Preferred lactones and ether-lactones are those wherein R' is a saturated bivalent aliphatic hydrocarbonradical having from 10 to 14 carbon atoms, R contains from 2 to 6 carbon atoms, A is oxygen, and x is 1 or 2.Illustrative macrocyclic esters and ether-esters which can be produced in accordance with the depolymerization process of this invention include: 3,6,9-tridecamethylene malonate, dodeca