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Table of heteroatom parameters
Source: G. Chemie 100 (1969) 1003
the -Values of the heteroatoms are determined based on the experimental valence orbital ionization potentials (VOIP) for the ionization of one (.A) or two (: A) electrons; the values thus also follow the gradation of the electronegativity of the atoms.
- Tab. 1
- Heteroatom parameters
| X | C-X | |||
|---|---|---|---|---|
| 1 | .C | 0,00 | C-C | 1,00 |
| 2 | F. | 2,84 | C-F | 0,68 |
| 3 | Cl | 1,45 | C-Cl | 0,57 |
| 4 | Br | 1,16 | C-Br | 0,38 |
| 5 | J | 0,78 | C-J | 0,19 |
| 6 | :O | 2,06 | C-O: | 1,31 |
| 7 | : O-CH3 | 1,96 | C = O | 1,93 |
| 8 | .O | 1,18 | C-N: | 1,30 |
| 9 | : N | 1,47 | C = N. | 1,06 |
| 10 | .N | 0,83 | N-O | 1,95 |
| 11 | : CH3 | 0,88 | C-CH3 | 0,18 |
Hints:
- .A - means that the atom contributes a π electron to the molecule (e.g. pyridine nitrogen)
- : A - means that the atom contributes two π electrons to the molecule (e.g. pyrrole nitrogen)
- Halogens contribute two π electrons (electron pair) to conjugation.
- : corresponds to the "heteroatom model" for hyperconjugation
