Deuterium isotope effect on the magnetic field dependence of CIDNP derived from biradicals

✍ Scribed by Charles Doubleday Jr.

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 368 KB
• Volume: 81
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(81)85350-x

✦ Synopsis

Incorporation of deuterium into the enobzable positions of several cyclic and bicyclic ketones alters the magnetic field dependence of CIDNP resulting from photolysis of the ketones. These results cannot be explained in terms of D-induced changes in the conformational populations of the biradicals formed in the photoiyses. We have examined the 13C CIDNP resulting from Norrtsh I photolysis of ketones I-111, both with and wthout deuterium in the eno'hzable positions, and find that some but not all of the ketones have their CIDNP magnetic field dependences significantly altered by D substitution_ The room-temperature photolyses were carried out on Ar-saturated 0.2 M methanol solutions m a photolysis chamber !ocated in a superconducting magnetic field. A recirculating flow system transferred the photolysls products from the photoly-sis chamber to the probe (kept under N2) of a Varian XL-100 NMR spectrometer. The 13C CIDNP intensities of the products were measured as a function of the supercon magnetic field strength to yield a field dependence (fd) curve. Greater than 95% D incorporation into the enolizable positions was achieved by phase-transfer-catalyzed exchange [l] with D,O/ OD-.