| PATENT ASSIGNEE'S COUNTRY | USA |
| UPDATE | 06.00 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 20.06.00 |
| PATENT TITLE |
Manufacture of 3,3',5,5'-tetramethyl-2,2'-biphenol |
| PATENT ABSTRACT | Coupling in aqueous medium of 2,4-dimethylphenol by persulfate anion or hydrogen peroxide in the presence of iron or iron compounds gives good yields of relatively pure 3,3',5,5'-tetramethyl-2,2'-biphenol. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 18.02.99 |
| PATENT REFERENCES CITED |
H. Raudnitz, Berichtigung, 64, 517-518, 1930. U.S. application No. 09/121,105, filed Jul. 23, 1998. R.G.R. Bacon et al.,,J. Chem. Soc.,, 2275-2280, 1954. S.L. Cosgrove et al.,J. Chem. Soc., 1726-1730, 1951. C.G. Haynes et al.,J. Chem. Soc., 2823-2831, 1956. A.G.M. Barrett et al., Tetrahedron Letters, 34, 2233-2234, 1993. R.G.R. Bacon et al.,J. Chem. Soc., 1339-1344, 1960. |
| PATENT CLAIMS |
What is claimed is: 1. A process for the production of 3,3',5,5'-tetramethyl-2,2'-biphenol, comprising, contacting in an aqueous medium at a temperature of about 0.degree. C. to about 100.degree. C., 2,4-dimethylphenol, persulfate anion, and a catalytically effective amount of iron or an iron compound. 2. The process as recited in claim 1 wherein said temperature is about 15.degree. C. to about 50.degree. C. 3. The process as recited in claim 1 wherein said persulfate anion is present as ammonium, sodium, or potassium persulfate. 4. The process as recited in claim 1 wherein a molar ratio of said oxidant to said 2,4-dimethylphenol is about 1.0. 5. The process as recited in claim 1 wherein said iron is present as an inorganic iron compound. 6. The process as recited in claim 5 wherein said inorganic iron compound is present in an amount of about 0.05 to about 10 mole percent of said 2,4-dimethylphenol. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The manufacture of 3,3',5,5'-tetramethyl-2,2'-biphenol in high yield is accomplished by the coupling of 2,4-dimethylphenol caused by a combination of iron or iron compound and persulfate anion or hydrogen peroxide in aqueous medium. TECHNICAL BACKGROUND Biphenols, including substituted biphenols are known compounds, and are used as chemical intermediates and as monomers. 3,3',5,5'-Tetramethyl-2,2'-biphenol (TMBP) is similarly useful, see for example U.S. patent application Ser. No. 121,105, filed Jul. 23, 1998. Biphenols can be made by the oxidative coupling of (mono)phenols, but often many different products are obtained, other types of products such as ketones are obtained, and/or overall yields are poor for other reasons. This reaction is particularly useful where the phenol is substituted with electron donating groups. Various oxidants may be used for the oxidative coupling of phenols, and one useful combination of reagents is a transition metal and an oxidizing agent, such as persulfate anion, see for instance R. G. R. Bacon et al., J. Chem. Soc., p. 2275-2280 (1954); S. L. Cosgrove et al., J. Chem. Soc., p. 1726-1730 (1951); C. G. Haynes et al., J. Chem. Soc., p. 2823-2831 (1956); and A. G. M. Barrett et al., Tetrahedron Letters, vol. 34, p. 2233-2234 (1993). The oxidation of 2,4-dimethylphenol (DMP) to TMBP has also been carried out by similar procedures and for the most part the yields of the desired TMBP have been low to moderate. It is noted that some of the oxidants and/or cocatalysts involve the use of relatively expensive metal compounds, which is a disadvantage for large scale commercial use. R. G. R. Bacon et al., J. Chem. Soc., p. 1339-1344 (1960) report the preparation of TMBP from DMP in relatively low yield using a combination of persulfate anion and silver cation. No mention is made of using iron in place of the more expensive silver. SUMMARY OF THE INVENTION This invention concerns a process for the production of 3,3',5,5'-tetramethyl-2,2'-biphenol, comprising, contacting in an aqueous medium at a temperature of about 0.degree. C. to about 100.degree. C., 2,4-dimethylphenol, an oxidant selected from the group consisting of persulfate anion and hydrogen peroxide, and a catalytically effective amount of iron or an iron compound. DETAILS OF THE INVENTION The process described herein is run in aqueous medium, that is liquid water. Small amounts (up to 25 volume percent) of other "solvents" may be present in the medium, but it is preferred that the medium be pure water, with of course other process ingredients. The process is carried out at about 0.degree. C. to about 100.degree. C., preferably about 15.degree. C. to about 50.degree. C. The persulfate anion may be added as part of any inorganic persulfate that, preferably, has some solubility in water. Preferred persulfates are ammonium persulfates and alkali metal persulfates. Ammonium, sodium or potassium persulfates are especially preferred. Hydrogen peroxide may be added as an aqueous solution, preferably an aqueous solution containing between 3 percent and 55 percent of hydrogen peroxide by weight. Persulfate anion is a preferred oxidant. DMP is commercially available from Aldrich Chem. Co., Milwaukee, Wis. The iron may be added in the form of metallic iron or a compound of iron. If iron metal is added, it may be used in the form of "pure" iron or iron in the form of an alloy from which iron may be extracted by the aqueous medium of the process. It is believed that if iron metal (or an alloy) are present, a "small amount" of iron is oxidized and extracted into the process medium. If an iron compound is used, the iron may be in the +2 or +3 form. It is preferred that any iron compound used be an inorganic compound such as iron sulfate or iron chloride. Although not critical, it is preferred that the molar equivalent ratio of DMP:oxidant is about 1.2:1.0 to about 1.0:1.2, more preferably about 1.0. This results in the most efficient usage of DMP and oxidant on a stoichiometric basis. The amount of iron present is not critical; a catalytically effective amount is present. By catalytically effective amount is meant an amount that will cause at least 25 percent of the DMP to have reacted at the temperature of the process in 100 hours or less. A useful range of iron compound is about 0.05 to about 10 mole percent of iron, based on the amount of DMP added, more preferably about 0.2 to about 5 mole percent. As described in Example 1, the product may simply be filtered from the aqueous medium in relatively pure form. If further purification is desired, it may be recrystallized from an appropriate solvent. In the Examples, "RT" is room temperature. References to the "product" and/or "biphenol" are to 3,3',5,5'-tetramethyl-2,2'-biphenol. |
| PATENT EXAMPLES | This data is not available for free |
| PATENT PHOTOCOPY | Available on request |
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