Inorganic compounds dielectric constant

Prepared from ethyne and ammonia or by dehydration of ethanamide. Widely used for dissolving inorganic and organic compounds, especially when a non-aqueous polar solvent of high dielectric constant is required, e.g. for ionic reactions. 

Luminescence has been used in conjunction with flow cells to detect electro-generated intennediates downstream of the electrode. The teclmique lends itself especially to the investigation of photoelectrochemical processes, since it can yield mfonnation about excited states of reactive species and their lifetimes. It has become an attractive detection method for various organic and inorganic compounds, and highly sensitive assays for several clinically important analytes such as oxalate, NADH, amino acids and various aliphatic and cyclic amines have been developed. It has also found use in microelectrode fundamental studies in low-dielectric-constant organic solvents. 

Dielectric constants for a selected group of inorganic and organic compounds are included in Tables 5.17 and 5.18. An extensive list has been compiled by Maryott and Smith, National Bureau Standards Circular 514, Washington, D.C., 1951. 

Both the dielectric constant and dipole moment are comparable to those of water, indicating that HF is a good solvent for inorganic compounds, but many organic compounds are also soluble. In general, the fluorides of +1 metals are much more soluble than those of +2 or +3 metals. At 11 °C, the solubility of NaF is approximately 30 g per 100 g of liquid HF, that of MgF2 is only 0.025 g, and that of A1F3 is 0.002 g. 

Acetonitrile. Acetonitrile is resistant to both oxidation and reduction, is transparent in the region 200-2000 nm, and is an excellent solvent for many polar organic compounds and some inorganic salts. Its dielectric constant of 37 permits reasonably high conductivities, although there is evidence of some association (see Table 7.8). It is less basic than dimethylformamide and dimethyl sulfoxide, and therefore does not solvate alkali metal cations as strongly. However, acetonitrile forms stable complexes with Ag(I) and Cu(I) ions. 

The solubility of inorganic compounds, such as e.g. salts, decreases in the same way as the solubility of organic compounds in the supercritical state increases. This decrease is combined with the decrease of the dielectric constant of water. The supercritical water oxidation process is described in the following figure. 

Because NH3(1) has a much lower dielectric constant than water, it is a better solvent for organic compounds but generally a poorer one for ionic inorganic compounds. Exceptions occur when complexing by NH3 is superior to that by water. Thus Agl is exceedingly insoluble in water but NH3(1) at 25°C dissolves 207 g/100 cm3. Primary solvation numbers of cations in NH3(1) appear similar to those in H20 (e.g., 5.0 0.2 and 6.0 0.5 for Mg2+ and Al3+, respectively), but there may be some exceptions. Thus Ag+ appears to be primarily linearly 2-coordinate in H20 but tetrahedrally coordinated as [Ag(NH3)4]+ in NH3(1). It has also been suggested that [Zn(NH3)4]2+ may be the principal species in NH3(1) as compared to [Zn(H20)6]2+ in H20. 

Sulfur dioxide (bp, -10°C Tc, 157.5°C Pc, 78 atm) is another interesting inorganic solvent. This compound has a high dielectric constant and low basicity (actually, it acts as an acid). To the best of my knowledge, there have been no articles that apply this solvent for the solvothermal synthesis of inorganic materials. However, the highly corrosive nature of this solvent may hmit its use in autoclaves. 

Ammonia has a medium-high dielectric constant (23.7 at —36°C) and good dissolving power toward inorganic salts, but less for nonpolar organic compounds. It can act as both an acid and a base the strongest possible acid in ammonia is ammonium ion and the strongest base the amide ion. The pK values of some weak acids have been determined in NH3 at -60°C [334]. 

DMSO is an excellent solvent for many inorganic salts and organic compounds. It is difficult to reduce and fairly resistant to electrolytic oxidation. Its dielectric constant is high (s = 47). It thus has many of the qualities desirable for a solvent for electrolysis, and it shows promise of being one of the most important electrochemical media [387]. The liquid range is from 18 to 189°C, which makes it somewhat inconvenient to get rid of DMSO in the workup. When used as solvent for electrolysis it must be considered that DMSO is not always inert but has a fair reactivity in certain reactions. DMSO is unfit for UV spectroscopy. Its autoprotolysis constant is 31.8. 

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