Table 2. Singlet–Triplet Energy Gaps (kcal/mol, Including ZPVE) for Nitrenium Ions Having Stable Singlet Statesa.
| R1 | R2 | M06-2X gas | M06-2X SMD-H2O | CBS-APNO | |
|---|---|---|---|---|---|
| 1 | H | H | 34.7 | 30.61 | 29.5 |
| 3 | CH3 | CH3 | 2.10 | –3.05 | 2.07 |
| 28 | HCO | H | –2.50 | –2.88 | –11.27 |
| 2 | CH3 | H | na | –6.67 | –11.38 |
| 21 | CH2=CH | tBu | –3.85 | –6.83 | |
| 20 | CH2=CH | CH3 | –4.88 | –8.30 | |
| 31 | CH2=CH | HCO | –5.10 | –10.27 | |
| 19 | CH2=CH | H | –5.67 | –9.94 | –9.08 |
| 24 | Ph | tBu | –7.97 | –8.97 | |
| 32 | CH3CO | CH3O | –9.12 | –13.23 | |
| 29 | CH3CO | H | –9.60 | –10.48 | |
| 32 | HCO | CH3O | –13.8 | –16.47 | |
| 23 | Ph | CH3 | –14.6 | –16.23 | |
| 22 | Ph | H | –19.76 | –21.80 | |
| 17 | cyclopropyl | tBu | –24.3 | –26.72 | |
| 25 | CH3O | H | –27 | –26.82 | –29 |
| 16 | cyclopropyl | CH3 | –27.2 | –28.13 | |
| 27 | CH3O | tBu | –27.6 | –27.48 | |
| 43 | HSO2 | H | –29.1 | –30.4 | |
| 34 | CH2=CH | CH3O | –30 | –28.68 | |
| 36 | CH2=CHCH2 | H | –40.5 | na | |
| 26 | CH3O | CH3 | –30.1 | –30.01 | |
| 15 | cyclopropyl | H | –33.0 | –33.37 | –35.2 |
| 18 | cyclobutyl | H | –36.7 | –44.75 |
a
Negative values denote singlet ground states.