Theoretical Investigation of the Reactivity of Sodium Dicyanamide with Nitric Acid

Vogelhuber, Kristen M.; Booth, Ryan S.; Annesley, Christopher J.

doi:10.1021/acs.jpca.7b11661

Cited by 8 publications

(15 citation statements)

References 25 publications

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“…This pathway is similar to that seen for the first steps in the DCA − and HNO 3 reaction, 10,30 and the free energy barrier here (78.7 kJ/mol) is significantly lower than for HNO 3 + DCA − (26.2 kcal/mol = 109.6 kJ/mol) determined previously (M06-2X/6-311++G(d,p)). 22 More work is needed to identify the ignition mechanism, and further work including reactive, direct molecular dynamics 38−40 is currently being pursued to better understand the hypergolic nature of this borohydride EIL.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Modern computational chemistry techniques allow for the calculation of a variety of properties. , In the present work, proposed transition state energies are studied alongside minimum free energy profiles, which can be used to propose probable energetic pathways. Results from the experimental portion of this study may help guide future studies and calculations by providing a basis upon which computational efforts can expand.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Decomposition and Hypergolic Reaction of a Dicyanoborohydride Ionic Liquid

et al. 2020

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In this study, in situ infrared spectroscopy techniques and thermogravimetric analysis coupled with mass spectrometry (TGA−MS) are employed to characterize the reactivity of the ionic liquid, 1-butyl-3-methylimidazolium dicyanoborohydride (BMIM + DCBH − ), in comparison to the well-characterized 1-butyl-3-methylimidazolium dicyanamide (BMIM + DCA − ) ionic liquid. TGA measurements determined the enthalpy of vaporization (ΔH vap ) to be 112.7 ± 12.3 kJ/mol at 298 K. A rapid scan Fourier transform infrared spectrometer was used to obtain vibrational information useful in tracking the appearance and disappearance of species in the hypergolic reactions of BMIM + DCBH − and BMIM + DCA − with white fuming nitric acid (WFNA) and in the thermal decomposition of these energetic ionic liquids. Attenuated total reflectance measurements recorded the infrared spectra of the reactant sample (BMIM + DCBH − ) and the liquid reaction products after reacting with WFNA. Computational chemistry efforts, aided by the experimental results, were used to propose key reaction pathways leading to the hypergolic ignition of BMIM + DCBH − + WFNA. Experimental results indicate that the hypergolic reaction of BMIM + DCBH − with WFNA generates both common and unique intermediates as compared to previous BMIM + DCA − + WFNA investigations: nitrous oxide was generated during both hypergolic reactions indicating that it may play a crucial role in the hypergolic ignition process, NO 2 was generated in significantly higher concentrations for BMIM + DCBH − than for BMIM + DCA − , CO 2 was only generated for BMIM + DCA − , and HCN was only generated during thermal decomposition and hypergolic ignition of BMIM + DCBH − .

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermal Decomposition and Hypergolic Reaction of a Dicyanoborohydride Ionic Liquid

et al. 2020

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“…This suggests that future work on larger clusters may be warranted. Recent theoretical results have also shown that sodium cations may accelerate the hypergolic ignition of dicyanamide with nitric acid, and follow‐on experiments validated this hypothesis by demonstrating lowered ignition delays with the addition of sodium to the reaction . While the bulk observation and theoretical calculations are consistent, controlled reactions of mixed clusters (e.g., alkylimidazolium/sodium dicyanamide clusters) with nitric acid vapor within a flow tube or ion trap – combined with kinetic, thermodynamic, and/or spectroscopic probes – would help bridge the gap between these two regimes and further validate (or rule out) the proposed mechanisms.…”

Section: Areas For Increased Contributions From Mass Spectrometrymentioning

confidence: 86%

Electrospray ionization enters the final frontier: Mass spectrometry's role in understanding electrospray thrusters and their plumes

Patrick

2020

Rapid Comm Mass Spectrometry

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Electrospray thrusters using ionic liquid (IL)-based propellants are quickly gaining popularity in spacecraft design. Mass spectrometry is especially well-suited to provide important knowledge on the fundamentals of how these systems work and on evaluating their efficiencies and impacts, given that the operating principles of electrospray thrusters closely mimics the mass spectrometry experimentin both ions are generated by electrospray and then enter a vacuum. Here, electrospray thruster technology and IL-based propellants are briefly introduced. This introduction is then followed by a discussion of mass spectrometry's current contribution to the study of IL-based electrospray thrusters with a focus on electrospray, dissociation, and spectroscopy studiesand a brief discussion of areas ripe for immediate contributions from the mass spectrometry community.

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“…, O 2 N−NHC(O)NHC(O)NH−NO 2 ) produced the same products, , the formation of DNB – during the preignition of DCA – was validated. Chambreau et al ’s work was followed by other experimental , and theoretical studies. , Nichols et al measured the reaction rate constant of DCA – with HNO 3 in a selected ion flow tube and calculated the reaction potential energy diagrams for DCA – reacting with one and two HNO 3 molecules . Vogelhuber et al modeled the cation effects on the hypergolicity of DCA – and identified lower reaction activation barriers by adding Na + .…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations, Reaction Pathway and Mechanism Dissection, and Kinetics Modeling of the Nitric Acid Oxidation of Dicyanamide and Dicyanoborohydride Anions

2020

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Direct dynamics simulations of HNO 3 with dicyanamide anion DCA − (i.e., N(CN) 2 − ) and dicyanoborohydride anion DCBH − (i.e., BH 2 (CN) 2 − ) were performed at the B3LYP/6-31+G(d) level of theory in an attempt to elucidate the primary and secondary reactions in the two reaction systems. Guided by trajectory results, reaction coordinates and potential energy diagrams were mapped out for the oxidation of DCA − and DCBH − by one and two HNO 3 molecules, respectively, in the gasphase and in the condensed-phase ionic liquids using the B3LYP/ 6-311++G(d,p) method. The oxidation of DCA − by HNO 3 is initiated by proton transfer. The most important pathway leads to the formation of O 2 N−NHC(O)NCN − , and the latter reacts with a second HNO 3 to produce O 2 N−NHC(O)NC(O)NH− NO 2 − (DNB − ). The oxidation of DCBH − by HNO 3 may follow a similar mechanism as that of DCA − , producing two analogue products: O 2 N−NHC(O)BH 2 CN − and O 2 N−NHC(O)BH 2 C(O)NH−NO 2− . Moreover, two new, unique reaction pathways were discovered for DCBH − because of its boron-hydride group: (1) isomerization of DCBH − to CNBH 2 CN − and CNBH 2 NC − and (2) H 2 elimination in which the proton in HNO 3 combines with a hydride-H in DCBH − . The Rice−Ramsperger−Kassel−Marcus (RRKM) theory was utilized to calculate reaction kinetics and product branching ratios. The RRKM results indicate that the formation of DNB − is exclusively important in the oxidation of DCA − , whereas the same type of reaction is a minor channel in the oxidation of DCBH − . In the latter case, H 2 elimination becomes dominating. The RRKM modeling also indicates that the oxidation rate constant of DCBH − is higher than that of DCA − by an order of magnitude. This rationalizes the enhanced preignition performance of DCBH − over DCA − with HNO 3 .

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Theoretical Investigation of the Reactivity of Sodium Dicyanamide with Nitric Acid

Cited by 8 publications

References 25 publications

Thermal Decomposition and Hypergolic Reaction of a Dicyanoborohydride Ionic Liquid

Thermal Decomposition and Hypergolic Reaction of a Dicyanoborohydride Ionic Liquid

Electrospray ionization enters the final frontier: Mass spectrometry's role in understanding electrospray thrusters and their plumes

Molecular Dynamics Simulations, Reaction Pathway and Mechanism Dissection, and Kinetics Modeling of the Nitric Acid Oxidation of Dicyanamide and Dicyanoborohydride Anions

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