Magnesium cations reactivity

Generally, sodium and potassium react only to a limited extent with proteins, whereas calcium and magnesium are somewhat more reactive. Transition metals, e.g., ions of Cu, Fe, Hg, and Ag, react readily with proteins, many forming stable complexes with thiol groups. Calcium cations and ferrous, cupric, and magnesium cations may be integral parts of certain protein molecules or molecular associations. Their removal by dialysis or sequestration appreciably lowers the stability of the protein structure toward heat and proteases. 

Berg, C., Beyer, M., Achatz, U., Joos, S., Niedner-Schatteburg, G., Bondybey, V.E. (1998) Stability and Reactivity of Hydrated Magnesium Cations. Chem. Phys. 239 379-392. 

CuFeS2. The reaction is carried out in a nearly saturated solution containing copper, potassium and iron as active essential constitutents together with sodium and magnesium as non-reactive cations to maintain the high chlorinity. 

These observations have been interpreted in terms of the hard-soft acid-base theory (77CJC4112), in which the salts of the harder cations, such as the Li+ ion, lead to C-alkylation, whilst the salts of the soft cations, such as the quaternary ammonium salts, are TV-alkylated. This interpretation is particularly relevant in understanding the reactivity of the heteroaryl-magnesium salts. The Mg2+ ion is a harder cation than the Li+ ion and, with the more strongly associated Grignard compounds, C-alkylation predominates. Generally, the pyrrole... 

Assessment of the role of the cation in MPV reduction is difficult, Conversion of alcohol to alkoxide certainly enhances the reactivity towards hydride donation, and aluminum ions aid via chelation in arranging alkoxide and carbonyl compound properly for reaction. However, alkoxides bearing cations other than aluminum may also exhibit good hydride-donating tendencies. Lithium isopropoxide reduces steroidal ketones efficiently and magnesium alkoxides derived from chiral alcohols have been used extensively in chiral syntheses. Isobomyloxy magnesium bromide (52) has been used widely for this purpose (equation 27). ... 

All soluble dyes contain reactive sites, and some may be incompatible with drug substances in the formulation. The anionic colors can also react with com-poimds containing polyvalent cations (such as calcium, magnesium, or aluminum) and precipitate. Certain dyes, such as FD C blue 2 and FD C red 3, exhibit such poor stability in aqueous solutions that they should never be used for coloring aqueous liquid products. 

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