Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Allyl radicals prepared by pyrolysis of 1,5-hexadiene or allyl bromide in a quartz pyrolyzer were directed at pressures of around 0.1 Pa through an unheated reactor filled loosely with pieces of MoO₃. All components of the gaseous phase were analyzed by means of a mass spectrometer; the pyrolyzer and the catalytic reactor were placed in a high vacuum part of the mass spectrometer close to its ionization chamber so that unstable reaction products could also be detected. Acrolein was found to be the main product of the catalytic reaction between MoO₃ and allyl radicals; other products were propylene, CO and CO₂. The above mentioned interaction of allyl radicals with unheated MoO₃ was compared with (i) the interaction of unheated MoO₃ with vapours of 1,5-hexadiene or allyl bromide heated below the respective temperature of pyrolysis; (ii) the interaction of MoO₃ heated to 510 K with unheated vapours of 1,5-hexadiene or allyl bromide. The difference between these three types of interactions and differences in the behaviour of 1,5-hexadiene and allyl bromide are discussed.