[C:1]([OH:15])(=[O:14])[CH2:2][CH2:3][CH2:4][CH2:5][CH2:6][CH2:7][CH2:8][CH2:9][CH2:10][C:11]([OH:13])=[O:12].[CH2:16](O)[CH2:17][CH2:18]O.[OH-].[K+]>>[O:12]1[C:11](=[O:13])[CH2:10][CH2:9][CH2:8][CH2:7][CH2:6][CH2:5][CH2:4][CH2:3][CH2:2][C:1](=[O:15])[O:14][CH2:18][CH2:17][CH2:16]1100 g of a polyester of undecanedioic acid and 1,3-propanediol, having a degree of polymerization of 29 and an acid number of 7 mg KOH/g, is mixed with 3 g of one of the catalysts listed in Table 2 (derived from French Pat. No. 796,410) in a distillation flask of a conventional vacuum distillation apparatus. The mixture is thermolyzed for 4-5 hours under vacuum (pressure: less than 0.5 mbar) at 270° C. The yields of crude 1,5-dioxacyclohexadecane-6,16-dione, based on the amount of polyester employed, are listed in Table 2.
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