Liquid ammonia acid-base reactions

Cas/liquid reaction 28 [CL 28] Acid-base reaction between ammonia and Bronsted inorganic acids... 

In solutions neither H+ nor e can exist in a free state they will be donated only if they are accepted within the solution, e.g., by another acceptor, which may be the solvent and thus cause solvation here the mere solvation of electrons is an exceptional case, but may occur, e.g., in liquid ammonia, where according to Kraus82 the strongly reducing alkali metals dissolve while dissociating into cations M+ and solvated electrons e, which, however, are soon converted into NH2" and H2 gas. Further, from the analogy with acid-base reactions and the definition of... 

Almost all of the reactions that the practicing inotganic chemist observes in the laboratory take place in solution. Although water is the best-known solvent, it is not the only one of importance to the chemist. The organic chemist often uses nonpolar solvents sud) as carbon tetrachloride and benzene to dissolve nonpolar compounds. These are also of interest to Ihe inoiganic chemist and, in addition, polar solvents such as liquid ammonia, sulfuric acid, glacial acetic acid, sulfur dioxide, and various nonmctal halides have been studied extensively. The study of solution chemistry is intimately connected with acid-base theory, and the separation of this material into a separate chapter is merely a matter of convenience. For example, nonaqueous solvents are often interpreted in terms of the solvent system concept, the formation of solvates involve acid-base interactions, and even redox reactions may be included within the (Jsanovich definition of acid-base reactions. 

Acid-base reactions. According to the solvent concept, the acidic species characteristic of liquid ammonia is NH4+ and the basic species is NH2. Neutralization reactions in liquid ammonia thus become equivalent to the reaction of these ions ... 

The formation of ammonium sulfate and ammonium nitrate aerosols is an acid-base reaction in the atmosphere. Ammonia neutralizes the acids. Sulfuric acid has a very low vapor pressure (< 10 atm) and thus exists in the atmosphere as liquid particles, which react with NH3 and H2O (reaction 22). 

It is apparent from the above definition that a substance cannot act as an acid unless a base is present to accept the protons. Thus, acids will undergo complete or partial ionization in basic solvents such as water, liquid ammonia, or ethanol, depending on the basicity of the solvent and the strength of the acid. But in neutral or inert solvents, ionization is insignificant. However, ionization in the solvent is not a prerequisite for an acid-base reaction, as in the last example in the table, where picric acid reacts with aniline. 

On the planet Baseacidopolous, the major solvent is liquid ammonia, not water. Ammonia autoionizes much Uke water (2NH3 NH4 + NH2 ). If instead of water, ammonia is used as a solvent (a) What is the formula of the cation that would indicate that a compound is an acid (b) What is the formula of the anion produced if a compound is a base (c) Look at the way that NaCl is formed from an acid-base reaction on earth and determine if NaCl can be a salt on Baseacidopolous. 

NH3 H2O NH4+ -r OH-the H2O is the conjugate acid of OH. The definition also extends the idea of acid-base reaction to solvents other than water. For instance, liquid ammonia, like water, has a high dielectric constant and is a good ionizing solvent. Equilibria of the type... 

ANSWER First add propyne to sodium amide in liquid ammonia. The following acid—base reaction will take place ... 

One of the advantages of the Bronsted-Lowry theory is that it can describe acid-base reactions in a nonaqueous medium like liquid ammonia. In liquid ammonia, HCl(g) donates a proton to NH3, forming NH4 and CL. No water is involved, so there are no H30 or OH ions formed. Ammonium and chloride ions are solvated by ammonia molecules, so instead of the usual aq , we might use am to show solvation by ammonia molecules. 

Since the proton affinity of hydrazine is similar to that of ammonia, acid-base reactions are similar to those in this solvent system. Many compounds are known to act as moderately strong acids, but only a few substances (notably the hydra-zides of the alkali metals) behave as bases. NaN2H3 may be obtained by drop wise addition of hydrazine to a suspension of finely divided sodium in dry ether. Electrolysis in liquid hydrazine gives nitrogen at the anode and hydrogen at the cathode . 

One important aspect of the Lowry-Bronsted theory is that, because it involves proton transfers, it does not necessarily have to involve water. It is possible to describe reactions in nonaqueous solvents, such as liquid ammonia, in terms of acid-base reactions. 

When 2-bromoanisole (160) reacts with sodium amide (NaNHg) in liquid ammonia (at -33°C), a reaction occurs to give 2-aminoanisole (165) along with 3-aminoanisole (166). This appears to be a substitution reaction where a hydrogen is replaced by -NHg. However, substitution occurs at two different carbon atoms, so direct substitution is ruled out as a mechanism. To rationalize these experimental observations, first recognize that sodium amide is a powerful base, and an acid-base reaction removes the hydrogen atom ortho to the bromine to give 161. 

Liquid ammonia is a base, so reactions with acids generally proceed to a greater degree than do the analogous reactions in water. For example, acetic acid is a weak acid in water, but it ionizes completely in liquid ammonia. Even though ammonia is a base, it is possible for protons to be removed, but only when it reacts with exceedingly strong bases such as N3, O2, or 11. Some of the important types of reactions that occur in liquid ammonia will now be illustrated. 

The activated methyl groups of 5,7-dimethyl-l,8-naphthyridin-2-one (106) can be selectively metallated, reaction with two equivalents of butyllithium giving (107), while with two equivalents of sodamide in liquid ammonia (108) is obtained. Both (107) and (108) gave appropriate products on treatment with electrophiles (81JOM(213)405>. A possible explanation of this result involves a coordination mechanism for the formation of (107) and an acid-base mechanism giving (108). 

Just as the cation produced by dissociation of water (H30+) is the acidic species in aqueous solutions, the NH4+ ion is the acidic species in liquid ammonia. Similarly, the amide ion, NH2, is the base in liquid ammonia just as OH- is the basic species in water. Generalization to other nonaqueous solvents leads to the solvent concept of acid-base behavior. It can be stated simply as follows A substance that increases the concentration of the cation characteristic of the solvent is an acid, and a substance that increases the concentration of the anion characteristic of the solvent is a base. Consequently, NH4C1 is an acid in liquid ammonia, and NaNH2 is a base in that solvent. Neutralization becomes the reaction of the cation and anion characteristic of the particular solvent to produce unionized solvent. For example, in liquid ammonia the following is a neutralization ... 

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