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Degradation Studies of Cyanex 301

Abstract : Despite the numerous studies found in the literature on CYANEX® 301, very few explain its degradation in depth. To the best of our knowledge none has explained the inconsistency between the “common knowledge” of “CYANEX® 301 degrades into CYANEX® 272” (dithiophosphinic acid degrading into the corresponding phosphinic acid) and the 31P spectrum obtained by NMR of the degradation compound. The 31P {1H} NMR analysis of a solution of CYANEX® 301 in prolonged contact with nitric acid shows a very complex spectrum, with resonances about 20 ppm downfield from what could have been expected. The degradation product giving those multiple resonances in a pattern that could be interpreted as a triplet of triplet is actually a dimer, where two molecules of CYANEX® 301 are linked by a disulfide bridge, corresponding to the condensation of the SH groups. The explanation of the complexity of the spectrum comes from the comparison with the spectrum obtained for the degradation of a stereoisomerically-purified CYANEX® 301. This purification led to the removal of the [R;S] and [S;R] isomers from the initial mixture, and yielded a white crystalline solid proven to comprise exclusively [R;R] and [S;S] isomers by XRD analysis. It was determined that the carbon chirality induced an asymmetry of the phosphorus atoms upon condensation, leading to a wide combination of magnetically non-equivalent P-31 nuclei, which can also exhibit coupling through the S-S bond The complete explanation of the NMR spectra was established and corroborated by elemental analysis
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https://hal-cea.archives-ouvertes.fr/cea-01267748
Contributor : Philippe Marc <>
Submitted on : Thursday, February 4, 2016 - 8:13:43 PM
Last modification on : Thursday, August 1, 2019 - 10:56:05 AM
Long-term archiving on: : Saturday, November 12, 2016 - 9:53:53 AM

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Philippe Marc, Radu Custelcean, John Klaehn, Dean Peterman, Lætitia Delmau. Degradation Studies of Cyanex 301. 17th Symposium on Separation Science and Technology for Energy Applications, Oct 2011, Gatlinburg, Tennessee, United States. ⟨cea-01267748⟩

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