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On the structure of chlorinated natural rubber. 1H- and 13C-NMR data

✍ Scribed by M.V. Eskina; A.S. Khachaturov; L.B. Krentsel; A.D. Litmanovich

Publisher
Elsevier Science
Year
1990
Tongue
English
Weight
419 KB
Volume
26
Category
Article
ISSN
0014-3057

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✦ Synopsis

and t3C-NMR spectra of compositionally homogeneous samples of chlorinated natural rubber containing 0.4-3.0 CI/C 5 have been investigated. In the samples of composition CI/C 5 ~< 1 there are no units containing > 1 chlorine atom, meaning that chlorine does not add to C-----C double bond. Simultaneously, unsaturation of the polymer decreases by approx. 10%. These data support a hypothesis about cyclization of the chain during the fast stage of chlorination (up to CI/C s = 1). However, quaternary C atoms typical of 6-membered cyclic structures, as postulated in the literature, have not been observed in spectra. Weak signals in the region 75-76 ppm indicate the existence of C \ C--C--C1 / C fragments. The data obtained suggest that 5-not 6-membered cycles are formed during chlorination of natural rubber. With an increase of the chlorination degree, signals in the olefinic region of spectra appear, indicating formation of exo-and internal C~--~ double bonds differing from analogous fragments forming in the fast stage of the reaction.

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