Lithium and water

Reductive processes are sometimes useful for conversion of polyiodinated pyrroles into compounds with fewer iodine atoms. Sequential action of butyl-lithium and water reduced tetraiodopyrrole to a mixture of 2,3,4-triiodopyrrole (63%) and 2,3,5-triiodopyrrole (3%). Zinc and acetic acid was able to reduce the tetraiodo compound to 3,4-diiodopyrrole which was converted by butyl-lithium and then dimethylformamide into 3-formyl-... 

Lithium is the most difficult of the alkali metals with which to obtain stable solutions since it cannot be distilled in glass. Three runs were carried out with lithium and water, but the results are inconclusive. In the first run, lithium prepared by evaporating a lithium-ammonia solution was used, and in the other runs the lithium was cut in a dry box and introduced into the ethylenediamine just prior to the run by means of a break-seal sidearm. The first two runs appeared to yield three rate constants, with values around 100, 20, and 7 Af-1 sec.-1, respectively and involved both infrared and visible absorptions. In the third run, a very dilute solution showing no infrared absorbance was used and resulted in a single rate constant of about 30 Af-1 sec.-1, obtained by following the decay of the 660 m/z absorbance. 

The reaction of lithium and water is a single-replacement reaction. Lithium replaces a hydrogen in water, and the products of the reaction are aqueous lithium hydroxide and hydrogen gas. Lithium hydroxide exists as lithium and hydroxide ions in solution. 

Single-replacement reactions Now that you ve seen how atoms and molecules rearrange in synthesis and combustion reactions, look closely at the reaction between lithium and water that is shown in Figure 10-8. The expanded view of the reaction at the molecular level shows that a lithium atom replaces one of the hydrogen atoms in a water molecule. The following chemical equation describes this activity. 

The reaction between lithium and water is one type of single-replacement reaction in which a metal replaces a hydrogen in a water molecule. Another type of single-replacement reaction occurs when one metal replaces another metal in a compound dissolved in water. For example. Figure 10-9 shows a single-replacement reaction occurring when a spiral of pure copper wire is placed in aqueous silver nitrate. The shiny crystals that are accumulating on the copper wire are the silver atoms that the copper atoms replaced. 

The most important chemical property of all the alkali metals, including lithium, is that they are extremely chemically reactive. For example, they all react vigorously with water, in the process forming hydrogen gas, shown in the following reaction between lithium and water ... 

All alkali metals react with water to produce hydrogen gas and the corresponding alkali metal hydroxide. A typical reaction is that between lithium and water ... 

Some people have suggested fusion as a future energy source, based upon abundant supplies of deutrium in water and tritium from lithium and water. Technical problems have so far prevented this from occurring, see ALSO Air Pollution Fossil Fuels. 

Single-replacement reactions The reaction between lithium and water is shown in Figure 9.12. The following chemical equation shows that a lithium atom replaces one of the hydrogen atoms in a water molecule. 

Write a balanced equation for the reaction between lithium and water. 

The acidic chloroaluminate IL [EMIMJCl-AlClj (5c = 0.67), combined with electropositive metals (Al, Zn, and li) and a proton source, has been applied to the stereoselective hydrogenation of aromatic compounds [62]. Anthracene, pyrene, and 9,10-dimethyIanfhracene were partially or completely hydrogenated, and the selectivity appears to be a function of the proton source. It was found, for example, that anthracene could be converted to dihydroanthracene in [EMIM]C1—AICI3 [x = 0.67) containing lithium and water, whereas in the presence of zinc and HCl gas complete hydrogenation was possible as shown in Scheme 2. 

The distinction between the activity series and the electrochemical series can be illustrated by adding lithium and potassium to water. Lithium reacts more slowly with water than potassium does, despite the former having a more negative electrode potential. The reaction between lithium and water to form lithium ions is more thermodynamically fevourable than that between potassium and water, but the reaction is slower. 

Wang H, Im D, Lee DJ, Matsui M, Takdeda Y, Yamamoto O, Imanishi N (2013) A composite polymer electrolyte protect layer between lithium and water stable ceramics for aqueous lithium-air batteries. J Electrochem Soc 160 A728... 

Experiments show that lithium reacts more slowly and less vigorously with water than do any of the other alkali metals. To explain this observation, it is necessary to consider what happens to the energy that is released by the reaction as the metal is oxidized by water. As the metal reacts, energy released by the reaction is used to heat the system, including unreacted metal. For all the alkali metals except lithium, energy released by the reaction is sufficient to melt the unreacted metal. The melting of the metal increases the rate of reaction because it causes more metal atoms to come into contact with water molecules. Because lithium metal does not melt as the reaction proceeds, the reaction of lithium and water is neither as fast nor as vigorous as it is for the other alkali metals. 

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