GreenRef project – final summary report
Chlorinated paraffins (CPs) are representatives of persistent organic pollutants that are considered a serious threat to the environment as well as human health. Hence, finding means for their identification and quantification in real samples (soil, water, humans, animals, etc.) is of utmost importance. The GreenRef project deals with the synthesis of new certified reference materials of CPs with the emphasis on labelled standards. Such compounds are imperative for quantitative analysis of CPs in real samples and therefore are of very high interest for countless analytical laboratories worldwide that deal with environmental toxicology. Currently there has been a lack of commercial standards available on the market which has hindered the analysis of CPs. The objective is to fill this gap to the benefit of the society.
During the project, several key aspects were investigated and successfully carried out. First, an optimized methodology for chlorination of unsaturated hydrocarbons was established. Various chlorination agents were screened, and the procedure was optimized with respect to reaction temperature and solvent used. High emphasis was dedicated to the elimination of overchlorinated side products that are otherwise difficult to remove during the product purification. The found optimized conditions were tested in a substrate scope using different olefins to prove the general applicability of the outlined concept.
Second, a robust protocol for the synthesis of the olefinic precursors of CPs was designed and optimized. The outlined procedure allows for highly efficient synthesis of the hydrocarbon backbone of a broad library of short-chain (C10-C13) and medium-chain CPs (C14-C17) and is potentially applicable on long-chain CPs (C18 and higher) as well. As a proof of concept, several CP standards were prepared using this methodology in junction with the aforementioned chlorination protocol.
Third, implementation of a labelled moiety into the CP backbone was investigated. A well-distinguishable isotopically labelled internal standard must contain at least three labelled carbon atoms to achieve a clear MS resolution of the standard from analyte. Two different approaches towards the synthesis of the labelled moiety bearing three labelled atoms were designed and tested. One of them provided good yields in the test reactions with native (not labelled) precursors and has proven to be easily implementable in the aforementioned general protocol for the synthesis of CP standards. The synthesis will be carried out as soon as the supplier delivers the ordered chemicals. The synthetic protocol for the labelled moiety is thoroughly optimized and is ready to be used.
Fourth, synthesis of eleven precursors for the implementation of the labelled moiety was carried out. These precursors were successfully tested in subsequent reactions leading towards the labelled CPs (using the prepared moiety from native precursors). An optimized protocol towards these CP standards, that serves as a proof-of-concept of the whole outlined methodology, was successfully established and will be applied in the foreseeable future as soon as the 13C-labelled precursors will be delivered.
To conclude, a robust synthetic protocol for the synthesis of short-chain and medium-chain CP standards including the crucial chlorination methodology was successfully established. The outlined procedure was further expanded to allow for the implementation of a sufficiently long labelled moiety. The synthesis of the key labelled fragment was successfully carried out using native precursors. Its incorporation into the CP chain was optimized and is ready to be implemented to reach the ultimate goal of isotopically labelled CP standards.
Articles on the synthesis, structure elucidation and NMR analysis is in progress. A patent application is in progress.
Articles and patents will be submitted first half of 2022 and will be available on the Chiron.no and chloffin.eu web-pages. Products released from the project are published at Chiron.no webpage and will be distributed as project flyers in preparation.
