Ab initio study of the effect of N-substituents on the properties of pyrazoles
A series of fourteen derivatives of pyrazole have been calculated at the MP2-6-31G∗∗ level. 1. N-H; 2. N-BH2;3. N-BH3−; 4. N-CH3; 5. N-CHO; 6. N-CF3; 7. N-NH2; 8. N-NO2; 9. N-OH; 10. N-AlH2; 11. N-SiH3; 13. N-SO2H; 14. N-oxide. The first thirteen are derivatives of the parent pyrazole nitrogen N(1) and the last one is pyrazole N-oxide. The substituents have been selected to cover a wide range of electronic effects. The theoretical results are discussed in relation with geometries, energies, vibrational spectra, Bader analysis and tautomerism (in the case 1-hydroxypyrazole/pyrazole N-oxide).