Collect. Czech. Chem. Commun. 1979, 44, 673-683

A mass spectrometric study of the allyl radical interaction with oxides: MoO3

Zdeněk Dolejšek and Jana Nováková

The J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, 121 38 Prague 2


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.