Characterization of brominated natural rubber by solution-state 2D NMR spectroscopy

摘要

Bromination of natural rubber was analyzed through nuclear magnetic resonance (NMR) spectroscopy, in which small H-1 and C-13 NMR signals, appearing after bromination of natural rubber, were positively assigned bylD and 2D NMR measurements. The brominated natural rubber (BrDPNR) was prepared by bromination of deproteinized natural rubber (DPNR) with N-bromosuccinimide (NBS) in dichloromethane at 303 K for 3 h under a nitrogen atmosphere. The C-13 NMR signals at 20.5, 22, 29, 29.8, 35.8, 40 and 112.4 ppm were assigned to the primary and the secondary carbons of the brominated trans-1,4-isoprene units, whereas the signals at 24.5 and 32.6 ppm were assigned to the primary and the secondary carbons of the brominated cis-1,4-isoprene units. During the bromination of DPNR with NBS, the isoprene units underwent cis-trans isomerization. (C) 2017 Elsevier B.V. All rights reserved.