<SUP>1</SUP><BBR RID="jp961456zb00001">H and<SUP>13</SUP>C Nuclear Polarization in Consecutive Biradicals during the Photolysis of 2,2,12,12-Tetramethylcyclododecanone

CIDNP effects arising in the geminate evolution of consecutive biradicals formed during the photolysis of 2,2,12,12-tetramethylcyclododecanone were investigated by the low- and high-field¹H and¹³C CIDNP and time-resolved¹H CIDNP methods. The¹H field dependence of nuclear polarization induced in the recombination and disproportionation products of the consecutive biradicals as well as the¹³C CIDNP spectra at low and high magnetic fields was analyzed. It was confirmed that two types of biradicals (acyl−alkyl and bisalkyl) of different chain lengths contribute to the spin polarization. Model calculations of the geminate recombination kinetics were based on the numerical solution of the stochastic Liouville equation for the Fourier transform of the biradical spin density matrix. A detailed kinetic analysis of the CIDNP effects allowed us to reveal all chemical transformations of the alkyl−acyl and bisalkyl biradicals and to estimate the probability of the “hidden” recombination of the biradicals to the starting ketone, as well as to determine the product distribution.