ANALYSIS OF NUCLEAR MAGNETIC RESONANCE SPECTRUM OF HEXAFLUORO-1,3-BUTADIENE

被引:36
作者
MANATT, SL
BOWERS, MT
机构
[1] Space Sciences Division, Jet Propulsion Laboratory, California Institute of Technology, Pasadena
[2] Department of Chemistry, University of California, Santa Barbara
关键词
D O I
10.1021/ja01044a010
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The analysis of the complex fluorine-19 nuclear magnetic resonance (nmr) spectrum of hexafluoro-1,3-butadiene (1) at 56.4 MHz has been carried out. The following spin-spin coupling constants, Jii in hertz, and chemical shifts, ψi(in parts per million relative to internal fluorotrichloromethane, were found: JAB = +50.74, JAB = +31.91, 7BC = -118.58, JABʹ = +2.45, JACʹ = +2.41, JBCʹ = +14.19, JAAʹ- = +4.80, JBBʹ = +11.31, JCCʹ = -30.30; ψA +93.8586, ψB +107.9558,ψC +179.6853. The relative magnitudes of JABʹ, JACʹ, and JBCʹ are rather similar to those reported for a large number of trifluorovinyl systems so the analysis was based on the previously determined signs for these three coupling constants. Because of the strongly coupled nature of the AAʹ-BBʹCCʹ spin system, no spectral assignments involving sign combinations for the other six couplings different from that given above could be found which would fit even approximately the experimental spectrum. The signs of all the long-range 5JFFʹ in 1 are positive, and the magnitudes are somewhat smaller than the analogous couplings in three other 1,1,4,4-tetrafluoro-1,3-alkadienes recently studied by Servis and Roberts. Available nmr data on other fluorobutadienes are discussed. Speculations regarding the mechanisms of the 5JFF couplings in 1 and other fluorobutadienes are presented. It is suggested that the two trifluorovinyl groups of 1 may not be coplanar. © 1969, American Chemical Society. All rights reserved.
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页码:4381 / &
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