Preparation of high quality ethephon using domestic diester bis-(2-chloroethyl)-2-chloroethylphosphonate as substrate

Article abstract of DOI:10.14233/ajchem.2013.14249

Ethephon has been widely used globally. However, few companies can manufacture high quality ethephon with content of 90% in China mainland. This work described a practical procedure, which utilizing bis-(2-chloroethyl)-2- chloroethylphosphonate 2 produced by local Chinese companies as substrate to prepare ethephon with content of over 90 % and high yield.

Full text of DOI:10.14233/ajchem.2013.14249

Asian Journal of Chemistry; Vol. 25, No. 11 (2013), 6463-6464
http://dx.doi.org/10.14233/ajchem.2013.14249
NOTE
Preparation of High Quality Ethephon Using Domestic Diester
bis-(2-chloroethyl)-2-chloroethylphosphonate as Substrate
*
WENLONG ZHANG and DEQUN SUN
Marine College, Shandong University at Weihai, Wehhua West Road No.180, Weihai 264209, P.R. China
Corresponding author: Fax: +86 631 5688303; Tel: +86 631 5688537; E-mail: dequn.sun@sdu.edu.cn
Received: 30 June 2012; Accepted: 14 May 2013)
*
(
AJC-13498
Ethephon has been widely used globally. However, few companies can manufacture high quality ethephon with content of 90% in China
mainland. This work described a practical procedure, which utilizing bis-(2-chloroethyl)-2-chloroethylphosphonate 2 produced by local
Chinese companies as substrate to prepare ethephon with content of over 90 % and high yield.
Key Words: Ethephon, Preparation, Diester.
Ethephon 4 is a plant growth regulator and promote plant
process is unsuitable for China companies to produce high
quality ethephon.
maturation. As a safe and clean product, it is worldwide used
in cotton, rubber, banana, tomato, tobacco, rice and other
plants. The Rhodia and The Jiangsu Electric Company Limited
China are the two major producers of ethephon. The export of
ethephon in China has been limited by low quality of ethephon.
The content of most of the ethephon produced in China is
lower than 80 %. In spite of some improvements on the basis
of old technology made by many enterprises in the 70's, there
are still some problems such as low content (60-70 %), low
Few researchers in China study how to improve the
content of ethephon higher than 90 % via domestic technology.
We reported our improved preparation by using domestic
diester 2 to produce ethephon with content of over 90 % in
high yield and furthermore the relationship between the GC
content of diester 2 and final product 4 was clarified.
Diester 2 (supplied by Shandong Dacheng pesticide
company); and other commercially available materials and
solvents were used without further purification. Gas chromato-
graph (Shimadzu): With FID detector and 2000 mm × 3 mm
glass or stainless steel column filled 10 % SE-30/Gas chrom
Q150-180 µm (80-100 mesh); NMR spectra were recorded in
1
yield and large waste discharge . The common synthetic route
employed in preparation of ethephon is described as following
(
Scheme-I).
British patent disclosed a method which can continu-
2
ously or intermittently manufacture ethephon by increasing
3
2
D O at 400 MHz. The chemical shift values are reported on
pressure from hydrogen chloride. The united states patent
described a process to product ethephon by adding concen-
trated hydrochloric acid to the reaction system and then cool-
the d scale with respect to TMS (δ 0.00) as internal standards.
Typical preparation of ethephon: Diester 2 (2083 g, GC
purity 87 %,1100 mL) was added to 2 L high-pressure reactor
(designed pressure: 2 Mpa). The vessel was sealed and then
heated with stirring. HCl gas was imported when temperature
was reached to 80 ºC. The pressure was set to 0.5 Mpa. The
reaction was heated to 150 ºC with efficient stirring. The
another part of diester 2 (574 g) was added after 500-600 mL
of by-product 1,2-dichloroethane was distillated out. The
reaction was finished until no 1,2-dichloroethane could be
distillated (totally, about 1200 mL of 1,2-dichloroethane was
collected during reaction). Then importing HCl gas was
stopped. The reaction mixture was cooled to 120 ºC and
concentrated in vacuum for 1 h. The mixture was cooled to
4
ing to separate phases. The united states patent disclosed a
procedure to separate and purify the product with benzene
based on previous method. All of these preparations actu-
ally share the same shortcomings, such as low content in the
final products and large amount of wastes. The united states
5
,6
patents reported a new strategy which used diester 2 as
reaction substrate to produce high quality ethephon (content
over 90 %) under high pressure of hydrogen chloride. This
reaction requires high-quality substrate 2 (purity = 99 %).
Since there is no substrate 2 with content or purity being
reached to 99 % in china mainland up to now, therefore, this

6
464 Zhang et al.
Asian J. Chem.
O
Cl
Cl
O
Cl
P O
P O
+
PCl3
Cl
O
step 1
O
step2
O
Cl
Cl
1
2
O
P OH
O
HCl gas
step 3
HCl gas
Cl
P OH
OH
Cl
Cl
+
Cl
+
Cl
Cl
O
step 4
Cl
3
4
Scheme-I: Synthetic procedure of ethephon
room temperature to give final product ethephon 4 as white
solid, 1240 g, yield 100.5 %. The content was 93 % by GC.
Conclusion
Through the improved process, the good quality ethephon
with content of over 90 % were obtained by using domestic
diester. The research work showed a clear relationship between
GC content of diester and quality of ethephon and this indication
could be valuable for production of high quality ethephon.
7
NMR data were in agreement with published values : H NMR
1
2
P, JH-P = 18.0, 3.58 (m, CH
(
D
2
O) δ ppm: 2.13 (d, 2H, CH
2
2
,
2
H-P
13
CH
133.0 Hz), 37.495 ppm (s, 2H). P (D
The conversion process of intermediate 2 into final
2
Cl, J = 14.12); C (D O) δ ppm: 30.09 (d, 2H, JP-C
2
31
=
2
O) δ ppm: 25.7.
product includings two reversible reactions (step 3 and step 4
in Scheme-I). We reasoned that the quality of final product 4
should rely upon both the quality of diester 2 and the conver-
sion of 2 and 3. The quality of 4 should be improved if both of
intermediate 2 and 3 can be converted completely into next
product respectively. One important strategy to fulfill this aim
is to remove by-product (1,2-dichloroethane) from reaction
both in step 3 and step 4 continuously. Another way is to use
good quality diester 2. In our preparation, domestic diester 2
was used as starting reactant, however, the procedure reported
in literatures was improved, especially by removing 1,2-
dichloroethane from reaction during the process, so that both
diester 2 and intermediate 3 could have excellent conversion.
Finally, the content and yield of ethephon were achieved over
REFERENCES
1
2
.
.
H.M. Zhang, Shanxi Sci. Technol., 6, 53 (2001).
S. Gerhard, R. Karl and S. Otto, Process for the Manufacture of 2-Chloro-
ethane-Phosphonic acid: GB patent, 1373513 (1974).
D.I. Randall and C. Vogel, Preparation of 2-Haloethylphosphonic Acid:
US Patent, 3808265 (1974).
3
4
.
.
D.I. Randall and R.W. Wynn, Mono-2-haloethyl Esters of 2-Haloethane-
phosphonic Acid: US Patent, 3626037 (1971).
5. J.E. Drach and B.J. Pendell, Process for the Manufacture of Aliphatic
Phosphonic Acids: US Patent, 4064163 (1977).
6
.
K.W. Young and J.J. Zullo, Process for the Production of Aliphatic
Phosphonic Acid: US Patent, 4728466 (1988).
7
.
L. Cauret, J.C. Brosse, D. Derouet and H. De Livonnière, Synth. Commun.,
27, 647 (1997).
8
9
.
.
L.R.An, C.H. Wang and M.Q. Li, Jiangsu Agrochemicals, 4, 21 (1998).
GC internal standard method to measure content of ethephon: The ethe-
phon was firstly converted completely into methyl ester by diazonium
methane to give dimethyl 2-chloroethyl phosphonate (5), which content
can be determined by GC through 10%SE-30 / Gas Chrom Q chromato-
graphy using p-nitrochlorobenzene as internal standard solution
Through this way, the content of ethephon could be measured.
9
0 % and nearly quantitative respectively. Furthermore, the
relationship between the GC content of diester 2 and final
product 4 showed that quality of ethephon would rise with
increasing of the GC content of diester 2. The content of 4
was about 84.0 % to 89.2 % when the GC content of 2 was 78
to 83 % (Table-1, entry 1-4) and it could reach over 90 %
while the GC content of diester 2 was 87 % (Table-1, entry 5
and 6).
O
O
CH N
2
2
ClCH CH P OH
2
P OMe
OMe
2
ClCH CH
2 2
OH
4
5
TABLE-1
INFLUENCE OF GC CONTENT OF DIESTER 2
ON ETHEPHON QUALITY
Entry
GC content (%) of diester 2
[
Content of ethephon (%)
[Ref. 9]
Ref. 8]
1
2
3
4
5
6
78
83
82
78
87
87
84.0
89.2
87.7
85.2
93.1
92.9