- Process for the preparation of pure alkaline earth alkoxides
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Production of metal-free, alkoxide-pure alkaline earth alkoxides involves use of an excess of an alcohol to effect alcoholytic alkoxide group exchange in solutions of optionally mixed alkoxides having shorter alkyl chains than the final product, the optionally mixed alkoxides being at least proportionately dissolved during the reaction. Production of metal-free, alkoxide-pure alkaline earth alkoxides of formula (I) involves alcoholysis of a solution of an optionally mixed alkoxide of formula (II) with an excess of an alcohol of formula (III), compound (II) being at least proportionately dissolved during the reaction. M(OR 1>) 2(I) M(OR 2>) x(OR 3>) y(OR 4>) z(II) HOR 1>(III) M : main Group II element; R 1>linear or cyclic 2-20C alkyl in (I) but is different from R 2>- R 4>in (II) in having at least one more carbon atom in the alkyl chain than the longest chain in R 2>- R 4>; R 2>- R 4>1-4C alkyl; and x, y and z : 0-2, with x + y + z = 2.
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Page/Page column 5
(2008/06/13)
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- Determination of Gas-Phase Ligand Binding Energies to Mg+ by FTMS Techniques
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Relative and absolute gas-phase binding energies of 12 organic molecules to Mg+ have been determined by four different methods involving Fourier transform mass spectrometry (FTMS).Mg+ is generated in the FTMS cell by pulsed laser ionization and reacts with the organic compounds to give MgL+ either by direct condensation or by a fast two-step displacememt reaction.The equilibrium constant (Keq) and the absolute rate constants (kf and kr) are obtained for the ligand exchange reaction: MgL+ + L' MgL'+ + L.The equilibrium constants are converted to free-energy differences and relative binding energies are calculated to give the Do(Mg+-L) scale.Entropy changes are assumed to be small and they are discussed in detail.The absolute gas-phase binding energies Do(Mg+-MeOH) and Do(Mg+-Me2CO) are assigned from equilibrium and photodissociation experiments to be 61 +/- 5 and 67 +/- 5 kcal/mol, respectively.The correlation of results from the different methods give a scale of relative and absolute bond energies to Mg+ for the 12 organic molecules examined.The results for Mg+ are compared with previously reported results on H+, CpNi+, Al+, Mn+, and Cu+.These comparisons show for this limited study on oxygen bases that Mg+ is a softer acid than H+ and Al+, very similar in acidity to Mn+ and Cu+, and a harder acid than CpNi+.
- Operti, Lorenza,Tews, Edward C.,Freiser, Ben S.
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p. 3847 - 3853
(2007/10/02)
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