When an O(P-3) atom reacts with a terminal alkene, RCH=CH2, a vinoxy radical can be produced by one of two mechanisms: (a) attachment of the oxygen atom to C1 followed by migration of a hydrogen atom from C1 to C2 and then release of the radical R, or (b) attachment of the oxygen atom to C2 followed or accompanied by release of the radical R. The hot band B <-- X spectra of partially deuterated vinoxys allow one to distinguish between these two possibilities. The general result is that vinoxy is produced in comparable amounts by the two mechanisms. In the reaction of O(P-3) atoms with ethylene, one of the product channels is a vinoxy and a hydrogen atom. A hydrogen atom can be directly released from the carbon atom to which the oxygen is attached or it can migrate to the other carbon forming a hot acetaldehyde. The latter then dissociates to form methyl and formyl radicals (mainly) or a hydrogen atom and a vinoxy radical. The hot band spectra of vinoxys from the reaction of O(P-3) with CHD=CHD and CH2=CD2 show that while both processes occur, the majority of the hydrogen atoms are released directly rather than indirectly. Fast hydrogen atoms produced by photodissociation of H2S were shown to abstract a hydrogen atom from the methyl group of acetaldehyde yielding a hydrogen molecule and vinoxy. The vinoxy is vibrationally very cold despite the large available energy.