Hexanoic acid, 6-[[1-oxo-6-[(1-oxo-2-propenyl)oxy]hexyl]oxy]-,2-ethyl-2-[[[1-oxo-6-[[1-oxo-6-[(1-oxo-2-propenyl)oxy]hexyl]oxy]hexyl]oxy]methyl]-1,3-propanediyl ester