Thermal Dehydrochlorination of Poly(vinyl chloride) in Syndiotactic Systems

1992 ◽  
Vol 57 (1) ◽  
pp. 93-106 ◽  
Author(s):  
Jaroslav Burda ◽  
Rudolf Lukáš
Keyword(s):  
Molecular Weight ◽  
Reaction Mechanism ◽  
Hydrogen Chloride ◽  
Vinyl Chloride ◽  
Quantum Chemical ◽  
Low Molecular Weight ◽  
Ionic Mechanism ◽  
Reaction Conditions ◽  
Poly Vinyl Chloride ◽  
Ionic Intermediates

The thermal dehydrochlorination of syndiotactic poly(vinyl chloride) sequences has been studied theoretically on low-molecular weight models ranging from vinyl chloride dimer to pentamer using the semiempirical quantum chemical MNDO method. Parameters obtained with saturated systems and their change caused by the proceeding elimination of hydrogen chloride accompanied by the formation of the corresponding unsaturated structures are discussed with respect to the repeated chloroallyl or α-chloropolyene activation of the dehydrochlorination process. The study of the assumed radical and ionic intermediates is used in discussing the reaction mechanism of dehydrochlorination, and the radical or ionic mechanism is supposed to be operative depending on the reaction conditions.

Dehydrochlorination of Poly(vinyl chloride) in Isotactic Systems

1993 ◽  
Vol 58 (2) ◽  
pp. 343-353 ◽  
Author(s):  
Jaroslav Burda ◽  
Rudolf Lukáš
Keyword(s):  
Molecular Weight ◽  
Point Of View ◽  
Low Molecular Weight ◽  
Ionic Mechanism ◽  
Polyene Chain ◽  
Subsequent Growth ◽  
Reaction Conditions ◽  
Poly Vinyl Chloride ◽  
Semiempirical Mndo ◽  
Thermodynamic Factors

The dehydrochlorination of isotactic, low-molecular-weight models of PVC, dimers to pentamers, was studied using the semiempirical MNDO method. The results obtained lead to the conclusion that the thermal dehydrochlorination of PVC can occur through either a radical or an ionic mechanism, depending on the reaction conditions. The arising conjugated polyene structures do not grow by the generally accepted "zip" mechanism, but rather through the "alternating growth" mechanism. A comparison was also made to the reactivity of isotactic and syndiotactic sequences from the point of view of kinetic and thermodynamic factors. It follows from the computations that the splitting off of the first HCl molecule is easier in the isotactic sequence, but that subsequent growth of the polyene chain occurs more readily in syndiotactic systems.

Low-molecular-weight glycerol esters as plasticizers for poly(vinyl chloride)

2014 ◽  
Vol 20 (2) ◽  
pp. 65-71 ◽  
Author(s):  
Oscar Yesid Suárez Palacios ◽  
Paulo César Narváez Rincón ◽  
Jean-Pierre Corriou ◽  
Mauricio Camargo Pardo ◽  
Christian Fonteix
Keyword(s):  
Molecular Weight ◽  
Vinyl Chloride ◽  
Low Molecular Weight ◽  
Poly Vinyl Chloride

Theoretical Study of Thermal Dehydrochlorination of Poly(vinyl chloride) Initiated by Tertiary Chlorine Groupings

1995 ◽  
Vol 60 (8) ◽  
pp. 1303-1309 ◽  
Author(s):  
Jaroslav Burda ◽  
Rudolf Lukáš
Keyword(s):  
Vinyl Chloride ◽  
Structural Defects ◽  
Low Molecular Weight ◽  
Chemical Methods ◽  
Poly Vinyl Chloride ◽  
Quantum Chemical Methods ◽  
Ionic Intermediates ◽  
Detailed Evaluation ◽  
Tertiary Carbon ◽  
Branched Structure

Thermal dehydrochlorination of syndiotactic poly(vinyl chloride) sequences initiated by structural defects possessing chlorine atoms bound on tertiary carbon atoms (branched structures) was theoretically studied on the low-molecular-weight models using the semiempirical quantum chemical methods MNDO and AM1. The results are compared with those obtained previously by studying the dehydrochlorination in syndiotactic sequences without defects. It was found that elimination of the first HCl molecule is much easier in the branched structure. However, this effect fast decreases with dehydrochlorination continuing along the chain due to its distinct localization in the closest vicinity of tertiary carbon atom. A detailed evaluation of possible radical and ionic intermediates revealed that for ionic mechanism of dehydrochlorination the effect of branching is perceptible slightly longer.

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