Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1998-07-14
2000-03-14
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568774, 568775, 568778, C07C 3930, C07C 3932
Patent
active
060375035
DESCRIPTION:
BRIEF SUMMARY
This is the U.S. National Stage Application of PCT/IL97/00019 filed Jan. 14, 1997 now WO97/26235 published Jul. 24, 1997.
1. Field of the Invention
This invention relates to a process for the preparation of p-fluorophenol by the hydrolysis of p-bromofluorobenzene. It particularly refers to a process which yields highly pure p-fluorophenol, obtained from a crude p-fluorophenol reaction product, which has an extremely low content of phenol and a low content of heavy by-products.
2. Background of the Invention
Aromatic fluorine compounds based on fluorobenzene are important intermediates for the manufacture of agrochemicals, pharmaceuticals and speciality polymers. One such fluorine compound is p-fluorophenol (hereinafter PFP). Various processes for the preparation of PFP are known in the art. Among them the following may be cited: direct fluorination of phenol, fluorination of p-aminophenol, hydroxylation of fluorobenzene, diazotization of p-fluoroaniline followed by hydrolysis of the diazonium salt, dealkylation of fluoroanisole or fluorophenetole, and hydrolysis of p-chlorofluorobenzene. A process which has received considerable attention in the art is the hydrolysis of p-bromofluorobenzene (hereinafter PBFB). Said hydrolysis has been carried out under basic conditions, under pressure, with or without a catalyst. The problems inherent in the preparation of PFP by the hydrolysis of PBFB are the low selectivity regarding PFP and the formation of phenol by-product. Phenol is not the only by-product formed; other by-products are, for instance, 4,4'-difluorodiphenyl ether (hereinafter DFDPE) and 4-fluoro-4'-hydroxydiphenyl ether (hereinafter FHDPE). Phenol, however, is a particularly undesirable by-product, because it is practically impossible to remove by distillation, and other methods known for its removal, such as melt crystallization or treatment with phthalic anhydride/H.sub.2 SO.sub.4, require an extra process step, which is detrimental to the economics of the process. Therefore considerable attention has been devoted in the art to the reduction of the amount of phenol formed, but the results have not been completely satisfactory.
Thus, U.S. Pat. No. 2,934,569 and GB 850888 disclose the hydrolysis of PBFB with Ca(OH).sub.2 as a base, and in the presence of a catalyst, whereby it is attempted to reduce the formation of phenol, but PFP is obtained in yields of only 50-70% and large amounts of DFDPE (10-15%) are formed.
Russian Patent 143404 describes the hydrolysis of PBFB using an alkali fluoride, such as NaHF.sub.2 or KOAc, as a base and Cu.sub.2 O as the catalyst. The reaction takes place at 250.degree. C. for 4 hours with a PFP yield of 73%.
DE 3430554 discloses the hydrolysis of PBFB in the presence of Ba(OH).sub.2 with Cu powder as a catalyst and a quaternary ammonium cocatalyst. Yields of up to 94.6% are mentioned.
U.S. Pat. No. 2,950,325 describes the basic hydrolysis of PBFB with alkaline earth metal oxides or hydroxides, which are said to avoid the formation of by-products such as phenol, "which are frequently formed when the stronger alkaline agent, e.g., potassium hydroxide or sodium hydroxide, is employed in the reaction".
In conclusion, the prior art teaches that the best way of carrying out the basic hydrolysis of PBFB comprises using a copper compound catalyst, and calcium or barium hydroxide as a base. Stronger bases, such as in particular sodium hydroxide, are said to produce bad results. The combined use of calcium hydroxide and copper catalysts, according to prior art, provides yields that may reach 70-75%.
It is a purpose of this invention to provide a process for the production of PFP which gives this product in high yields and a very low amount of phenol by-product.
It is a particular purpose of this invention to provide such a process which comprises the hydrolysis of PBFB and permits a reduction in the formation of phenol to amounts in the order of 0.1% and even below that amount.
It is a further purpose of this invention to provide such a process which does not involve the product
REFERENCES:
patent: 2934569 (1960-04-01), Kuehlewind, Jr.
patent: 2950325 (1960-08-01), Britton et al.
patent: 4940821 (1990-07-01), Pews et al.
Journal of Organic Chemistry, vol. 26, No. 11, Nov. 1961, Washington, D.C., pp. 4641-4645, XP002030172, M. M. Boudakian et al., Aromatic Fluorine Compounds. II. Synthesis of p-Fluorophenol by the Selective Hydrolysis of p-Bromofluorobenzene.
Chemical Abstracts, vol. 57, No. 8, Oct. 15, 1962, Columbus, Ohio; abstract No. 9744b, XP002030173 & SU 143 404 A, N.N. Vorontsonv, Jr., et al.
Adda Michel
Oren Jakob
Bromine Compounds Ltd.
Geist Gary
Padmanabhan Sreeni
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