Title of Invention

A PROCESS FOR THE ELECTROCATALYTIC OXIDATION OF ALKENES

Abstract

This invention relates to a process for electro catalytic oxidation of alkenes. More particularly it relates to a process for electro catalytic oxidation of alkenes by using a novel conducting polymer coated modified electrode as an anode. The process steps comprises preparing a solution of an alkene in an organic solvent such as herein described, adding an external electrolyte salt or acid selected from perchlorate, fluoroborate and phosphate to the above said solution, applying a potential of 0.4 - 0.9 V Vs SCE to a modified electrode for a period ranging from 200 to 2000 seconds at a temperature of 20-3 5°C to obtain the mixture of corresponding ketone and carboxylic acid.

Full Text

This invention relates to a process for electro catalytic oxidation of alkenes. More particularly it relates to a process for electro catalytic oxidation of alkenes by using a novel conducting polymer coated modified electrode as an anode. The novel conducting polymer coated modified electrode is prepared by a procedure as described and claimed in our co-pending patent application no. 0152 del 2002. Oxidation of alkenes to ketones, alcohols etc. using different types of catalysts such as palladium or ruthenium complexes has been known for several years (Synthesis. Vol. 7, 739, 1990). However, these types of reactions usually take place efficiently at high temperatures. Since high pressure builds up during the process, such reactions are carried out in closed high pressure reactors. This leads to hazardous condition due to possibilities of explosion. Hence, it is desirable to carry out such reactions at normal ambient conditions, which can be feasible by electrochemical methods. The electro-oxidation of alcohols using carbon or graphite electrodes has been reported before (Electrochim. Acta. Vol.44(15), 1999 p.2559-2569), but the current are not very high and the yield is poor when used for decene. In order to increase the electrode activity it is essential to modify the same and preferably make it electrocatalytic so that high yield and selectivity are obtained for alkenes. The preparation of the modified electrodes has been fully described and claimed in out co-pending application number 0152del2002. No process has yet been reported for electrocatalytic oxidation of alkene using a conducting polymer modified electrode. The inventors of the present invention are providing herewith a process using the modified electrode. The object of the present invention is to provide a process for electro-catalytic oxidation of alkenes using a modified electrode. Accordingly, the present invention provides a process for electro-catalytic oxidation of alkenes which comprises preparing a solution of an alkene in an organic solvent such as herein described, adding an external electrolyte salt or acid selected from perchlorate, fluoroborate and phosphate to the above said solution, applying a potential of 0.4 - 0.9 V Vs SCE to a modified electrode for a period ranging from 200 to 2000 seconds at a temperature of 20-35°C to obtain the mixture of corresponding ketone and carboxylic acid. In an embodiment of the present invention the alkene used for oxidation is a alkene having C > 5 selected from hexene, octene and decene. In an another embodiment the organic solvent used is selected from the group consisting of isopropanol, dimethyl formamide and solvent having solubility parameter higher than 10. In yet another embodiment the external electrolyte used is a salt or acid selected from perchlorate, fluoroborate and phosphate. In still another embodiment the potential applied across the electrodes is preferably 0.5 Volts (SCE). The invention is described herein by the following examples which are illustrative only and should not be construed to limit the scope of the invention in any manner. The modified electrode was prepared according the process described in the co-pending patent No. NF 381/01 EXAMPLE -1 In a three electrode electrochemical cell, 200 ml acetonitrile were taken to which 3.2 gm LiClO4 and. 3.8 ml decene were added in sequence. The clean microscopic glass plates were dip coated in a solution (1.0 wt%) of styrene-butadiene copolymer in toluene and dried at 50 ° C for 10 min. These were placed in a vacuum chamber, which was evacuated to 10 -6 torr and gold films deposited by thermal evaporation technique. These were then placed in the electrochemical cell with platinum counter electrode and SCE reference electrode . The electrolyte used consisted of 100 ml water (deionised), 100 ml n-methyl pyrrolidone, 8 ml hydrochloric acid (35%), 4 ml aniline and 0.08 gm copper phthalocyanine The conducting polymer deposition was carried out by applying a potential of 0.9V (SCE) for 180 s. The electrodes were removed, dried at room temperature and then used for electro-oxidation reaction as the anode EXAMPLE - 2 . Microscopic glass plates were dip coated in a solution (1.0 wt%) of polyvinyl butyral in methanol , dried and heated to 60 ° C for few minutes to drive off the solvent. These were placed in a vacuum deposition chamber which was evacuated to 10-6 torr and gold films ( 0.1 to 0.2 um thick) were deposited using thermal evaporation technique. The substrates with metallic coating were placed in an electrochemical cell as working electrode, platinum foil as counter electrode and SCE reference electrode. The electrolyte was a mixture of deionised water ( 100 ml ) and n-methyl pyrrolidone (100 ml) with 8 ml hydrochloric acid (35%) with 4 ml aniline and 0.04 grn copper phthalocyanine . The conducting polymer deposition was carried out by applying a potential of 0.9V (SCE) for 180 s. The electrodes were removed, dried at room temperature and then used for electro-oxidation reaction. EXAMPLE - 3 . Clean microscopic grade glass slides were dip coated in a solution (1.0 wt%) of polyvinyl butyral in methanol, dried and heated to 60 ° C for few minutes to drive off the solvent. These were placed in a vacuum deposition chamber which was evacuated to 10-6 torr and gold films (0.1 to 0.2.um thick) were deposited using thermal evaporation technique. The substrates with metallic coating were placed in an electrochemical cell as working electrode, platinum foil as counter electrode and SCE reference electrode. The electrolyte used consisted of 100 ml water (deionised), 100 ml n-methyl pyrrolidone, 8 ml hydrochloric acid (35%), 4 ml aniline and 0.08 gm copper phthalocyanine. The conducting polymer deposition was carried out by applying a potential of 0.9V (SCE) for 180 s. The electrodes were removed, dried at room temperature. EXAMPLE - 4 This example illustrates the process for electrocatalytic oxidation of decene using modified electrode The modified electrode as prepared in example 1 was placed in an electrochemical cell containing 200 ml actonitrile, 3.8 ml decene, 3.2 g. LiClCO4 and 0.34 g CuCl2. A potential of 0.6 Volts vs SCE was applied to the anode for a duration of 200 s. The anodic currents obtained for this electrode are given in Table 1. EXAMPLE - 5 This example illustrates the process for electrocatalytic oxidation of decene using modified electrode The modified electrode as prepared in example 1 was placed in an electrochemical cell containing 200 ml acetonitrile, 3.2 gm LiC1O4 and 3.8 ml decene. The anodic currents obtained for decane at an oxidation potential of 0.6 V SCE are given in Table-1 EXAMPLE - 6 This example illustrates the process for electrocatalytic oxidation of hexene using modified electrode The modified electrode as prepared in example2 was placed in an electrochemical cell containing 200 ml acetonitrile, 2.88 ml HC1O4, 2.5 ml hexene . The anodic currents obtained for these at an oxidation potential of 0.6 V SCE are given in Table - 1. Table - 1 : Comparison of electro-catalytic efficiency of modified electrodes (Table Removed) It is seen from the above results in Table-l that this process using the modified electrode gave much higher oxidative currents for the electro-oxidation of hexene and decene. Thus, the process for electroxidation of alkene using the electrodes as described in the present invention leads to much higher yield for the electro-oxidation of alkenes. The main advantage of the present invention are This process makes use of much cheaper material than metals / metallic complexes based on palladium, ruthenium etc. It also gives better results than the latter compounds ( see Table -1 comparing values for Example 2 with Example 3). We Claim: 1. A process for electro-catalytic oxidation of alkenes which comprises preparing a solution of an alkene in an organic solvent such as herein described, adding an external electrolyte salt or acid selected from perchlorate, fluoroborate and phosphate to the above said solution, applying a potential of 0.4 - 0.9 V Vs SCE to a modified electrode for a period ranging from 200 to 2000 seconds at a temperature of 20-35°C to obtain the mixture of corresponding ketone and carboxylic acid. 2. A process as claimed in claim 1 wherein the alkene used for oxidation is selected from hexene, octene and decene. 3. A process as claimed in claims 1& 2, wherein the organic solvent used is selected from the group consisting of isopropoanol, dimethyl formamide and solvent having solubility parameter higher than 10. 4. A process as claimed in claims 1-3, wherein the potential applied across the electrodes is preferably 0.5 Volts (SCE). 5. A process for the electro-catalytic oxidation of alkenes substantially as herein described with reference to the examples accompanying this specification.

Documents:

181-del-2002-abstract.pdf

181-del-2002-claims.pdf

181-del-2002-correspondence-others.pdf

181-del-2002-correspondence-po.pdf

181-del-2002-description (complete).pdf

181-del-2002-form-1.pdf

181-del-2002-form-18.pdf

181-del-2002-form-2.pdf

181-del-2002-form-3.pdf