Are Si–C bonds formed in the environment and/or in technical microbiological systems?

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Organosiloxanes are industrially produced worldwide in millions of tons per annum and are widely used by industry, professionals, and consumers. Some of these compounds are PBT (persistent, biaccumulative and toxic) or vPvB (very persistent and very bioaccumulative). If organosiloxanes react at all in the environment, Si–O bonds are hydrolyzed or Si–C bonds are oxidatively cleaved, to result finally in silica and carbon dioxide. In strong contrast and very unexpectedly, recently formation of new Si–CH3 bonds from siloxanes and methane by the action of microorganisms under mild ambient conditions was proposed (in landfills or digesters) and even reported (in a biotrickling filter, 30 °C). This is very surprising in view of the harsh conditions required in industrial Si–CH3 synthesis. Here, we scrutinized the pertinent papers, with the result that evidence put forward for Si–C bond formation from siloxanes and methane in technical microbiological systems is invalid, suggesting such reactions will not occur in the environment where they are even less favored by conditions. The claim of such reactions followed from erroneous calculations and misinterpretation of experimental results. We propose an alternative explanation of the experimental observations, i.e., the putative observation of such reactions was presumably due to confusion of two compounds, hexamethyldisiloxane and dimethylsilanediol, that elute at similar retention times from standard GC columns.

Original languageEnglish
JournalEnvironmental Science and Pollution Research
Issue number39
Pages (from-to)91492-91500
Number of pages9
Publication statusPublished - 08.2023

Bibliographical note

Open Access funding enabled and organized by Projekt DEAL

Publisher Copyright:
© 2023, The Author(s).

    Research areas

  • Biotrickling filter, Bond enthalpy, Decamethylcyclopentasiloxane, Dimethylsilanediol, GC retention time, Hexamethyldisiloxane, Octamethylcyclotetrasiloxane
  • Chemistry