Page 990 - Advanced Organic Chemistry Part A - Structure and Mechanisms, 5th ed (2007) - Carey _ Sundberg

974
5TS
∗
CHAPTER 11 ΔG (Kcal/mol)
Free Radical Reactions

8.49
4

2.69

7RS
5 5
5.29
7R (2.16)
0.71
6R 6R 6S

H
H
H H
H H
H
H
7S
4 H H H 7R H
H H
H
H 5TS H
H H + H H
6S
H 6R H
H
5
H H
H H
7RS
H
Fig. 11.3. Energy profile for rotation and ring opening of the cyclopropyl
methyl radical derived from CCSD(T)/cc-pvTZ computations. Reproduced
from J. Org. Chem., 68, 9441 (2003), by permission of the American
Chemical Society.

Another technique that is specific for radical processes is known as CIDNP, an
abbreviation for chemically induced dynamic nuclear polarization. 16 The instrumen-
tation required for such studies is an NMR spectrometer. CIDNP is observed as a strong
perturbation of the intensity of NMR signals in products formed in certain types of
free radical reactions. The variation in intensity results when the normal population of

16
H. R. Ward, Acc. Chem. Res., 5, 18 (1972); R. G. Lawler, Acc. Chem. Res., 5, 25 (1972).