Ammonia liquid solvent

The alkali metals have the interesting property of dissolving in some non-aqueous solvents, notably liquid ammonia, to give clear coloured solutions which are excellent reducing agents and are often used as such in organic chemistry. Sodium (for example) forms an intensely blue solution in liquid ammonia and here the outer (3s) electron of each sodium atom is believed to become associated with the solvent ammonia in some way, i.e. the system is Na (solvent) + e" (sohem). 

This procedure may be used for the preparation of finely-divided sodamide If the sodamide is to be used in any other solvent than liquid ammonia, the ammonia is allowed to evaporate whilst the new solvent is slowly added from a dropping funnel alternatively, the new solvent may be added before the ammonia evaporates. If dry sodamide is required, the product may be freed from the last traces of ammonia by evacuation at 100°. The sodamide prepared by this method must be used immediately if allowed to stand, it rapidly changes into explosive substances. 

Ammonia is a pungent, toxic gas that condenses to a colorless liquid at — 33°C. The liquid resembles water in its physical properties, including its ability to act as a solvent for a wide range of substances. Because the dipole moment of the NH3 molecule (1.47 D) is lower than that of the H20 molecule (1.85 D), salts with strong ionic character, such as KCI, cannot dissolve in ammonia. Salts with polarizable anions tend to be more soluble in ammonia than are salts with greater ionic character. For example, iodides are more soluble than chlorides in ammonia. Liquid ammonia undergoes much less autoprotolysis than water ... 

Certain solvents stabilize intermediates by strong solvation. The best known example is that of the electron itself which forms stable solutions in a number of solvents including liquid ammonia and hexamethyl-... 

This reaction is similar to 13-1 and, like that one, generally requires activated substrates. With unactivated substrates, side reactions predominate, though aryl methyl ethers have been prepared from unactivated chlorides by treatment with MeO in HMPA. This reaction gives better yields than 13-1 and is used more often. A good solvent is liquid ammonia. The compound NaOMe reacted with o- and p-fluoronitrobenzenes 10 times faster in NH3 at — 70°C than in MeOH. Phase-transfer catalysis has also been used. The reaction of 4-iodotoluene and 3,4-dimethylphenol, in the presence of a copper catalyst and cesium carbonate, gave the diaryl ether (Ar—O—Ar ). Alcohols were coupled with aryl halides in the presence of palladium catalysts to give the Ar—O—R ether. Nickel catalysts have also been used. ... 

Of greatest interest among the protic solvents are liquid ammonia (where solutions with a very low freezing point can be prepared) and anhydrous (glacial) acetic acid (which has a high proton-donating power). 

HF is that it attacks glass, so containers must be made of some inert material such as Teflon, a polytet-rafluoroethylene. The data for this nonaqueous solvent are shown in Table 10.4. As expected from the rather high heat of vaporization (which lies between the values for water and liquid ammonia) liquid HF has a liquid range that spans over 100 °C and a relatively high boiling point. 

Each of the following reactions takes place in aqueous solution. Write an equation that is analogous to each when the solvent is liquid ammonia. 

It is therefore apparent that dissociation constants may only be compared in the same solvent. Ammonia is a stronger donor than water, but liquid ammonia has a much lower dielectric constant than the latter. The acidity constant of hydrochloric acid in liquid ammonia is much lower than in water, in which it is completely ionized and completely dissociated, whereas the complete ionization in liquid ammonia is not followed by extensive ionic dissociation due to its low dielectric constant. On the other hand, the acidity constant of acetic acid is somewhat higher in liquid ammonia than in water since in the latter if Ion is much lower than in liquid ammonia, in which complete ionization is achieved. 

The design is such that operation at high pressure (400 lb./sq. in.) is readily feasible, permitting the device to be used, for example, with such solvents as liquid ammonia. 

Lithium salts exhibit general high solubility and a high degree of dissociation in other nnnaqueous solvents than liquid ammonia, such as liquid sulfur dioside and acetic acid. 

However, there are a number of complicating factors to consider. First, the basic conditions needed to form the enolate ions often lead to side reactions such as aldol addition and E2 elimination of RX compounds. Aldol addition is minimized if the carbonyl compound is a ketone with a structure unfavorable for aldol addition or if all of the carbonyl compound is converted to its enolate. To convert all of a simple carbonyl compound to its enolate usually requires a very strong base, such as NH2 in an aprotic solvent or liquid ammonia. Because the enolate anion itself is a strong base, best results are obtained when the halide, RX, does not undergo E2 reactions readily. 

Although many chemical reactions take place in water, it is often necessary to use other solvents, and liquid ammonia (b.p. —33°C) has been used extensively. Many of the reactions that occur in water... 

In general, from among the protic solvents, only liquid ammonia (the first used)1 is particularly useful, and is still used more than any other solvent despite the low temperature at which reactions have to be carried out (b.p. -33 °C) and the fact that solubilities of some aromatic substrates and salts (M+Nu-) are poor. Ammonia has the added advantage of being easily purified by distillation, being an ideal system for production of solvated electrons, and has very low reactivity with basic nucleophiles and radical anions, and aryl radicals. Also, poor solubilities can sometimes be ameliorated by use of cosolvents such as THF. In addition it can be used as a solvent for the in situ reductive generation of nucleophiles such as ArSe- and ArTe- ions, e.g. the formation of PhTe- from diphenyl ditelluride (equation 16).54 55... 

Ionization of liquid ammonia and water solutions.—Solutions of certain salts in liquid ammonia are good conductors of electricity so that liquid ammonia approaches water in its ionizing power. The effect, however, is largely due to the high speed at which the ions are supposed to travel in the solvent. For example, E. C. Franklin and H. P. Cady1 find that univalent ions travel, at —33°, nearly three lames as fast as in aq. soln. at 18°. Just as the solvent water, in the ionization theory of hydrolysis, is supposed to be ionized H20=0H -f-H, so in ammonolysis, the solvent ammonia is supposed to be ionized NH3==NH2-j-H . Sodamide, NaNH, furnishes sodium ions Na and amide ions NH 2 when dissolved in liquid ammonia, and it is to be considered as a base. It reddens phenolphthalein. The neutralization of this solution results in the union of H ions with NH2 ions to form ammonia molecules, just as the neutralization of bases is regarded as an effect of the union of H and OH ions. Acetamide, CH3.CO.NH2, ionizes in liquid ammonia in an analogous manner CH3.CO.NH2 CH3.CO.NH -f-H, and it thus behaves as an acid. 

Derivatives of alkaline, alkaline earth metals and phenols, naphtols, an-troles, etc. (pK> 10). These compounds are salts in their nature and, as the salts of strong bases and moderately weak acids, can exist in water solutions. They are soluble only in polar solvents (water, liquid ammonia), are prone to form adducts with phenols, water, etc., have high thermal stability and cannot be transferred into the gas phase. 

Solvent dyes are dyes that are soluble in alcohols, chlorinated hydrocarbon solvents, or liquid ammonia, and there appears to be considerable promise in dyeing the difficult-to-dye synthetics, polyesters, polyacrylates, and triacetates, from such solutions. 

Comparison of n values with solubility parameters for the various liquids and fluids, calculated as described by Giddings and coworkers (10), shows a general correlation for the less polar solvents. Ammonia and the polar liquid solvents diverge from this correlation, suggesting the operation of specific interactions which contribute to the greater magnitude of the shifts observed for ammoni a. 

Although no attempt will be made to describe the chemistry of all of the nonaqueous solvents listed in Table 5.4, the survey to this point has included ammonia as a basic solvent and liquid hydrogen fluoride as an acidic solvent. Another solvent that has been extensively utilized in both inorganic and organic chemistry is sulfur dioxide. Accordingly, we will give a brief survey of the chemistry of liquid sulfur dioxide for which the physical properties are presented in Table 5.8. 

The stability of the solvated electron in the various solvents varies greatly depending on the reactivity of the electron with the solvent. In liquid ammonia solvated electrons are stable for long periods in the blue solutions of alkali metals in ammonla(45). In watjr, eaq decays slowly by reaction (9) with a rate constant of 16 M s (46)... 

Other Electrolytic Solvents. Some liquids other than water can serve as ionizing solvents, with the power of dissolving electrolytes to give electrically conducting solutions. These liquids include liquid ammonia, hydrogen peroxide, and hydrogen fluoride. All of these liquids, like water, have very large dielectric constants. Liquids with... 

The solvent is liquid ammonia, at its boiling point -33 °C. The exact amount of the metal is used. In particular cases one or other set of conditions may give the better yield. In investigating a new acyloin coupling reaction the first choice would be heterogeneous conditions. 

Comparing the data of Sections 4 and 6 with those of Table 1 reveals that in the presence of lithium cations, associates containing two electrons are not formed in any of the studied solvents (hexamethylphosphotriamide, liquid ammonia, and methylamine). For other alkali metal cations, such associates have been detected. By the example of methylamine it has been shown that the tendency to formation of associates with two electrons increases while proceeding from cesium to potassium. The higher the tendency the less the concentration of electrons, i. e. the smaller the density of the cathode current at which the formation of associates (as revealed by the change in the slope of the voltammetric curve) can be observed. Note that lithium cations never form associates with two electrons. 

However, it should be remembered that at equal stoichiometry the nature of the associates in different solvents may differ. In liquid ammonia an associate represents, apparently, a triple ion e M e in which the electrons lose their paramagnetic properties, but retain other individual characteristics (optical spectrum, excess volume), whereas in other solvents (hexamethylphosphotriamide, liquid methylamine) new compounds — metal anions M" are most likely to be formed. 

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