AB-INITIO STUDY OF THE TAUTOMERIC FORMS OF SOME QUINOLINEDIONES

7,8-dihydroquinoline-4,5 (1H,6H)-dione (1) and 7,8-dihydroquinoline-2, 5-(1H,6H)-dione (2) in their tautomeric oxo and hydroxy forms have be en studied by ab initio Hartree-Fock calculations; tautomerization ene rgies predict a more stable hydroxy structure having an intramolecular hydrogen bond for compound 1, whereas the oxo form is slightly prefer red for compound 2. Fourier Transform-Infra Red (FT-IR) spectra in CHC l3 solution indicate that the predicted most stable tautomers in the v apour phase remain as such.