P. Matyus et al., DENSITY-FUNCTIONAL CALCULATIONS ON HETEROCYCLIC-COMPOUNDS .2. ON THE PROTONATION OF 4,5-DICHLORO-2-METHYL-3(2H)-PYRIDAZINONE, Heterocycles, 38(9), 1994, pp. 1957-1960
Studies on protonation of the title compound by DF and ab initio quant
um chemical methods as well as C-13-nmr relaxation measurements reveal
ed that O-protonation took place.