PURPOSE: To obtain 15-pentadecanolide or a mixture of 15-pentadecanolide with 15-pentadec-11(12)-enolide imparting aromatic characteristics to a perfume compsn., etc., by heat-treating bis-(13-oxabicyclo[10,4,0]hexadec-12-yl) peroxide in a specified org. solvent.

CONSTITUTION: Bis-(13-oxabicyclo[10,4,0]hexadec-12-yl) peroxide is heat-treated at 140-200°C in an org. solvent having 170-250°C b.p. made of an arom. deriv. of the formula [where R2 is H, each of R1 and R3 is isopropyl and R1 is at m- or p-position to R3; each of R1 and R2 is H and R3 is CH(CH3)2, CH2NH2, etc.; or R1 is H and R2 and R3 form an alicyclic nucleus in combination with C to which they bond], preferably 1,2,3,4-tetrahydronaphthalene to obtain the objective 15-pentadecanolide or the objective mixture of 15-pentadecanolide with ≤10 wt.% 15-pentadec-11(12)-enolide.