Table 3. CASSCF(10,8) Optimized Stationary Points and XMC-QDPT2(10,8) Single-Point Energies along the Reaction Coordinatea.
| relative energy difference, kcal/mol |
|||||||
|---|---|---|---|---|---|---|---|
| Rb | R′b | RO2• + R′O2•c | RO2···R′O2 | [ROO···OOR′]‡ | RO4R′ | [RO···O2···OR′]‡ | RO• + R′O• + 3O2 |
| H | H | 3.92 8.42 (19.17) | –0.32 2.95 | 4.19 4.13 | 0.00 | 2.34 1.71 | –12.46 9.57 (33.10) |
| Me | H | 3.09 10.88 (16.72) | –1.23 4.06 | 3.87 4.65 | 0.00 | 1.21 1.03 | –16.63 12.62 (27.22) |
| Me | Me | 0.88 3.72 (16.19) | –1.27 –0.56 | 1.40 –3.00 | 0.00 | 2.31 –3.42 | –17.41 3.98 (23.26) |
| Et | Et | 0.69 10.71 (15.14) | –1.73 5.38 | 1.53 –0.30 | 0.00 | 1.21 –0.74 | –18.37 13.64 (24.41) |
| iPr | iPr | –0.47 6.98 (15.24) | –2.92 1.23 | 1.06 –3.69 | 0.00 | 2.97 –5.40 | –17.17 12.08 (25.06) |
| Ac | Me | 7.48 19.37 (22.33) | 4.66 15.82 | d | 0.00 | 1.09 –0.44 | –20.33 14.30 (23.49) |
| Ac | Ac | 12.23 32.04 (27.43) | 8.66 26.33 | d | 0.00 | 0.05 –0.99 | –23.94 16.59 (22.68) |
| Allyl | Allyl | 1.31 14.30 (16.52) | –1.06 10.41 | 2.73 3.67 | 0.00 | 0.71 0.32 | –20.17 18.02 (23.51) |
| Ace | Ace | 2.36 19.65 (17.94) | –0.73 14.24 | 3.41 5.10 | 0.00 | 0.91 0.72 | –22.92 18.66 (22.75) |
| Ace | S-BuOH | 3.67 21.28 (16.67)e | –1.64 13.48 | 3.26 3.58 | 0.00 | 1.35 –2.82 | –21.49 45.69 (22.30)e |
| R-BuOH | R-BuOH | 3.02 21.55 (14.56)e | –2.40 13.45 | 6.64 6.76 | 0.00 | 1.11 –3.25 | –21.86 47.58 (21.80)e |
| R-BuOH | S-BuOH | 3.57 20.00 (15.24)e | –1.57 14.26 | 3.52 2.52 | 0.00 | 1.36 –3.65 | –20.87 18.70 (22.49)e |
| R-PrNO3 | R-PrNO3 | 3.44 28.03 (15.27)e | –1.82 18.61 | 3.72 5.08 | 0.00 | 1.46 –5.11 | –22.52 50.56 (22.02)e |
| R-PrNO3 | S-PrNO3 | 4.02 28.40 (14.94)e | –1.32 17.50 | 2.73 2.14 | 0.00 | 2.18 –4.59 | –21.65 25.09 (21.78)e |
a
Lightfaced values correspond to CASSCF energies, and bold values correspond to XMC-QDPT2 single-point energies. For comparison, values in brackets correspond to CCSD(T)-F12a/cc-pVDZ-F12 single-point total energies at ωB97X-D/aug-cc-pVTZ optimized geometries.
b
Data for R or R′ = H is presented for reference and comparison only: the dominant reaction pathway in these systems is not the mechanism studied here.
c
In the geometry optimizations, the distance between the two terminal oxygen atoms of the peroxyl moieties were frozen to 15 Å.
d
Barrierless formation reaction.
e
DLPNO-CCSD(T)-F12/cc-pVTZ-F12 used instead of CCSD(T)-F12a/cc-pVDZ-F12.