procedure to give a white crystalline product (7.6 g, 81%) that
was recrystallised from chloroform±petroleum ether (60±
saturated calomel electrode (SCE). The reaction was kept in an
inert atmosphere by the slow bubbling of nitrogen through the
solution. The compounds were added to an ef®ciently stirred
solution of aqueous NH4OAc (0.1 M) in the working
compartment and pH adjusted to ca. 9.0 with NH4OH and
maintained at this value for the duration of the experiment. The
solution was electrolysed at the appropriate potential (as
determined by CV, vs. SCE). Electrolysis was stopped when the
current returned to a low background value. The catholyte was
evaporated carefully (avoiding excessive foaming) using a
rotary evaporator at ca. 60 ³C. The residue was dissolved in
distilled water (40 ml) and to the solution was added Amberlite
IR 120 (30 ml, Hz-preactivated). The resin was decanted and
the supernatant was evaporated to dryness. Acetic acid was
removed by azeotropic distillation with toluene and water to
give a solid material, which was washed with ethanol to remove
soluble impurities. The solid product was dried under reduced
80 ³C). Mp 167±168 ³C (lit.10 167±168 ³C); IR n/cm21: 3200±
1
2500 (CO2H), 1689 (CLO), 661 (C±Br); H NMR (250 MHz,
CDCl3, dppm): 8.19 (1H, d, J~8.3 Hz, Ar, H-3), 8.16 (1H, d,
J~2.3 Hz, Ar, H-6), 8.12 (1H, s, Ar-CH-Br2), 8.00 (1H, dd,
J~8.3, 2.3 Hz, Ar, H-4), 7.25 (1H, s, Ar-CH-Br2).
Products
Polymer 3. 2,5-Bis(dibromomethyl)benzenesulfonic acid
(1b) (763 mg, 1.5 mmol) suspended in aqueous 0.1 M
NH4OAc (35 ml) was electrolysed at 21.3 V vs. SCE following
the general procedure described above. A viscous ¯uorescent
yellow solution was obtained after 3.3 F. Subsequent work-up
and drying gave a yellow solid (600 mg, 211%). IR (KBr), n/
cm21: 3500±2350 (NH4z, SO3H), 1680 (NH4z), 1627, 1604
(Ar, CLC), 1400 (NH4z), 1250±1100 (SO32, salt); 13C NMR
(75 MHz, solid, dppm): 140.4 (Ar, quaternary), 132.3 (Ar,
tertiary, CHLCH), 40.0 (CH2±CH2, weak signal), 21.2 (Me,
weak signal); (150 MHz, solution-D2O, dppm): 141±146 (Ar,
quaternary), 127±136 (Ar, tertiary, CHLCH), 75±80 (Ar±CH±
O), 45±47 (Ar±CH±(C)2 [crosslinking]), 35±40 (CH2±CH2,
pressure (0.5 mmHg, 24 h) and stored in
a desiccator.
Methylation of the polymers, when required, was accomplished
by heating (under re¯ux condition) the suspension of the
desired polymers in anhydrous MeOH for 4±5 days. Conver-
sion into sulfonamides required treatment with DMF at 100 ³C
until dissolution.11,12
1
weak signals), 22, 24 (Me, weak signals); H NMR (600 MHz,
solution-D2O, dppm): 6.7±8.3 (br s, Ar±H, CHLCH), 5.6±6.1 (br
s, CHLCH), 4.8±5.25 (ArCH±O), 2.90±3.60 (CH2±CH2, weak
signals), 2.1±2.7 (Me, weak signals); elemental analysis: ideal
formula, (C8H6SO3)n, found, (C8H5.7S0.9?H2O?N0.32H1.28)n (O
not analysed); molecular weight distribution, see Table 1.
Starting materials
Bromination of 1,4-dimethylarenes: general method. 2,5-
Dimethylbenzenesulfonic acid or 2,5-dimethylbenzoic acid
(0.04 mol) was added, under nitrogen to dry CHCl3 (300 ml).
The well-stirred suspension was heated under gentle re¯ux and
irradiated at close range with a 300 W UV lamp. Bromine
(0.082 or 0.164 mol, for dibromo or tetrabromo derivatives,
respectively), in dry CHCl3 (50 or 80 ml), was added dropwise
with vigorous re¯ux. During this period (ca. 2 h), HBr was
evolved copiously and when this ceased the solution was cooled
and the solvent removed. The solid product was recrystallised
from CHCl3±petroleum ether (60±80 ³C).
Polymer 4. 2,5-Bis(bromomethyl)benzenesulfonic acid (1a)
(688 mg, 2 mmol) suspended in 0.1 M NH4OAc (40 ml) was
electrolysed at 21.3 V vs. SCE as described in the general
procedure. When the current was returned to the background
level, electrolysis was stopped (1.6 F) and the viscous catholyte
solution was worked-up to give a beige solid (391 mg, 106%).
IR (KBr), n/cm21: 3413, 3161 (br, NH4z, SO3H), 1618 (Ar,
CLC), 1489, 1400 (NH4z), 1182, 1085, 1026 (SO32, salt); 13C
z
NMR (75 MHz, solid, dppm): NH4 salts, 140.8±138.4 (Ar,
2,5-Bis(bromomethyl)benzenesulfonic
acid
(1a). 2,5-
quaternary), 132.5 (Ar, tertiary), 37.1 (CH2±CH2), 22 (Me); 13
NMR (150 MHz, solution-D2O, dppm): 180 (CO2H), 147±138
and 138±132 (Ar, quaternary), 132±128 (Ar, tertiary), 41±33
C
Dimethylbenzenesulfonic acid (5.58 g, 0.03 mol) was bromi-
nated using the general procedure to give a white crystalline
product (4.1 g, 40%). Mp 96±98 ³C; IR (KBr), n/cm21: 1218,
1132 (SO3H), 634 (C±Br); 1H NMR (250 MHz, D2O/TSP,
dppm): 7.94 (1H, d, J~2.5 Hz, Ar, H-6), 7.62 (2H, m, Ar, H-
3,4), 4.98 (2H, s, Ar-CH2-Br), 4.62 (2H, s, Ar-CH2-Br).
1
(CH2±CH2), 24, 23 (Me); H NMR (600 MHz, solution-D2O,
dppm): 7.81±7.60 (Ar-H), 7.60±7.20 (Ar-H), 3.80±3.10 (CH2±
CH2), 2.3, 2.2 (Me); elemental analysis: ideal formula,
(C8H8SO3)n, found, C8H8S0.87?2H2O?N0.14H0.55 (O not ana-
lysed); molecular weight distribution, see Table 1.
2,5-Bis(dibromomethyl)benzenesulfonic acid (1b). 2,5-
Dimethylbenzenesulfonic acid (7.4 g, 0.04 mol) was bromi-
nated using the general procedure to give a white crystalline
product (14.2 g, 71%). This material was extracted with
dichloromethane (soxhlet) to remove remaining impurities.
Mp 146±147 ³C (lit.13 146.5±147.5 ³C; IR (KBr), n/cm21: 2925
Polymer 5. 2,5-Bis(dibromomethyl)benzoic acid (1d)
(936 mg, 2 mmol) in aqueous 0.1 M NH4OAc (40 ml) was
electrolysed at ±1.3 V vs. SCE as described in the general
procedure. After 2.8 F was consumed, the ¯uorescent viscous
solution was worked-up to give a yellow solid (305 mg, 104%).
IR (KBr), n/cm21: 3402 (CO2H), 1716 (CO2H), 1616 (Ar,
CHLCH); 13C NMR (150 MHz, solution-DMSO-d6, dppm):
168.6, 163.0 (CO2H), 120.0¡137.0 (Ar, CHLCH), 68.8±82.4
(ArCH-O), 45±60 (Ar±CH±(C)2 [crosslinking]), 37.7±40.0
1
(SO3H) 1218, 1132 (SO3H), 678 (C±Br); H NMR (600 MHz,
D2O/TSP, dppm): 8.18 (1H, d, J~8.1 Hz, Ar, H-3), 7.96 (1H, d,
J~2.1 Hz, Ar, H-6), 7.85 (1H, d, J~8.1, 2.1 Hz, Ar, H-4), 7.68
(1H, s, CH±Br2), 6.92 (1H, s, CH-Br2).
1
(CH2±CH2, weak signals), 21.99 (Me, weak signal); H NMR
2,5-Bis(bromomethyl)benzoic acid (1c). 2,5-Dimethylben-
zoic acid (7.4 g, 0.04 mol) was reacted with bromine (14 g,
0.082 mol) following the above general procedure to give white
crystalline 2,5-bis(bromomethyl)benzoic acid (1c) (3.6 g, 26%).
A second crop (3 g) was also isolated. Mp 115±116 ³C (lit.13
116 ³C); IR (KBr), n/cm21: 2970±2500 (CO2H), 1693 (CLO),
(600 MHz, solution-DMSO-d6, dppm): 7.0±8.5 (Ar-H), 5.80±
6.65 (CHLCH), 2.4±2.7 (Me); elemental analysis: ideal formula,
(C36H23?NH4)n, found, (C36.8H23?NH4)n (O not analysed);
molecular weight distribution, see Table 1.
1
1298±1200 (CO2H), 634 (C±Br); H NMR (250 MHz, CDCl3,
Copolymer 6. 2,5-Bis(bromomethyl)benzenesulfonic acid
(1a) (344 mg, 1.0 mmol) and 2,5-bis(bromomethyl)benzoic
acid (1c) (276 mg, 1.0 mmol) suspended in aqueous 0.1 M
NH4OAc (40 ml) were co-electrolysed at 21.3 V vs. SCE. The
pH of the catholyte was adjusted to ca. 9±10 before electrolysis
and maintained at this value throughout. Electrolysis was
stopped when the cell current went back to background level
dppm): 7.99 (1H, d, J~1.2 Hz, Ar, H-6), 7.47 (1H, dd, J~8.4,
1.2 Hz, Ar, H-4), 7.40 (1H, d, J~8.4 Hz, Ar, H-3), 4.98 (2H, s,
Ar±CH2±Br), 4.49 (2H, s, Ar±CH2±Br).
2,5-Bis(dibromomethyl)benzoic acid (1d). 2,4-Dimethylben-
zoic acid (3 g, 0.02 mol) was brominated using the general
J. Mater. Chem., 2000, 10, 2642±2646
2645