US2954410A - Metalation process - Google Patents

Description

United States W 21,954,410 Patented Sept. 27, 1960 METALATION PROCESS Charles E. Frank, Virgil L. Hansley, and John F.- Nobis, Cincinnati, Ohio, assignors to National Distillers and Chemical Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed July 31, 1957, Ser. No. 675,257

10 Claims. (Cl. 260-665) The present invention relates to a novel process for preparation of alkali metal derivatives of organic compounds containing an active hydrogen atom replaceable by an alkali metal and, additionally, to such a process wherein the alkali metal derivatives are converted to highly valuable substances, particularly organic acids.

In recently developed processes, it has been discovered that substances such as conjugated dienes and vinyl aromatic compounds, such as styrene and styrene having an alkyl substituent for a nuclear hydrogen atom, can be reacted with an alkali metal under conditions to ellect selective dimerization of the conjugated 'diene or vinyl aromatic compound. Such conditions include use of an alkali metal in finely divided form, a selected ether reaction medium, and preferably, a temperature below C. although somewhat higher temperatures, as for example, up to about 25 C. may be used. The selectivity of the reaction to dimerization of the diene or vinyl aromatic compound depends particularly on the use of the alkali metal in finely divided form. Thus, when the alkali metal is in finely divided form, such as particles of less than about 50 microns in size but greater than about microns, it is necessary to carry out the reaction in presence of a relatively small catalytic amount, based on the diene or vinyl aromatic reactant, of a substance such as a polycyclic aromatic compound, examples of which include naphthalene, anthracene, and terphenyls, biphenylene ethylene, etc. On the other hand, when the alkali metal is not only in finely divided form but is of controlled particle size characteristics falling within a rather well defined minimum amount of relatively large size particles and particularly low average particle size characteristics, the aforesaid reaction for selective dimerization can be carried out Without need of such catalytic substances, although such substances can be used if desired. Processes of the latter type, i.e., selective dimerization without need of use of the aforesaid catalytic substances, are disclosed in co-pending applications, S.N. 583,606, filed May 9, 1956, now U.S. Pat. No. 2,816,- 914), and SN. 556,469, filed December 30, 1955 (now U.S. Pat No. 2,816,936). The former co-pending application relates to selective dimerization of a vinyl aromatic hydrocarbon by reaction thereof with an alkali metal in dispersed form in which substantially more than about 50% of the alkali metal particles are not more than about 3 microns in size and, more preferably, not more than about one micron in size. More preferable embodiments include the use of an alkali metal which is in the form of a dispersion in which more than about 55% of the alkali metal particles are three or less microns in size and the average particle size is not more than about four microns, or in the form of a dispersion in which (a) more than about 75% of the alkali metal particles are not more than about three microns in size and preferably not more than about one micron, (b) the average particle size of the dispersion is not more than about one micron and (c) the dispersion is devoid of more than about 5% of alkali metal particles larger than about fifteen microns in size. Optimum results are generally obtained by use of an alkali metal dispersion in which all or substantially all of the alkali metal particles do not exceed about three microns in size and the average particle size is one or less microns.

For the selective dimerization of a conjugated diene, as disclosed in S.N. 556,469 (now U.S. Pat No. 2,816,- 936), the reaction is carried out with use of an alkali metal in which more than about 30% of the alkali metal particles are of less than about five microns in size and, more preferably, not more than about three microns in size. More preferred embodiments include the use of such a dispersion in which more than about 30% of the alkali metal particles are of less than about five microns in size and preferably not over about three microns, and the average particle size of the dispersion is not more than about ten microns; or such a dispersion in which (a) more than about 30% of the alkali metal particles do not exceed about three microns in size, ([1) the average particle size of the dispersion averages not more than about one micron and (c) the dispersion is devoid of more than about 10% of alkali metal particles larger than about fifteen microns in size. Optimum results are obtained by use of an alkali metal dispersion in which all or substantially all of the alkali metal particles do not exceed about three microns in size and the average particle size is one or less microns.

It has now been discovered that if processes as aforedescribed are carried out in the presence of an organic substance containing an active hydrogen atom, or if the selectively formed dialkali metal dimers are preformed and subsequently reacted with such an organic substance, a highly effective conversion occurs whereby an active hydrogen atom of said organic substance is replaced by an alkali metal atom. To effect such a reaction, however, certain controlled conditions must be employed including the residence time for contact of the organic substance containing the active hydrogen atom, the amount of said organic substance employed relative to the diolefin or vinyl aromatic subjected to the dimerization reaction, etc. As is described more fully hereinafter, when reference is made herein to residence time, it is intended to include the period of time which the organic substance is in contact with the olefin or vinyl aromatic undergoing dimerization with the alkali metalo'r the period of time of contact of the organic substance with the dimer product of reaction between the alkali metal and olefin or vinyl aromatic in cases wherein the organic substance is added subsequent to the formation of the dimerized product.

Thus, in accordance with this invention, the formation of metalated products (i.e., organic substances in which an active hydrogen atom has been replaced by an alkali metal atom) can be prepared in an in situ reaction or by preformation of the dialkali metal dimers utilizing as reactants an alkali metal in finely divided form of the aforesaid particle size characteristics, for reaction with a conjugated diolefin or a dimerizable vinyl aromatic hydrocarbon in a suitable liquid reaction medium, and an organic substance containing an active hydrogen atom. For such processes, the alkali metal should be in the form of a dispersion in which the particle size characteristics are as aforesaid depending on the dimerizable reactant employed so as to eifect selective dimerization Without requirements for a dimerization promotor such as a polycyclic aromatic compound.

Thus, in practice of this invention in which, for example, the alkali metal is sodium and the organic substance containing an active hydrogen atom is toluene, the toluene is metalated to benzylsodium; propylene is metalated to allylsodium, butene is metalated to butenyls'o'dium, Z-heptene is metalated to heptenylsodium, p-

3 xylene is metalated to p-methylbenzylsodium, l-phenyl- Z-butene is metalated to l-phenyl-1-sodio-2-butene, furan to u-furylsodium, etc.

Such metalated products can be carbonated to produce salts of organic acids, as, for example, benzyl sodium can be carbonated to ultimately yield phenylacetic acid; allylsodium to vinylacetic acid; butenyl sodium to methyl vinylacetic acid, p-methylbenzylsodium to p-tolylacetic acid, 1-phenyl-l-sodio-2-butene to 2-phenyl-3-pentenoic acid, and the like.

Accordingly, the following reactants and conditions may be employed in practice of the present invention:

(1) An aliphatic conjugated diolefin, and preferably, such diolefins of from 4 to 8 carbon atoms with specific examples including butadiene, isoprene, dimethyl butadiene, the pentadienes, as the methyl-1-3-pentadienes, and the like; styrene, ring substituted styrenes such as ortho, meta and para methyl styrene, ethyl styrenes, and the like and, in general, alpyl-ring substituted styrenes in which the alkyl group or groups contain from one to four carbon atoms.

(2) An organic substance containing an active hydrogen atom; i.e., a hydrogen atom replaceable by an alkali metal atom. Included therein are compounds such as aliphatic monoolefins containing at least three carbon atoms including propylene, butenes such as butene-l and butene-Z, pentenes such as pentene-l and pentene-2, hexenes such as hexene-l, -2, and -3, the heptenes, octenes, nonenes, decenes, etc.; aromatic compounds such as toluene, benzene, the xylenes such as p-xylene, 1-phenyl-2- butene, and heterocyclic compounds such as furan, thiophene, pyridine, and others.

(3) An alkali metal in finely divided form having the aforesaid particle size characteristics depending on the dimerizable reactant employed. Suitable examples thereof include sodium and potassium with sodium being preferred as it provides excellent selectivity of reaction and yield of desired products and is cheaper and more readily available. Use of chemically pure sodium is not essential, however, as mixtures containing a substantial amount of sodium are useful as are alloys of sodium and potassium, of sodium and calcium, and of sodium and lithium. The alkali metal dispersions are most conveniently prepared in a separate step preliminary to their use in the described reaction.

(4) The reaction is carried out in a suitable liquid reaction medium, including certain ethers, acetals, tertiary amines, etc. with examples thereof being dimethyl ether, dioxane, trimethyl amine, etc. However, preferred reaction mediums are aliphatic mono ether having a methoxy group, in which the ratio of the number of oxygen atoms to the number of carbon atoms is not less than 1:4. Examples include dimethyl ether, methyl ethyl ether, methyl n-propyl ether, methyl isopropyl ether, and mixtures of these methyl ethers. Certain aliphatic polyethers are also quite satisfactory. These include the acyclic and cyclic polyethers which are derived by replacing all of the hydroxyl hydrogen atoms of the appropriate polyhydric alcohol by alkyl groups. Typical examples are the ethylene glycol dialkyl ethers such as the dimethyl, methyl ethyl, diethyl, and methyl butyl ethers. The simple methyl monoethers, as dimethyl ether, and the dimethyl and diethyl ethers of ethylene glycol are preferred.

The ethers should not contain any groups such as hydroxyl, carboxyl and the like which are distinctly reactive towards sodium. Although the ether may react in some reversible manner, it must not be subject to extensive cleavage, as such cleavage action destroys the ether, uses up sodium and introduces into the reacting system sodium alkoxides which, in turn, tend to induce rubber forming reaction with the diene rather than the desired reaction.

Although the reaction medium should consist essentially of the aforesaid substances, other inert media can be present in limited amounts. In general, these inert media will be introduced with the sodium dispersion as the liquid in which the sodium is suspended and will act chiefly as diluents. The concentration of reaction medium in the reaction mixture should at all times be maintained at a sufficient level to have a substantial promoting efiect upon the desired dimerziation reaction.

In carrying out the reaction between the alkali metal and the aliphatic conjugated diolefin or vinyl aromatic compound as well as when such a reaction is carried out in situ in presence of the organic substance containing an active hydrogen atom, a temperature of below about 0 C. is employed with a preferred range being between 20 to 50 0., although in certain instances temperatures up to about 30 C. may be used with use of pressure if necessary or desired. However, when the selective reaction between the alkali metal and diolefin or vinyl aromatic compound is initially carried out at a relatively low temperature (e.g., below about 0 C.,) in absence of the organic substance containing the active hydrogen atom, and the latter substance is added following completion of the dimerization reaction, the temperature of the mixture containing the added organic substance is preferably raised to expedite its metalation by the dialkali metal dimer. Thus, the temperature may for example, be raised to 25 C. or higher, depending on the boiling point of the lowest boiling reactant, i.e. dimer product or the organic substance containing the replaceable hydrogen atom. Thus, following completion of the dimerization reaction and addition of the organic substance to be metalated, the temperature is preferably raised but is maintained below the boiling point of the lowest boiling reactant. Similarly, such temperature elevation can be used in the described in situ reaction following completion of the dimerization reaction so as to expedite the metalation of the organic substance present during the dimerization reaction. Moreover, in instances wherein it is desired to effect the metalation of the organic substance at an elevated pressure, higher temperatures may be used commensurate with boiling point characteristics, decomposition temperatures, etc. of the reactants and reaction products. For most satisfactory results, a residence time of three or more hours, such as four to six hours, is employed for the described metalation reactions although an appreciable amount of the desired reaction often occurs with a residence time of from about one half to one hour.

In preferred practice, a ratio of at least three mols of the organic substance containing an active hydrogen atom is used per equivalent of the alkali metal in the dimerized product of the dimerization reaction. Thus, for example, where the dimerized product is disodiooctadiene, it is preferred to use at least six moles of said organic substance per mole of disodiooctadiene. However, ratios as low as one mole of the organic substance per equivalent of sodium may be used but a higher relative concentration of the organic substance is used to expedite its metalation by the alkali metal of the dimer product. Thus, for example, in instances wherein the organic substance containing an active hydrogen atom serves as a reaction medium, molar ratios of ten, or higher mols of the organic substance per equivalent of sodium may be used.

In order to further describe the invention, the following embodiments are set forth for purposes of illustration and not limitation.

Example 1 To a reaction medium of 2000 ml. of dimethyl ether and two gram atoms of sodium (substantially all particles not more than about 3 microns, average particle size not more than 1 micron) as a 20% dispersion in mineral spirits, two (gr-am) moles of butadiene and six (gram) moles of propylene were added while maintaining the reaction mixture at a temperature of --50 C. The butadiene and propylene were added simultaneously at a rate of (2) grams/minute for the butadiene and 4% grams/minute for the propylene. Following completion of addition of the butadiene' and propylene, the reaction mixture was stirred for 5 /2 hours at approximately reflux temperature (40" C.), following which the mixture was poured onto an excess of crushed Dry 'Ice.- Volatile organic materials (dimethyl ether and CO .were

then allowed to evaporate and the resulting: dry salts were treated with steam and'dissolved in water to de--' stroy any residual sodium'and :to drive off any traces of volatile organic matter. The resulting solution of salts was then filtered and acidified with concentrated HCl to liberate the free acids from their salts. Extraction of the acids with diethyl ether, followed by stripping the:

Example 2 To a reaction medium of 1000 ml. of dimethyl ether, 1000 ml. of toluene, and two gram atoms of sodium (as defined in Ex. 1) as a 20% dispersion in mineral spirits was added 2 moles of butadiene at the rate of 2 g./minutes, while maintaining the temperature at 25 C. 'Following addition of the butadiene, the refrigeration was removed and the dimethyl ether allowed to evaporate. After two hours, the temperature had risen to C. and the mixture was treated with an additional 1000 ml. of toluene. Within two more hours the mixture had attained room temperature, where it was stirred for a final two hour period. The mixture was then carbonated on excess Dry Ice and the volatile materials were allowed to evaporate in the hood. The residual salts were dissolved with steam and hot water. After filtering the small amount of polymeric material that remained out of solution, the aqueous solution was acidified with concentrated hydrochloric acid. The resulting precipitate, when dried, weighed 234 g. representing an 86% yield of phenylacetic acid.

Example 3 An experiment was carried out similar to Example 2, except that furan was substituted for the toluene throughout the run. Processing of the carbonated mixture by the method described in Example 2 yielded 123 g. (55%) of a-furoic acid.

Example 4 An experiment was carried out similar to Example 1, except that six moles of Z-butene were substituted for the propylene. Processing the carbonation mixture as in Example 1 resulting in a 45% yield of an acid mixture consisting of 3-pentenoic acid and 2-methyl-3-butenoic acid. The individual acids were identified by hydrogenation to their saturated derivatives, which were isolated as the ethyl esters.

Example 5 To a reaction medium consisting of 2000 of dimethyl ether, and 0.75 gram atom of sodium (as per Ex. 1) as a 20% dispersion in mineral spirits, 0.75 mole of styrene dissolved in an equal volume of alkylate was added at a constant rate over a period of 40 minutes. Simultaneously and over the same period of time, 3 moles of propylene was passed in at a constant rate. During this and subsequent operations the temperature was held at 40 C. by external cooling. Following completion of the addition, the mixture was stirred 6 hours at 40 C., then carbonated on excess Dry Ice.

Processing of the carbonation mixture as in Example 1 yielded 21 g. {32%) of vinylacetic acid.

Example 6 To a reaction medium consisting of 1000 ml. of dimethyl ether and 0.75 gram atom of sodium (as in Ex. 1) as a 20% dispersion in mineral spirits 0.75 mole of styrene dissolved in an equal volume of mineral spirits was added over a period of 40 minutes at 30 C. The external cooling was removed and the mixture allowed to warm slowly to room temperature, during which time the dimethyl ether largely'evaporated. After 2 hours .the temperature had reached 0 C. and the mixture was tr'eated with an added 1000 ml. of toluene. After two more' hours (total of 4) the temperature had reached room temperature.v The mixture was stirred at room temperature for 2 hours (total contact time=6 hours), then carbonated on excess Dry Ice. Processing of the carbonated mixture as in Example 2 yielded 45 g. (44%) of phenylacetic acid.

Example 7 Example 8 An experiment was carried out similar to Example 2 except that 2 moles of isoprene was substituted for the butadicne and added at a rate of 2 g. per minute. Processing of the carbonated mixture as in Example 1 yielded 61% of phenylacetic acid.

While there are above disclosed but a limited number of embodiments of the invention herein presented, it 1s possible to produce still other embodiments without departing from the inventive concept herein disclosed, and it is desired therefore that only such limitations be imposed on the appended claims as are stated therein.

What is claimed is:

1. A process for preparation of alkali metal derivafives of organic compounds containing an active hydrogen atom replaceable by an alkali metal atom which comprises reacting in a liquid reaction medium (1) a dimerizable olefin from the group consisting of aliphatic conjugated dienes, styrene and styrene having an alkyl substituent for a nuclear hydrogen atom, with (2) a finely divided alkali metal as a dispersion in which more than about 30% of the alkali metal particles are of less than about five microns in size, the average particle size of the dispersion is not more than about ten microns and the dispersion is devoid of more than about 10% of alkali metal particles larger than about fifteen microns in size, to selectively dimerize said olefin to dialkali metal dimers of said olefin, and contacting the resulting reaction mixture containing said dialkali metal dimers with an organic compound containing an active hydrogen atom replaceable by an alkali metal atom for a period of time of at least about one-half hour to replace an active hydrogen atom of said organic compound with an alkali metal atom from said dialkali metal dimer.

2. A process for preparation of alkali metal derivatives of organic compounds containing an active hydrogen atom replaceable by an alkali metal atom which comprises providing a reaction mixture comprising (1) a dimerizable olefin from the group consisting of aliphatic conjugated dienes, styrene, and styrene having an alkyl substituent for a nuclear hydrogen atom, (2) a finely divided alkali metal dispersion in which more than about 30% of the alkali metal particles do not exceed about three microns in size, the average particle size of the dispersion is not more than about one micron and the dispersion is devoid of more than about 10% of alkali metal particles larger than about fifteen microns in size, (3) a liquid reaction medium in which the olefin selectively dimerizes to dialkali metal dimers of the olefin, and (4) an organic come 7 pound containing an active hydrogen atom replaceable by an alkali metal atom, maintaining saidmixture at a temperature at which the olefin is selectively dimerized to a dialkali metal dimer of said olefin and maintaining said organic compound containing an active hydrogen atom in contact with the alkali metal dimer thus formed for a period of at least one-half hour to replace an active hydrogen atom of said organic compound.

3. A process,'as defined in claim 1, wherein the selective 'dimerization reaction between the olefin and alkali metal is carried'out at a temperature of below about 0 C.

4. A process, as defined in claim 1, wherein the reaction mixture containing the alkali metal dimers is contacted with the organic compound containing an active hydrogen atom in a ratio of at least one mole of said organic compound per equivalent of the alkali metal in thedialkali metal dimer.

5. A process, as defined in claim 1, wherein the olefin is butadiene, the alkali metal is sodium as a dispersion of sodium particles substantially all of which do not exceed three microns in size and average not more than about one micron, the liquid reaction medium is dimethyl ether, the selective dimerization reaction is carried out at below about 0 C., the dialkali metal dimers are contacted with the organic compound containing an active hydrogen atom in a ratio of at least three mols of said organic compound per equivalent of alkali metal in said dialkali dimer, and said organic compound is maintained in contact with the dialkali metal dimers for a period of .at least about three hours.

6. A process, as defined in claim 2, wherein the reaction mixture is maintained at a temperature below about 8 0 C. to-selectively dimerize the olefin in presence of the organic compoundcontaining an active hydrogen atom, and the temperature of the resulting mixture containing the'dimerized olefin and said organic compound is raised to expedite replacement of an active hydrogen atom of said organic compound by an alkali'metal atom from the dialkali metal dimer of said olefin.

7. A process, as defined in claim 2, wherein the olefin is butadiene, the alkali metal is sodium, the liquid reaction medium is' dimethyl ether and the organic compound containing an active hydrogen atom is maintained 'in contact with the disodio dimers of butadiene.

' 8.A process, a defined in claim 2, wherein the reac- 'tion during selective dimerization of the olefin is carried out at below about 0 C.

9; A process, as defined in claim 2, wherein the reaction mixture contains the organic compound containing an active hydrogen atom in a ratio of at least one mole of said organic compound per equivalent of the alkali metal in the selectively formed dialkali metal dimers of the olefin.

10. A process, as defined in claim 2, wherein the organic compound containing an active hydrogen atom'replaceable by an alkali metal atom is a monoolefinic 25 aliphatic hydrocarbon.

UNITED STATES PATENTS References Cited in the file of this, patent 2,773,092 Carley et al Dec. 4, 1956 2,816,936 Hansley et al Dec. 17, 1957

Claims (1)

1. A PROCESS FOR PREPARATION OF ALKALI METAL DERIVATIVES OF ORGANIC COMPOUNDS CONTAINING AN ACTIVE HYDROGEN ATOM REPLACEABLE BY AN ALKALI METAL ATOM WHICH COMPRISES REACTING IN A LIQUID REACTION MEDIUM (1) A DIMERIZABLE OLEFIN FROM THE GROUP CONSISTING OF ALIPHATIC CONJUGATED DIENES, STYRENE AND STYRENE HAVING AN ALKYL SUBSTITUENT FOR A NUCLEAR HYDROGEN ATOM, WITH (2) A FINELY DIVIDED ALKALI METAL AS A DISPERSION IN WHICH MORE THAN ABOUT 30% OF THE ALKALI METAL PARTICLES ARE OF LESS THAN ABOUT FIVE MICRONS IN SIZE, THE AVERAGE PARTICLE SIZE OF THE DISPERSION IS NOT MORE THAN ABOUT TEN MICRONS AND THE DISPERSION IS DEVOID OF MORE THAN ABOUT 10% OF ALKALI METAL PARTICLES LARGER THAN ABOUT FIFTEEN MICRONS IN SIZE, TO SELECTIVELY DIMERIZE SAID OLEFIN TO DIALKALI METAL DIMERS OF SAID OLEFIN, AND CONTACTING THE RESULTING REACTION MIXTURE CONTAINING SAID DIALKALI METAL DIMERS WITH AN ORGANIC COMPOUND CONTAINING AN ACTIVE HYDROGEN ATOM REPLACEABLE BNY AN ALKALI METAL ATOM FOR A PERIOD OF TIME OF AT LEAST ABOUT ONE-HALF HOUR TO REPLACE AN ACTIVE HYDROGEN ATOM OF SAID ORGANIC COMPOUND WITH AN ALKALI METAL ATOM FROM SAID DIALKALI METAL DIMER.