Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2003-04-04
2004-02-17
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C552S293000, C552S309000, C552S310000
Reexamination Certificate
active
06693221
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of preparing in a single step, a mixture comprising a p-brominated phenol and a p-benzoquinone. More particularly the method relates to a method of preparing in a single step, a mixture of p-bromophenol and p-benzoquinone intermediates which may be separated and subsequently converted in single step transformations to dihydroxy aromatic compounds useful in the preparation of polycarbonate copolymers.
A variety of copolymers possessing useful and desirable properties comprise structural units derived from both hydroquinones and 4,4′dihydroxybiphenyls. Examples of include the polyether sulfone (CAS No. 90337-94-3) prepared from hydroquinone (HQ), 4,4′-dihydroxybiphenol (BP) and bis(4-chlorophenyl)sulfone; and the polyester (CAS No. 96892-06-7) derived from HQ, BP and a mixture of iso- and terephthalic acid. Additionally, polycarbonates comprising structural units derived from HQ, BP and another bisphenol comonomer (e.g. CAS No. 491588-47-7) show promise in a variety of materials applications.
Typically, the hydroquinone derivative and the 4,4′-dihydroxybiphenyl derivative used in the preparation of such polymers are prepared in independent manufacturing steps. Hydroquinone is typically prepared by air oxidation and fragmentation of 1,4-diisopropylbenzene, or by direct oxidation of phenol. Typically, 4,4′-dihydroxybiphenyl is obtained by oxidative coupling of 2,6-di-tert-butylphenol followed by acid mediated removal of the tert-butyl groups in the coupled product. Hydroquinones may be prepared as well by hydrolysis of a p-bromophenol as illustrated in U.S. Pat. No. 1,934,656. In addition, 4,4′-dihydroxybiphenyls may be prepared by reductive coupling of a p-bromophenol to the corresponding 4,4′-dihydroxybiphenyl as described in U.S. Pat. No. 5,177,258. Co-pending U.S. application Ser. No. 10/342,475 (filed Jan. 16, 2003) discloses an efficient means of preparing a p-bromophenol as a single intermediate which can be transformed by hydrolysis or reductive coupling into either a hydroquinone or a 4,4′-dihydroxybiphenyl. While this approach provides additional efficiencies based upon its use of a single intermediate p-bromophenol relative to known methods, improved methods continue to be sought, especially in light of the challenges presented by the rigorous conditions required for the hydrolytic transformation of the intermediate p-bromophenol to the corresponding hydroquinone.
The present invention is related to that described in co-pending U.S. application Ser. No. 10/342,475 (filed Jan. 16, 2003), but provides an alternate approach to the preparation of hydroquinones and 4,4′-dihydroxybiphenyls which eliminates the need for hydrolytic conversion of a p-bromophenol intermediate into the corresponding hydroquinone.
BRIEF SUMMARY OF THE INVENTION
In one aspect, the present invention provides a method preparing a mixture of a p-bromophenol and a p-benzoquinone, said method comprising contacting in a reaction mixture a hydroxyaromatic compound with:
(a) hydrogen bromide;
(b) at least one source of copper selected from the group consisting of copper compounds, and elemental copper; and
(c) oxygen gas;
said hydrogen bromide being present in an amount corresponding to between about 0.01 and about 0.2 moles of hydrogen bromide per mole of said hydroxyaromatic compound, said contacting taking place at a temperature in a range between about 20° C. and about 250° C.
In another aspect, the present invention relates to a method for the preparation of hydroquinones and 4,4′-dihydroxybiphenyls, said method comprising conversion of a mixture of a p-bromophenol and a p-benzoquinone into purified forms of the corresponding 4,4′-dihydroxybiphenyl derivative and the corresponding hydroquinone derivative.
DETAILED DESCRIPTION OF THE INVENTION
The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included herein. In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings.
The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
As used herein the term “polycarbonate” refers to polycarbonates incorporating structural units derived from one or more dihydroxy aromatic compounds and includes copolycarbonates and polyester carbonates.
As used herein, the term “melt polycarbonate” refers to a polycarbonate made by the transesterification of at least one diaryl carbonate with at least one dihydroxy aromatic compound.
“BPA” is herein defined as bisphenol A and is also known as 2,2-bis(4-hydroxyphenyl)propane, 4,4′-isopropylidenediphenol and p,p-BPA.
As used herein the term “aromatic radical” refers to a radical having a valence of at least one and comprising at least one aromatic ring. Examples of aromatic radicals include phenyl, pyridyl, furanyl, thienyl, naphthyl, phenylene, and biphenyl. The term includes groups containing both aromatic and aliphatic components, for example a benzyl group, a phenethyl group or a naphthylmethyl group. The term also includes groups comprising both aromatic and cycloaliphatic groups for example 4-cyclopropylphenyl and 1,2,3,4-tetrahydronaphthalen-1-yl.
As used herein the term “aliphatic radical” refers to a radical having a valence of at least one and consisting of a linear or branched array of atoms which is not cyclic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of aliphatic radicals include methyl, methylene, ethyl, ethylene, hexyl, hexamethylene and the like.
As used herein the term “cycloaliphatic radical” refers to a radical having a valance of at least one and comprising an array of atoms which is cyclic but which is not aromatic, and which does not further comprise an aromatic ring. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of cycloaliphatic radicals include cyclopropyl, cyclopentyl cyclohexyl, 2-cyclohexylethy-1-yl, tetrahydrofuranyl and the like.
The present invention relates to a method transforming a phenol I into a mixture of a p-bromophenol II and a p-benzoquinone III
wherein, in each of structures I, II and III, R
1
is independently at each occurrence a halogen, C
1
-C
20
alkyl group, C
4
-C
20
cycloalkyl group, or a C
4
-C
20
aryl group, and n is an integer from 0 to 4.
In one embodiment of the present invention a product mixture comprising p-bromophenol II and benzoquinone III is subjected to a separation step to provide p-bromophenol II and p-benzoquinone III in purified form. A significant advantage of the method of the present invention over known methods is that it provides the intermediate p-benzoquinone III which may be transformed under very mildly reducing conditions to hydroquinone derivative IV
wherein R
1
and n are defined as in structures I-III. Purified p-bromophenol II may be transformed via reductive coupling into 4,4′-dihydroxybiphenyl derivative V
wherein R
1
and n are defined as in structures I-III.
In one embodiment of the mixture comprising p-bromophenol II and p-benzoquinone III is subjected to mild reduction of the p-benzoquinone component to hydroquinone IV prior to separation from p-bromophenol II. Reduction methods for transforming benzoquinones into the corresponding hydroquinones are well known in the art and include catalytic reduction using hydrogen and a noble metal catalyst, for example reduction with hydrogen gas using palladium on charcoal as the catalyst at ambient temperature and pressure.
Physical methods which may be used to separate a mixture com
Chuck Timothy Leigh
Mills Ryan Christopher
Caruso Andrew J.
General Electric Company
Patnode Patrick K.
Shippen Michael L.
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