Table 2. Calculated Kinetic Characteristics of the Reactions of His with HO• and HOO• Radicals in the Gas Phasea.
| Mechanisms | IFb (cm–1) | ΔG≠c (kcal/mol) | Kd | Γe (%) | koverall | ||
|---|---|---|---|---|---|---|---|
| HOO• | f-HAT | 11OH | –2742.6 | 12.2 | 2.87 × 10–15 | 100 | 2.87 × 10–15 |
| RAF | C3 | –662.1 | 14.4 | 4.79 × 10–19 | 0 | ||
| C7 | –632.0 | 15.9 | 3.52 × 10–20 | 0 | |||
| C8 | –746.9 | 15.5 | 7.58 × 10–20 | 0 | |||
| HO• | f-HAT | 4OH | –515.4 | 0.5 | 4.63 × 10–12 | 10 | 4.52 × 10–11 |
| 11OHf | - | - | 7.28 × 10–12 | 16 | |||
| 12OH | –1731.5 | 4.4 | 2.65 × 10–12 | 6 | |||
| RAF | C3 | –144.8 | –0.3 | 4.10 × 10–12 | 9 | ||
| C4 | –458.8 | 7.1 | 8.40 × 10–14 | 0 | |||
| C5 | –334.7 | 2.2 | 4.04 × 10–12 | 9 | |||
| C6 | –416.9 | 5.1 | 1.45 × 10–12 | 3 | |||
| C7 | –320.9 | 3.7 | 3.53 × 10–12 | 8 | |||
| C8 | –371.2 | 2.6 | 4.00 × 10–12 | 9 | |||
| C9 | –460.9 | 7.9 | 1.93 × 10–14 | 0 | |||
| C10 | –272.5 | 0.4 | 4.05 × 10–12 | 9 | |||
| C11 | –244.1 | 0.8 | 4.04 × 10–12 | 9 | |||
| C12 | –371.5 | 3.4 | 3.56 × 10–12 | 8 | |||
| C13 | –496.2 | 7.0 | 9.76 × 10–14 | 0 | |||
| C14 | –452.8 | 5.0 | 1.63 × 10–12 | 4 | |||
a
The k values are in cm3 molecule–1 s–1.
b
Imaginary frequency.
c
Activation free energy.
d
Rate constant.
e
Branching ratio.
f
The relaxed scan indicates that the reaction is barrierless and the spontaneous H-transfer takes place.