SYNOPSISThe kinetics for dehydrochlorination and benzene formation has been studied during the degradation of two samples of poly(viny1 chloride) (PVC) at 180-200°C under vacuum with and without the removal of hydrogen chloride. The effects of various additives, such as organic phosphites, mercury, silver, gold, and glass upon the thermal degradation of PVC were investigated. Mercury, silver, and glass decrease the rate of autocatalytic dehydrochlorination of the polymer in the presence of hydrogen chloride but silver and glass do not affect PVC degradation rate in the absence of HCI. PVC thermal decomposition under vacuum with removal of HCI mostly proceeds by a molecular mechanism. At the same time, radical reactions take place. But there are some very endothermic stages of chain propagation, this is why in this case, the radical mechanism of PVC dehydrochlorination does not compete with the molecular one. In the presence of HCI, the rate of radical reactions increases and predominates over rate of molecular reactions.
Reactions of bis(hydroxy)- and bis(trimethylsiloxy)diphthalocyaninato silicon with KOH were studied in o-xylene or oligosiloxane in the presence of crown ether 15-cr-5 in vacuo at 190-200 °C by the means of electronic, EPR and 1 H NMR spectroscopy. Under gradual removing of H 2 O , consecutive formation of paramagnetic silicon diphthalocyanine monoanions (λ max 580 nm ), and diamagnetic silicon diphthalocyanine dianions (λ max 550 nm ) have been observed. The dianions react with H 2 O to regenerate silicon diphthalocyanine monoanions and then the starting silicon diphthalocyanine. Reaction of the dianion with O 2 results in a decomposition of silicon diphthalocyanine. 1 H NMR spectra of silicon diphthalocyanine dianion have proven the absence of a ring current in the π-electron system of the dianion.
The reaction of bis(trimethylsiloxy)triphthalocyaninatosilicon, Me 3 Si ( OSiPc )3 OSiMe 3 ( Pc 3) with KOH in o-xylene in the presence of 15-crown-5 in vacuum at 200°C has been studied by means of UV-vis, EPR and 1 H NMR spectroscopy. Upon gradual removal of H 2 O , the formation of mono- and dianions of Pc 3 with absorption bands positioned at 575-590 nm was observed. An EPR spectroscopic study revealed that both monoanionic and dianionic of Pc 3 are paramagnetic in solution. 1 H NMR spectra have shown the absence of a ring current in the π-electron system of dianion. The reaction of Pc 3 with KOH or metal Na led to degradation of the Si - O - Si - backbone happened.
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