Low-oxidation-potential conducting polymers: alternating substituted para-phenylene and 3,4-ethylenedioxythiophene repeat units.
Irvin, Jennifer A.; Reynolds, John R.
Polymer (1998), 39(11), 2339-2347.
Relevant Procedures:
2,5-dibromo-1,4-hydroquinone synthesis
Hydroquinone (0.968 mol) was combined with glacial acetic acid (500ml) and methylene chloride. A solution of Bromine (1.88 mol) in methylene chloride (100ml) was added dropwise over 2 hours at room temperature. After approx. half the bromine was added, all solids had dissolved. The solution was stirred at room temperature for 15 hours at which time the precipitate was collected by filtration and dried under vacuum over NaOH pellets. Recrystallization from isopropanol yeilded a white crystalline solid (m.p. 191-192C, 42% yeild)
1,4-dibromo-2,5-dimethoxybenzene synthesis
A solution of KOH (0.077 mol) in ethanol (100ml) was added slowly to a solution of 2,5-dibromo-1,4-hydroquinone (0.035 mol) in THF (200ml) under argon. The solution was stirred at room temperature for 3 hours, and then a solution of iodomethane (0.077mol) in THF (100ml) was added slowly with stirring. The mixture was stirred at 50C for 24 hours, then precipitated into water. The product was collected by filtration and recrystallized from ethanol to give a white crystalline solid (m.p. 144-147C, (lit. m.p. 142-143C), 86% yeild)
Internal rotation about aromatic carbon-oxygen bond. I. Preparation of sterically overcrowded polysubstituted phenol derivatives.
Boehm, Jaroslaw; Zamlynski, Waclaw.
Rocz. Chem. (1967), 41(4), 707-16. (In Polish)
CAN 67:53816 AN 1967:453816
Abstract
Tosyl and Me ethers of tri- and tetra substituted m-hydroxybenzoic acid, resorcinol, and hydroquinone derivs. did not appear in stereoisomeric forms which proved that the rotation of RO groups was not restricted. The ir spectra of tosylates confirmed the linear relation of the sym. and unsym. stretching frequencies of SO2 vibrations. Two polymorphic forms of 2,4,6-tribromo-3-methoxybenzoic acid (I) were isolated. Thus, a soln. of 14 g. m-hydroxybenzoic acid in 550 ml. H2O and 35 ml. 48% HBr in 65 ml. 30% H2O2 kept 12 hrs. afforded 16.48 g., in the first crop, of 2,4,6-tribromo-3-hydroxybenzoic acid (II), m. 147-8°. The filtrate treated with 5 ml. HBr and 10 ml. H2O, gave in the second crop 16.86 g. II. A soln. of 10 g. resorcinol and MeONa in MeOH (prepd. from 12 g. metallic Na in 150 ml. MeOH) was autoclaved during 10 hrs. at 190°/70 atm., then acidified and steam distd. to give in the residue 7.5 g. crude product (recrystd. from C6H6), which when chromatographed on Al2O3 and eluted with: C6H6-ligroine, yielded 70% 2,4,6-trimethylresorcinol, m. 151-2°. A boiling suspension of 27.5 g. hydroquinone in 300 ml. CCl4 was treated dropwise, during 3 hrs., with 160 g. Br in 150 ml. CCl4, then refluxed 10 hrs., cooled, washed with Na2SO3, and evapd. to give 85.5 g. of a crystn. ppt. The pptd. extd. with hot water afforded 22 g. 2,5-dibromohydroquinone, m. 186-7°. The water insol. residue recrystd. successively from AcOH, EtOH, and EtOH-Et2O consisted of a mixt., m. 247-57°, of tetrabromohydroquinone and tetrabromoquinone. Redn. of 8.5 g. of the mixt. in 250 ml. 80% AcOH, under reflux, with 10 g. Na2S2O4 in 100 ml. H2O gave quant. tetrabromohydroquinone, m. 244-6°. Redn. of the appropriate quinone with Na2S2O4 in 80% AcOH afforded 91% duroquinone, m. 234-5°, and 96% tetrachlorohydroquinone, m. 232-4°. Tosylation was carried out either in aq. KOH or in pyridine. A soln. of 7.4 g. II and 2.24 g. KOH in 100 ml. H2O stirred 12 hrs. with 3.8 g. p-MeC6H4SO2Cl (III) in 50 ml. C6H6, after sepn. of the aq.
layer and work up, afforded 3.84 g. II tosylate, m. 189-91°. Similarly, resorcinol yielded 92% di-tosyl deriv., m. 82-3°. A soln. of 3.91 g. 2,4,6-tribromo-3,5-dihydroxybenzoic acid (IV) in 100 ml. 3.5% aq. KOH was stirred during 20 hrs. with 5.7 g. III in 30 ml. C6H6. When acidified the aq. layer afforded a resin, which when washed with CHCl3 gave 1.63 g. of the starting material. When recrystd. from dil. EtOH, the CHCl3-insol. solid afforded 2.74 g. IV mono-tosylate, m. 207-9°. A general procedure for tosylation in pyridine at the molar ratio 1:3 phenol-III was given. A soln. of 0.01 mole corresponding phenol in 20 ml. anhyd. pyridine was treated dropwise at room temp. with 0.03 mole III in 20 ml. pyridine, the mixt. was kept 30 min. at 60° and poured into water to give the following tosylates (Ts = tosyl) (compd., m.p., and % yield given): 1,3-(OTs)2-2,4,6-Br3C6H, 224-7°, 94; 1-(OH)-3-(OTs)-2,4,6-Br3C6H, 163-7°, 31.6; 1,3-(OTs)2-2,4,6-Me3C6H, 134-6°, 88; 1-(OH)-3-(OTs)-2,4,6-Me3C6H, 88-9°, 10; 1,3-(OTs)2-2,4,6-I3C6H, 263-5°, 95; 1,4-(OTs)2-2,3,5,6-Br4C6, 272-3°, 88; 1,4-(OTs)2-2,3,5,6-Me4C6, 274-5°, 72. Etherification of II with CH2N2 gave I (Ia), m. 65-7° (cyclohexane). Another polymorphic form of I (Ib), m. 153-5°, was prepd. either by alk. hydrolysis of I Me ester or methylation of II with Me2SO4. When seeded with Ib the lower m. polymorph Ia gave Ib. The reverse transformation failed. Two cryst. alkaloid salts of Ib were reported: Ib brucine salt, m. 168-70°, [a]205800 -25.23° (c 0.48, CHCl3); Ib quinidine salt, m. 215-16°, [a]20580 124.6° (c 0.634, CHCl3). In all cases the fractional crystn. and column chromatog. showed the presence of only one deriv., and thus the lack of stereosiomerism.
Bromination of phenols by use of benzyltrimethylammonium tribromide.
Chem. Lett. (1987), (4), 627-30.
Abstract
The reaction of phenols with benzyltrimethylammonium tribromide in CH2Cl2-MeOH for 1 h at room temp. gave polybromophenols in good yields.
Reaction of thionyl bromide with dihydric phenols.
Saraf, S. D.; Malik, Z. A.; Bhatti, Z.
Pak. J. Sci. Ind. Res. (1972), 15(3), 160-1. (In English)
Abstract
Pyrocatechol reacted with SOBr2 to give the 4,5-dibromo deriv.; hydroquinone with SOBr2 gave the 2,5-dibromo deriv. Resorcinol gave a high m.p. solid which was not identified. A possible reaction mechanism was described.
We need some Chinese Bee's!!!
Wonder if this works for HBr + HNO3???
Improvement of methods for synthesis of dihalogeno-1,4-benzoquinones.
Guan, Xiaopei; Sun, Li; Yan, Hong; Su, Zhuang.
Beijing Gongye Daxue Xuebao (1997), 23(1), 35-38.
ISSN: 0254-0037.(In Chinese) CAN 128:34554 AN 1998:10205
Abstract
The method for synthesis of 2-bromo-, 2,5-dibromo-1,4-hydroquinone, 2,5-dibromo-, 2,5-dichloro-, 2,3-dichloro-1,4-benzoquinones was improved. E.g., 2,5-dichloroquinone was prepd. in 51.7% yield by treating quinone with HCl and HNO3.