Inorganic Nonaqueous Solvent
   HOME

TheInfoList



OR:

An inorganic nonaqueous solvent is a solvent other than water, that is not an
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
. These solvents are used in chemical research and industry for reactions that cannot occur in aqueous solutions or require a special environment. Inorganic nonaqueous solvents can be classified into two groups, protic solvents and aprotic solvents. Early studies on inorganic nonaqueous solvents evaluated ammonia, hydrogen fluoride, sulfuric acid, as well as more specialized solvents, hydrazine, and selenium oxychloride.


Protic inorganic nonaqueous solvents

Prominent members include ammonia, hydrogen fluoride, sulfuric acid,
hydrogen cyanide Hydrogen cyanide (formerly known as prussic acid) is a chemical compound with the chemical formula, formula HCN and structural formula . It is a highly toxic and flammable liquid that boiling, boils slightly above room temperature, at . HCN is ...
. Ammonia (and several amines as well) are useful for the generating solutions of highly reducing species because the N-H bond resists reduction. The chemistry of electrides and alkalides relies on amine solvents. The combination of HF and SbF5 is the basis of a
superacid In chemistry, a superacid (according to the original definition) is an acid with an acidity greater than that of 100% pure sulfuric acid (), which has a Hammett acidity function (''H''0) of −12. According to the modern definition, a superacid i ...
solution. Using this mixture, the conjugate acid of hydrogen sulfide can be isolated: :H2S + HF + SbF53SbF6


Autoionization

The limiting acid in a given solvent is the solvonium ion, such as H3O+ ( hydronium) ion in water. An acid which has more of a tendency to donate a
hydrogen ion A hydrogen ion is created when a hydrogen atom loses or gains an electron. A positively charged hydrogen ion (or proton) can readily combine with other particles and therefore is only seen isolated when it is in a gaseous state or a nearly particl ...
than the limiting acid will be a strong acid in the solvent considered, and will exist mostly or entirely in its dissociated form. Likewise, the limiting base in a given solvent is the solvate ion, such as OH ( hydroxide) ion, in water. A base which has more affinity for protons than the limiting base cannot exist in solution, as it will react with the solvent. For example, the limiting acid in liquid ammonia is the ammonium ion, NH4+ which has a p''K''a value in water of 9.25. The limiting base is the amide ion, NH2. NH2 is a stronger base than the hydroxide ion and so cannot exist in aqueous solution. The p''K''a value of ammonia is estimated to be approximately 34 (''cf.'' water, 14).


Aprotic inorganic nonaqueous solvents

Prominent members include
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
, sulfuryl chloride fluoride, dinitrogen tetroxide, antimony trichloride, and bromine trifluoride. These solvents have proven useful for study highly electrophilic or highly oxidizing compounds or ions. Several (SO2, SO2ClF, N2O4) are gases near room temperature, so they are handled using vacuum-line techniques. The generation of S7sup>+ and rS7sup>+ are illustrative. These highly electrophilic salts are prepared in SO2 solution. The preparation of Br3sup>+ salts also calls for a mixed solvent composed of SO2 and SO2FCl. Sulfuryl chloride fluoride is often used for the synthesis of noble gas compounds.


Autoionization

Many inorganic solvents participate in autoionization reactions. In the solvent system definition of acids and bases, autoionization of solvents affords the equivalent to acids and bases. Relevant autoionizations: : 2BrF3 BrF2+ + BrF4 : N2O4 ⇌ NO+ ( nitrosonium) + NO3 ( nitrate) : 2SbCl3 ⇌ SbCl2+ + SbCl4 : 2POCl3 ⇌ POCl2+ + POCl4 According to the solvent-system definition, acids are the compounds that increase the concentration of the solvonium (positive) ions, and bases are the compounds that result in the increase of the solvate (negative) ions, where solvonium and solvate are the ions found in the pure solvent in equilibrium with its neutral molecules: The solvent SO2 is relatively uncomplicated, it does not autoionize.


See also

* Nonaqueous titration * Protic solvent


References


External links

* {{Chemical solutions Solvents