the present invention relates to a novel antioxidant - peroxide compound of structure a , . sub . x -- an ]. sub . y a in which the definitions of x , y , r , an , x , and y are given in the summary of the invention section , for example , t - butyl peroxy - 3 - propionate , processes for producing polymeric compositions of enhanced oxidative stability via initiation of polymerization of ethylenically unsaturated monomers , curing of elastomers and unsaturated polyester resins , modification of polypropylene and other polymers and copolymers , and crosslinking of olefin polymers and copolymers , and the resulting polymers having enhanced oxidative stability .