A series of new 4-(3,4-dimethoxyphenethyl)-5-akyl/aryl-2H-1,2,4-triazol-3(4H)-ones (3a-g) was obtained by the reaction of ethyl 2-(ethoxy)(alkylidene/arylidene) hydrazinecarboxylate (1) and 2-(3,4-dimethoxyphenyl) ethanamine (2). Compounds 4a-f and 5 were synthesized from the reaction of corresponding compounds 3a-f and 3g with BBr3, respectively. With elemental analysis, IR, H-1-NMR, and C-13-NMR spectral data, 14 newly synthesized compounds were characterized. The structure of compound 3a was inferred through IR, H-1-and C-13-NMR, elemental analysis, and X-ray spectral techniques. In addition, the newly synthesized chemicals were screened for their antioxidant properties. Among the chemicals tested, 4a, 4c, 4d, 4f, and 5 exhibited the highest degree of antioxidant activity.