Collect. Czech. Chem. Commun. 1995, 60, 1310-1315

Quantum Chemical Study of Thermal Dehydrochlorination of Poly(vinyl chloride) Containing Aldehyde Groups

Jaroslav Burda

Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic


Thermal dehydrochlorination of syndiotactic oligomeric models of PVC with aldehyde groups is studied using semiempirical quantum chemical methods AM1 and MNDO. The possibility of both radical and ionic mechanism of HCl elimination is examined. From the results it follows that the homolytic detachment of chlorine from the carbon in β-position to the aldehyde group is preferred, followed by hydrogen splitting off. Hydrogen atom detachment from the carbon in α-position to the aldehyde group as the first step is found energetically less convenient. The dehydrochlorination of aldehyde-containing PVC model, especially of the first molecule from the chain, is remarkably easier in comparison with regular PVC model. However, the energetical preference is smaller for further HCl splitting off and, from the kinetic point of view, this process seems to be slower. The influence of the aldehyde group inductive effect on the driving force potential m(Ca-Cw) is apparent from the partial charge distributions.