Reinvestigation of the Structure of Dinitrogen Tetroxide, N2O4, by Gaseous Electron Diffraction

McClelland, Bruce W.; Gundersen, Grete; Hedberg, Kenneth

doi:10.1063/1.1677901

Cited by 98 publications

(28 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The NN and NO bond lengths of sym‐ N 2 O 4 with D 2h symmetry calculated at the UB3LYP level, 1.798 Å and 1.185 Å, are in close agreement with the experimental values by electron diffraction at 252 K, 1.782 ± 0.008 Å and 1.190 ± 0.002 Å, respectively . The potential energy diagram for the unimolecular reaction of N 2 O 4 based on UCCSD(T)//CBS‐limit energies is presented in Figure , and the related geometries are shown in Supporting Information Figure S1.…”

Section: Resultssupporting

confidence: 76%

A novel mechanism for the isomerization of N₂O₄ and its implication for the reaction with H₂O and acid rain formation

Raghunath

Lin

2017

Int J of Quantum Chemistry

View full text Add to dashboard Cite

We have discovered, by high-level quantum-chemical calculations, a new and predominant isomerization mechanism for N 2 O 4 ! ONONO 2 via a roaming-like transition state occurring unimolecularly or bimolecularly during collision with H 2 O. The new mechanism allows N 2 O 4 to react with H 2 O with a significantly lower barrier (< 13.1 kcal/mol) than the commonly known tight transition state (30-45 kcal/mol) by concurrent stretching of the NAN bond and rotation of one of the NO 2 groups to form trans-ONONO 2 , which then undergoes a rapid metathetical reaction with H 2 O in the gas phase and in aqueous solution. The results have a significant implication for the hydrolysis of N 2 O 4 in water to produce HONO and HNO 3 . Rate constants for the isomerization and hydrolysis reactions have been predicted for atmospheric modeling applications. K E Y W O R D S HONO and HNO 3 formation, N 2 O 4 hydrolysis, N 2 O 4 isomerization and reaction, roaming-like transition state | I N TR ODU C TI ONNitrogen oxides play important roles in a wide variety of reactions in upper and lower atmospheric systems. Symmetric N 2 O 4 (commonly referred to as nitrogen tetroxide [NTO]) is among the most stable dinitrogen oxides in the gas phase, with a substantial concentration at low temperature under atmospheric pressure conditions. N 2 O 4 is the key precursor for the formation of HONO, which is the major source of OH radicals in the troposphere. [1] The less stable nitrosonium nitrate (ONONO 2 ), a structural isomer of N 2 O 4 (D 2h ), is known to be much more reactive than the latter symmetrical one. ONONO 2 has been proposed to be responsible for the hydrolysis of NTO to produce HONO and HNO 3 in laboratory experiments, [2] in which ONONO 2 was assumed to form via the interface-catalyzed isomerization of NTO. [2][3][4][5][6][7][8] The high reactivity of ONONO 2 toward H 2 O has been confirmed by high-level quantum chemical calculations by Zhu et al. [9] ; the predicted potential energy surface (PES) for the H 2 OAONONO 2 reaction was able to quantitatively account for the experimentally determined third-order kinetics for the 2NO 2 1 H 2 O ! HONO 1 HNO 3 reaction in the gas phase [10][11][12] involving the ONONO 2 directly formed by the barrierless association of 2NO 2 molecules. A similar very fast reaction of ONONO 2 with hydrazine was proposed earlier by Lai et al. [13] to account for the hypergolic ignition of the well-known hydrazine-NTO propellant system.Several authors have theoretically investigated the isomerization of NTO to ONONO 2 . [14][15][16] Pimentel et al. [14] reported the isomerization barrier as 31.3 kcal/mol in the gas phase and 21.1 kcal/mol in aqueous solution at 298 K using the B3LYP/13s8p(2d,1f) method. Lai et al. [15] obtained an isomerization barrier of 42.2 kcal/mol in the gas phase at the G2M(CC1)//B3LYP/6-31111G(3df,2p) level of theory. More recently, Liu and Goddard [16] also located a transition state for isomerization at the RCCSD(T)/CBS level as high as 45.6 kcal/mol. The major focus of the present work ...

show abstract

Section: Resultssupporting

confidence: 76%

A novel mechanism for the isomerization of N₂O₄ and its implication for the reaction with H₂O and acid rain formation

Raghunath

Lin

2017

Int J of Quantum Chemistry

View full text Add to dashboard Cite

show abstract

“…The possible pathways for the reaction NTO + UDMHZ are shown in Figure 1 and the associated geometries are presented in Figure 2. The predicted structure of sym-N 2 O 4 with D 2h symmetry at the B3LYP level have NÀ O and NÀ N bond lengths of 1.185 Å and 1.798 Å, respectively; they are consistent with the values obtained by electron diffraction at 252 K, 1.190 � 0.002 Å and 1.782 � 0.008 Å [24]. In the N 2 O 4 + UDMHZ reaction, their initial interaction forms a pre-reaction van der Waals complex UDMHZ:N 2 O 4 (LM1) with an association energy 6.0 kcal/mol.…”

Section: N 2 O 4 (D 2h ) + Udmhzsupporting

confidence: 83%

Ab Initio Chemical Kinetics for Nitrogen Tetroxide Reactions with 1,1‐ and 1,2‐Dimethylhydrazines

Huyen

Raghunath

Lin

2020

Propellants Explo Pyrotec

View full text Add to dashboard Cite

This work employed the quantum‐chemical method at the CCSD(T)/6‐311+G(3df,2p)//B3LYP/6‐311+G(3df,2p) level to study the mechanisms and kinetics of N2O4 (NTO) with H2NN(CH3)2 and CH3NHNHCH3 hypergolic initiation reactions, the processes critical to the chemical rocket propulsion of the N2O4‐hydrazine propellant systems. The reaction of N2O4 with the dimethylhydrazines (DMHZ's) can be started by the fast reaction of DMHZ's with ONONO2, taking place after the novel N2O4→ONONO2 transformation with each of DMHZ's as a spectator within the NTO‐DMHZ collision complexes, through loose, roaming‐like transition states during the bimolecular encounters. The barriers for such isomerization processes were found to be 7.2 and 9.9 kcal/mol for H2NN(CH3)2 and CH3NHNHCH3, respectively. The kinetics of these reactions have been computed in the temperature range 200–2000 K; the results indicate that under the ambient temperature and pressure condition, the half‐life of NTO in the presence of an excess amount of H2NN(CH3)2 is predicted to be 3.3×10−5 s. The results of a similar estimate for CH3NHNHCH3 is about 2 orders of magnitude longer; both estimates indicate that very effective hypergolic reactions can occur upon mixing in these systems.

show abstract

“…We chose the B3LYP/aVDZ method because it provides a geometry that is acceptably close to that suggested by a gas phase electron diffraction study, 13 and it can be readily employed in an IRC calculation. We chose the B3LYP/aVDZ method because it provides a geometry that is acceptably close to that suggested by a gas phase electron diffraction study, 13 and it can be readily employed in an IRC calculation.…”

Section: N 2 Omentioning

confidence: 99%

“…We chose the B3LYP/aVDZ method because it provides a geometry that is acceptably close to that suggested by a gas phase electron diffraction study, 13 and it can be readily employed in an IRC calculation. 13 We note that the MP2/aVDZoptimized geometry gives a considerably longer N-N bond length, namely, 1.853 Å. We also present for comparison the results from a CCSD͑T͒/aVDZ optimization.…”

Section: N 2 Omentioning

confidence: 99%

Ab initio study of the torsional potential energy surfaces of N2O3 and N2O4: Origin of the torsional barriers

Halpern

Glendening

2007

The Journal of Chemical Physics

View full text Add to dashboard Cite

Intrinsic reaction coordinate (IRC) torsional potentials were calculated for N(2)O(4) and N(2)O(3) based on optimized B3LYP/aug-cc-pVDZ geometries of the respective 90 degrees -twisted saddle points. These potentials were refined by obtaining CCSD(T)aug-cc-pVXZ energies [in the complete basis set (CBS) limit] of points along the IRC. A comparison is made between these ab initio potentials and an analytical form based on a two-term cosine expansion in terms of the N-N dihedral angle. The shapes of these two potential curves are in close agreement. The torsional barriers in N(2)O(4) and N(2)O(3) obtained from the CCSD(T)/CBS//B3LYP/aug-cc-pVDZ calculations are 2333 and 1704 cm(-1), respectively. For N(2)O(4) the torsion fundamental frequency from the IRC potential is 87.06 cm(-1), which is in good agreement with the experimentally reported value of 81.73 cm(-1). However, in the case of N(2)O(3) the torsional frequency found from the IRC potential, 144 cm(-1), is considerably larger than the reported experimental values 63-76 cm(-1). Consistent with this discrepancy, the torsional barrier obtained from several different calculations, 1417-1718 cm(-1), is higher than the value of 350 cm(-1) deduced from experimental studies. It is suggested that the assignment of the torsional mode in N(2)O(3) should be reexamined. N(2)O(4) and N(2)O(3) exhibit strong hyperconjugative interactions of in-plane O lone pairs with the central N-N sigma* antibond. Hyperconjugative stabilization is somewhat stronger at the planar geometries because 1,4 interactions of lone pairs on cis O atoms promote delocalization of electrons into the N-N antibond. Calculations therefore suggest that the torsional barriers in these molecules arise principally from a combination of 1,4 interactions and hyperconjugation.

show abstract

Reinvestigation of the Structure of Dinitrogen Tetroxide, N2O4, by Gaseous Electron Diffraction

Cited by 98 publications

References 22 publications

A novel mechanism for the isomerization of N₂O₄ and its implication for the reaction with H₂O and acid rain formation

A novel mechanism for the isomerization of N₂O₄ and its implication for the reaction with H₂O and acid rain formation

Ab Initio Chemical Kinetics for Nitrogen Tetroxide Reactions with 1,1‐ and 1,2‐Dimethylhydrazines

Ab initio study of the torsional potential energy surfaces of N2O3 and N2O4: Origin of the torsional barriers

Contact Info

Product

Resources

About

Reinvestigation of the Structure of Dinitrogen Tetroxide, N2O4, by Gaseous Electron Diffraction

Cited by 98 publications

References 22 publications

A novel mechanism for the isomerization of N2O4 and its implication for the reaction with H2O and acid rain formation

A novel mechanism for the isomerization of N2O4 and its implication for the reaction with H2O and acid rain formation

Ab Initio Chemical Kinetics for Nitrogen Tetroxide Reactions with 1,1‐ and 1,2‐Dimethylhydrazines

Ab initio study of the torsional potential energy surfaces of N2O3 and N2O4: Origin of the torsional barriers

Contact Info

Product

Resources

About

A novel mechanism for the isomerization of N₂O₄ and its implication for the reaction with H₂O and acid rain formation

A novel mechanism for the isomerization of N₂O₄ and its implication for the reaction with H₂O and acid rain formation