Experimental spectroscopic parameters for the caffeic acid rotamers I–IV.
| Rotamer I | Rotamer II | Rotamer III | Rotamer IV | |
|---|---|---|---|---|
| A a | 2262.22348 (78)e | 2263.95 (20) | 2271.20 (49) | 2272.9750 (10) |
| B | 321.88280 (31) | 322.45623 (55) | 323.51160 (12) | 324.00522 (45) |
| C | 281.96625 (23) | 282.4286 (54) | 283.36153 (98) | 283.77359 (41) |
| Δ b | −1.1 | −1.1 | −1.2 | −1.2 |
| μ a | Observed | Observed | Observed | Observed |
| μ b | Observed | — | — | Observed |
| μ c | — | — | — | — |
| σ c | 14.4 | 11.6 | 18.2 | 14.9 |
| N d | 55 | 16 | 14 | 27 |
a
A, B, and C represent the rotational constants (in MHz); μa, μb, and μc are the electric dipole moment components.
b
Δ = Ic − Ia − Ib in μÅ2. Conversion factor: 505 379.07 μÅ2 MHz.
c
Rms deviation of the fit (kHz).
d
Number of fitted transitions.
e
Standard error in parentheses in units of the last digit.