Bulletin of the Korean Chemical Society

Korean Chemical Society (대한화학회)
권호 표지
DOI QR코드

DOI QR Code

Theoretical Studies on the Gas-Phase Pyrolysis of 2-Alkoxypyrimidines, 2-Alkoxypyrazines, 4-Ethoxypyrimidine and 3-Ethoxypyridazine

  • Published : 1992.02.20
Download PDF
⟨ Previous Next ⟩

Abstract

The gas-phase pyrolysis reactions of 2-alkoxypyrimidines(II), 2-alkoxypyrazines(III), 4-ethoxypyrimidine(IV) and 3-ethoxypyridazine(V) are investigated theoretically using the AM1 MO method. These compounds pyrolyze in a concerted retro-ene process with a six-membered cyclic transition state (TS). The relative order of reactivity if (IV)>(II)>(III)>(V), which can be rationalized by the two effects arising from electron-withdrawing power of the aza-substituent: (ⅰ) Electron withdrawal from the C-O bond accelerates the rate and (ⅱ) electron withdrawal from the $N^1$-atom, that is participating in the six-membered TS, deactivates the reaction. We are unable to explain the experimental result of the greatest reactivity for pyridazine, (V), with our AM1 results. The reactivity increase accompanied by successive methylation of the ethoxy group, ethoxytert-butoxy, is due to a release of steric crowding in the activation process.

Keywords

References

  1. Bull. Korean Chem. Soc. Determination of Reactivity by MO theory I. Lee;H. Y. Park;B.-S. Lee
  2. The Chemistry of the Functional Groups, Supplementary Volume B. Acid Derivatives R. Taylor; S. Patai(Ed.)
  3. J. Chem. Soc., Perkin Trans v.2 R. Taylor
  4. J. Chem. Soc., Perkin Trans. v.2 R. Taylor;M. P. Thorne
  5. J. Chem. Soc., Perkin Trans. v.2 S. de B. Norfolk;R. Taylor
  6. J. Chem. Soc., Perkin Trans. v.2 N. Al-Awadi;R. F. Al-Bashir;O. M. E. El-Dosouqui
  7. J. Phys. Chem. v.94 I. Lee;O. J. Cha;B.-S. Lee
  8. J. Phys. Org. Chem. v.3 I. Lee;O. J. Cha;B.-S. Lee
  9. Bull. Korean Chem. Soc. v.12 I. Lee;O. J. Cha;B.-S. Lee
  10. Bull. Korean Chem. Soc. B.-S. Lee;C. K. Kim;I. Lee
  11. J. Chem. Soc., Perkin Trans. v.2 N. Al-Awadi;J. Ballam;P. R. Hemblade;R. Taylor
  12. J. Chem. Soc., Perkin Trans. v.2 R. Taylor
  13. Bull. Korean Chem. Soc. v.11 I. Lee;O. J. Cha;B.-S. Lee
  14. J. Am. Chem. Soc. v.107 M. J. S. Dewar;E. G. Zoebisch;E. F. Healy;J. J. P. Stewart
  15. Theory and Practice of MO Calculations on Organic Molecules I. G. Csizmadia
  16. J. Am. Chem. Soc. v.93 M. J. S. Dewar;S. Kirscbner
  17. J. Am. Chem. Soc. v.94 J. W. McIver;A. Komornicki
  18. AMPAC: Austin Model 1 Package(QCPE No. 506) M. J. S. Dewar
  19. J. Chem. Soc., Perkin Trans v.2 N. Al-AWadi;R. Taylor
  20. J. Am. Chem. Soc. v.20 K. Fikui;T. Yonezawa;H. Shingu
  21. J. Am. Chem. Soc. v.97 K. Fukui;S. Inagaki
  22. J. Am. Chem. Soc. v.98 S. Inagaki;H. Fujimoto;K. Fukui
  23. Theory of Orientation and Stereoselection K. Fukui
  24. J. Chem. Soc., Perkin Trans v.2 N. Al-Awadi;R. Taylor
  25. I. Lee;C. K. Kim
  26. Chem. Rev. v.60 C. H. Depuy;R. W. King
  27. J. Chem. Soc. A. Maccoll