Thirty 3-substituted- and 3,4-disubstituted -4,5-dihydro- 1,2,4-triazo
l - 5-ones (seven being new compounds) were synthesized and their prot
on magnetic resonance spectra were measured in trifluoroacetic acid (T
FA). The protonation shifts observed on comparison of the spectra run
in DMSO-d6 and TFA were attributed to an amidinium-type resonance of t
he resulting cations in the acidic medium.