Magnetic field and magnetic isotope effects in organic photochemical reactions. A novel probe of reaction mechanisms and a method for enrichment of magnetic isotopes

Journal Article · Wed Oct 01 04:00:00 EDT 1980 · Acc. Chem. Res.; (United States)

DOI:https://doi.org/10.1021/ar50154a005· OSTI ID:6584504

Turro, N J; Kraeutler, B

A brief qualitative description of the theory of intersystem crossing (ISC) in radical pairs is presented. It provides a simple unified theoretical basis for understanding chemically induced nuclear polarization (CIDNP), the magnetic spin isotope effect, and magnetic field effects on chemical reactions. Examples are given in which the magnetic spin isotope effect is employed to separate /sup 13/C (a magnetic isotope) from /sup 12/C (a nonmagnetic isotope) more efficiently than any mechanism involving a conventional mass isotope effect, and to separate selectively /sup 17/O (a magnetic isotope) from /sup 16/O and /sup 18/O (nonmagnetic isotope), which is impossible via a conventional mass isotope effect. Examples are also provided for which the magnetic field effect is utilized to control the efficiency of cage reactions of radical pairs. The observation of magnetic isotope and magnetic field effects on the photolysis of dibenzyl ketone in micellar solution is not an isolated finding. Numerous other ketones (phenyl adamantyl ketone, phenyl benzyl ketone, etc.) have been found to exhibit analogous behavior. The ideas discussed may be employed in principle, to design chemical reactions that will separate magnetic isotopes from their nonmagnetic colleagues. The key features are the requirement of a singlet-triplet crossing along the reaction coordinate, the availability of a hyperfine hole at the molecular geometry corresponding to the hole, and sufficient time for the representative point to find the hole when it arrives in the region of phase space corresponding to the hole. Magnetic field and magnetic isotope effects provide a complement to CIDNP for probing mechanisms of radical reactions.

• Research Organization: Columbia Univ., New York
• OSTI ID: 6584504
• Journal Information: Acc. Chem. Res.; (United States), Journal Name: Acc. Chem. Res.; (United States) Vol. 13:10; ISSN ACHRE
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400202* -- Isotope Effects
Isotope Exchange
& Isotope Separation
400203 -- Isotope Exchange & Isotope Separation-- (-1987)
400500 -- Photochemistry
AROMATICS
CARBON 12
CARBON 13
CARBON ISOTOPES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DECOMPOSITION
ELECTRON SPIN RESONANCE
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
ISOTOPE EFFECTS
ISOTOPE SEPARATION
ISOTOPES
KETONES
KINETICS
LIGHT NUCLEI
MAGNETIC FIELDS
MAGNETIC RESONANCE
NONMETALS
NUCLEI
ORGANIC COMPOUNDS
OXYGEN
OXYGEN 16
OXYGEN 17
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PEROXIDES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PRODUCTION
RADICALS
REACTION KINETICS
RESONANCE
SEPARATION PROCESSES
STABLE ISOTOPES
TEMPERATURE EFFECTS