Butene on Zinc Oxide

These results are similar to those with propylene insofar as they indicate dissociative adsorption of the olefin. The hydrogen that yields the hydroxyl has not been identified but it seems reasonable to suppose that, once again, the allylic hydrogen is lost. Results with butene, however, do differ from those with propylene in two respects first, the dissociation (as evidenced by the OH band) is rapid but not instantaneous as found for propylene second, dissociatively adsorbed butene is more easily removed by room temperature evacuation than dissociatively adsorbed propylene. These facts suggests that steric effects are present hence, the kinetic behavior of these two species may be quite different. 

Firm assignments for these C=C bands require more detailed experiments but a tentative assignment can be made. The bands at 1550-1570 cm-1 are probably due to a ir-allyl species the shift from the double-bond region for butenes is about 100 cm-1 compared to the shift of 107 cm-1 observed for the 7r-allyl formed from propylene, but the butene is less firmly held. With propylene we observed a x-complex in which the shift in C=C stretch was about 30 cm-1. We believe the band at 1610 cm 1 

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