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Iron-free mechanochemical limonene inverse vulcanization
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Resumo(s)
An iron-free mechanochemical-assisted limonene inverse vulcanization is reported. The process makes use of only limonene and sulphur, industrial waste by-products, under mild conditions (ca. 40 °C) and short time (2 h) using a zirconium oxide reactor and a planetary ball mil. The obtained high value products are light yellow solids, readily soluble in chloroform, optically active oligosulfides, which are different from polysulfides reported under conventional conditions (ca. 185 °C), as confirmed by NMR spectroscopy and mass spectrometry. A general reaction mechanism is proposed, initiated by homolytic sulphur ring opening triggered by mechanical stress, and involving thiirane intermediates, via an addition–elimination reaction of sulphur to the limonene double bonds.
Descrição
Funding information:
This research was funded by Fundação para a Ciência e a Tecnologia, Ministério da Ciência, Tecnologia e Ensino Superior (FCT/MCTES Portugal), through projects PTDC/EQU-EQU/ 32473/2017 and PTDC/MECONC/29327/2017. The Associate Laboratory Research Unit for Green Chemistry – Clean Technologies and Processes – LAQV is financed by national funds from FCT/MCTES (UIDB/QUI/50006/2020) and co-funded by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145- FEDER-007265). We thank Dr Conceição Oliveira (Mass Spectrometry Facility at CQE, node IST/RNEM campus Alameda) for performing the mass spectrometry experiments.