The stereochemistry of the oxidative dehydrogenation of allyl alcohol-3-d1 over a silver catalyst

The stereochemistry of the oxidative dehydrogenation of (Z)-allyl alcohol-3-d₁ to acrolein over a silver catalyst has been studied using microwave spectroscopy for analyses. With oxygen present randomization was less than 16% over the temperature range 160-290 °C. In the absence of oxygen acrolein was still produced by dehydrogenation but randomization rose to 60-80% and some propionaldehyde-d₁ was observed. Under both conditions repassage of stereolabeled acrolein along with unlabeled allyl alcohol led to similar amounts of randomization to the above. The data indicate that the reaction of allyl alcohol occurs with retention of alkene stereochemistry while a repeated readsorption process leads to randomization in the acrolein. It would appear likely that the primary interaction of acrolein and allyl alcohol with the reduced silver is via the oxygen atom of each. Thus the chemistry does not involve the formation of π-allyl intermediates as observed with oxide catalysts.