Electronic aluminium compounds

These reagents demonstrate two important properties of boron and aluminium compounds. Xf you are uncertain of tbe periodic table just check to see where these two elements come. Neutral tervalent B and Al compound are electron deficient ... 

The active centres are greatly affected by the cocatalyst which, in the case discussed above, is the organo-aluminium component. As an acceptor part of the centre, it reduces the electron density on the donor (titanium). This facilitates monomer addition by insertion. Thus the activity of the centre is a function of the acidity of the aluminium component. The partly hydrolyzed organo-aluminium compound of general formula... 

D. B. Chambers, G. E. Coates, and F. Glockling Electron-impact studies on organo-beryllium and -aluminium compounds, pp. 157-164 (3). 

Table Effective masses of electrons (nin) and holes (mp) for aluminium compounds (in units of the electron...

Table 4.1-49 Electron and hole mobilities tn and /Xp of aluminium compounds...

Firouzabadi, H., Iranpoor, N. and Nowrouzi, E, The facile and efficient Michael addition of indoles and pyrrole to a,/ -unsaturated electron-deficient compounds catalyzed by aluminium dodecyl sulfate trihydrate [A1(Ds)3] 3H2 0 in water, Chem. Commun., 2005, 789-791. 

Tableir.l-W Effective masses of electrons ( ) and holes (/Wp) for aluminium compounds (in units of the electron mass mo). Aluminium nitride (AIN), calculated values aluminium phosphide (AIP), calculated from band structure aluminium arsenide (AlAs), calculated from band structure data Aluminium antimonide (AlSb), theoretical estimates...

Solutions with aluminium compounds are nebulised into an argon plasma, where all components are vaporised. The ions produced are entrained in the plasma gas and introduced into a mass spectrometer, sorted according to their mass-to-charge ratios, and quantified with a channel electron multiplier. Aluminium is determined at mass 27 amu. 

M.p. 296 C. Accepts an electron from suitable donors forming a radical anion. Used for colorimetric determination of free radical precursors, replacement of Mn02 in aluminium solid electrolytic capacitors, construction of heat-sensitive resistors and ion-specific electrodes and for inducing radical polymerizations. The charge transfer complexes it forms with certain donors behave electrically like metals with anisotropic conductivity. Like tetracyanoethylene it belongs to a class of compounds called rr-acids. tetracyclines An important group of antibiotics isolated from Streptomyces spp., having structures based on a naphthacene skeleton. Tetracycline, the parent compound, has the structure ... 

In each of the examples given so far each element has achieved a noble gas configuration as a result of electron sharing. There are. however, many examples of stable covalent compounds in which noble gas configurations are not achieved, or are exceeded. In the compounds of aluminium, phosphorus and sulphur, shown below, the central atoms have 6. 10 and 12 electrons respectively involved in bondinc... 

Both these molecules exist in the gaseous state and both are trigonal planar as indicated by reference to Table 2.8. However, in each, a further covalent bond can be formed, in which both electrons of the shared pair are provided by one atom, not one from each as in normal covalent bonding. For example, monomeric aluminium chloride and ammonia form a stable compound ... 

This compound, which contains atoms arranged tetrahedrally around the boron atom, can readily be isolated from a mixture of dimethyl ether and boron trichloride. On occasions a chlorine atom, in spite of its high election affinity, will donate an electron pair, an example being found in the dimerisation of gaseous monomeric aluminium chloride to give the more stable Al2Clg in which each aluminium has a tetrahedral configuration ... 

Scandium is not an uncommon element, but is difficult to extract. The only oxidation state in its compounds is -I- 3, where it has formally lost the 3d 4s electrons, and it shows virtually no transition characteristics. In fact, its chemistry is very similar to that of aluminium (for example hydrous oxide SC2O3, amphoteric forms a complex [ScFg] chloride SCCI3 hydrolysed by water). 

In its general corrosion behaviour, beryllium exhibits characteristics very similar to those of aluminium. Like aluminium, the film-free metal is highly active and readily attacked in many environments. Beryllium oxide, however, like alumina, is, a very stable compound (standard free energy of formation = —579kJ/mol), with a bulk density of 3-025g/cm as compared with 1 -85 g/cm for the pure metal, and with a high electronic resistivity of about 10 flcm at 0°C. In fact, when formed, the oxide confers the same type of spurious nobility on beryllium as is found, for example, with aluminium, titanium and zirconium. 

Yamase and Goto406 determined first- and second-order rate coefficients for the aluminium chloride-catalysed reaction of halide derivatives of benzoic acid (lO5 = F, 1.73 Cl, 4.49 Br, 4.35 I, 0.81) and phenylacetic acid (105fc2 = F, 12 Cl, 21 Br, 9 I, 6) with benzene. The maxima in the rates for the acid chloride are best accommodated by the assumption that a highly (but not completely) polarised complex takes part in the transition state. Polarisation of such a complex would be aided by electron supply, and consistently, the acetyl halides are about a hundred times as reactive as the benzoyl compounds (see p. 180, also Tables 105 and 108). 

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