Process for preparing .alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its lower alkyl ester

A process for producing an .alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its ester, that has a high Young's modulus and that is useful as a material for polyesters capable to form self-extinguishing fibers and films. Thus .alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its ester is obtained by reacting .alpha.,.omega.-bis(phenoxy)alkane-4,4'-dicarboxylic acid or its ester with chlorine in the presence of a solvent selected from the group consisting of lower fatty acid having 2 to 6 carbon atoms, hydrocarbon chloride having 1 to 8 carbon atoms, and carbon chloride having 1 to 2 carbon atoms, in high yield.

FIELD OF THE INVENTION 
This invention relates to a process for preparing 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
lower alkyl ester in high yield. 
DESCRIPTION OF THE PRIOR ART 
It is known that a polyester is obtained by condensation reaction of 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
derivatives represented by the following formula 
##STR1## 
(wherein R denotes a radical selected from hydrogen and lower alkyl 
radical, n denotes an integer of 2,4, and 6), 
and an alkylene glycol (Published Examined Japanese Patent Application Nos. 
1795/74 and 13238/74). 
In the prior art, the above mentioned chlorinated dicarboxylic acid was 
prepared by a process comprising chlorinating p-hydroxy benzoic acid or 
its ester, and reacting the resulting product with 
.alpha.,.omega.-dihalogeno polymethylene(Published Examined Japanese 
Patent Application No. 11899/75). 
##STR2## 
However, in the ether forming reaction of this prior art, when 
.alpha.,.omega.-dibromo polymethylene is used as a reactant, the yield is 
60 to 75 percent (refer to the Examples of Published Examined Japanese 
Patent Application No. 11899/75), but the following problem has existed. 
That is, since NaBr which is by-produced in the reaction causes the severe 
corrosion of the metal, the usual reaction vessel made of stainless steel 
was not able to be used. 
Moreover, .alpha.,.omega.-dibromo polymethylene is expensive. On the other 
hand, when .alpha.,.omega.-dichloro polymethylene is used as a starting 
material, the yield is at most 40 percent (refer to Comperative Examples 
in the present invention). Therefore, since the total yields of the 
halogenation reaction and the ether forming reaction become even lower, 
the preparation method is disadvantageous to adapt for industrial use. 
Accordingly, the object of the invention is to provide an economical 
process for preparing pure 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
lower alkyl ester in high yield. 
The foregoing object is effectively accomplished by heating 
p-hydroxybenzoic acid or its lower alkyl ester with alkylene dichloride, 
to obtain .alpha.,.omega.-bis(phenoxy)alkane-4,4'-dicarboxylic acid or its 
lower alkyl ester (ether forming reaction), and reacting it with chlorine 
in the presence of a particular solvent(chlorination reaction). 
Typical reactions are: 
##STR3## 
DISCLOSURE OF THE INVENTION 
The present invention is a process for preparing 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
lower alkyl ester which comprises reacting 
.alpha.,.omega.-bis(phenoxy)alkane-4,4'-dicarboxylic acid or its lower 
alkyl ester with chlorine in the presence of a solvent selected from the 
group consisting (a) lower fatty acid having 2 to 6 carbon atoms, (b) 
hydrocarbon chloride having 1 to 8 carbon atoms, and (c) carbon chloride 
having 1 to 2 carbon atoms, in the absence or presence of a catalyst at a 
lower temperature than boiling point of said solvent. 
Furthermore, the present invention is a process wherein 
.alpha.,.omega.-bis(phenoxy)alkane-4,4'-dicarboxylic acid or its lower 
alkyl ester obtained by heating p-hydroxybenzoic acid or its lower alkyl 
ester with alkylene dichloride is used as a starting material. 
In general, when a complicated compound having a high molecular weight is 
chlorinated, many by-products are produced lowering the purity or yield of 
the product, since the complicated compound has various positions capable 
of being chlorinated. Therefore the chlorination reaction is usually 
carried out in a simple compound having a low molecular weight, prior to 
the other reaction. 
However, in the present invention, it has found that 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
lower alkyl ester can be prepared by selective mono-chlorination in the 
ortho-position to the neighboring oxygen atom of the aromatic ring of the 
.alpha.,.omega.-bis(phenoxy)alkane-4,4'-dicarboxylic acid or its lower 
alkyl ester. 
PREFERRED EMBODIMENT OF THE INVENTION 
Hereinafter, the present invention is described in detail. 
.alpha.,.omega.-bis(phenoxy)alkane-4,4'-dicarboxylic acid or its lower 
alkyl ester, prepared by various methods, may be used as a starting 
material. 
A preferable method for preparation is the reaction of p-hydroxybenzoic 
acid or its lower alkyl ester with alkylene dichloride. p-Hydroxybenzoic 
acids or their lower alkyl esters, used in this reaction include, for 
example, p-hydroxybenzoic acid, methyl p-hydroxybenzoate, ethyl 
p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, and 
the like. Among them, p-hydroxybenzoic acid or its methyl ester may be 
preferably used. 
As alkylene dichloride, .alpha.,.omega.-dichloro polymethylene dichloride 
having 1 to 6 carbon atoms may be used. Alkylene dichlorides include, for 
example, ethylene dichloride, butylene dichloride, hexamethylene 
dichloride, and the like. Among them, ethylene dichloride may be 
preferably used. The amount of alkylene dichloride may be about 0.5 to 1.5 
times the molar amount of p-hydroxybenzoic acid or its lower alkyl ester. 
The reaction of p-hydroxybenzoic acid or its lower alkyl ester and alkylene 
dichloride may be carried out at a temperature in the range of about 
80.degree. to about 200.degree. C. The reaction may be carried out either 
at atmospheric pressure or at stressed pressure, preferably at stressed 
pressure. Thus obtained 
.alpha.,.omega.-bis(phenoxy)alkane-4,4'-dicarboxylic acid or its ester may 
be isolated and purified for example, by cooling the reaction mixture, 
filtrating the deposited crystal, and washing it with lower alcohol or 
water. 
.alpha.,.omega.-bis(phenoxy)alkane-4,4'-dicarboxylic acids or their lower 
alkyl esters, used as a starting material, include, for example, 
1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, 
1,4-bis(phenoxy)butane-4,4'-dicarboxylic acid, 
1,6-bis(phenoxy)hexane-4,4'-dicarboxylic acid, and their dimethyl ester, 
diethyl ester, dipropyl ester, and dibutyl ester and the like. Dimethyl, 
diethyl, dipropyl, dibutyl ester of 
1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid; dimethyl, diethyl, 
dipropyl, dibutyl ester of 1,4-bis(phenoxy)butane-4,4'-dicarboxylic acid; 
dimethyl, diethyl, dipropyl, dibutyl ester of 
1,6-bis(phenoxy)hexane-4,4'-dicarboxylic acid, may be preferably used. In 
particular dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate is most 
preferably used. 
Lower fatty acids having 2 to 4 carbon atoms used as a solvent include, for 
example, acetic acid, propionic acid, butanoic acid, and the like. Among 
them, acetic acid may be most preferably used. 
Hydrocarbon halides and carbon halides used as a solvent include, for 
example, chlorobenzene, chlorotoluene, chloroxylene, dichlorobenzene, 
dichlorotoluene, trichlorobenzene, trichlorotoluene, carbon 
tetra-chloride, hexachloroethane, chloroform, dichloroethane, 
trichloroethane, tetrachloroethane, and the like. More than two solvents 
may be simultaneously used. Among them, chlorobenzene, dichlorobenzene and 
tetrachloroethane may be preferably used, and in particular 
dichlorobenzene (especially ortho-dichlorobenzene) or 
1,1,2,2-tetrachloroethane may be most preferably used. 
In the above mentioned reaction, a 2 to 4 mole ratio of 
chlorine/dicarboxylic acid or its lower ester of starting material, may be 
preferably employed, especially preferably 2 to 3.5. 
The reaction was carried out by firstly dissolving the dicarboxylic acid or 
its ester in the above mentioned solvent to obtain the solution, and then 
blowing the chlorine gas through the solution. The reaction temperature 
may be employed below the boiling point. In particular a range of 
90.degree. to 140.degree. C. may be suitable employed, when acetic acid, 
o-dichlorobenzene, or 1,1,2,2-tetrachloroethane, and the like that is 
preferable solvent in the present invention is used. 
The solvent is required in an amount to dissolve the dicarboxylic acid or 
its ester of the starting material. For example, when dimethyl 
1,2-bis(phenoxy)ethane-4,4'-dicarboxylate is employed as a starting 
material, the amount of acetic acid may be more than about 3 times, 
preferably 4 to 10 times, and the amount of ortho-chlorobenzene may be 
more than 1 times, preferably 2 to 15 times, and the amount of 
tetrachloroethane may be more than 1 times, preferably 1 to 9 times. 
Still, when carbonchloride or hydrocarbon chloride is employed as a 
solvent, in the above mentioned reaction, Lewis acid, especially boron 
trifluoride, iodide, sulfuric acid, more preferably iodide may be added as 
a catalyst. By the addition, the yield improves. 
The reaction may be carried out at any pressure including atmospheric 
pressure, or stressed pressure, reduced pressure. For industrial use, 
atmospheric pressure or slightly stressed pressure may be preferably 
employed. 
The reaction may be carried out batchwise, continously or semicontinously. 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
ester, the objective of the present invention, is efficiently obtained in 
high yield by cooling the reaction mixture after chlorination and 
filtering the product or by pouring the reaction mixture into a large 
quantity of water, filterating the precipitate, washing, and drying. 
Moreover, the crystal of 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
ester obtained by the present invention, were white. The prior art had the 
following defect. That is, the crystals of 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
ester obtained by the prior art was coloured yellow because of a slight 
amount of coloured impurities which, could not be removed by the usual 
purification techniques (For example, a polymer colored brown was obtained 
by the polymerization reaction of this dicarboxylic or its ester and 
alkylene glycol). In present invention, the white crystals, not coloured 
yellow, can be obtained.

This invention will be more clearly understood by the following examples. 
In the examples, all parts are by weight, and b-values are units to denote 
the yellowish degree (the higher the b-value is, the more yellowish the 
crystals and the like are), as measured by Sand M Colour Computer produced 
by Suga Shikenki Co. 
EXAMPLE 1 
Into a vessel equipped with a reflux condenser, were charged 50 g (0.15 
mole) of dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate and 450 g of 
acetic acid. Then, the temperature of the reaction vessel was raised to 
95.degree. to 105.degree. C. with stirring. 
After dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate was completely 
dissolved, the reaction mixture was maintained at the same temperature 
with introducing 23 g (0.33 mole) of the chlorine gas into the reaction 
vessel for two hours. 
Thereafter, the reaction mixture was cooled to the room temperature. The 
white precipitates formed were filtered off and dried. The yield of this 
white precipitates was 90%. 
The melting point of the compound purified by recrystallization from 
toluene was 204.degree. to 206.degree. C., and the colour tone (b value) 
was 2.1, which was excellent (the recrystallization yield was 92%). 
Thus obtained compound was confirmed to be dimethyl 
1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, the objective by the 
elemental analysis as shown in Table 1. 
TABLE 1 
______________________________________ 
Found Calculated 
(%) (%) 
______________________________________ 
C 54.2 54.1 
H 4.1 4.0 
Cl 17.7 17.8 
______________________________________ 
COMATIVE EXAMPLE 1 
93 g (0.5 mole) of methyl 3-chloro-4-hydroxybenzoate and 27 g (0.5 mole) of 
sodium methylate were dissolved in 600 g of methanol. 25 g (0.25 mole) of 
ethylenedichloride was added to this solution, and then the reaction 
mixture was maintained with stirring at 150.degree. C. for 6 hours in a 1 
liter autoclave. 
Thereafter, the reaction mixture was poured into the large quantity of 
water. The yellow precipitates formed were filterated off and dried. 
The melting point of the obtained dimethyl 
1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate was 192.degree. to 
195.degree. C., and the yield was 34%, which was extremely low. The colour 
tone (b value) was 8.7, which was inferior. 
EXAMPLE 2 
Into a vessel equipped with a reflux condenser, were charged 50 g (0.15 
mole) of dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate and 1000 g of 
propionic acid. Then, the temperature of the reaction vessel was raised to 
115.degree. to 118.degree. C. with stirring. 
After dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate was completely 
dissolved, the reaction mixture was maintained at the same temperature 
with introducing 23 g (0.33 mole) of the chlorine gas into the reaction 
vessel for 2 hours. 
Thereafter, the reaction mixture was poured into the large quantity of 
water. The white precipitates formed were filterated off and dried. The 
yield of this white precipitates was 80%. 
The melting point of the compound purified by recrystallization from xylene 
was 203.degree. to 205.degree. C., and the colour tone (b value) was 2.0, 
which was excellent (the recrystallization yield was 92%). 
Thus obtained compound was confirmed to be dimethyl 
1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, the objective by the 
elemental analysis as shown in Table 2. 
TABLE 2 
______________________________________ 
Found Calculated 
(%) (%) 
______________________________________ 
C 54.3 54.1 
H 4.2 4.0 
Cl 17.6 17.8 
______________________________________ 
EXAMPLE 3 
Into a vessel equipped with a reflux condenser, were charged 50 g (0.15 
mole) of dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate, 150 g of 
tetrachloromethane, and 0.2 g of iodine. Then, the temperature of the 
reaction vessel was raised to 110.degree. C. with stirring. 
After dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate was completely 
dissolved, the reaction mixture was maintained at the same temperature 
with introducing 27 g (0.38 mole) of the chlorine gas into the reaction 
vessel for 2 hours. 
Thereafter, the reaction mixture was cooled. The white precipitates formed 
were filterated off and dried. The yield of this white precipitates was 
91%. 
The melting point of the compound purified by recrystallization from 
toluene was 204.degree. to 205.degree. C., and the colour tone (b value) 
was 2.2, which was excellent (the recrystallization yield was 90%). 
Thus obtained compound was confirmed to be dimethyl 
1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, the objective by the 
elemental analysis as shown in Table 3. 
TABLE 3 
______________________________________ 
Found Calculated 
(%) (%) 
______________________________________ 
C 54.3 54.1 
H 4.0 4.0 
Cl 17.6 17.8 
______________________________________ 
EXAMPLE 4 
Into a vessel equipped with a reflux condenser, were charged 50 g (0.15 
mole) of dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate, 100 g of 
ortho-dichlorobenzene, and 0.2 g of iodine. Then, the temperature of the 
reaction vessel was raised to 130.degree. C. with stirring. 
After dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate was completely 
dissolved, the reaction mixture was maintained at the same temperature 
with introducing 27 g (0.38 mole) of the colorine gas into the reaction 
vessel. 
Thereafter, the reaction mixture was cooled. The white precipitates formed 
were filterated off and dried. The yield of this white precipitates was 
70%. 
The melting point of the compound purified by recrystallization from 
toluene was 200.degree. to 203.degree. C., and the colour tone (b value) 
was 2.2, which was excellent (the recrystallization yield was 91%). 
Thus obtained compound was confirmed to be dimethyl 
1,2-bis(chlorophenoxy)ethane-4,4'-dicarboxylate, the objective by the 
elemental analysis as shown in Table 4. 
TABLE 4 
______________________________________ 
Found Calculated 
(%) (%) 
______________________________________ 
C 54.0 54.1 
H 4.1 4.0 
Cl 18.0 17.8 
______________________________________ 
EXAMPLE 5 
Into a vessel equipped with a reflux condenser, were charged 54 g (0.15 
mole) of diethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate, 216 g of 
tetrachloroethane, and 0.2 g of iodine. Then, the temperature of the 
reaction vessel was raised to 105.degree. to 115.degree. C. with stirring. 
Further, the reaction mixture was maintained with introducing 27 g (0.38 
mole) of the chlorine gas into the reaction vessel by the similar manner 
to Example 1. 
Thereafter, the reaction mixture was cooled. The white precipitates formed 
were filterated and dried. The yield of this white precipitates was 86%. 
The melting point of the compound purified by recrystallization from xylene 
was 149.degree. to 153.degree. C., and the colour tone (b value) was 2.0, 
which was excellent (the recrystallization yield was 91%). 
Thus obtained compound was confirmed to be diethyl 
1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, the objective by the 
elemental analysis as shown in Table 5. 
TABLE 5 
______________________________________ 
Found Calculated 
(%) (%) 
______________________________________ 
C 56.1 56.2 
H 4.5 4.7 
Cl 16.8 16.6 
______________________________________ 
EXAMPLE 6 
Into a vessel equipped with a reflux condenser, were charged 54 g (0.15 
mole) of dimethyl 1,4-bis(phenoxy) butane-4,4'-dicarboxylate, and 450 g of 
acetic acid. Then, the temperature of the reaction vessel was raised to 
115.degree. to 120.degree. C. with stirring. 
Afterwords, the reaction was conducted with introducing 23 g (0.33 mole) of 
the chlorine gas into the reaction vessel by the similar manner to Example 
1. 
Thereafter, the reaction mixture was poured into the large quantity of 
water. The white precipitates formed were filterated and dried. The yield 
of this white precipitates was 85%. 
The melting point of the compound purified by recrystallization from ethyl 
acetate was 172.degree. to 174.degree. C., and the colour tone (b value) 
was 2.4, which was excellent (the recrystallization yield was 84%). 
Thus obtained compound was confirmed to be dimethyl 
1,4-bis(2-chlorophenoxy)butane-4,4-dicarboxylate the objective by the 
elemental analysis as shown in Table 6. 
TABLE 6 
______________________________________ 
Found Calculated 
(%) (%) 
______________________________________ 
C 56.1 56.2 
H 4.6 4.7 
Cl 16.7 16.6 
______________________________________ 
EXAMPLE 7 
Into a vessel equipped with a reflux condenser, were poured 54 g (0.15 
mole) of dimethyl 1,4-bis(phenoxy)butane-4,4'-dicarboxylate, 100 g of 
ortho-dichlorobenzene, and 0.2 g of iodine. Then, the temperature of the 
reaction vessel was raised to 130.degree. C. with stirring. 
Further, the reaction was conducted with introducing 27 g (0.38 mole) of 
the chlorine gas into the reaction vessel by the similar manner to Example 
1. 
Thereafter, the reaction mixture was cooled. The white precipitates formed 
were filterated off and dried. The yield of this white precipitates was 
80%. 
The melting point of the compound purified by recrystallization from ethyl 
acetate was 174.degree. to 176.degree. C., and the colour tone (b value) 
was 2.7, which was excellent (the recrystallization yield was 84%). 
Thus obtained compound was confirmed to be dimethyl 
1,4-bis(2-chlorophenoxy)butane-4,4'-dicarboxylate, the objective by the 
elemental analysis as shown in Table 7. 
TABLE 7 
______________________________________ 
Found Calculated 
(%) (%) 
______________________________________ 
C 56.0 56.2 
H 4.6 4.7 
Cl 16.9 16.6 
______________________________________ 
EXAMPLE 8 
Into a vessel equipped with a reflux condenser, were charged 58 g (0.15 
mole) of 1,6-bis(phenoxy)hexane-4,4'-dicarboxylate, 2,000 g of carbon 
tetrachloride, and 0.2 g of iodine. Then, the temperature of the reaction 
vessel was raised to 60.degree. C. with stirring. 
Further, the reaction mixture was maintained with introducing 27 g (0.38 
mole) of the chloride gas into the reaction vessel by the similar manner 
to the Example 1. 
Thereafter, the reaction mixture was cooled. The white precipitates formed 
were filterated and dried. The yield of this white precipitates was 72%. 
The melting point of the compound purified by recrystallization from 
ethanol was 82.degree. to 84.degree. C., and the colour tone (b value) was 
2.6, which was excellent. 
Thus obtained compound was confirmed to be dimethyl 
1,6-bis(2-chlorophenoxy)hexane-4,4'-dicarboxylate, the objective by the 
elemental analysis as shown in Table 8. 
TABLE 8 
______________________________________ 
Found Calculated 
(%) (%) 
______________________________________ 
C 49.9 50.4 
H 4.0 4.2 
Cl 27.7 27.1 
______________________________________ 
EXAMPLE 9 
348 g (2 mole) of sodium salt of methyl 4-hydroxybenzoate was added to 300 
g of methanol. Then, 200 g (2 mole) of ethylenedichloride was added to the 
solution and the reaction mixture was maintained with stirring at 
180.degree. C. for 4 hours in 5 liter autoclave. 
Thereafter, the reaction mixture was charged into the large quantity of 
water. The white precipitates formed were filterated off and dried. The 
yield of the crude dimethyl 1,2-bis(2-henoxyl)ethane-4,4'-dicarboxylate 
was 62%. 
Into a vessel equipped with a reflux condenser, were charged 100 g (0.3 
mole) of thus obtained dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate 
and 1,000 g of acetic acid. Then, the reaction mixture was maintained in a 
similar manner to Example 1. 
The crude dimethyl 1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate was 
obtained (the yield was 93% and the melting point was 201.degree. to 
204.degree. C.). The colour tone (b value) was 2.7, which was excellent. 
The total yield was 58%. 
COMATIVE EXAMPLE 2 
Into a vessel equipped with a reflux condenser, were charged 304 g (2 mole) 
of methyl 4-hydroxybenzoate and 800 g of acetic acid. 
Then, methyl 4-hydroxybenzoate was completely dissolved, the reaction was 
conducted with introducing 156 g (2.2 mole) of the chlorine gas into the 
reaction vessel. 
Thereafter, the reaction mixture was cooled to the room temperature and 
then charged into the large quantity of water. 276 g of the white 
precipitates formed were obtained (the yield was 74%). 
The melting point of the compound purified by recrystallization from 
methanol-water solvent was 106.degree.-108.degree. C. (the 
recrystallization yield was 91%). The results of the elemental analysis of 
this compounds were well agreed with the calculated value of methyl 
3-chloro-4-hydroxybenzoate. 
The ether forming reaction mixture was maintained in a similar manner to 
Example 1, using thus obtained 93 g (0.5 mole) of 
methyl-3-chloro-4-hydroxybenzoate and ethylenedichloride. 
The crude dimethyl 1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate was 
obtained (the yield was 37% and the melting point was 193.degree. to 
197.degree. C.). The colour tone (b value) was 8.4, which is yellow and 
inferior. The total yield was 25%. 
When this Comparative Example 2 was compared with Example 9, in this 
Comparative Example 2, the total yield was lower, the colour tone of the 
obtained dimethyl 1,2-bis(2-chlorophenoxyethane)-4,4'-dicarboxylate was 
inferior and the melting point was lower. 
EXAMPLE 10 
Into 3 liter of the autoclave, 138 g (1 mole) of 4-hydroxybenzoic acid, 100 
g (2.5 mole) of sodium hydroxide, 130 g (1.3 mole) of ethylene dichloride 
and 250 g of water. Then, the reaction mixture was stirred at 130.degree. 
C. for 14 hours. The reaction mixture was cooled, and then dissolved in 
hot water, and then the pH was adjusted to 1.0 with 10% of hydrochloric 
acid. 
The deposited precipitates were hot-filtered, washed with water, and dried. 
Thus, the crude 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid was obtained 
in a 73% yield. 
600 g of methanol and 30 g of sulfuric acid were added to 151 g of thus 
obtained 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid in 3 liter 
autoclave. The reaction mixture was maintained at 130.degree. C. for 5 
hours. Thus, dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate was 
obtained in a 81% yield. 
The colour tone (b value) was 2.8, which was excellent, and the total yield 
was 54%. 
COMATIVE EXAMPLE 3 
Into a vessel equipped with a reflux condenser, were charged 138 g (1 mole) 
of 4-hydroxybenzoic acid and 1,500 g of acetic acid. After 
4-hydroxybenzoic acid was completely dissolved, the reaction mixture was 
maintained with introducing 78 g (1.1 mole) of the chlorine gas into the 
reaction vessel for 6 hours. 
Thereafter, the reaction mixture was cooled to room temperature and charged 
into the large quantity of water. The white precipitates formed were 
obtained (the yield was 76%). 
This white precipitates was purified by recrystallization from methanol. 
Into 1 liter autoclave were charged 86 g (0.5 mole) of thus obtained 
3-chloro-4-hydroxybenzoic acid, 50 g (1.25 mole) of sodium hydroxide, 65 g 
(0.65 mole) of ethylene dichloride, and 125 g of water. Then, the reaction 
mixture was stirred at 130.degree. C. for 14 hours. 
The reaction mixture was cooled, and then dissolved in hot water, and then 
pH was adjacted to 1.0 with 10% of hydrochloric acid. The deposited 
precipitates were hot-filtered, washed with water, and dried. Thus, the 
crude 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid was obtained in a 58% 
yield. 
120 g of methanol and 6 g of sulfuric acid were added to 37 g of thus 
obtained dimethyl 1,2-bis(phenoxy)ethane-4,4'-dicarboxylate in 1 liter 
autoclave. The reaction mixture was maintained at 130.degree. C. for 5 
hours. Thus, dimethyl 1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate 
was obtained in a 76% yield. 
The colour tone (b value) was 7.9, which was yellow and inferior. The total 
yield was 29%. In this comparative Example, the total yield was lower, the 
colour tone of the obtained dimethyl 
1,2-bis(chlorophenoxy)ethane-4,4'-dicarboxylate was inferior, and the 
melting point was lower than those in Example 10. 
INDUSTRIAL UTILIZABILITY 
.alpha.,.omega.-bis(2-chlorophenoxy)alkane-4,4'-dicarboxylic acid or its 
ester obtained in the present invention are useful for a material of high 
Young's modulus polyester, which can be applied to the reinforcing 
meterials for rubbers such as tire cords, conveyer belt, belts for power 
transmission.