Phototransformation of Perchlorate to Chloride in the Presence of Polysilanes

Carmen Lazar; Annamaria Halasz; Chantale Beaulieu; Sonia Thiboutot; Guy Ampleman; Jalal Hawari

doi:10.1071/CH07245

RESEARCH ARTICLE

Phototransformation of Perchlorate to Chloride in the Presence of Polysilanes

Carmen Lazar ^A , Annamaria Halasz ^A , Chantale Beaulieu ^A , Sonia Thiboutot ^B , Guy Ampleman ^B and Jalal Hawari ^A ^C

+ Author Affiliations

- Author Affiliations

^A Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Ave., Montréal, Québec, H4P 2R2, Canada.

^B Defence Research Establishment Valcartier, 2459 Boulevard Pie XI Nord Val-Bélair, Québec, G3J 1X5, Canada.

^C Corresponding author. Email: Jalal.Hawari@nrc.ca

Australian Journal of Chemistry 60(11) 857-861 https://doi.org/10.1071/CH07245
Submitted: 17 July 2007 Accepted: 2 August 2007 Published: 1 November 2007

Abstract

Perchlorate is a uniquely stable chemical described as an emerging thyroid disrupting agent that is presently detected in several terrestrial and aquatic matrices. The present study was undertaken to deoxygenate perchlorate to the chloride anion photolytically in the presence of dodecamethylcyclohexasilane (Me₂Si)₆ 1. It is found that photolysis of 1 in the presence of dry NaClO₄ in tetrahydrofuran (THF) at 254 nm leads to the disappearance of the salt. The removal of ClO₄^– occurred with the concurrent formation of ClO₃^– and ClO₂^–, which disappear to eventually produce the chloride anion quantitatively. The two cyclic silanes (Me₂Si)₅ 3 and (Me₂Si)₄ 4 in addition to several other siloxanes that include (Me₂SiO)₃, (Me₂SiO)₄, and (Me₂Si)_xO₂ (x = 4 and 5) were also detected. When the reaction was repeated using uniformly labelled ¹⁸O-[ClO₄^–] it was found that oxygen incorporated in the siloxane products was derived from perchlorate. Mixing 1 with perchlorate in THF in the dark or adding the salt to 1 after the latter being photolyzed in THF did not deoxygenate ClO₄^–. Based on experimental evidence gathered thus far it is concluded that dimethylsilylene, Me₂Si: 2, a reactive intermediate produced by the photolysis of 1, is in part responsible for the deoxygenation of perchlorate. Direct oxygen transfer from ClO₄^– to the silanes during photolysis is also suggested as a potential route of deoxygenating ClO₄^–.

References

Phototransformation of Perchlorate to Chloride in the Presence of Polysilanes

Abstract

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