Synthesis
2,2',3,3'-ODPA and 2,3,3',4'-ODPA are synthesised using 3-Chlorophthalic anhydride as a raw material by chemical reaction
[1]. The specific synthesis steps are as follows:
Step1: 3-Chlorophthalic anhydride (348.83 g) was taken
in a 2000-mL, three-necked, round-bottom flask
fitted with a mechanical stirrer and a reflux condenser. About 1100 mL of glacial acetic acid were
added. It was stirred for 20 min at 50 °C to dissolve the anhydride completely. Then, 198 g of
aqueous methylamine solution (ca. 59.35 g of
methylamine) were dropped in the flask. The resulting mixture was heated to reflux for 4 h and
subsequently cooled to room temperature. The
white crystals were filtered and dried; 314 g were
obtained (yield: 84%, mp: 101–103 °C).
Step2: 3-(2,3-Dimethylphenoxy) phthalic acid (32.90 g)
and potassium hydroxide (10.4 g) were dissolved
in 1000 mL of water, and the solution was heated
to about 80 °C. Then, solid potassium permanganate (116.6 g) was added gradually several times
until the purple did not fade within 30 min. After
reflux for 5 h, the excess potassium permanganate was destroyed with ethanol. The filtrate was
acidified to a pH of 1 after concentration to 200
mL and cooled to room temperature. The acid
solution was allowed to stand overnight, and the
white precipitation was collected by filtration and
dried and then purified by sublimation at 267 °C
in vacuo. About 31.35 g of dianhydride (yield:
88%) were obtained; mp: 243–244 °C (lit.16 236 –
238 °C, lit.18 237 °C).
IR (KBr): 1860, 1786 (CAO str), 1261 (asym
COO str), 1048 cm1 (sym COO str). 1
H NMR
(300 M, DMSO): (ppm), 8.03– 8.01 (d, 2H), 7.98 –
7.92 (t, 2H), 7.60 –7.57 (d, 2H). ELEM. ANAL. Calcd.
for C16H6O7: C, 61.95%; H, 1.95%. Found: C,
61.87%; H, 1.93%.
Step3: The reactions were the as same as the synthesis
of 2,2,3,3-ODPA except for the replacement of
2,3-xylenol as 3,4-xylenol. The final dianhydride
was recrystallized from the mixed solvents of acetic anhydride and toluene; mp: 177–178 °C (lit.16
174 –175.5 °C, lit.18 170 °C).
IR (KBr): 1854, 1770 (CAO str), 1265 (asym
COO str), 1081 (sym COO str) cm1
. 1
H NMR
(300 MHz, DMSO-d6): (ppm) 8.17– 8.14 (d, 1H),
8.10 – 8.08 (d, 1H), 8.05– 8.00 (t, 1H), 7.75–7.74 (d,
1H), 7.71 (s, 1H), 7.70 –7.68 (d, 1H). ELEM. ANAL.
Calcd. for C16H6O7: C, 61.95%; H, 1.95%. Found:
C, 61.90%; H, 1.97%.
