Poly dechlorination

Much work has been carried out in order to elucidate the molecular structure of poly(vinyl chloride). In 1939, Marvel, Sample and Roy dechlorinated PVC with zinc dust to give linked cyclic structures (Figure 12.9). 

Starnes and Bovey (1) pioneered the method of I3C NMR analysis of reduced poly(vinyl chloride) (PVC) to study the microstructure of PVC. Tri-n-butyltin hydride ((n-Bu)3SnH) was found to completely dechlorinate PVC resulting in polyethylene (PE) whose microstructure (branching, end-groups, etc.) could be sensitively studied by 13C NMR. 

Isotope fractionation between the vapor phase and the dissolved aqueous phase has been studied only for toluene and trichloroethylene (carbon only [545, 690]). Fractionation associated with adsorption has been quantified only for toluene in regard to sample extraction using a poly(dimethylsilo-xane)-coated solid-phase microextraction fiber [373] and qualified for benzene, toluene, and ethylbenzene based on high-pressure liquid chromatography analyses of isotopically labeled and unlabeled compounds (carbon and hydrogen [692]). Isotope fractionation associated with the reductive dechlorination of chlorinated ethylenes by zero-valent iron and zinc has been... 

Poly(chlorotrifluoroethylene) (PCTFE) is produced on a modest scale as a melt-process-able, chemically resistant material, but is much less important than PVDF. The monomer is manufactured by the dechlorination of 1,1,2-trichlorotrifluoroethane (CFC 113) using zinc metal. 

Phthalocyanine complexes, deposited as a film on a metal of the same kind as their central metal ion, appeared to be active for hydrazine decomposition 48)-Wholly organic polymers, prepared by the dechlorination of poly vinylidene chloride 62> were also shown to be active, but the ammonia and hydrogen produced reacted with the catalyst, a problem also encountered with the polychelate catalysts. 

Astafiev, I. V. Catalytic Activity of Organic Polymers. II. Catalytic Proporties of a Polymer Obtained by Dechlorination of Poly(vinylidene Chloride). Kinetika Katal. 3, 364(1962). 

The photodechlorination of 2,2/,3,3/,6,6/-hexachlorobiphenyl and of three commercial mixtures of polychlorinated biphenyls solubilized in an aqueous solution of poly(sodium styrenesulphonate-co-2-vinylnaphthalene) was studied with the use of solar-simulated radiation426,427. The reaction was found to be photosensitized by the naphthalene antenna units present in the copolymer. Exciplex formation and generation of radical anions lead to dechlorination. 

Detection of trichloroacetic acid via dechlorination to its di- and mono-chloroderivatives was also studied on a pyrolitic graphite electrode modified by Hb immobilized in poly-3-hydrobutyrate membrane (Ma et al. 2005). 

Dechlorination of poly (vinyl chloride) (PVC) prepared by polymerisation of vinyl chloride (VC) with butyllithium (BuLi) was investigated under the conditions of high pressure and high temperature water. Dechlorination was induced completely and polyene product was formed from PVC under high pressure and high temperature. The polymers obtained from polymerisation of VC with the BuLi revealed different decomposition behaviour from that obtained with radical initiator such as lauryl peroxide. This was attributed to the different chemical structure of the sample PVC. Complete dechlorination of PVC could be achieved in hot water under the conditions of 19.3 MPa and 300 deg.C. 3 refs. 

M. A. Uddin, Y. Sakata, Y. Shiraga, A. Muto, K. Murata, Dechlorination of chlorine compounds in poly(vinyl chloride) mixed plastics derived oil by solid sorbents, Ind. Eng. Chem. Res., 38, 1406-1410 (1999). 

At present, no evidence exists for long runs of either meso or racemic placements in the Wurtz dechlorination reaction used in the synthesis of polysilylenes. Deviation from a random stereochemical polymerization has been suggested by West et al. (3) in the case of poly(phenylmethylsilylene) (PPMS). An analysis of Si NMR triads indicates that addition of monomer units with the same stereochemistry is preferred, which results in an increase in the intensity of syndiotactic and isotactic triad structures compared with a random stereochemical polymerization. 

Complete dechlorination of polychlorobenzenes has been accomplished using a palladium catalyst at room temperature and 3-4 atmospheres pressure. 41 The presence of a surfactant also facilitates this reaction. 34, M2 Very good yields of 3,5-dichloroaniline were obtained by the selective hydrodechlorination of poly-chloroanilines over palladium in acidic medium (Eqn. 20.60). 43,M4 Dehydrochlorination of polychlorophenols under these conditions gave good yields of 3,5-dichlorophenol. 44... 

Essentially complete reductive dechlorination of the precursor poly(chlorofluoroethylene)s to PVF was achieved after 24 h at 60"C in tetrahydrofuran with a molar excess of tri(n-butyl)tin hydride and 1 mol% of azo6i s(isobutyronitrile) (11). The reaction mixture was homogeneous until dechlorination was almost complete, after which the mixture turned cloudy owing to the insolubility of PVF. 

Poly (trifluoroethy sty rene) THF after deehlorination Dechlorination is thi... 

Dichloroketene, generated by the ultrasound-promoted dechlorination reaction of thrichloroacetyl chloride with zinc, adds to the carbon-carbon double bonds of poly(methyl-l-phenyl-1-silane-c s-pent-3-ene) [271]. This can be illustrated as follows ... 

The assignment was confirmed by examination of poly (vinyl fluoride) free from inverted units. This material was made by reductive dechlorination of poly(l-fluoro-l-chloroethylene) by means of tri-n-butyltin hydride the bulky chlorine atom in the monomer effectively prevents head-to-head growth. The F spectrum of poly (vinyl fluoride) prepared by this indirect route contained only the signals in the range 178-185 ppm. 

A series of ethylene-vinyl chloride (E-V) copolymers was generated [27] by the reductive dechlorination of poly (vinyl chloride) (PVC) [28]. Each E-V copolymer has the same average chain length (approx. 1000 repeat units) and polydispersity. High-resolution solution NMR revealed [27] their random-like comonomer sequence distributions, which were quantitatively determined to the comonomer sequence triad-level (see chapter 2). E-V copolymers with less than 40% V units were observed [29] to crystallize, and the stabilities, structures and morphologies of their crystals were observed [29,30] and analyzed by DSC, X-ray and electron diffraction, and electron microscopy. 

Poly(vinyl chloride) has received rather little attention over the past two years, though there is still some interest in replacing the chlorine of poly(vinyl chloride) with other substituents. Hence, reductive dechlorination with LiAlHj has been used... 

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