Ammonium chloride, acidic behavior

There is nothing unusual about the acidic behavior of ammonium salts. In fact, any protonated amine can function as a proton donor. Because of this, many amine salts have been used as acids in synthetic reactions. If the chlorides are used, the amine salts are known as amine hydrochlorides. One of the earliest amine hydrochlorides studied with regard to its behavior as an acid is pyridine hydrochloride (pyridinium chloride), C5H5NH+C1. In the molten state, this compound undergoes many reactions of the type just shown. 

Many years ago, L. F. Audrieth studied numerous reactions of amine hydrochloride salts. These compounds contain a cation that is a protonated amine that can function as a proton donor. Consequently, the molten salts are acidic and they undergo many reactions in which they function as acids. This behavior is also characteristic of ammonium chloride as well as pyridine hydrochloride (or pyridinium... 

Compounds related to aniline, either directly or by oxidation, and to nitrobenzene by reduction, are numerous and important. When nitrobenzene is reduced in the presence of hydrochloric acid by tin or iron, the product is aniline (colorless liquid in die presence of water by zinc, the product is phenylhydroxylamine (white solid) in the presence of methyl alcohol by sodium alcoholate 01 by magnesium plus ammonium chloride solution, the product is azoxybenzene (pale yellow solid) by sodium stannitc, or by water plus sodium amalgam, the product is azobcnzcnc (red solid) in the presence of sodium hydroxide solution by zinc, the product is hydrazobenzene (pale yellow solid). The behavior of other nitrocompounds is similar to that of nitrobenzene. 

The second exception was specific for HZSM-5 that had been acidified with ammonium chloride and which had large particle sizes. The differential heat curve at 416-423 K for these samples passed through a maximum at relatively low coverages. This behavior could be explained by the combination of three independent phenomena immobile adsorption, mass-transfer limitations, and preferential location of the most energetic acid sites in the internal pores of the zeolite structure. Apparently, the strongest sites were not accessible to ammonia when the first doses were introduced but became progressively covered when further ammonia was added. Electron paramagnetic resonance studies (93) provided data to support this hypothesis. 

The slight temperature effect was confirmed further by observing the behavior of methyl red in ammonium chloride solutions. Noyes (p. 21) has reported that the dissociation constant of ammonia is independent of temperature. Since Kw increases 100 times, the pH of the boiling solution must be considerably decreased, and the color of solution must of necessity be shifted to the acid side. This was confirmed experimentally as follows. Several drops of methyl red added to a 0.2 N ammonium chloride solution showed an intermediate color (pH = 5.1). Boiling produced a much more intense red, although not quite the color of methyl red at a pH of 4.2. After cooling, the color corresponded to the original pH. 

L1T Litmanovich, E.A., Chemikova, E.V., Stoychev, G.V., and Zakharchenko, S.O., Unusual phase behavior of the mixture of poly(acryhc acid) and poly(diallyldimethyl ammonium chloride) in acidic media. Macromolecules, 43, 6871, 2010. 

The free radical polymerizations of 3-[(2-Acrylamido-2-mefliyl propyl)dimethylammonio]-l-propanesulfonate with acrylamide and/or acrylic acid, and 3-(i Tj -diallyl-i /-methylammonio)-l-propanesulfonate with A, iV diailyl-i, iV-dimethyl ammonium chloride or AT,A/-diallyl-iV,-methyl amine have been studied. Reactivity ratios indicate random incorporation of comonomers. Molecular weights range from 3.0 x 10 to 15.1 x 10 g mol for the acrylamido-based copolymers and from 2.2 x 10 to 6.0 x 10 g mol for the cyclocopolymers. Second virial coefficients and viscosities decrease as sulfobetaine content increa s for each of the copolymers. A transition from polyelectrolyte to polyampholyte behavior is observed with added NaCl for those copolymers with sulfobetaine monomer incorporation greater than 40 mol%... 

Research continues on mass transfer and the factors affecting the process. The experiments are executed with the solvent iso-octane and the surfactant ricinoleic acid. Initial results on the behavior of the size of generated drops are shown in Fig. 23. These drops are generated in a clear aqueous phase in the transfer column. To obtain stable single drops, very low concentrations of ions—in particular ammonia— are needed. With more than 0.5 m% of ions resulting from the salts ammonium chloride and ammonium sulfate, stable drop generation cannot be achieved for concentrations of ricinoleic acid of 3.0 m% with capillary diameters... 

We have also noted that chloride accumulation on indoor zinc or aluminum surfaces can occur at dramatically different rates (0. At locations where large differences are observed, hydrogen chloride has been implicated to be the source of much of the chloride accumulation. This difference in behavior was attributed, in part, to the slightly higher acidity and higher ammonium content of the aluminum surfaces, both of which will inhibit the reaction of hydrogen chloride with aluminum and will enhance the volatilization of hydrogen chloride. 

The sulfonate moiety is only weakly nucleophilic in water, and the effects of micellized SB3-16 upon hydrolyses are generally very similar to those of cationic micelles (Tables IV-VI). This behavior suggests that in both systems the substrates bind close to the quaternary ammonium centers and that the sulfonate moiety, like a micellar-bound counteranion, is in the water and therefore not interacting strongly with the substrate (65). The only exceptions to this generalization were observed with hydrolyses of some acid chlorides (Table V). In these reactions, the balance between bond making and breaking seems to be very sensitive to the reaction medium (58). 

Since the behavior of ammonia, toward hydrogen chloride is similar to that of water and of platimo chloride, it also should yield an acid in forming annnnnomate with hydrogen chloride. This is in fa< t tho fibr when ammonium... 

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