WOBBLcaffeine
IR spectrum look like caffeine
OK
caffeine (C8H10N4O2, 194.19 g/mol), by GFN2-xTB: its strongest IR band is at 1712 cm-1, the C=O stretch, its dipole is 3.98 D, dissolving in water is worth -43.9 kJ/mol. At 298 K its entropy is 470.8 J/(mol K) and its heat capacity 211.0 J/(mol K).
dipole
3.98 D
strongest IR band
1712 cm-1
HOMO-LUMO gap
3.40 eV
entropy at 298 K
470.8 J/(mol K)
Confidence high
- passed geometry convergence, minimum, SCF convergence
Simulation
Checks
| status | check | result |
|---|---|---|
| pass | geometry convergence | GFN2-xTB stopped after 18 steps with the largest force at 0.0029 eV/A, under the 0.003 eV/A it aims for |
| pass | minimum | all 66 frequencies are real, so the structure is a true minimum, after following 1 imaginary mode downhill |
| pass | SCF convergence | all 612 GFN2-xTB single points converged within 300 iterations |
| info | thermochemistry | ideal gas at 298 K and 101 kPa with a rotational symmetry number of 1, and 4 soft modes under 100 cm-1 treated as hindered rotors |
Properties
| energy | -42.154507 Eh (GFN2-xTB) |
| dipole | 3.977 D |
| HOMO and LUMO | -10.59 eV and -7.19 eV |
| zero point energy | 478.71 kJ/mol |
| H, S and G at 298 K | 516.53 kJ/mol, 470.81 J/(mol K) and 376.16 kJ/mol above the electronic energy |
| heat capacity Cp | 211.02 J/(mol K) |
| solvation in water | -43.9 kJ/mol |
Strongest IR bands
| cm-1 | km/mol | mode |
|---|---|---|
| 666 | 42.7 | N-C-H bend |
| 691 | 56.6 | N-C-H bend |
| 990 | 47.1 | N-C-H bend |
| 1034 | 57.4 | N-C-H bend |
| 1233 | 39.2 | C-N stretch |
| 1248 | 47.7 | N-C-H bend |
| 1322 | 91.5 | C-N stretch |
| 1450 | 136.7 | H-C-H bend |
| 1525 | 142.9 | N-C-H bend |
| 1578 | 214.8 | C-N stretch |
| 1712 | 996.4 | C=O stretch |
| 1733 | 482.8 | C=O stretch |
Assumptions
- caffeine as RDKit ETKDG distance geometry relaxed with MMFF94, the lowest of 1 conformers, refined with GFN2-xTB, good to about 0.02 A in bond lengths, 2.5 degrees in angles and 8% in frequencies.
- One molecule in the gas phase unless a solvent is named, and a solvent is a continuum (ALPB) rather than explicit molecules.
- Thermochemistry treats the molecule as an ideal gas, a rigid rotor and harmonic oscillators, with modes under 100 cm-1 blended into free rotors.
- The HOMO-LUMO gap from GFN2-xTB is a trend only, often off by over 1 eV, so it is not an optical gap.