Patent Application
20060170118
1. Field of Invention
This invention relates to the production of alkali-metalated alpha toluenes, their analogs and polymers.
2. Description of Prior Art
Currently benzyllithium is produced by the reaction of toluene with butyllithium, which is itself produced by the reaction of butyl bromide with elemental lithium at −80C. Benzylsodium has been produced by the reaction of chlorotoluene and sodium and rearranging the product to form the title compound (U.S. Pat. No. 4,084,061). The disadvantages of these processes are the difficulties of working with elemental alkali metals, low reaction temperatures and less than quantitative yields. Also there is currently no method for producing polyphenylene paradimethylene.
Several objects and advantages of the present invention are:
(A) Increased yield of product
(B) Less waste-no side reactions
(C) Uses low cost alkali metal hydroxides
(D) Reaction occurs at ordinary temperatures
(E) Cost of product will be less than by existing methods
In accordance with the present invention a process to produce compounds of toluene where one hydrogen of the methyl group is replaced by an alkali metal atom, analogs of these compounds and their polymers by dissolving toluene in an aprotic polar solvent in which the acidity of toluene is greater than that of water, such as DMSO, under an inert atmosphere, such as argon, adding an alkali metal hydroxide, such as lithium or sodium hydroxide to produce benzyllithium or benzylsodium and an equimolar quantity of water, then removing the solvent and water under reduced pressure, whereby the solid alpha-metalated toluene is obtained.
The ability of an alkali metal to replace hydrogen in a compound is a function of the acidity of the compounds. This acidity is described by the term pKa. Sodium, as typical of alkali metals, will disproportionate from a less acidic compound to a more acidic compound. In DMSO, the pKa of toluene is 28.3 and the pKa of water is 29.2 (acidity increases as pKa decreases). The acidity of compounds in aprotic solvents has no relation to their acidity in protic solvents, these may by greater or lesser depending on the compound. For example, in protic solvents water has a pKa of 15 and toluene has a pKa of 35. The benzyl cation has five resonance structures which allow it to delocalize the charge of the alkali metal ion, ortho, ortho, para, alpha-1,3,5 cyclohexatriene and alpha-2,4,6 cyclohexatriene, while the hydroxyl ion has dipole inductive effect. In aprotic solvents resonance delocalization is enhanced, while dipole inductive effect is decreased, thus a procedural advantage is realized by using aprotic solvents to perform the reaction.
One tenth mole of toluene (9.2 grams) is dissolved in 100 ccs of DMSO at 25C under an inert atmosphere of argon. One tenth mole of lithium hydroxide is added to form one tenth mole of benzyllithium (11.4 grams) and one tenth mole of water (1.8 grams). The water and DMSO are removed under reduced pressure (10 mm Hg) leaving the solid benzyllithium which is best stored in hexane.
One tenth mole of ethylbenzene (10.6 grams) is dissolved in 100 ccs of DMSO at 25C under an inert atmosphere of propane. One tenth mole of sodium hydroxide (4.0 grams) is added to form one tenth mole of alpha-sodium ethylbenzene (12.8 grams) and one tenth mole of water (1.8 grams). The water and DMSO are removed under reduced pressure (10 mm Hg) leaving the solid alpha-sodium ethylbenzene which is best stored under hexane.
One tenth mole of isopropylbenzene (12.0 grams) is dissolved in 100 ccs of DMSO at 25C under an inert atmosphere of argon. One tenth mole of potassium hydroxide (4.0 grams) is added to form one tenth mole of alpha-potassium isopropylbenzene (15.9 grams) and one tenth mole of water (1.8 grams). The water and DMSO are removed under reduced pressure (10 mm Hg) leaving the solid alpha-potassium isopropylbenzene which is somewhat insoluble in hexane. The solubility can be improved by the addition of crown ethers, such as crown 6 ether, but these ethers will be gradually attacked by alpha-potassium isopropylbenzene.
One tenth mole of parachloro toluene (11.6 grams) is dissolved in 100 ccs of DMSO at 25C under an inert atmosphere of argon. One tenth mole of sodium hydroxide (4.0 grams) is added to form one tenth mole of parachloro benzylsodium (13.8 grams) and one tenth mole of water (1.8 grams). The water and DMSO are removed under reduced pressure (10 mm Hg), leaving the solid parachloro benzylsodium which is dissolved in a suitable high boiling solvent such as dibutyl ether or dimethoxy ethane in the presence of a copper catalyst such as copper sulfate or finely divided copper metal and heated to 170C for 5 hours to form polyphenylene paradimethylene and sodium chloride.
Accordingly, the reader will see the production of benzyllithium and related compounds by using alkali metal hydroxides in aprotic polar solvents is more convenient than current methods.
Furthermore, the process has additional advantages in that
Although the process contains specifities, these should not be construed as limiting the scope of the invention, but merely providing illustrations of some of the presently preferred embodiments of the invention. For example, other inert gasses may be used, and other solvents may be used. Thus the scope of the invention should be determined by the appended claims and their legal equivalents rather than by the examples given.
