TABLE 3.
Calculated C=O and O–H stretching frequencies of a protonated carboxylic group
| No. of H-bonds | Type of H-bond | C=O frequency (cm−1) | ΔFrequency of C=O (cm−1)* | O–H Freq (cm−1) | ΔFrequency of O–H (cm−1)* |
|---|---|---|---|---|---|
| 0 | HO–C=O | 1776.4 | 0 | 3542.6 | 0 |
| 1 | HO–C=O | 1787.8 | +11.4 | 3538.2 | −4.4 |
| 1 | HO–C=O | 1740.6 | −35.8 | 3537.7 | −4.9 |
| 1 | HO–C=O | 1744.1 | −32.3 | 3213.9 | −328.7 |
| 2 | HO–C=O | 1705.5 | −70.9 | 2860.2 | −682.4 |
*
The shifts in the C=O and the O–H stretching frequencies are due to hydrogen-bonding interactions. A methanol molecule is employed as the hydrogen-bond partner to the COOH group.