Synthesis of bis (ether nitrile)s and bis (ether acid)s from simple aromatic diols by meta-fluoro displacement from 3-fluorobenzonitrile

Article abstract of DOI:10.1039/a701127j

There is interest in synthesizing bis(ether acid)s and related compounds to use as monomers in order to prepare processable aromatic polymers, such as poly(ether amide)s and poly(ether ester)s. We have now found that it is possible to prepare efficiently

Full text of DOI:10.1039/a701127j

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Synthesis of bis(ether nitrile)s and bis(ether acid)s from simple aromatic diols by
meta-fluoro displacement from 3-fluorobenzonitrile†
GeoÂrey C. Eastmond* and Jerzy Paprotny
Donnan L aboratories, Department of Chemistry, University of L iverpool, PO Box 147, L iverpool, UK L 69 3BX
There is interest in synthesizing bis(ether acid)s and related compounds to use as monomers in order to prepare processable
aromatic polymers, such as poly(ether amide)s and poly(ether ester)s. We have now found that it is possible to prepare eÃciently
bis(3-cyanophenoxy)phenylenes by fluoro displacement from 3-fluorobenzonitrile and phenylene diols or their derivatives, such as
substituted catechols, and to convert those bis(ether nitrile)s to bis(3-carboxyphenoxy)phenylenes which can be used in the
synthesis of poly(ether amide)s and poly(ether ester)s. The meta-fluoro displacement is performed at elevated temperatures in
N-methylpyrrolidinone.
Following the development of processable poly(ether imide)s
I,1 we recently demonstrated that major enhancement in
processability can be achieved by modifying the substitution
pattern of the aromatic unit Ar between the ether linkages in
I, especially by inclusion of 1,2-linked units derived from
catechol or substituted catechols.2 It is logical to extend these
concepts to the synthesis of poly(ether amide)s and poly(ether
ester)s to achieve similar improvements in processability over
conventional aromatic polyamides.3
the same substitution pattern, there are nine possible isomers:
ppp(X) , pmp(X) , pop(X) , mpm(X) , opo(X) , etc.
2
2
2
2
2
Where substitution patterns of the terminal rings are para
or ortho, formation of the ether linkages by aromatic nucleo-
philic displacement (S Ar) reactions between a diol (to form
N
the central ring) and a suitably activated nitro- or halo-benzene
(Scheme 1) is easily achieved; Evers et al.5 used chloro displace-
ment reactions while we used fluoro displacement.3 In these
reactions an activating group X may be a precursor of a
desired X in structures II. Thus, MCN or MNO groups are
2
activating groups and are also precursors to MCOOH and
MNH , respectively. The leaving group Y is preferably NO
2
2
or F and is strongly activated if it is ortho- or para- to X. In
this way we have prepared a variety of popX and oooX
2
2
bis(ether acid)s and bis(ether amine)s from catechol and
substituted catechols and have used these in the synthesis of
poly(ether amide)s and poly(ether ester)s.3 These syntheses are
relatively trivial. pop(CN) and pop(COOH) have also
2
2
recently been prepared by others and used in the synthesis of
poly(ether amide)s.7,8
A problem has been to prepare such materials in which the
substitution pattern in the outer rings is meta, e.g. as mpmX ,
2
mmmX or momX , eÃciently because, according to the rules
2
2
of S Ar reactions, if Y is meta to X it is not suÃciently
N
activated to leave. Evers et al. recognised this problem and
synthesized mpm(COOH) by a two-stage process, reacting the
2
sodium salt of meta-cresol with dibromobenzenes in pyridine
To achieve this end, poly(ether amide)s can be prepared
from either/or both bis(ether acid)s or bis(ether amine)s of
structure II, with diÂerent substitution patterns at each aro-
matic residue. Thus, the synthesis of substances with structure
II is of interest. A number of bis(ether nitrile)s IIa, used in
poly(benzoxazole) synthesis,4 bis(ether acid)s IIb, a bis(ether
acid chloride) IIc5 and a bis(ether amine) IIc6 have long been
known. Evers et al.5 used an aromatic nucleophilic displace-
ment reaction between p-chlorobenzonitrile and various diols
to prepare bis(ether nitrile)s directly, some of which were
hydrolysed to the bis(ether acid)s. Thus, Evers et al. prepared
bis(ether nitrile)s and bis(ether acid)s and devised a nomencla-
ture based on the substitution patterns of the rings, e.g.
ppp(COOH) , pop(COOH) .5 We have adapted this system to
in the presence of copper() chloride and oxidizing the resulting
dialkyl species with potassium permanganate in pyridine to
obtain the diacid in 38% overall yield.5 Synthesis of the
mpm(CN) was a five-stage synthesis with a yield of 8.5%.
2
We have now demonstrated that, when X is MCN, meta-
fluoro displacement is easily achieved in high yield according
to Scheme 2 at elevated temperatures when fluorobenzonitrile
III is reacted, under suitable conditions, with a diol IV
(Table 1). Thus, mom(CN) -type bis(ether nitrile)s become
2
immediately available and, after hydrolysis, bis(ether acid)s of
2
2
allow for substituents on the rings, thus we have, for example,
p(3Me)op(COOH) for the diacid in which the terminal rings
2
are para-linked and unsubstituted while the central ring is
ortho-linked and carries a 3-methyl substituent. For unsubsti-
tuted species II which are symmetrical, i.e. the outer rings have
† Presented in part at ‘Polycondensation ’96’, International Symposium
on Polycondensation, Paris, 1996.
Scheme 1
J. Mater. Chem., 1997, 7(8), 1321–1326
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Scheme 2
Table 1 Diols used in fluoro displacement reactions with mnemonics
Synthesis of 1,2-bis(3-cyanophenoxy)benzene [mom(COOH) ]
Procedure A. Catechol (>99%) (44 g, 0.4 mol) and 500 ml
2
used in bis(ether nitrile) and bis(ether acid) nomenclature
N-methylpyrrolidone (NMP) were placed in a flask equipped
with magnetic stirrer bar, thermometer, nitrogen inlet, Dean
Stark trap and reflux condenser. The mixture was thoroughly
deoxygenated with a stream of nitrogen. Anhydrous potassium
carbonate (100 g) and xylene (100 ml) were added. Under a
stream of nitrogen, the mixture was brought to the boil and
dried azeotropically. 3-Fluorobenzonitrile (100 g) was added
and reflux continued for 6 h with a flask temperature of
178–184 °C. Then, over a period of 2 h, most of the xylene was
distilled o while the temperature rose to 204 °C. The dark
brown mixture was precipitated into 4 l of ice–water mixture,
the solid was filtered o and washed with deionized water
until neutral. The brown crystalline mass was recrystallized
from 1.5 l of methanol and 200 ml of water to yield 109 g
(crude yield 87.3%) of brown crystals. The crude dinitrile was
treated with Norit decolourizing agent and recrystallized from
1 l of methanol and 80–100 ml of water three times. The final
yield of white crystals was 83 g (66.5% theoretical), mp
99–100 °C, with a further 6.4 g of slightly coloured crystals;
details are recorded in Table 2.
diol
code
mnemonic
Procedure B. This procedure was similar to Procedure A
except that toluene was used to remove water azeotropically;
flask temperature was 140 °C. The product was isolated as in
Procedure A and purified by two recrystallizations with decol-
ourizing charcoal from methanol–water (551); results are pre-
sented in Table 2.
Procedure C. This procedure was identical to Procedure B
except that dimethylformamide (DMF) was used as solvent;
the reaction temperature was 120 °C and results are presented
in Table 2.
the type mom(COOH) etc. and, subsequently, bis(ether acid
2
chloride)s, including their derivatives from substituted cat-
echols, are also available (Scheme 2). Bis(ether nitrile)s can be
used directly in the synthesis of poly(benzobisoxazole)s;4
bis(ether acid)s can be used in the synthesis of poly(ether
amide)s and poly(ether ester)s. We report here the synthesis of
the bis(ether nitrile)s and bis(ether acid)s from catechol, and
2,3-dihydroxynaphthalene, the bis(ether nitrile) from 3,5-di-
tert-butylcatechol and other related materials. Diols VIa–f
used are identified in Table 1 where their mnemonics used in
the above nomenclature are defined. Polymers were prepared
from some of the monomers to demonstrate their use in
polymer synthesis.
Preparation of 1,2-bis(3-carboxyphenoxy)benzene [mom
(COOH) ]. Bis(ether nitrile) mom(CN) (80 g) was placed in
2
2
a round-bottomed flask with a solution of 80 g of potassium
hydroxide in 130 ml of water, followed by 100 ml of methanol.
The mixture was refluxed for 10 h, after which evolution of
ammonia could not be detected. The mixture was diluted to
2.5 l and acidified to pH 1.5. The product was filtered o and
dispersed in 2.5 l of deionized water, warmed to 80–90 °C,
filtered and washed three times with deionized water. The wet
cake was dissolved in 2 l of acetic acid and tetrahydrofuran
(THF) (451). Other diacids were prepared similarly from the
corresponding bis(ether nitrile)s, and data are given in Table 3;
Experimental
Materials
3-Fluorobenzonitrile was obtained from Fluorochem. Other
reagents were obtained from Aldrich Chemical Company and
were used without further purification (catechol was recrys-
tallized from toluene) or were general laboratory reagents.
the discrepancy between melting points of mmm(COOH)
NMR and melting point data were confirmed from independent
syntheses by two workers.
2
found in this work and ref. 4 is unexplained but our analytical,
1322
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Table 2 Synthesis of bis(ether nitrile)s
elemental analysis (%)
melting
yield
(%)
designationa
procedure
C
H
N
point/°C
mom(CN)
calc.
76.91
77.1
3.87
3.81
8.97
8.93
2
A
B
C
A
A
B
found
99–100
87 (crude)
99.2–99.7
70
20
78
mpm(CN)
calc.
76.91
76.91
76.91
76.76
79.54
79.77
79.21
79.38
76.91
76.90
3.87
3.87
3.87
3.84
3.89
3.88
6.64
6.67
3.87
3.84
8.97
8.90
8.97
8.89
7.73
7.71
6.60
6.58
8.97
8.94
143.4–143.7
139.5–141b
90.2–90.6
81–82c
2
found
calc.
mmm(CN)
m(2,3N)om(CN)
m(3,5dtB)om(CN)
49
51
52
96
2
found
calc.
157–158
2
found
calc.
118–119
2
B
found
calc.
pop(CN)
C
116.8–117.3
116.5–117.5b
117–118d
2
found
116.5–118e
105.4–105.8
ooo(CN)
C
calc.
76.91
77.07
3.87
3.85
8.97
9.02
85
2
found
aSystematic names: mom(CN) =1,2-bis(3-cyanophenoxy)benzene; mpm(CN) =1,4-bis(3-cyanophenoxy)benzene; mmm(CN) =1,3-bis(3-cyano-
2
2
2
phenoxy)benzene; m(2,3N)om(CN) =2,3-bis(3-cyanophenoxy)naphthalene; m(3,5dtB)om(CN) =1,2-bis(3-cyanophenoxy)-3,5-di-tert-butylben-
2
2
zene; pop(CN) =1,2-bis(4-cyanophenoxy)benzene; ooo(CN) =1,2-bis(2-cyanophenoxy)benzene. bRef. 5. cRef. 9. dRef. 7. eRef. 8.
2
2
Table 3 Synthesis of bis(ether acid)s and a bis(ether acid chloride)
elemental analysis (%)
melting
yield
(%)
designation
C
H
Cl
point/°C
mom(COOH) a
calc.
68.57
68.49
68.57
68.57
68.57
68.40
72.00
72.14
68.57
68.57
68.57
68.60
62.03
61.89
4.03
3.99
4.03
4.03
4.03
4.04
4.03
3.98
4.03
4.02
4.03
3.97
3.12
3.12
265–267
99
2
found
calc.
mpm(COOH)
318.9–319.2
305–313b
205.5–206.1
269–274b
260–262
257–258
257–258c
255–256d
184–185
2
found
calc.
70
80
89
mmm(COOH)
2
found
calc.
m(2,3N)om(COOH)
2
found
calc.
pop(COOH)
84
2
found
ooo(COOH)
calc.
90
63
2
found
calc.
mom(COCl)
18.31
17.47
74–76
2
found
aSystematic names: mom(COOH) =1,2-bis(3-carboxyphenoxy)benzene; mpm(COOH) =1,4-bis(3-carboxyphenoxy)benzene; mmm(COOH) =
2
2
2
1,3-bis(3-carboxyphenoxy)benzene; m(2,3N)om(COOH) =2,3-bis(3-carboxyphenoxy)naphthalene; pop(COOH) =1,2-bis(4-carboxyphenoxy)
2
2
benzene; ooo(COOH) =1,2-bis(2-carboxyphenoxy)benzene; mom(COCl) =1,2-bis[3-(chlorocarbonyl)phenoxy]benzene. bRef. 5. cRef. 7. dRef. 8.
2
2
Syntheses of 1,2-bis(4-cyanophenoxy)benzene [pop(CN) ],
Preparation of polymers by the phosphorylation technique.
Anhydrous calcium chloride (0.6 g) and lithium chloride (0.2 g)
were dissolved in anhydrous NMP (13 ml), under a nitrogen
atmosphere. Anhydrous pyridine (4 ml) was added, followed
by 1,2-bis(3-carboxyphenoxy)benzene (0.70 g, 2 mmol) and
para-phenylenediamine (PPD; 2 mmol). The mixture was
stirred under nitrogen and triphenyl phosphite (2 ml) was
added. The temperature was raised to 105 °C for 5 h when
additional triphenyl phosphite (1 ml) and pyridine (1 ml) were
added and the mixture was stirred at 110 °C. The resulting
viscous liquid was poured into 300 ml of methanol–water
(80:20). The polymer was filtered o and extracted with boiling
methanol for 1 h. The yield of polymer was 0.78 g. Other
2
1,2-bis(2-cyanophenoxy)benzene [ooo(CN) ] and their corre-
2
sponding diacids pop(COOH) and ooo(COOH) . Fluoro dis-
2
2
placements from p-fluorobenzonitrile and o-fluorobenzonitrile
were performed with catechol according to procedure C to
yield pop(CN) and ooo(CN) , respectively. The bis(ether
2
2
nitrile)s were hydrolysed to pop(COOH) and ooo(COOH)
2
2
as described above for mom(COOH) . Details are given in
2
ref. 3 and results in Tables 2 and 3.
Preparation of 1,2-bis(3-chlorocarbonylphenoxy)benzene
[mom(COCl) ]. 1,2-Bis(3-carboxyphenoxy)benzene (10 mmol)
2
was boiled under reflux, protected with a calcium chloride
guard tube, in a nitrogen atmosphere with ca. 20 mmol of
thionyl chloride for 2 h. Excess thionyl chloride was distilled
o under vacuum which was finally reduced to 0.2–0.5 Torr.
The crude acid chloride was dissolved in 50 ml of cyclohexane,
about one third of which was then distilled oÂ, and the residual
solution left to crystallize. The crude acid chloride was sublimed
from a thoroughly degassed melt at ca. 200 °C at 0.5 Torr
pressure (Table 3).
poly(ether amide)s were prepared similarly from pop(COOH)
2
and m-phenylenediamine (MPD) and from m(2,3N)om
(COOH) with MPD.
2
Polymers from 1,2-bis(3-chlorocarbonylphenoxy)benzene
[mom(COCl) ] and MPD. MPD (1 mmol) was dissolved in
2
7 ml of N,N-dimethylacetamide (DMAC) containing 8.7%
CaCl and 0.7 ml of pyridine. The mixture was cooled to
2
J. Mater. Chem., 1997, 7(8), 1321–1326
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−14 °C, mom(COCl) (1 mmol) was added and the mixture
converted to mom(COCl) by reaction with thionyl chloride
2
2
was stirred vigorously for 2.5 h during which period it became
(Table 3).
very viscous. The mixture was kept overnight at ca. 0 °C in a
Thus, it is now possible to prepare readily a series of
monomers, bis(ether nitrile)s, bis(ether acid)s and bis(ether
acid chloride)s of type II in which the terminal aromatic rings
are meta-substituted. These monomers can be, and have been,
used in the synthesis of poly(ether amide)s or poly(ether ester)s.
The synthesis of representative poly(ether amide)s is described
in the preceding section.
refrigerator, followed by 24 h at room temperature. The poly-
mer was precipitated into MeOH–H O, twice extracted with
2
boiling MeOH and dried.
Syntheses of poly(ether ester) by transesterification. mom-
(COOH) (3.0 mmol), hydroquinone diacetate (3.0 mmol),
2
In contrast, synthesis of equivalent dinitro species IId, pre-
cursors to diamines IIe, by fluoro displacement from meta-
fluoronitrobenzene is not eÂective under comparable con-
ditions. When the corresponding fluoro displacement reaction
was performed with catechol under reaction conditions equival-
ent to Procedures A or B only black tars were recovered and
we failed to extract pure dinitro compound.
dibutylin oxide (0.002 g) and m-terphenyl (3–4 g) were melted
and stirred under nitrogen. Within 1–1.5 h the temperature
was raised to 340 °C. The reaction was run for 5–8 h, gradually
raising the temperature to 370–380 °C. After cooling to 110 °C
the viscous melt was poured into acetone or into toluene–
methanol (40560). The polymer was filtered o and extracted
with boiling acetone or methanol and dried. Yields of polymer
were ca. 80%. Polymers were subjected to preliminary testing
for solubility and for ability to pull fibres from the melt.
It is of interest to consider the eÂectiveness of the displace-
ment reaction with meta-activated species. Electron-with-
drawing groups meta to a leaving group are less activating
than the same group in an ortho- or para-position. Even so,
meta-nitro and nitrile groups do have some activating propen-
sity. Terrier has commented that, ‘while two nitro groups may
Instruments
1H and 13C NMR spectra were recorded on a Bruker AMX400
spectrometer. Accurate molar masses were determined on a
VG Analytical 7070E mass spectrometer.
provide suÃcient activation to allow clean S Ar processes to
N
occur, single meta-nitro groups are too weakly activated for
S Ar processes and there is a high tendency to react by
N
alternative pathways’.10 In addition, it is usual to consider that
Results and Discussion
the nitrile group is less activating than the nitro group.10
However, in this work, we find that, at elevated temperatures,
a single nitrile group in a meta-position is suÃcient to activate
fluoro displacement and there is no reason to believe that
Synthesis of monomers and precursors
Experiments demonstrated that the eÃcient synthesis of
bis(ether nitrile)s, precursors to bis(ether acid)s, where CN is
meta to the ether linkage is very sensitive to reaction conditions.
Conditions for fluoro displacement from meta-fluorobenzo-
reaction proceeds by other than a normal S Ar process.
N
meta-Nitro displacement reactions are uncommon but are
known in, for example, nitro displacement from meta-dinitro-
benzene by methoxide or thiophenoxide anion in hexamethyl-
phosphoramide (HMPA) at room temperature,11 between the
same reagents in chlorobenzene (80 °C) under phase transfer
conditions12 and by potassium fluoride in HMPA at 180 °C.13
nitrile were optimised for the parent mom(CN) as Procedure A.
2
These reaction conditions were also applied to the syntheses
of mpm(CN) and mmm(CN) with the results presented in
2
2
Table 2.
Bis(ether nitrile)s were also prepared from 2,3-dihydroxy-
naphthalene and 3,5-di-tert-butylcatechol to give m(2,3N)
om(CN) and m(3,5dtB)om(CN) , respectively; the syntheses
Idoux et al. have shown that m-NO and m-CN will activate
2
nitro displacement and m-NO fluoro displacement by 2,2,2-
2
trifluoroethoxide anion at 25 °C.14 Yoshikawa et al. have now
2
2
of these materials were not optimised, and conditions used
were Procedure B. Results are presented in Table 2. Data for
demonstrated that it is possible, by reacting m-dinitrobenzene
in aprotic solvents with various bisphenols, to achieve m-nitro
displacement in the presence of a base such as potassium
carbonate at elevated temperatures. They achieved good yields
(>90%) with many bisphenols but <60% with hydroquinone
and did not report results with other phenylene diols.15 The
use of diols without prior formation of the phenoxide anion is
important with catechol and its derivatives because of oxidative
side reactions and there is no prior report of catechols being
used in m-nitro displacement or m-fluoro displacement
reactions.
mom(CN) show that success in these reactions, in terms of
2
yield and cleanliness of product, is very dependent on the
reaction temperature. We previously found, when synthesizing
pop(CN) and ooo(CN) , that cleaner products were obtained
2
2
by performing the nitrodisplacement reaction in DMF,
Procedure C (Table 2); purity of the bis(ether nitrile) intermedi-
ates assists in producing pure bis(ether acid)s necessary for
synthesis of high molecular mass polymers. However, in the
synthesis of mom(CN) -type species Procedure C was unsatis-
2
factory; reaction yields were low (ca. 20%) and products black.
Kirst and Una showed that fluoro displacement between
nitrofluorobenzenes and methoxide with a para-nitro group is
faster than with a meta-nitro group by a factor of ca. 103 at
100 °C; this factor decreases at higher temperatures.16 Taking
values of s− for para-CN and meta-CN as 0.88 and 0.56,
respectively, it is estimated that, at 100 °C, para-CN is less
It was only with diÃculty that a satisfactory sample of
mom(CN) was obtained by Procedure C, despite giving a
2
96% yield of pure pop(CN) . Optimum conditions for the
2
synthesis of mom(CN) are NMP as solvent with a reflux
2
temperature of ca. 180 °C. Thus, conditions required to produce
good yields of pure products from meta-activated species diÂer
significantly from those where ortho- or para-activation is used.
It is also necessary to perform the reactions under an atmos-
phere of nitrogen to minimise side reactions which lead to
dark products. Nevertheless, it is now clear that pure materials
reactive than para-NO by a factor of ca. 100 and that meta-
2
CN is less reactive than para-CN by a factor of ca. 80.17 These
data still predict that meta-NO would be more reactive than
2
meta-CN. Despite our observation that meta-CN-activated
fluoro displacement is more eÂective than the meta-NO -
2
of type mom(CN) can readily be achieved (Table 2).
activated reaction, there is no obvious reason to invoke a
2
Hydrolyses of all mxm(CN) species (x represents any substi-
pathway other than normal fluoro displacement.
2
tution pattern of the central aromatic ring or other aromatic
The exact compositions of species with meta-outer rings
species) are readily achieved and a typical set of reaction
conditions is described above. Hydrolysis produces pure
bis(ether acid) in high yield (Table 3). Further, to prepare high
molecular mass polyamides it is most convenient to react acid
were confirmed by accurate mass determinations by mass
spectrometry. The calculated molar mass for mxm(COOH)
2
species is 350.07904 and observed masses were 350.07889,
350.07855 and 350.07889 for mpm(COOH) , mmm(COOH)
2
2
chlorides with diamines and, to this end, mom(COOH) was
and mom(COOH) respectively; the calculated value for
2
2
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Table 4 1H NMR parameters for bis(ether acid)s in [2H ]DMF; chemical shifts and coupling constants for designated protons and proton pairs
7
diacid
mpm
mmm
mom
pop
chemical shifts and coupling constants
d
H(2,3,5,6)7.24;H(2∞,5∞)7.60;H(4∞)7.80;H(6∞)7.35
(2∞,4∞)1.50;(2∞,6∞)2.54;(4∞,5∞)7.69;(4∞,6∞)1.07(5∞,6∞)8.24
H(2)6.86;H(4,6)6.93;H(5)7.50;H(2∞)7.63;H(4∞)7.82;H(5∞)7.60;H(6∞)7.39
(2,4)2.35;(4,5)8.21;(2∞,4∞)1.54;(2∞,6∞)2.58;(4∞,5∞)7.70;(4∞,6∞)0.98;(5∞,6∞)8.18
H(3,4,5,6)7.36;H(2∞)7.45;H(4∞)7.73;H(5∞)7.50;H(6∞)7.18
(2∞,4∞)1.49;(2∞,6∞)2.67;(4∞,5∞)7.64;(4∞,6∞)1.03;(5∞,6∞)8.22
H(3,4,5,6)7.34;H(2∞)7.01;H(3∞)8.0
J/Hz
d
J/Hz
d
J/Hz
d
J/Hz
d
(2∞,3∞)8.98
ooo
H(3)7.01;H(4,5)7.19;H(6)7.01;H(3∞)7.90;H(4∞)7.25;H(5∞)7.56;H(6∞)7.10
(3∞,4∞)7.78;(3∞,5∞)1.48;(4∞,5∞)7.33;(4∞,6∞)0.95;(5∞,6∞)8.22
J/Hz
m(2,3N)om(COOH) was 400.09518 compared with an exper-
and ooo(COOH) were soluble in NMP. An example high
2
2
imental value of 400.09518; errors were all less than 0.0005.
molecular mass poly(ether amide) was prepared from
Any alternative pathway might be expected involve isomeriz-
ation and formation of isomers during reaction but no such
change of substitution pattern occurs. NMR evidence is quite
clear that meta-fluoro displacement with diols gives rise to
meta-nitrile ethers. Splitting patterns for mom, mpm, mmm, ppp,
pmp, pop and ooo bis(ether nitrile)s and bis(ether acid)s are all
diÂerent and entirely consistent with the products of the
various species being obtained by normal aromatic nucleophilic
displacement reactions with retention of substitution patterns.
Thus, for all species VIII with meta-substitution in the outer
rings, 1H NMR spectra show distinctive spectra with very
similar chemical shifts and coupling constants for those protons
(Table 4); in Table 4 primes are used to denote protons in the
outer aromatic rings, absence of primes refers to protons on
the central ring. This pattern is quite diÂerent from those for
para- and ortho-substitution in the outer rings. In addition,
the splitting pattern for protons on the central rings for
mom(COOH) and pop(COOH) are identical complex mul-
mom(COCl) and MPD.
2
The low molecular mass poly(ether amide)s prepared from
mom(COOH) and PPD or MPD by the phosphorylation
2
technique were fusible and short fibres could be pulled from
the melts. The higher molecular mass poly(ether amide) pre-
pared from mom(COCl) and MPD was also fusible and long
2
fibres could (>10 cm) be drawn from the melt. The poly(ether
ester) prepared from mom(COOH) and hydroquinone diacet-
2
ate by the transesterification procedure described above was
also fusible and short, brittle fibres could be drawn from
the melt.
Conclusions
We have demonstrated the feasibility of performing eÃcient
meta-displacement reactions between m-fluorobenzonitrile and
phenylene diols, including catechol and its derivatives, to
produce bis(ether nitrile)s in NMP at elevated temperatures
and, from them, bis(ether acid)s which can be readily incorpor-
ated into poly(ether amide)s or poly(ether ester)s. This develop-
ment completes the possibilities of making bis(ether acid)s and
related compounds based on structure II with all possible
substitution patterns at all aromatic rings.
2
2
tiplets characteristic of an AA∞BB∞ system with a small coupling
constant; the pattern for ooo(COOH) is somewhat diÂerent
2
and is resolved into two multiplets but still characteristic of
an AA∞BB∞ system with a slightly increased coupling constant.
Further, the calculated chemical shifts for all protons in the
outer rings and for all carbons in all rings are almost identical
with those observed from 1H and 13C NMR.18 Thus, there is
no doubt that initial substitution patterns of the rings are
The authors wish to thank E. I. du Pont de Nemours and Co
Inc. for financial support which enabled this work to be
undertaken, Professor D. Bethell for useful discussion on
nucleophilic substitution reactions and Dr M. Gibas (Silesian
Technical University, Gliwice) for help with NMR spectroscopy
and calculation of theoretical chemical shifts.
maintained during the S Ar process.
N
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