The O(D-1)+C3H5 reaction has been investigated using the universal crossed molecular beam method. A number of reaction pathways have been observed. One of the most interesting channels is the H2CO/HCOH+C2H4 process, in which H2CO products are clearly identified. Experimental results indicate that the H2CO products are likely produced through a long-lived complex formation process, for which insertion of O(D-1) into the C-C bond should be responsible.