Spin Catalysis of Chemical Reactions

Abstract

The spin catalysis of chemical reactions is a physical phenomenon of spin transformation of chemically reactive species induced by the exchange interaction of these species with external spin carriers. It manifests itself in the radical pair recombination, cis-trans isomerization of molecules with double bonds, recombination of spin-polarized and spin-aligned hydrogen atoms at cryogenic temperatures, etc. The theory and quantitative kinetics of spin catalysis in three-and four-spin systems are considered. Quantitative hierarchy of spin carriers with respect to their spin catalytic efficiency is discussed.

Recent advances in spin chemistry

“…Experiment has perfectly confirmed these predictions (Fig. 6) 16 O 2 molecules. The former is due to MIE, the latter is induced by CIE [5].…”

“…MIE in quartet-doublet spin conversion selects magnetic 17 O nuclei into peroxy radicals, resulting in impoverishment of the remaining molecular oxygen with 17 O. In contrast, oxygen molecules with 18 O react slower than those with 16 O, resulting in CIE-induced enrichment of molecular oxygen with 18 O. Experiment has perfectly confirmed these predictions (Fig.…”

“…Neither decay of nitroxyls nor formation of any byproducts was observed, so this is a case of true paramagnetic catalysis [16]. The rate constants k 0 and k c of direct and catalytic isomerization are expressed by equations k 0 = 10 5 exp(-27000/RT), s −1 k c = 10 12 exp(-27000/RT), s catalytic reaction.…”

“…The encounter pair of freely diffusing peroxy radicals either recombines resulting unstable tetraoxide RO 4 radicals. Due to MIE, which differentiates the rates of spin conversion, the recombination probability of peroxy radicals with terminal 17 O atoms is higher than that of radicals with 16 O and 18 O atoms. As a result, the tetraoxide and, consequently, the recovered oxygen is enriched with 17 O, while the hydroperoxide molecules are enriched with 16 O and 18 O.…”

“…Due to MIE, which differentiates the rates of spin conversion, the recombination probability of peroxy radicals with terminal 17 O atoms is higher than that of radicals with 16 O and 18 O atoms. As a result, the tetraoxide and, consequently, the recovered oxygen is enriched with 17 O, while the hydroperoxide molecules are enriched with 16 O and 18 O. Figure 3 demonstrates isotope enrichment of molecular oxygen as a function of oxygen conversion; the higher chemical conversion the larger number of recovered oxygen molecules and the higher isotope enrichment.…”