To 15 ml (0.33 mol) of nitric acid was added at 45C while stirring 1 g of diethylene glycol from the overall amount of 5.9 g (0.06 mol), and the mixture was heated to 65C. After the end of nitrogen oxides evolution and cooling the mixture to 45-50C another portion of diethylene glycol was added. Overall time of the reagent addition to the reaction mixture was 1 h. The mixture was kept at 45C for 40 min and then it was heated at 80C for 30 min. The solvent was removed in a vacuum at 70C, the residue was dried by azeotropic distillation with benzene using Dean-Stark trap, then the product was fi ltered off and recrystallized from acetone-benzene mixture. 3,6-Dioxaoctanedioic acid (VIII) was similarly obtained. Yield 7.3 g (89%), colorless crystals. Rf 0.20 (E), mp 76-77C (mp 75-76C [13]). IR spectrum, |í, cm-1: 3167 (OH), 2914 (CH), 1733 (C=O acid), 1410, 1229 (C-O), 1121 (C-O). Mass spectrum, m/z (Irel, %): 178.5 [M]+ (76), 200.9 (55), 216.8 (46).
