MECHANISM OF THE FAST PROTOLYTIC REACTIONS IN
PARAMAGNETIC ACID–BASE SYSTEMS
Masalimov A.S.
E.A.Buketov named Karaganda State University
e-mail: [email protected]
The EPR-spectroscopic and quantum-chemical investigations of the kinetic and
mechanism of the fast intermolecular proton transfer (IPT) and proton exchange
(IPE) reactions in solutions al-low to suppose that the initial electron transfer process from bases molecule (Y) to acids molecule (XH) begin these chemical interactions:
Here: XH is the stable semiquinone radical 3,6-di-tert.buthyl-2-oxyphenoxyl
(I) – paramagnetic H-acid or spin probe, A and C are molecular and ionic complexes with hydrogen bonds, B’ is the ion-radical pair.
Proton transfer reaction inside of complex B depends on values of ionization
potential (IP) of bases Y. If alkali metals with very values of IP interrupt the hydrogens atom from waters molecule and another H-acids, the amines, nitrogencentered bases give ionic pair C, after ion-radical recombination inside intermediate B’.
The fast IPE reactions between two H-acids may be presented with the next
usual scheme:
Here: asterisk denotes the acids proton with another orientation of spin.
The EPR-investigation show that the fast IPE reactions between spin probe I
and organic OH-acids have more less values of the rates constants than IPE
reactions I with NH-acids. Obviously that the fast IPE reaction contains two
concerted chan-nel of the IPT processes going inside four-centered cyclic
complexes with two hydrogen bonds B and B+. EPR spectra of the intermediate C
register in mixture I with carbon acids and C+ in solutions with amines. Evidently
that the mechanism of the each fast IPT transfer channel of common IPE reaction
(2) may be described with scheme (1).