Kinetics of Cyclization of Hevea Latex

Gordon, M.

doi:10.1021/ie50494a032

Cited by 31 publications

(13 citation statements)

References 16 publications

(29 reference statements)

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“…data for a bicyclic structure for cyclized rubber, viz., 40%. 4 The latter values obviously differ from the values of 56 to 58% reported by previous workers ( 5 , 7, 12) for monocyclic structures.…”

Section: Kinetics and Mechanismcontrasting

confidence: 62%

“…Synthetic polyisoprenes also undergo cyclization quite readily ( 2 ) , but polybutadienes require fairly drastic conditions (3). This reaction has been considered for some time to involve a carbonium ion mechanism, although there is a controversy as to whether the product consists of monocyclic (2,(4)(5)(6)(7)(8) or polycyclic (3, 9, 10) ring structures. Thus, Gordon (4)(5)(6), who studied the kinetics of cyclization of hevea latex, considered the reaction to involve the protonation of a double bond in cis-polyisoprene, followed by an attack of the-resulting carbonium ion on an adjacent double bond, both occurring in the Markownikoff sense, t o form a cyclic carbonium ion which then deprotonates to give structure I.…”

Section: Introductionmentioning

confidence: 99%

“…If the protonation step is reversible (4), some cis-trans isomerization might occur during the cyclization reaction since release of the proton from its original point of attachment would re-establish the double bond. On thermodynamic grounds, the new double bond would be expected to be predominantly trans.…”

Section: Introductionmentioning

confidence: 99%

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The Reaction of Polyisoprene With Titanium Tetrachloride

Golub¹,

Heller²

1963

Can. J. Chem.

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The reaction of titanium tetrachloride with hevea, balata, and synthetic cis-polyisoprene in benzene a t 80' C has been studied. The most prominent change in the infrared spectra of these polymers is the nearly total disappearance of the 12 p band after prolonged reaction with TiCI4. The diminution of this band, associated with the loss of the original -C(CHB)=CH-units, whether cis or trans, follolved pseudo-first-order kinetics, the rate varying with [TiC14]*, where n is 1.0 in the case of the cis polymers and 1.5 in the case of the trans polymer. Contrary t o previous reports, practically no cis-trans isomerization of polyisoprene occurs in the course of this reaction, the data being explained entirely by cyclization. U7ith the help of cis-1,4 polymers of isoprene-3-d and 2-methyl-da-l,3-butadiene-1,l-dz, it was concluded that cyclization, involving a TiC14-induced carbonium ion mechanism, leads to the formation of six-membered rings fused into predominantly bicyclic structures, connected b y methylene groups and/or uncyclized monomer units. Each of the fused ring structures contains a single tetra-, tri-, or di-substituted double bond, the relative amounts of which are in the order tetra-> tri-> di-substituted.

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Section: Kinetics and Mechanismcontrasting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

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The Reaction of Polyisoprene With Titanium Tetrachloride

Golub¹,

Heller²

1963

Can. J. Chem.

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“…Effects of reaction time and temperature on the degree of cyclization were studied to get the information for the kinetic of cyclization in DPNR latex. For example for kinetic of cyclization in NR latex, Gordon [19] has reported results for the kinetics of the cyclization reaction using sulphuric acid as the cyclizing reagent. The progress of the reaction was followed dilatometrically.…”

Section: Introductionmentioning

confidence: 99%

“…The progress of the reaction was followed dilatometrically. Typical curves were reported by Gordon [19] for the variation of extent of reaction with reaction time. It was found that the occurrence of an initial period of reduced rate was attributed to the need for the sulphuric acid to diffuse into the rubber particles before the maximum rate of reaction time could be achieved.…”

Section: Introductionmentioning

confidence: 99%

Activation Energy and Thermodynamic Parameters of Cyclization in Purified Natural Rubber Latex Using a Trimethyl Silyl Triflate

Riyajan

2009

Journal of Elastomers & Plastics

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The property of natural rubber (NR) is more interesting, except for some properties which need to improve. The cyclization reaction is an interesting reaction for modified NR to thermoplastic elastomer. The kinetic cyclization of deproteinized natural rubber (DPNR) or purified NR latex effectively performed in latex phase by using trimethylsilyl-trifluoromethane sulphonate or trimethyl silyl triflate (TMSOTF) is studied at various temperatures and times. The cyclized products are confirmed by NMR spectroscopies including one and 2D NMR. The kinetic of cyclization is investigated. It is found that the degree of cyclization in DPNR is a function of cyclization conditions. The rate constant (k) is 200 (s À1 ) at 1008C based on 95% of regression and the activation energy of cyclization in DPNR latex is 147.66 kJ/mol. Some thermodynamic parameters: enthalpy, entropy, and free energy activation of 144.6 kJ/mole, À269.11 J/mole, and 246.9 kJ/mole, respectively, are obtained for the cyclization of DPNR. The kinetic and thermodynamic parameters of cyclization obtained from this study indicate that an increase in the process temperature would increase the rate of cyclization formation. *

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Rubber, 2. Natural

Greve¹

2000

Ullmann's Encyclopedia of Industrial Chemistry

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The article contains sections titled: 1. Introduction 2. Rubber Extraction 3. Composition of Natural Rubber Latex 4. Biosynthesis of Natural Rubber 5. Commercial Extraction of Natural Latex 6. Production of Natural Rubber 6.1. Extraction by Evaporation of Water (Evaporation, Spray Drying) 6.2. Coagulation 7. Classification 7.1. Technically Classified (TC) Rubber 7.2. Standard Malaysian Rubber (SMR) 7.3. Standardized Indonesian Rubber (SIR) 8. Physical and Technological Properties of Solid Rubber 9. Uses 10. Modification 10.1. Hydrogenated Natural Rubber 10.2. Chlorinated Natural Rubber 10.3. Hydrohalogenated Natural Rubber 10.4. Cyclized Natural Rubber 10.5. Resin‐Modified Natural Rubber 10.6. Poly(Methyl Methacrylate)‐Grafted Natural Rubber 10.7. Superior‐Processing Natural Rubber 10.8. N ‐Phenylcarbamoylazoformate‐Modified Natural Rubber 10.9. Polystyrene‐Grafted Natural Rubber 10.10. Epoxidized Natural Rubber (ENR) 10.11. Degraded Natural Rubber 10.12. Thermoplastic Natural Rubber 11. Compounding 12. Summary

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Kinetics of Cyclization of Hevea Latex

Cited by 31 publications

References 16 publications

The Reaction of Polyisoprene With Titanium Tetrachloride

The Reaction of Polyisoprene With Titanium Tetrachloride

Activation Energy and Thermodynamic Parameters of Cyclization in Purified Natural Rubber Latex Using a Trimethyl Silyl Triflate

Rubber, 2. Natural

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