What is it about?
Reaction of perfluoroallyl chloride with perfluoroalkyl iodides, RFI (RF = C4F9, C6F13, C8F17), in an autoclave at 180–250 °C gave terminal perfluoroolefins, CF2-CF-CF2-RF (2–4) as the sole reaction products. Isomeric fluoroolefins containing an internal double bond and telomeric products were not observed in the reaction mixture. The yields were dependent on the reaction temperature and on the chain length of RFI: the highest preparative yield of olefin 2 (RF = C4F9) was obtained at 200 °C (26%), while in the syntheses of olefins 3 and 4 (RF = C6F13 and C8F17, respectively) highest yields were achieved at 250 °C (41% and 74%, respectively). The presence of CuI or a peroxide initiator had a negative influence on the yield of products. Formulae have been assigned to the fragments in the mass spectra of products 2–4, and fragmentation sequences have been proposed.
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Why is it important?
Reaction of perfluoroallyl chloride with perfluoroalkyl iodides, RFI (RF = C4F9, C6F13, C8F17), in an autoclave at 180–250 °C gave terminal perfluoroolefins, CF2-CF-CF2-RF (2–4) as the sole reaction products. Isomeric fluoroolefins containing an internal double bond and telomeric products were not observed in the reaction mixture. The yields were dependent on the reaction temperature and on the chain length of RFI: the highest preparative yield of olefin 2 (RF = C4F9) was obtained at 200 °C (26%), while in the syntheses of olefins 3 and 4 (RF = C6F13 and C8F17, respectively) highest yields were achieved at 250 °C (41% and 74%, respectively). The presence of CuI or a peroxide initiator had a negative influence on the yield of products. Formulae have been assigned to the fragments in the mass spectra of products 2–4, and fragmentation sequences have been proposed.
Perspectives
The radical reaction of monoiodoperfluoroalkanes RFI (RF = C4F9, C6F13, C8F17) and diiodoperfluoroalkanes I-Q-I (Q = C4F8, C6F12) with allyl acetate initiated by peroxidic initiators is described. Under the reaction conditions employed, the conversion of both RFI and IQI was complete in most cases. The reactions of RFI also yielded some 2:1 telomers which are new compounds which have been characterized. In certain cases, the telomers were isolated in preparative yield up to 34%. Both 1:1 adducts [RFCH2CHICH2OCOCH3, (2a-c)] and 2:1 telomers (5a-c) underwent subsequent thermal rearrangement [formation of RFCH2CH(OCOCH3)CH2I, (3a-c), and telomers (6a-c), respectively] at elevated temperatures. In the reaction of diiodides IQI, monoadducts [CH3COOCH2CHICH2QI, (9a,b)] and diadducts [(CH3COOCH2CHICH2)2Q (10a,b)] were formed, but no telomeric and rearranged products were found under the reaction conditions employed. On the other hand, isolated mono- (9) and di-adducts (10) underwent a similar rearrangement to the compounds 2a-c and 5a-c at elevated temperatures. Regioisomeric primary and rearranged products could be distinguished by mass spectrometry in which characteristic signals for a series of compounds with different RF groups were found.
Dr Vladimír Církva
Institute of Chemical Process Fundamentals
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This page is a summary of: Radical additions to fluoroolefins. Thermal reaction of perfluoroallyl chloride with perfluoroalkyl iodides as a selective synthesis of terminal perfluoroolefins, Journal of Fluorine Chemistry, November 1995, Elsevier,
DOI: 10.1016/0022-1139(95)03202-o.
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