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EC number: 203-004-2
CAS number: 102-08-9
No specific study was performed to assess the hydrolysis of 1,3-diphenyl-2-thiourea.It is well recognised that thioureas are stable in aqueous medium. Several data have been used in a "Weight of Evidence" approach in order to confirm this information.
No specific study was performed to assess the hydrolysis of 1,3-diphenyl-2-thiourea but it's well recognised that thioureas are stable in aqueous medium.Several data have been used in a "Weight of Evidence" approach in order to confirm this information.
Several publications from William H.R. and David G. Walker present the conclusions of kinetic studies of thiourea derivatives. These studies have been performed in aqueous media at elevated temperatures. The authors indicate that this reaction is independent on pH and give rate constants (k) obtained at various temperatures. Half-life can be estimated with the following equation: Half-life (t ½) = ln (2) / k
Following data are given for a temperature of 100°C:
-methylthiourea: the constant k is comprised between 0.65 x 10-7s and 2.09 x 10-7s.
k = 0.65 x 10-7(t ½) = 10 663 802.78 sec = 123 days
k = 2.09 x 10-7(t ½) = 3 316 493.69 sec = 38 days
-dimethylthiourea: the constant k is 2.23 x 10-7s.
(t ½) = 3 108 283.32 sec = 36 days
-sym-dimethylthiourea: the constant k is 2.5 x 10-7s.
(t ½) = 2 772 588.7 sec. = 32 days
Furthermore, considering its structure, the authors suggest that hydrolysis is unimportant. Indeed, hydrolysis of dimethythiourea should form ammonia: from pH 1 to pH 11, no ammonia was detected by their sensitive tests in reacted solutions of this compound.
This stability in aqueous medium is also mentioned in a publication from Schmidt-Bleek F.et al.which quotes several data obtained on chemicals by "German Chemical Industry" and "highly experienced research institutes of the German federal Republic sponsored by the Umweltbundesamt".
At last, regarding the analytical monitoring performed during ecotox studies (up to 96 hours), which show that 1,3-diphenyl-2-thiourea measured concentrations were maintained close to 100% of the nominal concentrations (Gancet, 2013: "N,N’- DIPHENYL THIOUREA – Fish (Danio rerio), acute toxicity test under static conditions"), one can consider that hydrolysis of 1,3-diphenyl-2-thiourea - if any - is not significant.
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