Hydrogenated 1,4-polyisoprene spectrum

Hydrogenated 1,4-po1yisoprene. Figure 5 shows the 22.6 MHz NMR spectrum of the hydrogenated 1,4-polyisoprene sample. The... 

Figure 5. Proton noise-decoupled 22.6-MHz C-13 NMR spectrum of the hydrogenated 1,4-polyisoprene sample. Perdeuteriohenzene solution at 25°C with TMS as internal reference. Approximately 5000 pulses with an acquisition time of 0.7 sec and a flip angle of 30°.

A minor part was assigned to radicals—CH2—CH=CH—CH—CH2— formed by hydrogen abstraction from one of the a methylene groups. These radicals were not resonance-stabilized at -196° C due to steric hindrance. On heating, a singlet spectrum similar to the one observed for 1,4-polyisoprene was observed and interpreted as due to polyenyl radicals -fCH=Cf% H—. 

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