Table 2. Bond Dissociation Enthalpy (BDE) of O-CH3 for Molecules with Different Substituents in Group II (Units in kcal/mol).
| substituent | compound# | o-position | m-position | p-position |
|---|---|---|---|---|
| NH2 | 7 | 53.7 | 64.2 | 57.3a |
| OH | 8 | 51.8/57.0b | 64.6 | 60.4a |
| OCH3 | 9 | 59.0 | 66.1a | 59.6a |
| CONH2 | 10 | 57.8/61.9b | 66.5 | 65.9 |
| CH3 | 11 | 63.3 | 64.4 | 63.3a |
| F | 12 | 62.0 | 66.2 | 63.6 |
| Cl | 13 | 62.4 | 66.4a | 64.3 |
| Br | 14 | 62.5 | 66.5 | 64.7 |
| CCl3 | 15 | 64.8 | 65.1 | 65.9 |
| H | 1 | 65.3b | 65.3 | 65.3 |
| COOCH3 | 16 | 65.0 | 65.7 | 65.8 |
| CF3 | 17 | 66.1 | 66.0 | 66.9 |
| COOH | 18 | 66.5 | 66.4 | 66.8 |
| CHO | 19 | 67.7 | 67.4 | 66.6 |
| NO2 | 20 | 66.7 | 67.8 | 68.4 |
| CN | 21 | 67.7 | 68.3a | 67.5 |
a
Data from ref (11).
b
Two different structures (substituent group oriented toward the −OCH3 group of the ring favoring the hydrogen bond formation is shown in bold, see text).