) has been proposed, well-defined examples are without precedent. Herein, we discuss the generation and electronic structure of a NiIII -NH2 species that undergoes bimolecular coupling to generate a NiII 2 (N2 H4 ) complex. This hydrazine adduct can be further oxidized to a structurally unusual Ni2 (N2 H2 ) species; this releases N2 in the presence of NH3 , thus establishing a synthetic cycle for Ni-mediated AO. Distribution of the redox load for H2 N-NH2 formation via NH2 coupling between two metal centers presents an attractive strategy for AO catalysis using Earth-abundant, late first-row metals.

Electrospun nanofibrous sheet doped with a novel triphenylamine based salicylaldehyde fluorophore for hydrazine vapor detection

Abstract Successful synthesis of a novel triphenylamine based salicylaldehyde fluorophore (compound 1) was performed via Suzuki cross-coupling reaction. Subsequently, the identification the hydrazine vapor of an electrospun nanofiber sheet combined with compound 1 depending on solid condition was described. Furthermore, cellulose acetate (CA) combined with the electrospun nanofiber sheet based on compound 1 was formed by applying the electrospinning technique where the average diameter was 324.6 ± 91.6 nm. The sensing nanofiber sheet exhibited a sensitive and selective reaction to hydrazine vapor with a linear concentration range of 0.2-1 %w/v in aqueous solution according to the analysis of fluorescence images using ImageJ. Moreover, it exhibited the elevated selectivity with hydrazine across 21 convenient interferences. Initial findings revealed the nanofibrous mat’s sensitivity and selectivity in terms of the identification of hydrazine via naked-eye detection under backlight 365 nm with fluorescent turn-off mode. Additionally, the generation of compound 1 and the hydrazone product (compound 1-HZ) was investigated through the use of 1H-NMR titration and HRMS, which affirmed the formation of hydrazine with a proton chemical shift at 7.95 ppm, HRMS of compound 1-HZ at m/z = 380.1764 [1-HZ+H]+). It has been demonstrated that the nanofibrous mat offers a basic and suitable method for detecting water vapour in water environments as well as industrial chemical setting.

Experimental and numerical analysis of the autoignition behavior of NH3 and NH3/H2 mixtures at high pressure

Abstract Measurements of autoignition delay times of NH3 and NH3/H2 mixtures in a rapid compression machine are reported at pressures from 20–75 bar and temperatures in the range 1040–1210 K. The equivalence ratio, using O2/N2/Ar mixtures as oxidizer, varied for pure NH3 from 0.5 to 3.0; NH3/H2 mixtures with H2 fraction between 0 and 10% were examined at equivalence ratios 0.5 and 1.0. In contrast to many hydrocarbon fuels, the results indicate that, for the conditions studied, autoignition of NH3 becomes slower with increasing equivalence ratio. Hydrogen is seen to have a strong ignition-enhancing effect on NH3. The experimental data, which show similar trends to those observed previously by He et al. (2019) [28] , were used to evaluate four NH3 oxidation mechanisms: a new version of the mechanism described by Glarborg et al. (2018) [29] , with an updated rate constant for the formation of hydrazine, NH2 + NH2 (+M) = N2H4 (+M), and the literature mechanisms from Klippenstein et al. (2011) [30] , Mathieu and Petersen (2015) [25] , and Shrestha et al. (2018) [31] . In general, the mechanism from this study has the best performance, yielding satisfactory prediction of ignition delay times both of pure NH3 and NH3/H2 mixtures at high pressures (40–60 bar). Kinetic analysis based on present mechanism indicates that the ignition enhancing effect of H2 on NH3 is closely related to the formation and decomposition of H2O2; even modest hydrogen addition changes the identity of the major reactions from those involving NHx radicals to those that dominate the H2/O2 mechanism. Flux analysis shows that the oxidation path of NH3 is not influenced by H2 addition. We also indicate the methodological importance of using a non-reactive mixture having the same heat capacity as the reactive mixture for determining the non-reactive volume trace for simulation purposes, as well as that of limiting the variation in temperature after compression, by limiting the uncertainty in the experimentally determined quantities that characterize the state of the mixture.

Asymmetric Electrophilic Amination and Hydrazination of Acyclic α-Branched Ketones for the Formation of α-Tertiary Amines and Hydrazines

Chiral α-tertiary amines can be accessed directly through the electrophilic amination of α-branched ketones utilizing di-tert-butyl azodicarboxylate as the electrophilic nitrogen source. This proce...