Group II

In alkaline media it is reported that the reaction of e-q with Zn(II) is reversible and that the Zn(I) is hydrolyzed (142). Unfortunately, because of uncertainty regarding the degree of hydrolysis in both oxidation states, no thermochemical data could be derived. Ershov and Sukhov used periodicity arguments to estimate p/fa = 7-9forZn+ (117). 

Our recommended values place Cd+ as a weaker reducing agent than Zn+, in accord with common sentiment. It is expected that both species should be quite reactive and that Zn+ should easily reduce Cd+. This process was reported by Baxendale et al. (38), but Meyerstein and Mulac 

Unlike Zn+ but like Hg+, Cd+ rapidly dimerizes to from Cd22+ (177). Almost nothing is known of the reactivity of this unstable species except that it reduces the f-butanol radical. 

According to Buxton et al., Cd+ and Zn+ react with N20 to form CdO+ and ZnO+, respectively (71). These species are reported to oxidize Br and I to Br2 and I2, but Cl is unreactive. From this we may infer that these species are good oxidants with E° 1.9 V. 

There is some evidence that Cd(I) is hydrolyzed in alkaline media (142), and a p/fa of 7-9 for Cd+ was estimated on the basis of periodicity (117). 

Reagents i, ether (for hydride preparation) or THF (for silane synthesis ),—78 C ii, HClfaq.) iii, MetSiCl iv, Me SiHCI. 

Perfluorovinylmagnesium bromide, which has been used in studies on the reaction of perfluoropropene oxide with Cirignard reagents (see p. 130),i also featui in the above investigations of the exchange route (see p. 268). 4JT-Decafluorobi(yclo-[2,2,1 ]hept-l-ylmagnesium iodide has found employment in the synthesis of bis-(4 -decafluorobicyclo [2,2,1 ]hept-l-yl)mercury (1) (see below).  

Mercury.—The bridgehead mercurials (1) and (2), prepared, respectively, from the corresponding lithium (3) or magnesium (4) compound and a mercuric halide and from the lithium derivative (5) and mercuric chloride, have seen service in studies on polyfiuorobicyclo [2,2,1 ]heptyl derivatives of sulphur (see p. 290). Each mercurial undergoes fluoride-initiated (CsF in DMF at 80 C) reaction with sulphur to yidd the corresponding mercaptide (6), presumably via a transient intermediate with pronounc carbanionic character (c/. refs. 16, 17) or even a polyfluorobicyclo- 

Treatment of hexafluorothioacetone dimer, (CF8)2C S C(CF8)2 S, withKF-HgF2 in DMF also provides a solution containing bis(perfluoroisopropyIthio)mercury.i  

The discussion section of the paper (ref. 17, p. 2765) dealing with this point could be mis-read owing to the numbers allocated to the two mercurials being interchanged. 

Several further modifications of the general reaction type depicted in equation (1) and documented last year have appeared. Thus, reactions of R MgBr with BrCR =CR OR (R = Et or SiMea) in the presence of a Ni diphosphine complex give R R C=CR OR in respectable yields.  

Bourgain-Commerson, J.-F. Normant, and J. Villieras, J. Chem. Research (S), 1977, 183. 

Magnesium.- An efficient one-pot synthesis of -terphenyls has been reported that involves the reaction of an aryl Grignard reagent 

Allylic acetates undergo an asymmetric coupling with ArMgX, in the presence of a chiral nickel(II) catalyst, to give (83) in up to 

Although sulphones have developed a central role in synthetic chemistry, the removal of this residue, after, for example, an alkylation step, can be problematic. Sodium amalgam is frequently used, but the toxicity of this reagent can be a limiting factor. 

It has now been reported that magnesium in methanol is an effective alternative reagent for reductive desulphonylation.  

Magnesium.—As is the case with the lithium cation, magnesium readily chelates with oxygen and nitrogen donors in a molecule. This forms the basis for the 

The further utility of Grignard reagents can be seen in the metal-catalysed regioselective addition of phenylmagnesium bromide to alkyl compounds (69, X = OH, OR, or Cl). Alkyl derivatives (69a, X = Ph) are formed from (69a, 

Aminoalkenes (72) are readily prepared from dimethylaminopropyl chloride, magnesium, and the corresponding ketones (R R CO) in a one-pot procedure which is reported to result in higher yields than those obtained by a stepwise method. Another one-pot method involves the reaction between an alkyl halide (R R CHX), magnesium, and CS2 followed by LDA-R X to yield keten-thioacetals (73).  

Ishikawa, H. Watanabe, T. Miyake, and M. Sato, J. Chem. Soc., Chem. Commun., 1981,718. 

Miodownik, J. Kreisberger, M. Nussim, and D. Avnir, Synth. Commun., 1981,11, 241. 

Structurally characterised mercury derivatives include linearly bonded 

3 Gallium. - Spectroscopically characterised clusters [Re4 (t3-C3aRe CO)5)4-(CO)j 2l reported, with preliminary structural data for the former species. 28 

Digermane complexes [Fe(GeH2GeH3)X(CO)4] (X = GeH3,GS2H5) have been prepared.Structures are reported for two confomers of [Ge Mn(C0)2Cp )2] with linear multiple Mn-Ge-Mn bonding.Trigonal-planar co-ordination of Ge or Sn occurs in (E = Ge,Sn). Clusters tM3( i-H)(ER3)(CO)j oL] (M = Ru,0s E Ge,Sn) are readily synthesised. 

Magnesium.—The general reaction outlined in equation (2) is catalysed by a variety of transition metal derivatives and is especially useful for coupling a saturated unit with an unsaturated one. 

Compound (55) can be prepared provided that the temperature is kept below about 25 °C. It behaves as a 3-oxobutyl anion. Compound (56), itself readily prepared from anthranilic acid, is converted into 2-substituted benzodithioles (57) by reaction with Grignard reagents. Reaction of (58) with Grignard reagents in the presence of a Cu catalyst gives (59) (or sometimes dialkyl-a)S-unsaturated 

Seebach, K.-H. Geiss, and M. Pohmakotr, Angew. Chem. Internat. Edn., 1976,15, 437. A. A. Ponaras, Tetrahedron Letters, 1976, 3105. 

The complex triazine (60) is alkylated to give (61) on reaction with Grignard reagents. In their reactions with RMgX, compounds (62) undergo reductive alkylation to (63), whilst (64) undergoes overall displacement of CN by R. 

---

The usual acceptor and donor dopants for Al Ga As compounds are elements from groups II, IV and VI of the periodic table. Group II elements are acceptors and group VI elements are donors. Depending on the growth conditions. Si and Ge can be either donors or acceptor, i.e. amphoteric. This is of special interest in LEDs. 

There is a marked contraction in size on the formation of an ion, the percentage contraction decreasing as the percentage loss in electrons decreases (for example Na Na" involves loss of one of eleven electrons, Cs -+ Cs" the loss of one of fifty-five electrons). Some values for Group II and III elements are shown in Tables 2.2 and 2.3 respectively. 

Group II elements can be seen to follow a pattern very like that found in Group I. Note, however, that the energy required to attain a noble gas configuration is considerably higher indicating that the elements will be less metallic or electropositive in their chemistry (Chapter 6). 

These elements form two groups, often called the alkali (Group I) and alkaline earth (Group II) metals. Some of the physical properties usually associated with metals—hardness, high m.p. and b.p.—are noticeably lacking in these metals, but they all have a metallic appearance and are good electrical conductors. Table 6.1 gives some of the physical properties. 

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. 

The alkali metals of Group I are found chiefly as the chlorides (in the earth s crust and in sea water), and also as sulphates and carbonates. Lithium occurs as the aluminatesilicate minerals, spodimene and lepidolite. Of the Group II metals (beryllium to barium) beryllium, the rarest, occurs as the aluminatesilicate, beryl-magnesium is found as the carbonate and (with calcium) as the double carbonate dolomite-, calcium, strontium and barium all occur as carbonates, calcium carbonate being very plentiful as limestone. 

Most of the metals react with water and, therefore, with any aqueous solution giving effectively M (Group D and M " (Group II) ions ... 

The lower members in Group II form essentially ionic halides, with magnesium having intermediate properties, and both magnesium bromide and iodide dissolve in organic solvents. 

Other Group II halides are essentially ionic and therefore have relatively high m.p., the melts acting as conductors, and they are soluble in water but not in organic solvents. 

As with the hydroxides, we find that whilst the carbonates of most metals are insoluble, those of alkali metals are soluble, so that they provide a good source of the carbonate ion COf in solution the alkali metal carbonates, except that of lithium, are stable to heat. Group II carbonates are generally insoluble in water and less stable to heat, losing carbon dioxide reversibly at high temperatures. 

Group II hydrogencarbonates have insufficient thermal stability for them to be isolated as solids. However, in areas where natural deposits of calcium and magnesium carbonates are found a reaction between the carbonate, water and carbon dioxide occurs ... 

The elements in Group II of the Periodic Table (alkaline earth metals) are. in alphabetical order, barium (Ba). beryllium (Be), calcium (Ca). magnesium (Mg), radium (Ra) and strontium (Sr). 

It is immediately obvious that the transition metals are more dense, harder, and have higher melting points and boiling points than the main group metals (for example, the metals of Group II,... 

Unlike cadmium and mercury and, in fact, all metals of Group II, zinc dissolves readily in alkalis forming zincates. in which the zinc atom is contained in a complex hydroxo-anion, for example ... 

Group II. Compounds soluble in water, but insoluble in ether. 

Group II. The classes 1 to 5 are usually soluble in dilute alkali and acid. Useful information may, however, be obtained by examining the behaviour of Sails to alkaline or acidic solvents. With a salt of a water-soluble base, the characteristic odour of an amine is usually apparent when it is treated with dilute alkali likewise, the salt of a water soluble, weak acid is decomposed by dilute hydrochloric acid or by concentrated sulphuric acid. The water-soluble salt of a water-insoluble acid or base will give a precipitate of either the free acid or the free base when treated with dilute acid or dilute alkali. The salts of sulphonic acids and of quaternary bases (R4NOH) are unaflFected by dilute sodium hydroxide or hydrochloric acid. 

The polyhydric alcohols of Solubility Group II are liquids of relatively high boiling point and may be detected inter alia by the reactions already described for Alcohols (see 6). Compounds containing two hydroxyl groups attached to adjacent carbon atoms (1 2-glyeols), a-hydroxy aldehydes and ketones, and 1 2-diketones may be identified by the periodic acid test, given in reaction 9. 

The simple sugars or monosaccharides are polyhydroxy aldehydes or ketones, and belong to Solubility Group II. They are termed tetroses, pentoses, hexoses. etc. according to the number of carbon atoms in the long chain constituting the molecule, and aldoses or ketoses if they are aldehydes or ketones. Most of the monosaccharides that occur in nature are pentoses and hexoses. 

The following classes of sulphur compounds occur in Solubility Groups II, III and VII sulphonic acids and derivatives, ArSO,OR sulphinic acids and derivatives, ArSOOR mercaptans, RSH thiophenols, ArSH sulphides or thioethers, RSR disulphides, RSSR sulphoxides, RR S->0 ... 

Sulphonic acids. The aromatic sulphonic acids and their alkali metal salts are soluble in water, but insoluble in ether (Solubility Group II). They are best characterised by conversion into crystalline S-benzyl-iso-thiuronium salts (see Section IV,33,2 and 111,85,5), which possess characteristic melting points. A more time-consuming procedure is to treat the well-dried acid or... 

Sulphinic acids. Aromatic sulphinic acids are found in Solubility Group II. They may be detected by dissolving in cold concentrated sulphuric acid and adding one drop of phenetole or anisole when a blue colour is produced (Smiles s test), due to the formation of a para-substituted aromatic sulphoxide. Thus the reaction with benzenesulphinic acid is ... 

Step 1. Extraction and separation of the acidic components. Shake 5-10 g. of the sohd mixture (or of the residue R obtained after the removal of the solvent on a water bath) with 50 ml. of pure ether. If there is a residue (this probably belongs to Solubihty Group II or it may be a polysaccharide), separate it by filtration, preferably through a sintered glass funnel, and wash it with a Uttle ether. Shake the resulting ethereal solution in a smaU separatory funnel with 15 ml. portions of 5 per cent, aqueous sodium hydroxide solution until all the acidic components have been removed. Three portions of alkaU are usuaUy sufficient. Set aside the residual ethereal solution (Fj) for Step 2. Combine the sodium hydroxide extracts and wash the resulting mixture with 15-20 ml. of ether place the ether in the ETHER RESIDUES bottle. Render the alkaline extract acid to litmus with dilute sulphuric acid and then add excess of sohd sodium bicarbonate. 

Grignard reagents are prepared from organic halides by reaction with magnesium a Group II metal... 

---