Table 3. Relative Electronic Energies (ΔE), Enthalpies at 0 K (ΔH0° = Δ(E+ZPE)), and Free Energies at Room Temperature (ΔG°) for the Alanine Conformersa.
| Conformer | Label | ΔEChSb | ΔErDSD | ΔH0H°c | ΔGH°d | ΔZPEe | Δ(TΔS)f | ΔG°g |
|---|---|---|---|---|---|---|---|---|
| ttt | I | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| cg–c | II– | 35.6 | 29.5 | 172.5 | 316.5 | –28.1 | –46.8 | 241.6 |
| cgc | II | 103.1 | 106.4 | 215.6 | 321.4 | –26.7 | –20.4 | 274.3 |
| tg–t | III– | 432.6 | 412.8 | 443.0 | 386.4 | –12.5 | 42.1 | 416.0 |
| tgt | III | 436.0 | 410.1 | 452.1 | 329.9 | h | –81.0 | h |
| ga–t | I′ | 396.5 | 406.7 | 389.7 | 448.0 | 6.5 | –25.7 | 428.8 |
| gat | I′– | 446.6 | 480.5 | 425.9 | 490.4 | –8.1 | –19.8 | 462.5 |
| ggt | III′ | 613.5 | 655.6 | 592.4 | 631.7 | 4.0 | –0.8 | 634.9 |
| gg–t | III′– | 789.7 | 782.7 | 774.3 | 804.6 | 1.3 | –5.7 | 800.2 |
| tsc | Ic | 1736.0 | 1730.3 | 1681.6 | 1696.1 | –0.7 | –16.0 | 1679.4 |
| ts–c | III–c | 1980.5 | 1968.5 | 1928.2 | 2006.6 | –54.3 | –12.5 | 1839.8 |
| g–tc | I′c | 2116.5 | 2123.5 | 2052.8 | 2105.8 | –28.1 | –24.8 | 2052.9 |
| gtc | I′–c | 2154.9 | 2165.3 | 2043.0 | 1983.5 | 27.3 | 25.2 | 2036.0 |
a
All the data are in cm–1.
b
JunChSF12 at rDSD geometries.
c
JunChSF12 electronic energies with rDSD harmonic ZPE.
d
JunChSF12 electronic energies with rDSD harmonic ZPE and thermal contributions.
e
Difference between anharmonic and harmonic ZPE at the B3 level.
f
Difference between quasi-harmonic and harmonic TΔS (see text for details).
g
Sum of columns 6, 7, and 8.
h
No minimum at the B3 level.