PMR and chemical evidence for stereospecificity in reaction of cis- and trans-1-phenyl-4-tert-butylcyclohexanol with hydrogen chloride. PMR analysis of the reaction of several substituted 1-arylcyclohexyl systems with hydrogen chloride and fluorosulfuric acid-antimony pentafluoride-sulfur dioxide

1972 ◽  
Vol 37 (3) ◽  
pp. 528-530 ◽  
Author(s):  
K. Darrell. Berlin ◽  
Reginald O. Lyerla ◽  
Don E. Gibbs
Keyword(s):  
Sulfur Dioxide ◽  
Hydrogen Chloride ◽  
Antimony Pentafluoride ◽  
Cis And Trans ◽  
Substituted 1 ◽  
Chemical Evidence

Configuration of Free-Radicals. Non-stereospecificity of cis- and trans-2-Butene-Sulfur Dioxide Copolymerizations

1957 ◽  
Vol 79 (5) ◽  
pp. 1253-1256 ◽  
Author(s):  
Philip S. Skell ◽  
Robert C. Woodworth ◽  
James H. McNamara
Keyword(s):  
Free Radicals ◽  
Sulfur Dioxide ◽  
Cis And Trans

Cis-Trans Isomerization of Natural Rubber under the Influence of Hydrogen Chloride or Ethylaluminum Dichloride

1960 ◽  
Vol 33 (4) ◽  
pp. 985-987 ◽  
Author(s):  
I. I. Boldyreva ◽  
B. A. Dolgoplosk ◽  
E. N. Kropacjeva ◽  
K. V. Nel'son
Keyword(s):  
Natural Rubber ◽  
Hydrogen Chloride ◽  
Benzene Solution ◽  
Polymer Chains ◽  
Trans Content ◽  
Aluminum Compounds ◽  
Cis And Trans ◽  
Chloride Activity ◽  
Made In

Abstract We have established earlier that organo-aluminum compounds, and titanium tetrachloride, bring about the isomerization of the cis-isoprene units in natural rubber into the trans. The isomerization process, as influenced by the above materials, proceeds at appreciable velocity even at room temperature. The present communication reports the results of investigating the cis-trans isomerism of natural rubber as influenced by hydrogen chloride and ethylaluminum dichloride. The isomerizing action of hydrogen chloride upon unsaturated acids and stilbene was dislosed earlier in a series of papers. We investigated the action of dry hydrogen chloride and ethylaluminum dichloride on benzene solutions of natural rubber under the conditions described earlier. Hydrogen chloride was introduced in the form of a saturated benzene solution. In investigating the hydrogen chloride activity, each polymer sample was examined for unsaturation, chlorine content of the polymer chains and microstructure. The latter was characterized with the aid of infrared absorption spectra. As in the previous report, quantitative determination of the cis and trans content was made in the 840 cm−1 region, where the intensity and contour are substantially dissimilar for natural rubber and guttapercha. Furthermore, an additional inspection was made qualitatively in other regions of the IR spectrum (1100–1150 cm−1 and 1300–1330 cm−1), the feasibility of utilizing the 1300–1330 cm−1 region having been reported in a recent publication by Golub, who investigated the isomerization of natural rubber and guttapercha under the influence of selenium at temperatures of 180–220°.

Cis-Trans Isomerization in Natural Polyisoprenes

1960 ◽  
Vol 33 (2) ◽  
pp. 445-456 ◽  
Author(s):  
J. I. Cunneen
Keyword(s):  
Sulfur Dioxide ◽  
Natural Rubber ◽  
Ultraviolet Light ◽  
Low Temperatures ◽  
Structural Changes ◽  
Trans Isomers ◽  
Gutta Percha ◽  
Trans Isomerization ◽  
Cis And Trans Isomers ◽  
Cis And Trans

Abstract The cis and trans isomers of many simple olefins and conjugated polyolefins can be interconverted by the action of heat, light, and various catalysts, and in many such systems the changes in geometric configuration can be readily followed and the isomers separated and identified. Previous attempts to isomerize natural rubber and gutta-percha by treatment with ultraviolet light and various chemicals gave no detectable cis-trans isomerization, and in general configurational changes in unconjugated polyolefins have been unknown until recently when Golub converted the cis-1,4 units in polybutadiene into the corresponding trans units. This isomerization was achieved by irradiation of the cis-polymer with ultraviolet light in the presence of various organic bromides and sulfur compounds, but apparently this method did not isomerize natural rubber. In attempts to retard the rate of crystallization of natural rubber at moderately low temperatures—i.e., −10° to −40° C—by the attachment of side groups which would interfere with the molecular packing, it was observed that very small amounts of thiol acids were remarkably effective. This suggested that structural changes other than simply the attachment of side groups were occurring in the polyisoprene molecule. Recently it was found that thiol acids could interconvert the cis and trans forms of a simple trialkyl ethylene—e.g., 3-methylpent-2-ene—and subsequently, the isomerization of natural rubber and gutta-percha by these reagents was also observed. Following this, natural rubber, gutta-percha, squalene and cis and trans forms of 3-methylpent-2-ene have also been isomerized by treatment with sulfur dioxide and allied compounds; this work, including an investigation of the physical properties of the vulcanizates obtained from some of the isomerized polyisoprenes, is described in the present paper.

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