Microwave‐Assisted Synthesis of Novel 2,4‐Dihydro‐5‐[4‐(trifluoromethyl)phenyl]‐3 H ‐1,2,4‐triazol‐3‐ones and Potentiometric Determination of Their p K a in Nonaqueous Solvents

The novel 4‐amino‐ or 4‐aryl‐substituted 2,4‐dihydro‐5‐[(4‐trifluoromethyl)phenyl]‐3 H ‐1,2,4‐triazol‐3‐ones 3a – 3g were synthesized by reaction of N ‐(ethoxycarbonyl)‐4‐(trifluoromethyl)benzenehydrazonic acid ethyl ester ( 2 ) and primary amines or hydrazine by microwave irradiation. Compounds 3a – 3g were potentiometrically titrated with tetrabutylammonium hydroxide (Bu 4 NOH) in four nonaqueous solvents, i.e. , i PrOH, t BuOH, MeCN, and N,N ‐dimethylformamide (DMF). Also half‐neutralization potential values and the corresponding p K a values were determined in all cases.