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Environmental fate & pathways

Hydrolysis

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No specific study was performed to assess the hydrolysis of 1,3-dibutyl-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. The hydrolysis study of DBTU is therefore waived according to section 1.2 of annex XI of REACh regulation EC 1907/2006 as it can be concluded from a weight of evidence that DBTU is hydrolytically stable at environmental temperature and pH. 

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No specific study was performed to assess the hydrolysis of 1,3-dibutyl-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 date 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-dibutyl-2-thiourea measured concentrations were maintained closed to 100% of the nominal concentrations, one can consider that hydrolysis of 1,3-dibutyl-2 -thiourea is negligible under environmental conditions.