Abstract
Carbonyl‐13C hyperfine splitting constants (hfs) in a number of radicals are analyzed in terms of a Karplus–Fraenkel‐type equation. Spin densities are determined semiempirically from 17O and 1H hfs and from MO calculations. The analysis gives QCOC = 36.0 G and QOCC = −24.3 G . These results are compared with independent theoretical calculations using SCFMO wavefunctions for formaldehyde.