Table 3. Relative Overall Rate Constants (log krel)a for the Nitration of Benzene, Alkylbenzenes, Halobenzenes, and Anisole. Also Reported Are Shifts of the Molecular Electrostatic Potential at 1.5 Å over the Centroid of the Aromatic Ring; and Shifts of Phenol ν(OH) Stretching Frequencies (in cm–1) upon π-Hydrogen Bonding in CCl4 Solventa.
| species | log krela | Δν(OH)exp [cm–1] | ΔV (1.5) (a.u.) B3LYP/6-311++G(3df,2pd)b |
|---|---|---|---|
| benzene | 0.00 | 48 | 0.0000 |
| toluene | 1.41 | 58 | –0.0029 |
| ethylbenzene | 1.36 | 59 | –0.0033 |
| isopropylbenzene | 1.32 | 55 | –0.0030 |
| tert-butylbenzene | 1.29 | 60 | –0.0033 |
| 1,2-dimethylbenzene | 2.28 | 68 | –0.0048 |
| 1,3-dimethylbenzene | 2.46 | 69 | –0.0051 |
| 1,4-dimethylbenzene | 2.47 | 71 | –0.0050 |
| 1,2,3-trimethylbenzene | 2.96 | 75 | –0.0073 |
| 1,2,4-trimethylbenzene | 3.03 | 78 | –0.0072 |
| 1,3,5-trimethylbenzene | 2.98 | 77 | –0.0075 |
| 1,2,3,4-tetramethylbenzene | 3.33 | 87 | –0.0095 |
| 1,2,3,5-tetramethylbenzene | 3.27 | 88 | –0.0098 |
| 1,2,4,5-tetramethylbenzene | 3.34 | 85 | –0.0091 |
| pentamethylbenzene | 3.41 | 93 | –0.0117 |
| fluorobenzene | –0.92 | 38 | 0.0114 |
| chlorobenzene | –1.52 | 33 | 0.0134 |
| bromobenzene | –1.52 | 37 | 0.0140 |
| iodobenzene | –1.00 | 38 | |
| anisole | 2.27 | 60 | –0.0020 |
| rc | 0.991 | 0.969 |
a
Relative rate with respect to benzene (kbenzene = 1). See ref (18) and references therein for the sources of experimental kinetic data and Δν(OH)exp shifts.
b
Theoretical computations for modeled nitromethane solvent.
c
The correlation coefficients (absolute values are shown) refer to the linear regressions between the experimental log krel values and the predicted values according the 2nd order polynomial expressions.