Dinitrogen tetroxide, dissociation

Dinitrogen tetroxide dissociates into nitrogen dioxide N204(g) 2N02(g)... 

Other liquid inorganic compounds show the auto-dissociation characteristic of water and liquid ammonia for example, dinitrogen tetroxide (p. 231), as well as undergoing the more familiar homolytic dissociation... 

Dinitrogen tetroxide, N2O4, as a liquid, has some power as a solvent, and appears to dissociate slightly to give nitrosyl nitrate, thus ... 

A flask of volume 5.00 L is evacuated and 43.78 g of solid dinitrogen tetroxide, N,Q4, is introduced at — 196°C. The sample is then warmed to 25°C, during which time the N204 vaporizes and some of it dissociates to form brown NO, gas. The pressure slowly increases until it stabilizes at 2.96 atm. 

Considering nitration with the help of N02/N204 in an aprotic medium, one should avoid a simplified approach to its mechanism. Of course, radical dissociation of dinitrogen tetroxide is clear and usual. However, two ionic routes of dissociation of N204 are also possible in aprotic media ... 

Dissociation energies must be considerably greater than 1 7 if the entity R1-R2 is to be sufficiently stable to be recognized as a molecule. In practice there are wide variations in Z)(Ri - R2) from molecule to molecule. At the lower end of the scale we have )(N02 -NO2) in dinitrogen tetroxide as low as 12-9 kcal mole in accordance with the well-known ease of dissociation of this compound. At the other end we have the molecules carbon monoxide and nitrogen where D is probably more than 200 kcal mole"h Appreciable dissociation of CO and IS2 can only take place at temperatures usually found only in certain Hames and detonations. 

Nernst pointed out in 1904 that in a dissociating gas, energy transfer could take place as follows molecules absorb energy at the hot surface and are dis.sociated subsequent recombination at the cold surface releases this energy as thermal energy. He showed that this would result in a great increase in the coefficient of thermal conductivity with temperature as a gas became dissociated, and that this could be seen to occur in dinitrogen tetroxide He considered that the measured coefficient of thermal conductivity, could be wTitten... 

The quantity K is called the equilibrium constant of the reaction of dissociation of dinitrogen tetroxide to nitrogen dioxide. The equilibrium constant is independent of the pressure of the system, or of the concentration of the reacting substances. It is, however, a function of the temperature. 

It is a surprising fact that the species NO2+ and N02 (Equation 2) have never been recognized as free ions in liquid dinitrogen tetroxide, although the latter would appear to dissociate heterol) cally in its addition compounds with strong electron acceptors. The 1 to 1 addition compound with boron trifluoride has been shown to have the structure N02+[BF3.N02] , and its powerful nitrating properties are consistent with the presence of the NO2+ ion (17,51). 

Vapor Sttate. Here the situation is much simpler. Ionic species are no longer present, and in the absence of nitric oxide the choice lies merely between nitrogen dioxide and dinitrogen tetroxide. The proportions vary very much with temperature at 21.15° C., the tetroxide is 15.9% dissociated, whereas dissociation to NO2 is complete at 140°. It does not necessarily follow, however, that reaction at low temperatures involves dinitrogen tetroxide, as reaction with olefins clearly shows. 

To obtain further evidence for the reaction scheme outlined above, the reaction has been carried out in the gas phase (7). Dimanganese decacarbonyl vapor and dinitrogen tetroxide were mixed at 60° C. A smoke was formed immediately the gases came into contact, which settled to a very pale yellow powder. This was the nitro compound, Mn(C0)5N02, containing only a trace of the nitrate, which may well have been formed by oxidation of the nitro compound under these conditions. The increased yield of Mn(C0)5N02 in the gas as compared with the liquid state is consistent with the free-radical interpretation, since heterolytic dissociation of the tetroxide is no longer possible. 

Nickel Carbonyl. Reaction of nickel carbonyl with dinitrogen tetroxide in the liquid state follows that outlined for cobalt carbonyl. No nitrite is observed in the product, which is pure Ni(N03)2.2N204 heating gives the anhydrous nitrate. It has been customary to attribute the production of nitrate in this way to the heterolytic dissociation of the tetroxide which is possible in the liquid state. This is certainly true of solvolytic processes—e.g.,... 

Dinitrogen tetroxide, N2O4. The chemistry of this oxide, the dimer of the dioxide, is most interesting, for the molecule can apparently dissociate in three different ways. Thermal dissociation takes place according to the equation... 

This dissociation is complete at 140°C. Liquid dinitrogen tetroxide has good solvent properties and is used as a nitrating agent. 

In the gas phase, nitrogen dioxide is actually a mixture of nitrogen dioxide (NO2) and dinitrogen tetroxide (N2O4). If the density of such a mixture is 2.3 g/L at 74°C and 1.3 atm, calculate the partial pressures of the gases and Kp for the dissociation ofN204. 

P12.6 The dissociative gas and important rocket propellant dinitrogen tetroxide is in rapid equilibrium with nitrogen dioxide following the reaction ... 

Dinitrogen tetroxide, N2O4, is a colorless gas (boiling point, 21°C), which dissociates to give nitrogen dioxide, NO2, a reddish-brown gas. 

The amount of nitrogen dioxide formed by dissociation of dinitrogen tetroxide,... 

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