Fluid dinitrogen tetroxide at very high pressure and high temperature: observation of the nitrite isomer

Abstract

components must refer to N2/Rh/Ti02.Although the integrated area for the N2 band in the 2250-cm-' region of Figure 9 was lower in each spectrum at a given pressure than was its analog in Figure 1, a Langmuir isotherm fit from the band area data in Figure 9 provided an adsorption equilibrium constant of 0.541 atm-i. This was significantly higher than the value (0.376 obtained from the data of ~i~~~~ 1. This indicata that the =avst r e d u d near SMSI -&tions J. Phys. Chem. 1992, 96, 7092-7096 the N2 infrared band were higher for the latter case. 4.High-pressure infrared studies are useful for obtaining equilibrium adsorption data at ambient and higher temperatures. Acknowledgment.We thank the Strategic Defense Initiative Organization's Office of Innovative Science and Technology through Contract N60921-91-C-0078 with the Naval Surface Warfare Center for support of this work. to a greater extent wGh N2 than did the one treated under mild reduction conditions. This is in agreement with the findings of Resasco and Haller for chemisorption measurements of N2 on Rh/Ti02 reduced at 473 and 773 K. 19 We must conclude that the integrated band areas of the 2250-cm-' band decreased in Figure 9 relative to Figure 1, not because of a decline in coverage but rather because of poor infrared transmission following hightemperature reduction. It should be noted that the integrated area for the N2 physisorption band at ca. 2330 cm-' increased slightly for the high-temperature reduced Rh/Ti02 and Ti02 films relative to those reduced at low temperature. This observation, although opposite to that for the N2 chemisorption band for Rh/Ti02, would seem to support the conclusions of Burch and Flambard that high-temperature reduced TiOz itself enhances N2 adsorption at 298 K.20 ConclusionsSeveral conclusions can be drawn from this work. 1. There is definitely a support effect on the chemisorption of N2 on supported Rh. For samples reduced at low temperature (473 K) and exposed to N2 at 298 K, the adsorption equilibrium constant was in the order Ti02 > AI2O3, SO2. Variable-temperature experiments forRh/Ti02 reduced under mild conditions provided a heat of adsorption for N2/ Rh/Ti02 extrapolated to zero coverage of -10.2 kcal/mol. 3. For a Rh/Ti02 film reduced under vigorous conditions (borderline SMSI), the N2 adsorption equilibrium constant at 298 K (0.541 atm-') was greater than for those reduced at lower temperature (0.376 atm-'), even though the integrated areas for References and Notes (1) Wey, J. P.; Burkett, H. D.; Neely, W. C.; Worley, S. D.Infrared and UV-visible absorption spectra have been obtained for samples of N2O4 contained in diamond-anvil cells at high pressures and high temperatures. Infrared spectra allow characterization of the phase and chemistry of N20, as a function of temperature and pressure, while UV-visible absorption spectra allow an independent measure of AH and correlation with previous measurements. Three new peaks appear in the IR spectra at low pressures and elevated temperatures in the liquid phase, one i...

Nitrosonium Nitrate, an Isomer of N2O4 in IF5

“…Self oxidation of NO at 79±80 K gives a red solid which is described by its IR spectrum as NO + NO 3 ± , and which also has been observed by warming of one of the two (syn and anti) isomers of ON±O±NO 2 [6,7]. Both ON±O±NO 2 and NO + NO 3 ± have been also observed by vibrational spectroscopy at high pressure [8,9]. Furthermore it is assumed that weak electron donor solvents will form adducts of the type D → N 2 O 4 , whereas strong electron donor solvents will stabilize the ionic form NO + NO 3 ± [10].…”

Methods for direct alkene diamination, new & old

“…60 The reaction of nitrogen dioxide with alkenes is also made complex by virtue of the delicate equilibrium that exists between this compound, dinitrogen tetroxide (N 2 O 4 ; 28 ) 61 and its nitrite isomer 26 (Scheme 1). 62 Furthermore, in polar media, both 26 and 28 can undergo heterolytic dissociation to form nitrosonium-nitrate ( 29 ) and nitronium-nitrite ( 30 ) ion pairs, which can also participate in the addition process. 63 As a consequence, reactions of N 2 O 4 -NO 2 with alkenes are often complex, display significant solvent effects and lead to the formation of numerous products, as exemplified by 2,3-dimethyl-2-butene ( 31 ) (Scheme 2).…”

Modeling the vapor–liquid equilibrium and association of nitrogen dioxide/dinitrogen tetroxide and its mixtures with carbon dioxide

“…Nitrogen dioxide (NO 2 ) is notoriously known to self associate in the liquid phase to produce dinitrogen tetroxide (N 2 O 4 ) according to Equation 1 [8]. In the liquid phase, N 2 O 4 can also additionally isomerizes [22]. In the vapor phase, it was shown that dimerization also occurs, while the formation of trimers, tetramers or sequential indefinite self-association hypothesis can be discarded [23].…”