Ionic solutions and their pivotal roles in organic and biological systems

Ionic solutions are known to affect the static and dynamic behaviour of organic and biological systems through ion-solvent interactions. With respect to organic systems, spectacular enhancement in both the reaction rates and stereoselectivities in the Diels-Alder (D-A) reactions are noted in presence of ionic solvent media. Several D-A reactions otherwise were not possible or were very sluggish. Application of ultrahigh external pressure could be obviated by using the ionic solutions. In the case of biological systems, the thermal stabilities of the DNA duplexes have been noted to vary with the type of counterions available ill system. Variations in the rates Of D-A reactions and thermal stability of DNA duplexes in ionic solutions have been discussed in terms of internal pressure, a ion-solvent interaction quantity and a volume parameter. Useful correlations are noted between internal pressure and reaction rates of the D-A reactions. More significantly, the correlations exposed in connection with the thermal stability of DNA duplexes are simple, thought-provoking and present radical departure from our current understanding on the ion-DNA interactions.