Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/01—Products
  • C25B3/13—Organo-metallic compounds

Definitions

• This invention relates to the preparation of organo metallic compounds, and more particularly to a new and improved process for making tetraethyl lead.
• a process in which the anode is dissolved by electrolyzing is sometimes referred'to herein as a sacrificial anode process. 7
• One of the objects of the present invention is to provide a new and improved sacrificial anode process for processing organo metallic compounds.
• Another object of the invention is to provide a new and improved sacrificial anode process for producing organic lead compounds.
• Still a further object of the invention is to provide a new and improved sacrificial anode process for producing tetraethyl lead.
• organo metallic compounds can be produced by electrolyzing a substantially anhydrous solution of a Grignard 3,07,858 Patented Nov. 7, 1961 include organic chlorides, bromides and iodides.
• the halogen portion of the added organic halide does not have to be the same as the halogen portion of the Grignard reagent.
• the free hydrocarbon radicals derived from the Grignard reagent during electrolysis combine with the anode material to form the corresponding organo metallic compound which can be separated from the electrolyte in any suitable manner.
• the cathode may be composed of a suitable conducting but non-reactive material such as platinum, stainless steel, graphite or other conducting material which does not dissolve in the electrolyte.
• the cathode may be composed of the same material as the anode.
• both the cathode and the anode can betcomposed of lead. It is preferable, however, that the anode be composed of lead and the cathode of stainless steel.
• the invention is particularly valuable in the preparation of tetraethyl leadand this preparation will be used to illustrate the practice of the invention.
• a lead anode and preferably a stainless steel cathode are placed in a solution of ethyl magnesium chloride dissolved in a suitable organic solvent.
• a suitable organic solvent preferably employed for this purpose is the dibutylether of diethylene glycol.
• An electrolyzing current is passed into the ethyl magnesium chloride solution (Grignard solution) in sufiicient amount to cause the lead anode to be dissolved.
• Ethyl chloride is passed into the ethyl magnesium chloride solution either intermittently or continuously in sufiicient amount to react with the magnesium liberated at the cathode to reconvert it to ethyl magnesium chloride.
• the free ethyl radicals react at the anode with the lead to form tetraethyl lead.
• Magnesium chloride is a by-product of this process.
• the tetraethyl lead is removed in any suitable manner from the organic solvent solution. Where a high boiling solvent is used such as dibutyl ether of diethylene glycol, the tetraethyl lead is preferably removed by distillation.
• the residual solvent solution, before or after the removal of the tetraethyl lead, is treated to remove the magnesium chloride.
• This can be done by adding a substance which forms "an insoluble compound with the magnesium chloride, :for example, dioxane, and filtering the insoluble precipitate.
• the solvent solution from which the magnesium chloride has been removed is then recirculated to the cell in which the electrolyzing action is carried out or to a suitable container where it is used as a solvent for additional quantities of Grignard reagent.
• the removal of a partially electrolyzed solution from the electrolyzing cell can be carried out intermittently or con- 7 tinuously.
• the solution in the electrolyzing cell is prefreagent in an organic solvent for the Grignard reagent using a sacrificial anode and adding an organic halide to the electrolyte, the organic radical of which corresponds to the organic radical of the Grignard reagent being used.
• an organic halide as used herein is intended to erably agitated with suitable mechanical stirring or other agitating means.
• Example I A solution of ethyl magnesium chloride in the dibutyl ether of diethylene glycol was charged into an electrolyzing solution in a stainless steel closed pressure cell having five stainless steel plate cathodes and six lead plate anodes spaced one-fourth inch apart, the anode and cathode areas each being .310 square cm.
• the normality ofthe ethyl magnesium chloride in the solution was 1.27 and the total number of moles of ethyl magnesium chloride charged were 2.15 so that the total amount of solution was approximately 1700 cc.
• a magnetic stirrer was provided beneath the electrodes to agitate the solution.
• Example 11 The general procedure was the same as in Example I except that the normality of the ethyl magnesium chloride charged to the cell was 0.9. The total moles of ethyl magnesium chloride charged were 1.58. The molar ratio of ethyl chloride to ethyl magnesium chloride in solution was 2.5. The temperature of operation was 55-60 C. The electrolyzing action was carried out until approximately 63.5% by weight of the ethyl magnesium chloride had been converted. At this point .58 mole of ethyl magnesium chloride was recovered and .35 mole of ethane and ethylene had been evolved without taking into consideration the solubility of these gases in the solution.
• the percentage yield of tetraethyl lead based on ethyl magnesium chloride was approximately 80.5 and the percentage by-product gas approximately 17.5.
• the current used was 12.5 volts, at an initial conductance of 0.47 ampere, rising in fifteen minutes to 0.6 ampere and continuing at 0.6 ampere for 76.5 hours.
• Example Ill The electrolyzing process was carried out as in Example I except that the normality of the ethyl magnesium chloride charged was 1.0. The total moles of ethyl magnesium chloride charged were 1.75. The molar ratio of ethyl chloride to ethyl magnesium chloride in solution was 7.0. The temperature of operation was 65-85 C. The electrolyzing action was carried out until there was a 72.5% by weight conversion of the ethyl magnesium chloride. At this point 0.48 mole of ethyl magnesium chloride was recovered from the solution in the cell. The yield of tetraethyl lead based on ethyl magnesium chloride was about 73.5% by weight and the by-product gas amounted to 13.2% by weight.
• the voltage used in the foregoing process was 12 volts at a conductance of 0.15-0.18 ampere for 12 hours, rising to 2.3 amperes at the end of 14 hours, then dropping to 0.75 ampere after 24 hours, finally dropping to 0.36 ampere after 34 hours.
• Example IV The procedure was the same as in Example I except that the normality of the ethyl magnesium chloride charged was 0.94. The total moles of ethyl magnesium chloride charged were 1.44. The molar ratio of ethyl chloride to ethyl magnesium chloride in solution was 7.4. The temperature of operation was 3338 C. The electrolyzing process was carried out until 85% of the ethyl magnesium chloride had been converted. The yield of tetraethyl lead based on ethyl magnesium chloride was 84% by weight and the yield of by-product gas was approximately 16% by weight. The voltage used was 14 volts at an amperage of .95 ampere for 45 hours, then 26 volts at an amperage decreasing from 0.9 to 0.13 ampere in 15 hours.
• Example V The process was carried out as described in Example I except that the dimethylether of ethylene glycol was used as a solvent, the normality of the ethyl magnesium chloride charged was 0.82, the total moles charged were 1.43, the molar ratio of ethyl chloride to ethyl magnesium chloride in solution was 1.0 and the temperature of operation was 50 C. to 65 C.
• the voltage of the electrolyzing current was 12 volts for one-half hour at 4.9 amperes dropping to 3.1, thereafter 26 volts with the amperage dropping from 3.1 to .05 amperes in 22 hours.
• a white solid separated from the clectrolyzing solution which appeared to be the etherate of magnesium chloride.
• the supernatant liquid was hydrolyzed in water to yield tetraethyl lead.
• R represents the organic radical
• X represents the halogen atom of the Grignard reagent
• M represents the metal of the sacrificial anode which, in this case for the purpose of illustration, has a valence of 4
• Mg is the conventional symbol for magnesium.
• Equation D shows why the optimum molar ration of organic halide to magnesium is approximately 1:1. From the foregoing examples it is apparent that as this ratio is increased by-product gases are formed, apparently due to the higher concentration of free radicals which can combine with each other and tend to do so rather than combine with the metal of the anode.
• the metal M in equation C can be another metal which is capable of being electrolyzed in a Grignard reagent.
• examples of such other metals are calcium, zinc, cadmium, manganese, mercury, lanthanum, thallium, arsenic, bismuth, tellurium and selenium.
• the radical R in equations C and D can be another organic radical which forms a Grignard reagent, for example, methyl, ethyl, propyl, isopropyl, butyl and higher homologues, phenyl, benzyl, and
• the radical X can be, for example, chlorine, bromine or iodine.
• other organic lead compounds or other organic metal compounds can be prepared by substituting other Grignard reagents for the ethyl magnesium chloride inthe foregoing examples and by using the corresponding organic halides in place of ethyl chloride.
• Specific examples of such other Grignard reagents are ethyl magnesium bromide, isopropyl magnesium chloride, isopropyl magnesium bromide, butyl magnesium bromide, amyl magnesium bromide, butyl magnesium chloride,.amyl magnesium chloride, and higher alkyl hom- :ologues.
• phenyl magnesium chloride, phenyl magnesium bromide, or mixtures of phenyl and ethyl :magnesium chloride or mixtures of phenyl and ethyl magnesium bromide can be electrolyzed to produce other organic lead compounds (or other sacrificial anode metals) containing the phenyl radical or both the phenyl and ethyl radicals or both phenyl and other alkyl radicals .in case a higher alkyl magnesium halide is substituted for the ethyl magnesium halide.
• benzyl magnesium chloride and benzyl chloride can be employed in electrolyzing a lead or other sacrificial anode.
• the molar ratio of Mg(X) :RMgX does not exceed 2:1 becauseit has been noted that resin formation occurs if the Mg(X) content becomes too high. It is therefore desirable to control the Mg(X) content by removing Mg(X) in any suitable manner. This can be accomplished in some instances by using a specific solvent which will form an etherate with the Mg(X) as in Example V, or by adding dioxane which also forms a com- .plex insoluble substance, or by adding another material such as pyridine which forms a complex insoluble substance.
• the insoluble. complexes containing the Mg(X) canthen be removed from the electrolyzed solutioneither before or after separation of the organo metallic compound by filtration or other suitable means and the residual solution is returned for re-use in the electrolyzing cell.
• the invention has'been operated over a wide range of current densities and at varying voltages.
• the spacing and size of the electrodes will determine the current density.
• Cells of the type used in the examples canbeoperated at a low voltage around 2.5 to '3 volts in 'which case the current density is around 10.01 ampere per square centimeter.
• Direct current voltages of I OO-and 300 volts "have also been used but, in general, it is desirable to use direct current voltages around 2 to 25 volts. 1
• the temperatures used can vary rather widely depending upon the type of cell employed, the solvent used, and the nature of the organo metallic compound.
• the process is normally carried out at temperatures above the freezing point of the solution and below the boiling points of the solvent and organo metallic compound. High current densities tend to heat the "solution and cooling may be applied, if necessary. In general, good results are obtained at temperatures Within the range of 20 C. to 85 C.
• the exampleshigh boiling solvents for theGrignard reagent have been used. It is usually preferableto employ solvents which have a boiling point higher than the boiling point of the organo metallic compound which is being produced in the process.
• the dibutyl ether of diethylene glycol has a boiling point substantially higher than the boiling point of tetraethyl lead. This makes it possible to distil offthe tetraethyl lead and return the residual solvent to the electrolytic cell. In this way, the
• process can be carried out continuously by continuously removing a partially electrolyz'eds'olution from the cell, separating the tetraethyl lead by distillation and returning the residue.
• An alternative procedure is to use a solvent which forms an insoluble precipitate with the magnesium chloride, thus making it possible to separate the magnesium chloride from the solvent which is recirculated to the cell.
• the invention is not limited to any particular solvent except that the solvent must be relatively inert under the conditions of the process.
• the solvent should not contain any labile hydrogen which is readily reactive. It is also desirable that the solvent have sufficient conductivity to permit passage of the current between the anode and the cathode.
• Solvents containing aliphatic hydrocarbon groups connected to oxygen atoms or nitrogen atoms are especially useful. Hydrocarbon solvents have poor conductivity and are less desirable. Low boiling solvents such as diethyl other can be employed but are difiicult to handle and require different methods for separating the organo metallic compounds therefrom. Solvents such as tetrahydrofurane can be employed.
• the process can be carried out with solvents for the Grignard reagent in which the'organo metallic compound is insoluble.
• suitable solvents are dimethyl ether, diethyl ether, diisopropyl ether, and higher molecular weight dialkyl ethers, including the others of polyoxyethylene glycols, polyoxypropylene glycols and polyoxyethylene-polyoxypropylene glycols which are liquid under the conditions of reaction. Special mention may be made of the dimethyl ether of diethylene glycol, the dipropyl ether of diethylene glycol, the dibutyl ether of diethylene glycol and the dimethyl ether of dipropylene glycol.
• solvents containing nitrogen are trihexylamine, triamylamine, pyridine and quinoline.
• the pressure used in carrying out the process can also be varied and may be subatmospheric, atmospheric or superatmospheric.
• the pressures used in the electro lytic cell are normally suflicient to maintain the liquid phase with the particular solvent and temperature conditions employed.
• the organic halide is a relatively volatile halide, such as ethyl chloride
• superatmospheric pressures in the cell normally prevail. For instance, in the examples pressures up to 50 pounds per square inch have been employed.
• the pressure used will also vary depending upon the quantity of the organic halide introduced into the solution to be electrolyzed. The type of solvent used is a major factor in determining the pressure.
• tetraethyl lead using diethyl ether as a solvent the operation is preferably conducted at elevated temperatures around C. and pressures sufiicient to minimize the formation of lead metal.
• the process can be operated until a considerable amount of tetraethyl lead is formed after which at least a part of the electrolyte is removed from the cell, some of the excess solvent is distilled, some of the desired product is separated and the residue comprising unreacted Grignard reagent and magnesium chloride etherate, together with some tetraethyl lead in the form of a slurry is recycled to the cell.
• An alternative is to electrolyze the cell to exhaustion before separating the end products.
• the excess organic halide is available to react with magnesium that normally forms or deposits on the cathode. This not only makes it possible to remove the magnesium but at the same time re sults in the formation of additional quantities of Grignard reagent. Furthermore, it is no longer necessary to take precautions in order to prevent bridging of the magnesium between the cathode and the anode and it is possible to use cells in which the electrodes are relatively closely spaced. This in turn makes it possible to provide relatively large anode areas in a relatively small space.
• a process for preparing alkyl lead compounds which comprises electrolyzing, using a lead anode, a substantially anhydrous solution of a Grignard reagent in a substantially inert organic solvent for said Grignard reagent employing an electrolyzing current etfective to cause said lead anode to dissolve in said solution of said Grignard reagent in said organic solvent, adding an excess of an alkyl halide over that required for the formation of the Grignard reagent, and recovering from the resultant product an alkyl lead compound consisting of alkyl radicals linked directly to metallic lead.
• a process for preparing tetraalkyl lead compounds which comprises electrolyzing, using a lead anode, a substantially anhydrous solution of a Grignard reagent in a substantially inert organic solvent for said Grignard reagent employing an electrolyzing current effective to cause said lead anode to dissolve in said solution of said Griguard reagent in said organic solvent, adding an excess of an alkyl halide to said solution over the amount required I to form said Grignard reagent, and recovering from the resultant product a tetraalkyl lead compound consisting of alkyl radicals linked directly to metallic lead.
• a process for preparing tetraethyl lead which comprises electrolyzing, using a chemically inert cathode and a lead anode, a substantially anhydrous solution of ethyl magnesium chloride in a substantially inert organic solvent for said ethyl magnesium chloride employing an electrolyzing current effective to cause said lead anode to dissolve in said solution of said ethyl magnesium chloride in said organic solvent, adding about 0.9 mole of ethyl'chloride to said solution per mole of ethyl magnesium chloride, and recovering tetraethyl lead from the rmultant solution.
• a process for preparing tetraethyl lead which comprises electrolyzing, using a chemically inert cathode and a lead anode, a substantially anhydrous solution of ethyl magnesium chloride in a substantially inert organic solvent for said ethyl magnesium chloride employing an electrolyzing current efiective to cause said lead anode to dissolve in said solution of said ethyl magnesium chloride in said organic solvent, said solvent having a boiling point higher than the boiling point of tetraethyl lead, adding extraneous ethyl chloride to said solution in an amount sufiicient to increase the conductance of the electrolyzing solution, separating tetraethyl lead from said solution and using the residual solution for further electrolyzing.
• a process for preparing tetraethyl lead which comprises electrolyzing, using a chemically inert cathode and a lead anode, a substantially anhydrous solution of ethyl magnesium chloride in a substantially inert organic solvent for said ethyl magnesium chloride employing an electrolyzing current eifective to cause said lead anode to dissolve in said solution of said ethyl magnesium chloride in said organic solvent, said solvent having a boiling point higher than the boiling point of tetraethyl lead, adding extraneous ethyl chloride to said solution in an amount sufiicient to'increase the conductance of the electrolyzing solution, separating magnesium chloride from said solution, distilling tetraethyl lead from the residual solution and returning the residual solution after distillation of said tetraethyl lead for further use in the electrolyzing process.
• a process for preparingtetraethyl lead which comprises electrolyzing, using a chemically inert cathode and a lead anode, a substantially anhydrous solution of ethyl magnesium chloride in a substantially inert organic solvent for said ethyl magnesium chloride employing an electrolyzing current effective to cause said lead anode to dissolve in said solution of said ethyl magnesium chloride in said organic solvent, said solvent having a boiling point higher than the boiling point of tetraethyl lead, adding extraneous ethyl chloride to said solution in an amount sufiicient to increase the conductance of the electrolyzing solution, distilling tetraethyl lead from said solution, separating magnesium chloride from the residual solution and returning the residual solution from which the magnesium chloride has been separated for further use in the electrolyzing process.
• a process for preparing tetraalkyl lead compounds which comprises electrolyzing, using a lead anode, a substantially anhydrous solution of a Grignard reagent in a substantially inert solvent for said Grignard reagent employing an electrolyzing current effective to cause said lead anode to dissolve in said solution of said Grignard reagent in said organic solvent, adding to said solution an alkyl halide in sufticient amount to increase the conductance of the clectrolyzing solution, and rextovering from the resultant product a tetraalkyl lead compound consisting of alkyl radicals linked directly to metallic lead.
• a process for preparing tetraalkyl lead compounds which comprises electrolyzing, using a lead anode, a substantially anhydrous solution of a Grignard reagent in a substantially inert organic solvent for said Grignard reagent employing an electrolyzing current effective to cause said lead anode to dissolve in said solution of said Grignard reagent in said organic solvent, adding to said solution extraneous alkyl halide in a molar ratio of 0.9 to 7.4 moles of said alkyl halide per mole of said Grignard reagent, and recovering from the resultant product a tetraalkyl lead compound consisting of alkyl radicals linked directly to metallic lead.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Priority Applications (9)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25206049

Family Applications (1)

Country Status (6)

Cited By (12)

Family Cites Families (1)

• 0
  • BE BE590453D patent/BE590453A/xx unknown
  • NL NL251295D patent/NL251295A/xx unknown
• 1959
  • 1959-05-06 US US811262A patent/US3007858A/en not_active Expired - Lifetime
• 1960
  • 1960-04-11 GB GB12771/60A patent/GB882005A/en not_active Expired
  • 1960-04-29 SE SE4296/60A patent/SE306532B/xx unknown
  • 1960-05-02 DE DEN18263A patent/DE1171919B/de active Pending

Non-Patent Citations (1)

Also Published As

Similar Documents