A mass balance for the transformation of metformin to Y and the decomposition of Y to C could not yet be established. Putative reaction intermediates and side products are not commercially available and the quantification of Y at trace concentrations was not successful due to decomposition of the Decitabine during enrichment. An overall transformation rate of metformin to C of ≤1% in tap water matrix was estimated (Section 3.8). During quantitative preparation of both transformation products (Sections 2.2 and 2.3) a maximum yield of 41% was determined for the conversion of metformin to Y and a conversion rate of ≤60% was estimated for the conversion of Y to C.
3.8. Detection of Y and C at trace concentration levels
4. Conclusions and prospects
Two hitherto undescribed chlorine-transformation products of metformin, Y and C, were discovered and characterized. Purification and crystallization of the substances allowed the structural elucidation by single-crystal X-ray structure determination. Primarily, metformin is transformed into the metastable triazole-derivate Y, which further decomposes to the chloroorganic nitrile C. The transformation of metformin was observed at trace concentrations of reactants as expected during practical water treatment processes. Whereas trace quantities of Y were found to rapidly decompose in tap water, the persistence of C in the drinking water distribution network appears likely. No significant degradation of C was observed in tap water.