On the basis of determining the crystal structure of three kinds of the title compounds displaying different herbicidal activities, semi-empirical AM1 method was applied to study the electronic structure of herbicidal 1, 2, 4-triazolo[1, 5-a] pyrimidine-2-sulfonamides compounds. At the same time, the structure-activity relationships of this kind of herbicides were also discussed in view of conformation and electronic structure. The results indicate that 1, 2, 4-triazolo[1, 5-a] pyrimidinyl moiety might be an important active site, of which the potency of electric charge translocation has a great influence on the herbicidal activity of this kind of compounds.

Key words: PHARMACODYNAMICS, BIOLOGICAL ACTIVITY, CRYSTAL STRUCTURE, QUANTUM CHEMISTRY, STRUCTURE ACTIVITY RELATIONSHIP, ELECTRONIC STRUCTURE, RING STRUCTURE, PYRIMIDINAMINE P, ACTIVE SITE, ACETAMIDE-GROUP HERBICIDES