Title of Invention	AN IMPROVED PROCESS FOR THE ELECTROCHEMICAL PREPARATION OF PARA CHLOROVENZALDEHYDE
Abstract	An improved process for the preparation of para-chlorobenzaldehyde which comprises oxidizing para chloro toluene using electrochemically generated cerium(IV) methane sulphonate characterized in that electrolysing the said cerium(IV) methane sulphonate in methane sulphonic acid at a current density of 5 - 15 A/dm2 in an undivided cell in a mole ratio of Para-chlorotoluene to cerium (IV) methane sulphonate 1:4 to 1 :5.6 at a temperature of 75 -80°C for a period of 30 to 45 minutes with vigorous stirring to obtain a solution and recovering the para-chlorobenzaldehyde by extraction method.

Title of Invention

AN IMPROVED PROCESS FOR THE ELECTROCHEMICAL PREPARATION OF PARA CHLOROVENZALDEHYDE

Abstract

An improved process for the preparation of para-chlorobenzaldehyde which comprises oxidizing para chloro toluene using electrochemically generated cerium(IV) methane sulphonate characterized in that electrolysing the said cerium(IV) methane sulphonate in methane sulphonic acid at a current density of 5 - 15 A/dm2 in an undivided cell in a mole ratio of Para-chlorotoluene to cerium (IV) methane sulphonate 1:4 to 1 :5.6 at a temperature of 75 -80°C for a period of 30 to 45 minutes with vigorous stirring to obtain a solution and recovering the para-chlorobenzaldehyde by extraction method.

Full Text	The present invention relates to an improved process for the electrochemical preparation of para chlorobenzaldehyde. The present invention perticularly relates to an improved process for the preparation of para-chlorobenzaldehyde by oxidizing para-chlorotoluene using electrochemically generated cerium (IV) methanesulphonate in methane sulphonic acid as oxidizing agent. Para-chlorobenzaldehyde (PCB) is an important starting material for the manufacture of dyes and dyestuff intermediates. It is also used in the production of corrosion inhibitor. (Kirk & Othmer's Encyclopedia of Chemical Technology, III edition, Vol.3.363 (1964)) Hitherto Para-chlorobenzaldehyde has been prepared by the side chain chlorination of toluene followed by hydrolysis of the product benzalchloride or by partial oxidation of toluene with oxygen (Jiin Jiang, Journal of applied chemistry 18, 298-303, (1988), Wiley, organic synthesis, New York 1963, vol.4.698). There are various other manufacturing processes, but at present, they do not have any industrial importance. The major disadvantage of the current process is the low selectivity and the highly toxic chlorine effluent. More over recent publication deal with direct anodic oxidation of para-chlorotoluene to obtain a promising route for commercial para-chlorobenzaldehyde synthesis. The selectivity of these process does not exceed 75% yield in dry methanol or ethanol containing expensive NaBF4, NaClO4 or EtNBF4 as a supporting electrolyte (ref. D.Hermeling Ger.off.DE.4, 201,544(1993), H.Wendt, S.Bitterlich E. Lodowics and Z.Liu, Electrochemica Acta 37(11) 1959-1969(1992). The electrochemical process using cerium(IV) in sulphuric acid has also been carried out, but cerium(IV) in sulphuric acid has the drawback of marginal solubility, low conversion and low current efficiency. The invented process is an improved process giving an yield of 75-80% and high conversion using cerium(IV)methanesulphonate. The main objective of this invention is to develop a method for the preparation of para chlorobenzaldehyde by oxidizing para-chlorotoluene using electrochemically generated cerium (IV) methanesulphonate in methane sulphonic acid as oxidizing agent. In the present invention, para- chlorobenzaldehyde was prepared in a batch reactor at a temperature of 75 - 80° C with vigorous stirring. The main advantage of this process is that the oxidant Cerium (IV) methane sulphonate can be regenerated in high conversion and hence the process is very economical. Also, the organic oxidation is fast under these conditions where the cerium salts are soluble and the organic products are immiscible with the aqueous solutions making the facile product separation. The yield of the desired aldehyde was substantially increased by the character of the solvent or the supporting electrolyte employed in the electrochemical oxidation substantially influenced the yield of the desired aldehyde. Accordingly the present invention provides an improved process for the preparation of para-chlorobenzaldehyde which comprises oxidizing para chloro toluene using electrochemically generated cerium(IV) methane sulphonate characterized in that electrolysing the said cerium(IV) methane sulphonate in methane sulphonic acid at a current density of 5 - 15 A/dm2 in an undivided cell in a mole ratio of Para-chlorotoluene to cerium (IV) methane sulphonate 1:4 to 1 :5.6 at a temperature of 75 - 80°C for a period of 30 to 45 minutes with vigorous stirring to obtain a solution and recovering the para-chlorobenzaldehyde by extraction method. The solvent used for extraction may be selected from chloroform, dichloromethane or mixture thereof. In an embodiment of the invention the electrochemically generated oxidant Ce(IV) methane sulphonate is generated in an undivided electrochemical cell at an anode current density of 5-15A/dm2 using diemensionally stable anode (DSA)/O2 type anode and stainless steel cathode. In another embodiment of the invention maximum yield of para chloro benzaldehyde may be obtained using the oxidant having a concentration of 6.0 molar free methane sulphonic acid. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the invention. Example 1: Electrochemical oxidation step Cell type : undivided Anode : DSA - O2 (1dm2) (Dimensionally stable anode) Cathode : Stainless Steel (1dm2) Electrolyte : Cerium (III) methane sulphonate 0.6 molar (2 lit) Concentration of free Methanesulfonic acid 5 molar Current passed 10 A Current density 10 A/dm2 Temperature 50 ° C Cell voltage 3.4V Duration 7.5 hrs Current efficiency 38 % Conversion 83 % Chemical oxidation step (under Nitrogen atmosphere) Concentration of Ce(IV) Methane sulphonate : 0.49 molar (2 lit) Concentration of free Methane sulphonic acid : 5 molar Para chlorotoluene taken: 0.25 moles (31.8 g) Temperature : 80 ° C Duration : 30 min Yield of para-chloro benzaldehyde : 76% (24.2 gm) Example 2: Electrochemical oxidation step Cell type Divided Anode DSA-O2(1 dm2) Cathode Stainless Steel (1 dm2) anolyte Cerium (III) methanesulphonate 0.6 molar (2 lit) Catholyte : Methanesulphonicacid 5 molar(2.0 lit) Cell Voltage 3.8V Current passed 10A Current density 10 A/dm2 o Temperature 50 C Cell voltage 3.4V Duration 4.9 hrs Current efficiency : 50 % Conversion : 83 % Chemical oxidation step (under Nitrogen atmosphere) Concentration of Ce(IV) Methane sulphonate : 0.495 molar (2 lit) Concentration of free Methane sulphonic acid : 6.0 molar Para-chlorotoluene taken: 0.25 moles (31.8 gm) o Temperature : 80 C Duration : 30 min Yield of para-chloro benzaldehyde : 76% (26.6 gm) Example 3: Electrochemical oxidation step Cell type : Undivided Anode : DSA-O2(ldm2) Cathode : Stainless Steel (1dm2) Electrolyte : Cerium (III) methane sulphonate 0.6 molar (2 lit) Concentration of free Methanesulfonic acid 5.0 molar Cell Voltage 3.8V Current passed 10 A Current density 10 A / dm2 o Temperature 50 C Duration 7.5 hrs Current efficiency 38 % Conversion : 83 % Chemical oxidation step (without Nitrogen atmosphere) Concentration of Ce(IV) Methane sulphonate : 0.5 molar (2 lit) Concentration of free Methane sulphonic acid : 5.0 molar Para-chlorotoluene taken: 0.25 moles (31.8 gm) Temperature : 80 ° C Duration : 30 min Yield of para-chloro Benzaldehyde : 64 % (22.4 gm) The main advantages of the present invention are 1. Cerium (IV) in aqueous methane sulphonic acid is an excellent reagent for the oxidation of para-chlorotoluene to para- chlorobenzaldehyde. 2. This electrochemical oxidation of Ce (III)/Ce (IV) can be carried out with high conversion and high current efficiency. 3. The advantage of using methanesulfonate among various anions is its high stability toward oxidation. 4. High selectivity and high solubility of Ce (IV) methanesulfonate in aqueous methanesulphonic acid. 5. The conversion of the para-chlorotoluene is high. The formation of para-chlorobenzaldehyde is higher compared with chemical methods. 6. There is no bye-product formation in comparison with chemical methods. 7. No spent reagent disposal. Hence this process is eco-friendly. 8. This process is competitive with all known commercial routes. We claim : 1. An improved process for the preparation of para-chlorobenzaldehyde which comprises oxidizing para chloro toluene using electrochemically generated cerium(IV) methane sulphonate characterized in that electrolysing the said cerium(IV) methane sulphonate in methane sulphonic acid at a current density of 5 - 15 A/dm2 in an undivided cell in a mole ratio of Para-chlorotoluene to cerium (IV) methane sulphonate 1:4 to 1 :5.6 at a temperature of 75 - 80°C for a period of 30 to 45 minutes with vigorous stirring to obtain a solution and recovering the para-chlorobenzaldehyde by extraction method. 2. An improved process as claimed in claim 1 wherein the solvent used for extraction of para-chlorobenzaldehyde is selected from l,2dichloromethane , chloroform and mixture therof. 3. An improved process for the preparation of para-chlorobenzaldehyde as herein described with reference to the examples.

Full Text

The present invention relates to an improved process for the electrochemical preparation of para chlorobenzaldehyde.
The present invention perticularly relates to an improved process for the preparation of para-chlorobenzaldehyde by oxidizing para-chlorotoluene using electrochemically generated cerium (IV) methanesulphonate in methane sulphonic acid as oxidizing agent.
Para-chlorobenzaldehyde (PCB) is an important starting material for the manufacture of dyes and dyestuff intermediates. It is also used in the production of corrosion inhibitor. (Kirk & Othmer's Encyclopedia of Chemical Technology, III edition, Vol.3.363 (1964))
Hitherto Para-chlorobenzaldehyde has been prepared by the side chain chlorination of toluene followed by hydrolysis of the product benzalchloride or by partial oxidation of toluene with oxygen (Jiin Jiang, Journal of applied chemistry 18, 298-303, (1988), Wiley, organic synthesis, New York 1963, vol.4.698). There are various other manufacturing processes, but at present, they do not have any industrial importance.
The major disadvantage of the current process is the low selectivity and the highly toxic chlorine effluent. More over recent publication deal with direct anodic oxidation of para-chlorotoluene to obtain a promising route for commercial para-chlorobenzaldehyde synthesis. The selectivity of these process does not exceed 75% yield in dry methanol or ethanol containing expensive NaBF4, NaClO4 or EtNBF4 as a supporting electrolyte (ref. D.Hermeling Ger.off.DE.4, 201,544(1993), H.Wendt, S.Bitterlich E. Lodowics and Z.Liu, Electrochemica Acta 37(11) 1959-1969(1992). The electrochemical process using cerium(IV) in sulphuric acid has also been carried out, but cerium(IV) in sulphuric acid has the drawback of marginal solubility, low conversion and low current efficiency. The invented process is an improved process giving an yield of 75-80% and high conversion using cerium(IV)methanesulphonate.
The main objective of this invention is to develop a method for the preparation of para chlorobenzaldehyde by oxidizing para-chlorotoluene using electrochemically generated cerium (IV) methanesulphonate in methane sulphonic acid as oxidizing agent. In the present invention, para-

chlorobenzaldehyde was prepared in a batch reactor at a temperature of 75 - 80° C with vigorous stirring.
The main advantage of this process is that the oxidant Cerium (IV) methane sulphonate can be regenerated in high conversion and hence the process is very economical. Also, the organic oxidation is fast under these conditions where the cerium salts are soluble and the organic products are immiscible with the aqueous solutions making the facile product separation. The yield of the desired aldehyde was substantially increased by the character of the solvent or the supporting electrolyte employed in the electrochemical oxidation substantially influenced the yield of the desired aldehyde.
Accordingly the present invention provides an improved process for the preparation of para-chlorobenzaldehyde which comprises oxidizing para chloro toluene using electrochemically generated cerium(IV) methane sulphonate characterized in that electrolysing the said cerium(IV) methane sulphonate in methane sulphonic acid at a current density of 5 - 15 A/dm2 in an undivided cell in a mole ratio of Para-chlorotoluene to cerium (IV) methane sulphonate 1:4 to 1 :5.6 at a temperature of 75 - 80°C for a period of 30 to 45 minutes with vigorous stirring to obtain a solution and recovering the para-chlorobenzaldehyde by extraction method.
The solvent used for extraction may be selected from chloroform, dichloromethane or mixture thereof.
In an embodiment of the invention the electrochemically generated oxidant Ce(IV) methane sulphonate is generated in an undivided electrochemical cell at an anode current density of 5-15A/dm2 using diemensionally stable anode (DSA)/O2 type anode and stainless steel cathode.
In another embodiment of the invention maximum yield of para chloro benzaldehyde may be obtained using the oxidant having a concentration of 6.0 molar free methane sulphonic acid.
The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the invention.
Example 1:
Electrochemical oxidation step

Cell type : undivided
Anode : DSA - O2 (1dm2) (Dimensionally
stable anode)
Cathode : Stainless Steel (1dm2)
Electrolyte : Cerium (III) methane sulphonate
0.6 molar (2 lit)
Concentration of free
Methanesulfonic acid 5 molar
Current passed 10 A
Current density 10 A/dm2
Temperature 50 ° C
Cell voltage 3.4V
Duration 7.5 hrs
Current efficiency 38 %
Conversion 83 %
Chemical oxidation step (under Nitrogen atmosphere)
Concentration of Ce(IV)
Methane sulphonate : 0.49 molar (2 lit)
Concentration of free
Methane sulphonic acid : 5 molar
Para chlorotoluene taken: 0.25 moles (31.8 g)
Temperature : 80 ° C
Duration : 30 min
Yield of para-chloro
benzaldehyde : 76% (24.2 gm)
Example 2:
Electrochemical oxidation step
Cell type Divided
Anode DSA-O2(1 dm2)
Cathode Stainless Steel (1 dm2)
anolyte Cerium (III) methanesulphonate
0.6 molar (2 lit)
Catholyte : Methanesulphonicacid 5 molar(2.0 lit)

Cell Voltage 3.8V
Current passed 10A
Current density 10 A/dm2
o
Temperature 50 C
Cell voltage 3.4V
Duration 4.9 hrs
Current efficiency : 50 %
Conversion : 83 %
Chemical oxidation step (under Nitrogen atmosphere)
Concentration of Ce(IV)
Methane sulphonate : 0.495 molar (2 lit)
Concentration of free
Methane sulphonic acid : 6.0 molar
Para-chlorotoluene taken: 0.25 moles (31.8 gm)
o
Temperature : 80 C
Duration : 30 min
Yield of para-chloro
benzaldehyde : 76% (26.6 gm)
Example 3:
Electrochemical oxidation step
Cell type : Undivided
Anode : DSA-O2(ldm2)
Cathode : Stainless Steel (1dm2)
Electrolyte : Cerium (III) methane sulphonate
0.6 molar (2 lit)
Concentration of free
Methanesulfonic acid 5.0 molar
Cell Voltage 3.8V
Current passed 10 A
Current density 10 A / dm2
o
Temperature 50 C
Duration 7.5 hrs
Current efficiency 38 %

Conversion : 83 %
Chemical oxidation step (without Nitrogen atmosphere)
Concentration of Ce(IV)
Methane sulphonate : 0.5 molar (2 lit)
Concentration of free
Methane sulphonic acid : 5.0 molar
Para-chlorotoluene taken: 0.25 moles (31.8 gm)
Temperature : 80 ° C
Duration : 30 min
Yield of para-chloro
Benzaldehyde : 64 % (22.4 gm)
The main advantages of the present invention are
1. Cerium (IV) in aqueous methane sulphonic acid is an excellent
reagent for the oxidation of para-chlorotoluene to para-
chlorobenzaldehyde.
2. This electrochemical oxidation of Ce (III)/Ce (IV) can be carried out
with high conversion and high current efficiency.
3. The advantage of using methanesulfonate among various anions is its
high stability toward oxidation.
4. High selectivity and high solubility of Ce (IV) methanesulfonate in
aqueous methanesulphonic acid.
5. The conversion of the para-chlorotoluene is high. The formation of
para-chlorobenzaldehyde is higher compared with chemical methods.
6. There is no bye-product formation in comparison with chemical
methods.
7. No spent reagent disposal. Hence this process is eco-friendly.
8. This process is competitive with all known commercial routes.

We claim :
1. An improved process for the preparation of para-chlorobenzaldehyde which comprises
oxidizing para chloro toluene using electrochemically generated cerium(IV) methane
sulphonate characterized in that electrolysing the said cerium(IV) methane sulphonate
in methane sulphonic acid at a current density of 5 - 15 A/dm2 in an undivided cell in a
mole ratio of Para-chlorotoluene to cerium (IV) methane sulphonate 1:4 to 1 :5.6 at a
temperature of 75 - 80°C for a period of 30 to 45 minutes with vigorous stirring to
obtain a solution and recovering the para-chlorobenzaldehyde by extraction method.
2. An improved process as claimed in claim 1 wherein the solvent used for extraction of
para-chlorobenzaldehyde is selected from l,2dichloromethane , chloroform and mixture
therof.
3. An improved process for the preparation of para-chlorobenzaldehyde as herein
described with reference to the examples.

Documents:

1294-del-2001-abstract.pdf

1294-del-2001-claims.pdf

1294-del-2001-correspondence-others.pdf

1294-del-2001-correspondence-po.pdf

1294-del-2001-description (complete).pdf

1294-del-2001-form-1.pdf

1294-del-2001-form-18.pdf

1294-del-2001-form-2.pdf

1294-del-2001-form-3.pdf

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Patent Number

231036

Indian Patent Application Number

1294/DEL/2001

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

28-Feb-2009

Date of Filing

28-Dec-2001

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH,

Applicant Address

RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	KUMARASAMY KULANGIAPPAR	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, KARAIKUDI-630003, TAMILNADU, INDIA.
2	ARUNACHALAM MUTHUKUMARN	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, KARAIKUDI-630003, TAMILNADU, INDIA.
3	MANICKAM ANBU KULANDAINATHAN	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, KARAIKUDI-630003, TAMILNADU, INDIA.
4	THASAN RAJU	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, KARAIKUDI-630003, TAMILNADU, INDIA.
5	VENKATASUBRAMANIAN KRISHNAN	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE, KARAIKUDI-630003, TAMILNADU, INDIA.

PCT International Classification Number

C07C

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA