ACID CATALYSED REACTION OF 1,2,5-THIADIAZOLES-OXIDE DERIVATIVES IN AQUEOUS SOLUTION

NORA EYLER; ADRIANA CAÑIZO; PAULA VITALE; MARIA V. MIRÍFICO

Los Cocos, Córdoba

Conferencia; 9º Conferencia Latinoamericana de Fisico Química Orgánica; 2007

Comité Organizador CLAFCO - Dra. Pierini

The chemistry of the 1,2,5-thiadiazole-1,1-dioxide derivatives (T) has received considerableattention due to potential applications in fine chemical, farmacology and synthetic organic shield. Inthis work, the temperature and pH effects on the rate constant values (kobs) corresponding to thehydrolysis of the tittle compounds (Scheme) has been investigated. The proposed mechanismindicates that the predominant molecular species ot T in water is the substituted thiadiazolineresulting from water addition to one –C=N- bond.The reaction kinetics of Ts ca. 3 x 10-5 M in water at different pH values from 2 to 6 and in thetemperature range of 40 to 70 ºC, was followed by UV absorption at different spectral regions foreach T. Sulfamide, a common reaction product of hydrolysis, is not optically active under thoseconditions. The reactions were followed at constant ionic strenght mantained with NaClO4 (0.1 M).An analysis of the correlation of the physical property measured (Absorbance), with theconcentration of absorbing species shows that generally the rate constant value (kobs) is a measureof the first order disappearance of T.The results indicate that the nucleophilic addition of water to the >C=N double bond of theheterocycle of each T is subject to different specific acid catalysis.