Nitrate dissociation

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

An alternative approach is to assume, in the light of the experimental evidence just mentioned, that the reactions of cations and neutral molecules have similar values of (or, equivalently, of log ( /l mol and to try to calculate the difference which would arise from the fact that the observed entropy of activation for a minority free base includes a contribution from the acidic dissociation of the conjugate acid in the medium in question (see (5) above). Consider the two following reaction schemes one (primed symbols) represents nitration via the free base, the other the normal nitration of a non-basic majority species (unprimed symbols) ... 

Acid—Base Chemistry. Acetic acid dissociates in water, pK = 4.76 at 25°C. It is a mild acid which can be used for analysis of bases too weak to detect in water (26). It readily neutralizes the ordinary hydroxides of the alkaU metals and the alkaline earths to form the corresponding acetates. When the cmde material pyroligneous acid is neutralized with limestone or magnesia the commercial acetate of lime or acetate of magnesia is obtained (7). Acetic acid accepts protons only from the strongest acids such as nitric acid and sulfuric acid. Other acids exhibit very powerful, superacid properties in acetic acid solutions and are thus useful catalysts for esterifications of olefins and alcohols (27). Nitrations conducted in acetic acid solvent are effected because of the formation of the nitronium ion, NO Hexamethylenetetramine [100-97-0] may be nitrated in acetic acid solvent to yield the explosive cycl o trim ethyl en etrin itram in e [121 -82-4] also known as cyclonit or RDX. 

Aluminum nitrate is available commercially as aluminum nitrate nonahydrate [7784-27-2], A1(N02)3 9H20. It is a white, crystalline material with a melting point of 73.5°C that is soluble in cold water, alcohols, and acetone. Decomposition to nitric acid [7699-37-2], HNO, and basic aluminum nitrates [13473-90-0], A1(0H) (N03) where x + = 3, begins at 130°C, and dissociation to aluminum oxide and oxides of nitrogen occurs above 500°C. 

Decomposition and Detonation Hazard. Ammonium nitrate is considered a very stable salt, even though ammonium salts of strong acids generally lose ammonia and become slightly acidic on storage. For ammonium nitrate, endothermic dissociation from lowering pH occurs above 169°C. 

Silver bromide crystals, formed from stoichiometric amounts of silver nitrate and potassium bromide, are characterized by a cubic stmcture having interionic distances of 0.29 nm. If, however, an excess of either ion is present, octahedral crystals tend to form. The yellow color of silver bromide has been attributed to ionic deformation, an indication of its partially covalent character. Silver bromide melts at 434°C and dissociates when heated above 500°C. 

The existence of the nitronium ion in sulfuric-nitric acid mixtures was demonstrated both by cryoscopic measurements and by spectroscopy. An increase in the strong acid concentration increases the rate of reaction by shifting the equilibrium of step 1 to the right. Addition of a nitrate salt has the opposite effect by suppressing the preequilibrium dissociation of nitric acid. It is possible to prepare crystalline salts of nitronium ions, such as nitronium tetrafluoroborate. Solutions of these salts in organic solvents rapidly nitrate aromatic compounds. ... 

At higher concentrations the Raman spectra of aqueous solutions of alkali nitrates and of nitric acid have been investigated. Nitric acid was found to be incompletely dissociated, though for the alkali nitrates no evidence of incomplete dissociation was found. Since accurate measurements on solutions of nitric acid have not been made at concentrations below 4.0 molar, it is not certain how the extrapolation to infinite... 

Complex formation reactions. These depend upon the combination of ions, other than hydrogen or hydroxide ions, to form a soluble, slightly dissociated ion or compound, as in the titration of a solution of a cyanide with silver nitrate... 

The intensity of a flare is largely determined by its temp, which in turn depends on the stability of the reaction products. In order to generate grey body radiation which encompasses the spectral sensitivity of the human eye (0.4— 0.74pm), 3000°K should be exceeded. Whereas this is possible using nitrates and perchlorates with alkaline earth metals as well as Zr, Ti and Hf (Ref 34) (H, C, B, Si and P form oxides which dissociate at high temps), in practice Mg and A1 are found to be best in terms of heat output, cost, and transparency to visible radiation... 

These fragments either combine intramolecularly to form the ortho and para nitro compounds or dissociate completely and then undergo an intermolecular reaction to form the same products. The theory was not developed to include a detailed transition state and no mention was made of how the para isomer was formed. Reduction of the cation-radical could give the amine (which was observed experimentally76), but one would expect the concurrent formation of nitrogen dioxide and hence nitrite and nitrate ions however, the latter has never been... 

Figure 15. Isotherms of internal mobilities in alkali-alkaline earth nitrate mixtures. The mobility of the alkali ion is always greater than that of the alkaline earth ion. (Reprinted from T. Koura, H. Matsuura, and I. Okada, "A Dynamic Dissociation Model for Internal Mobilities in Molten Alkali and Alkaline Earth Nitrate Mixtures,"/ Mol. Liq. 73-75 195, Fig. 4, Copyright 1997 with permission from Elsevier Science.)...

Concentrated nitric acid can effect nitration but it is not as reactive as a mixture of nitric acid with sulfuric acid. The active nitrating species in both media is the nitronium ion, NOz+, which is formed by protonation and dissociation of nitric acid. The concentration of NOz+ is higher in the more strongly acidic sulfuric acid than in nitric acid. 

It can be seen from Figure 5.18 that the KD values for zirconium are higher than those for hafnium at all nitric acid concentrations. This is because the dissolution of zirconium nitrate (Zr(N03)4) into zirconyl (Zr02+) and nitrate (NOj) ions takes place to a lower extent as compared to the corresponding dissolution of hafnium nitrate in an aqueous medium. Hence, separation is feasible. However, at higher nitric acid concentrations the separation factor is reduced significantly because the dissociation of hafnium nitrate (Hf(NOs)4) decreases sharply with increasing nitric acid concentration, with the result that the separation factor, p, falls off rapidly. Hence, the separation process calls for the adjustment of the nitric acid concentration to a suitably low value. 

It will be instructive to explain the matter stated above by an example. The conductance of silver in solution at 18 °C is given as 55.7 and of nitrate ion as 60.8. The specific conductivity (K) of AgN03 in N/10 solution at 18 °C is 0.00947 mhos. From all these given data it is the aim of the present example to calculate the percentage of dissociation of the salt at its given concentration. It may be noted that in this illustration the specific conductivity (K) in N/10 solution is 0.00947 mhos. The volume containing 1 g-equiv. is 10,000 ml. Therefore,... 

Comments on the thermal nitration of enol silyl ethers with TNM. The strikingly similar color changes that accompany the photochemical and thermal nitration of various enol silyl ethers in Table 2 indicates that the preequilibrium [D, A] complex in equation (15) is common to both processes. Moreover, the formation of the same a-nitroketones from the thermal and photochemical nitrations suggests that intermediates leading to thermal nitration are similar to those derived from photochemical nitration. Accordingly, the differences in the qualitative rates of thermal nitrations are best reconciled on the basis of the donor strengths of various ESEs toward TNM as a weak oxidant in the rate-limiting dissociative thermal electron transfer (kET), as described in Scheme 4.40... 

In the past, dissociation of the nucleoprotein complex has been brought about by salt solutions or by heat denaturation,129 but, more recently, decomposition has been effected by hydrolysis with trypsin,126 or by the use of dodecyl sodium sulfate130 or strontium nitrate.131 Some virus nucleoproteins are decomposed by ethyl alcohol.132 This effect may be similar to that of alcohol on the ribonucleoproteins of mammalian tissues. If minced liver is denatured with alcohol, and the dried tissue powder is extracted with 10% sodium chloride, the ribonucleoproteins are decomposed to give a soluble sodium ribonucleate while the deoxyribonucleoproteins are unaffected.133 On the other hand, extraction with 10 % sodium chloride is not satisfactory unless the proteins have first been denatured with alcohol. Denaturation also serves to inactivate enzymes of the tissues which might otherwise bring about degradation of the nucleic acid during extraction. 

It should be noted that different authors give slightly different versions of the above reactions, but there are two major points, which are always the same (i) in basic solutions peroxynitrite exists only in the relatively stable m-conformation. which prevents its rearrangement into nitrate and makes possible to dissociate into hydroxyl and nitrite radicals (Reaction 36). (ii) 7>acidic solutions and rapidly rearranges into nitrate (Reaction 38). 

Fe(III) displacement of Al(III), Ga(III), or In(III) from their respective complexes with these tripodal ligands, have been determined. The M(III)-by-Fe(III) displacement processes are controlled by the ease of dissociation of Al(III), Ga(III), or In(III) Fe(III) may in turn be displaced from these complexes by edta (removal from the two non-equivalent sites gives rise to an appropriate kinetic pattern) (343). Kinetics and mechanism of a catalytic chloride ion effect on the dissociation of model siderophore-hydroxamate iron(III) complexes chloride and, to lesser extents, bromide and nitrate, catalyze ligand dissociation through transient coordination of the added anion to the iron (344). A catechol derivative of desferrioxamine has been found to remove iron from transferrin about 100 times faster than desferrioxamine itself it forms a significantly more stable product with Fe3+ (345). 

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