Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
1997-03-10
2001-05-22
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S201000, C568S656000, C562S083000, C562S125000, C562S493000, C560S254000
Reexamination Certificate
active
06235949
ABSTRACT:
The present invention relates to a process for the preparation of halogenated derivatives, preferably halogenated aromatic derivatives. More specifically, it relates to the preparation of aromatic derivatives that have a halogen atom attached directly to the aromatic ring. More specifically still, it relates to the preparation of fluorobenzenes.
It has been known for quite some time, e.g., from the teachings of U.S. Pat. No. 4,075,252, that fluorobenzene can be prepared from anilines by a diazotization reaction or by using a triazene intermediary and decomposing triazene or diazonium salt in hydrofluoric acid. These prior art techniques always require a two-step process. The process may be performed continuously, e.g., in accordance with European Patent EP 205,019, but still requires a step in which the azonium salt is formed and a step in which it is decomposed.
The original amines are costly compounds that are indispensable in such a process and considerably increase the ultimate cost of the fluorobenzene produced.
British Patent 1,582,427 discloses the preparation of fluorobenzene through contact, at approximately 200° C., between a phenyl and a hydrofluoric acid solution containing a Lewis acid in a quantity of between 0.5% and 25% by weight, computed with respect to the quantity of hydrofluoric acid used. In reactions of six hours in duration the output of fluorobenzene is always less than 25%.
European Patent 118,247 describes a process for preparing fluorobenzene by passing a fluoroformic acid ester over platinated alumina at a temperature of from 200°-600° C. This process, which is performed in gas phase with a fluorobenzene output that is claimed to be as high as 60%, was treated more thoroughly in a later publication (Ashton, D. P. et al., “The Preparation of Fluoroarenes By The Catalytic Decarboxilation of Aryl Flouro Formates,” Journal of Flourene Chemistry, 27, 1985, 263 and 274). It suffers from a number of disadvantages, including the cost of the reagent and production of large quantities of numerous by-products. Furthermore, the catalyst is poisoned very quickly and the necessary regeneration makes the process too costly to contemplate its use on an industrial scale. The explanation given for the poisoning of the catalyst is its degradation under the effect of hydrofluoric acid.
Consequently, one of the purposes of the present invention is to provide a process for preparing aryl halides that will eliminate or lengthen the regeneration cycles. A further purpose of the invention is to provide a separate process that uses less costly raw materials.
REFERENCES:
patent: 3270069 (1966-08-01), Olah
patent: 3283018 (1966-11-01), Christe et al.
patent: 4620040 (1986-10-01), Alsop
patent: 4847442 (1989-07-01), Nalelwajek
patent: 1582427 (1981-01-01), None
Garcia Herve
Gilbert Laurent
Ratton Serge
Rochin Christophe
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Rhodia Chimie
Siegel Alan
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