期刊
MOLECULES
卷 17, 期 5, 页码 6001-6010出版社
MDPI AG
DOI: 10.3390/molecules17056001
关键词
metathesis degradation; natural rubber; mandarin oil; alkylidene-ruthenium catalysts
资金
- National Council for Science and Technology of Mexico (CONACYT)
- CONACyT-SEMARNAT [23432]
- ICyTDF [4312]
This study reports on the degradation of natural rubber (NR) via cross-metathesis with mandarin oil and d-limonene, an abundant compound in essential oils; that were used as chain transfer agents (CTAs) and green solvents. Reactions were performed in the presence of the ruthenium-alkylidene catalysts (PCy3)(2)(Cl)(2)Ru=CHPh (I) and (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (II), respectively. Catalyst II bears an N-heterocyclic carbene ligand (NHC) bounded to the ruthenium atom, which has a strong basic character; therefore it is more active toward trisubstituted olefins in comparison with catalyst I. In both cases, isolated monoterpene-terminated isoprene oligomers were obtained as products of the cross-metathesis degradation of NR. In the presence of catalyst II molecular weight values around M-n x 10(2) and yields of 80% were obtained; whereas with catalyst I, the molecular weights of products were about M-n x 10(4) with yields ranging 70 to 74%. The composition and yield of NR degradation products were determined by GC/MS (EI) analysis and it was found that the oligomers obtained have primarily one vinyl group and one terpene-monocyclic group at the chain end, with isoprene units A(m) = 2, 3 y 4.
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