Table 2.
Calculated enthalpies of activation (kcal/mol) for addition of dimethylamine and piperidine to C1 of the 2,4-dinitrophenyl halides: MP2/6-31+G*//HF/6-31+G* (gas phase) and MP2/6-31+G*//HF/6-31+G* (methanol).a
| halide | MP2/6-31+G*//HF/6-31+G* (gas phase) | MP2/6-31+G*//HF/6-31+G* (methanol) | iν (cm−1)b |
|---|---|---|---|
| dimethylamine | |||
| fluoride | 1.2 | 1.4 | 424 (238)c |
| chloride | 6.1 | 5.1 | 445 |
| bromide | 2.2 | 1.4 | 450 |
| piperidine | |||
| fluoride | 6.6 | 6.7 | 387 |
| chloride | 11.0 | 9.9 | 408 |
| bromide | 5.9 | 5.2 | 411 |
a
Zero point energies were calculated at the HF/6-31+G* level and corrected according to the recommendations of Scott, A. P.; Radom, L. J. Phys. Chem. 1996, 100, 16502.18 Thermal corrections were not made. Gas phase geometries were used for the solvent calculations using the polarizable continuum model (PCM).
b
Each transition state had just one imaginary frequency; it corresponded to the reaction coordinate motion for addition of the nucleophile to the substrate.
c
At MP2/6-31+G*.