Group I metals

From Table 6.1, it is easy to see that Group II metals are more dense, are harder and have higher m.p. and b.p. than the corresponding Group I metals. 

All the following compounds are charactenzed by ionic bonding between a group I metal cation and a tetrahedral anion Wnte an appropriate Lewis structure for each anion remembenng to specify formal charges where they exist... 

A useful alternative to catalytic partial hydrogenation for converting alkynes to alkenes IS reduction by a Group I metal (lithium sodium or potassium) m liquid ammonia The unique feature of metal-ammonia reduction is that it converts alkynes to trans alkenes whereas catalytic hydrogenation yields cis alkenes Thus from the same alkyne one can prepare either a cis or a trans alkene by choosing the appropriate reaction conditions... 

Group I metals—sodium is the one usually employed—in liquid ammonia as the solvent convert alkynes to trans alkenes The reaction proceeds by a four step sequence in which electron transfer and proton transfer steps alternate... 

Reduction of arenes by catalytic hydrogenation was described m Section 114 A dif ferent method using Group I metals as reducing agents which gives 1 4 cyclohexadiene derivatives will be presented m Section 1111 Electrophilic aromatic substitution is the most important reaction type exhibited by benzene and its derivatives and constitutes the entire subject matter of Chapter 12... 

We saw m Section 9 10 that the combination of a Group I metal and liquid ammonia is a powerful reducing system capable of reducing alkynes to trans alkenes In the pres ence of an alcohol this same combination reduces arenes to nonconjugated dienes Thus treatment of benzene with sodium and methanol or ethanol m liquid ammonia converts It to 1 4 cyclohexadiene... 

Section 1111 An example of a reaction m which the ring itself reacts is the Birch reduction The ring of an arene is reduced to a nonconjugated diene by treatment with a Group I metal (usually sodium) m liquid ammonia m the presence of an alcohol... 

The reaction of an alkyl halide with lithium is an oxidation-reduction reac tion Group I metals are powerful reducing agents... 

Birch reduction (Section 11 11) Reduction of an aromatic nng to a 1 4 cyclohexadiene on treatment with a group I metal (Li Na K) and an alcohol in liquid ammonia Boat conformation (Section 3 7) An unstable conformation of cyclohexane depicted as... 

Halides of the less electropositive metals are quickly reduced to highly dispersed and very active metal powders if they are exposed to ultrasonic waves in the presence of lithium and other group I metals(20). Ultrasound not only accelerates the reduction of the halides but also increases the rate of subsequent reactions of these less active metals. These reactions are covered in the chapter by K. Suslick. 

Pure alkaline-earth metals are very shiny, and are also good conductors of heat and electricity. They are not as soft as the Group I metals, but they can be cut with a strong knife. 

All hydroxides of the Group I metals are strong bases. The hydroxides of the heavier Group II metals (Ca, Sr, and Ba) are also strong bases. Mg(OH)2 is not very soluble in water, yielding relatively little OH (aq). 

Basinska and Domka511 showed that addition of most alkali metals (Na, and especially K, Rb, or Cs) led to remarkable improvements in the water-gas shift rates, as shown in Table 118. The loading of Ru was 0.5% and the Group I metal/Ru atomic ratio was 1 1. The alkali metals were deposited from aqueous solutions of their corresponding nitrates (except for Rb, where RbCl was used). The alkali/Fe oxide was then calcined at 600 °C. Ru was added by impregnation of RuC13 in acetone, and the catalyst was re-calcined at a lower temperature of 400 °C. 

Ab initio computations have so far proved to be reliable structural tools for neutral carboranes and their anions. They have been used to predict the carborane geometries for six-vertex, eight-vertex, and 11-vertex nido-carboranes,67-69 and for 5-12 vertex r/aro-carboranes.70,71 However, carborane anions in the presence of a group I metal cation may form ion-pair anions with one cation tightly bound to the carborane anion (see Chapter 3.03).72,73 Even computations on a salt with a carborane anion in a non-coordinating solvent would need to include the cation for computed shifts that tally with observed NMR data.74... 

Table 4 Electrochemical data and group I metal cation dependence of ferrocene amide aza crown ethers and model analogues.

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