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Title: Enthalpy of Formation of N 2 H 4 (Hydrazine) Revisited

Abstract

In order to address the accuracy of the long-standing experimental enthalpy of formation of gas-phase hydrazine, fully confirmed in earlier versions of Active Thermochemical Tables (ATcT), the provenance of that value is re-examined in light of new high-end calculations of the Feller-Peterson-Dixon (FPD) variety. An overly optimistic determination of the vaporization enthalpy of hydrazine, which created an unrealistically strong connection between the gas phase thermochemistry and the calorimetric results defining the thermochemistry of liquid hydrazine was identified as the probable culprit. The new enthalpy of formation of gas-phase hydrazine, based on balancing all available knowledge, was determined to be 111.57 ± 0.47 kJ/mol at 0 K (97.41 kJ/mol at 298.15 K). Close agreement was found between the ATcT (even excluding the latest theoretical result) and FPD enthalpies.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3]
  1. Department of Chemistry Washington State University, Pullman, Washington 99164-4630, United States
  2. Chemical Sciences and Engineering Division Argonne National Laboratory Argonne, Illinois 60439, United States
  3. Chemical Sciences and Engineering Division Argonne National Laboratory Argonne, Illinois 60439, United States; Computation Institute, The University of Chicago, Chicago, Illinois 60637, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Office of Basic Energy Sciences - Chemical Sciences, Geosciences, and Biosciences Division
OSTI Identifier:
1389317
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory; Journal Volume: 121; Journal Issue: 32
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Feller, David, Bross, David H., and Ruscic, Branko. Enthalpy of Formation of N 2 H 4 (Hydrazine) Revisited. United States: N. p., 2017. Web. doi:10.1021/acs.jpca.7b06017.
Feller, David, Bross, David H., & Ruscic, Branko. Enthalpy of Formation of N 2 H 4 (Hydrazine) Revisited. United States. doi:10.1021/acs.jpca.7b06017.
Feller, David, Bross, David H., and Ruscic, Branko. 2017. "Enthalpy of Formation of N 2 H 4 (Hydrazine) Revisited". United States. doi:10.1021/acs.jpca.7b06017.
@article{osti_1389317,
title = {Enthalpy of Formation of N 2 H 4 (Hydrazine) Revisited},
author = {Feller, David and Bross, David H. and Ruscic, Branko},
abstractNote = {In order to address the accuracy of the long-standing experimental enthalpy of formation of gas-phase hydrazine, fully confirmed in earlier versions of Active Thermochemical Tables (ATcT), the provenance of that value is re-examined in light of new high-end calculations of the Feller-Peterson-Dixon (FPD) variety. An overly optimistic determination of the vaporization enthalpy of hydrazine, which created an unrealistically strong connection between the gas phase thermochemistry and the calorimetric results defining the thermochemistry of liquid hydrazine was identified as the probable culprit. The new enthalpy of formation of gas-phase hydrazine, based on balancing all available knowledge, was determined to be 111.57 ± 0.47 kJ/mol at 0 K (97.41 kJ/mol at 298.15 K). Close agreement was found between the ATcT (even excluding the latest theoretical result) and FPD enthalpies.},
doi = {10.1021/acs.jpca.7b06017},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
number = 32,
volume = 121,
place = {United States},
year = 2017,
month = 8
}
  • A new upper limit to the adiabatic ionization energy of trans-hydroxyoxomethyl, EI(t-HOCO){<=}8.195{+-}0.022 eV, is provided, producing a lower limit to the enthalpy of formation, {Delta}H{sub f 0}{sup o}(t-HOCO){>=}-45.8{+-}0.7 kcal/mol ({>=}-46.5{+-}0.7 kcal/mol at 298 K). The spectrum shows progressions in C{double_bond}O and C-O stretches of HOCO{sup +} and provides evidence for the excitation of OCO bend. In addition, the data tentatively suggest an ionization onset as low as 8.06{+-}0.03 eV. While it is not clear whether the latter corresponds to cis or trans isomer, it may indicate that {Delta}H{sub f 0}{sup o}(HOCO) is even higher.
  • The appearance energy of the CH{sub 2}{sup +} fragment from CH{sub 2}CO has been carefully remeasured and fitted by a model curve, producing EA{sub 0}(CH{sub 2}{sup +}/CH{sub 2}CO) = 13.743 {+-} 0.005 eV. This value can be sequentially propagated through selected thermochemical cycles to yield individual values for El(CH{sub 2}), D{sub 0}(H-CH{sub 2}), {Delta}H{sup o}{sub f 0}(CH{sub 2}CO). A set of values with a statistically larger weight is produced by analyzing a local thermochemical network, which combines the present measurement with thirteen other experimental determinations from the literature and encompasses the enthalpies of formation of CH{sub 3}, CH{sub 3}{sup +},more » CH{sub 2}, CH{sub 2}{sup +}, and CH{sub 2}CO. The recommended simultaneously adjusted thermochemical values are: {Delta}H{sup o}{sub f 0}(CH{sub 3}) = 35.86 {+-} 0.07 kcal/mol (35.05 {+-} 0.07 kcal/mol at 298 K), {Delta}H{sup o}{sub f 0}(CH{sub 3}{sup +}) = 262.73 {+-} 0.06 kcal/mol (261.83 {+-} 0.06 kcal/mol at 298 K), {Delta}H{sup o}{sub f 0}(CH{sub 2}) = 93.18 {+-} 0.20 kcal/mol (93.31 {+-} 0.20 kcal/mol at 298 K), {Delta}H{sup o}{sub f 0}(CH{sub 2}{sup +}) = 332.92 {+-} 0.19 kcal/mol (333.04 {+-} 0.19 kcal/mol at 298 K), {Delta}H{sup o}{sub f 0}(CH{sub 2}CO) = -11.10 {+-} 0.21 kcal/mol (-11.85 {+-} 0.21 kcal/mol at 298 K), as well as D{sub 0}(H{sub 3}C-H) = 103.42 {+-} 0.03 kcal/mol (104.99 {+-} 0.03 kcal/mol at 298 K), D{sub 0}(H{sub 2}C-H) = 108.95 {+-} 0.20 kcal/mol (110.35 {+-} 0.20 kcal/mol at 298 K), D{sub 0}(H{sub 2}C{double_bond}CO) = 77.08 {+-} 0.02 kcal/mol (78.73 {+-} 0.02 kcal/mol at 298 K), El(CH{sub 3}) = 9.3830 {+-} 0.0005 eV, and El(CH{sub 2}) = 10.3962 {+-} 0.0036 eV. These values are in excellent agreement with current and several previous experimental measurements. The recommended enthalpy of formation of CH{sub 2} implies that the reaction of singlet methylene with water is essentially thermoneutral (to within {+-}0.2 kcal/mol) at 0 and 298 K, and slightly endothermic (0.5 {+-} 0.2 kcal/mol) at 1000 K.« less
  • The appearance energy of the CH{sub 2}{sup +} fragment from CH{sub 2}CO has been carefully remeasured and fitted by a model curve, producing EA{sub 0}(CH{sub 2}{sup +}/CH{sub 2}CO) = 13.743 and 0.005 eV. This value can be sequentially propagated through selected thermochemical cycles to yield individual values for EI(CH{sub 2}), D{sub 0}(H-CH{sub 2}), {Delta}H{degree}{sub f0}(CH{sub 2}), and {Delta}H{degree}{sub f0}(CH{sub 2}CO). A set of values with a statistically larger weight is produced by analyzing a local thermochemical network, which combines the present measurement with thirteen other experimental determinations from the literature and encompasses the enthalpies of formation of CH{sub 3}, CH{submore » 3}{sup +}, CH{sub 2}, CH{sub 2}{sup +}, and CH{sub 2}CO. The recommended simultaneously adjusted thermochemical values are: {Delta}H{degree}{sub f0}(CH{sub 3}) = 35.86 {+-} 0.07 kcal/mol (35.05 {+-} 0.07 kcal/mol at 298 K), {Delta}H{degree}{sub f0}(CH{sub 3}{sup +}) = 262.73 {+-} 0.06 kcal/mol (261.83 {+-} 0.06 kcal/mol at 298 K), {Delta}H{degree}{sub f0}(CH{sub 2}) = 93.18 {+-} 0.20 kcal/mol (93.31 {+-} 0.20 kcal/mol at 298 K), {Delta}H{degree}{sub f0}(CH{sub 2}{sup +}) = 332.92 {+-} 0.19 kcal/mol (333.04 {+-} 0.19 kcal/mol at 298 K), {Delta}H{degree}{sub f0}(CH{sub 2}CO) = {minus}11.10 {+-} 0.21 kcal/mol ({minus}11.85 {+-} 0.21 kcal/mol at 298 K), as well as D{sub 0}(H{sub 3}C-H) = 103.42 {+-} 0.03 kcal/mol (104.99 {+-} 0.03 kcal/mol at 298 K), D{sub 0}(H{sub 2}C-H) = 108.95 {+-} 0.20 kcal/mol (110.35 {+-} 0.20 kcal/mol at 298 K), D{sub 0}(H{sub 2}C{double{underscore}bond}CO) = 77.08 {+-} 0.02 kcal/mol (78.73 {+-} 0.02 kcal/mol at 298 K), EI(CH{sub 3}) = 9.3830 {+-} 0.0005 eV, and EI(CH{sub 2}) = 10.3962 {+-} 0.0036 eV. These values are in excellent agreement with current and several previous experimental measurements. The recommended enthalpy of formation of CH{sub 2} implies that the reaction of singlet methylene with water is essentially thermoneutral (to within {+-}0.2 kcal/mol) at 0 and 298 K, and slightly endothermic (0.5 {+-} 0.2 kcal/mol) at 1,000 K.« less
  • The reactions of anhydrous HBr and HCl with trans-(Mo(N/sub 2/)/sub 2/(triphos)(PR/sub 3/)), where triphos = PhP(CH/sub 2/CH/sub 2/PPh/sub 2/)/sub 2/(PR/sub 3/ = PPh/sub 3/(1), PMePh/sub 2/ (2)), in tetrahydrofuran (THF) solution to produce ammonia and in benzene solution to produce hydrazine and ammonia have been examined. Complex 1 reacted with HBr in THF to produce 1.5 mol of N/sub 2//mol of 1 and routinely ca. 0.72 mol of NH/sub 3//mol of 1, respectively, and MoBr/sub 3/(triphos) (greater than or equal to94% yield). No more than a trace of hydrazine was detected. Total nitrogen balance was increased to 100% when amountsmore » of HBr were added periodically during the reaction. The reaction of 1 or 2 with HBr or HCl led to the rapid loss of 1 mol of N/sub 2/ and the formation of a pair of isomeric hydrazido(2-) complexes, (MoX(NNH/sub 2/)(triphos)(PR/sub 3/))X (PR/sub 3/ = PPh/sub 3/ for 1 A(X) and 1 B(X), PPh/sub 2/Me for 2A(X) and 2B(X); X = Br, Cl). The same mixtures were formed in the absence of solvent. The presence of two isomers was the result of the position of the phenyl group on the central phosphorus atom of the triphos ligand relative to the hydrazido(2-) ligand. 48 references, 3 figures, 3 tables.« less