BACKGROUND OF THE INVENTION 
The present invention relates to the preparation of brominated aromatic 
compounds. More specifically, it relates to ring brominated 
hydroxyaromatic compounds. 
It is known to prepare brominated alkyl phenols. See, e.g., Can. J. Chem., 
Volume 61, pages 1045-1052 (1983); and Russian Chemical Reviews, Volume 
32, pages 75-93 (1963). Brominated tetraalkylhydroxyaromatic compounds 
having 2 aromatic rings also have been prepared in the past. Brominated 
tetraalkyl biphenols having the benzene rings directly linked have been 
prepared from tetraalkyl diphenoquinones; see, e.g. U.S. Pat. Nos. 
3,929,908; 3,956,403 and 4,058,570. However, when brominating compounds 
wherein the aromatic rings have an alkylene bridge, the products typically 
do not have bromine on the aromatic rings. For example, Bradley and 
Sanders, J. Chem. Soc., Volume 1962, pages 480-486 (1962) disclose the 
reaction of 3,3',5,5'-tetra-t-butylstilbenequinone with HBr to yield 
.alpha.,.beta.-dibromo-4,4'-dihydroxy-3,3',5,5'-tetra-t-butyldibenzyl. 
Kharasch and Joshi, J. Org. Chem., Volume 22, pages 1435-1438 (1957) 
disclose the reaction of bromine with 
4,4'-methylenebis(2,6-ditertiarybutylphenol) in the presence of acetic 
acid to give 1-bromo-1,1-bis-(3,5-ditertiarybutyl-4-hydroxyphenyl)methane. 
The compound 2,2'-(1,2-ethanediyl)bis(3,5-dibromo-4,6-dimethylphenol) has 
been prepared by the hydrogenation of 
4',5,6',7-tetrabromo-3',5',6,8-tetramethyl-3,4-dihydrospiro(2H-1-benzopyra 
n-2,1'-[3,5]cyclohexadien)-2'-one; Ann., Volume 548, pages 48-77 at page 57 
(1939); and by the bromination of 
2,2'-(1,2-ethanediyl)bis(4,6-dimethylphenol). 
In view of the deficiencies of prior art bromination methods, it would be 
desirable to have a simple method for the preparation of novel ring 
brominated polymethylene-bridged di(dialkylhydroxyaromatic) compounds 
having terminal para hydroxyl moieties. 
SUMMARY OF THE INVENTION 
The present invention is such a process for the preparation of novel 
ring-brominated polymethylene-bridged di(dialkylhydroxyaromatic) compounds 
having terminal para hydroxyl moieties and at least one bromine atom meta 
relative to at least one of said hydroxyl moieties. The process comprises 
containing a brominating agent with a tetraalkyl dihydroxydiaromatic 
polymethylene-bridged compound under reaction conditions such that there 
is formed a di-, tri, or tetra ring-brominated tetraalkyl 
dihydroxydiaromatic polymethylene-bridged compound. Surprisingly, the 
polymethylene-bridge does not cleave under bromination conditions, nor do 
the products contain benzyl bromine atoms. The ring brominated novel 
compounds of the invention are highly stable and are useful as chemical 
intermediates in the preparation of valuable chemical compounds. 
For example, the compounds of the present invention can be reacted with 
epichlorohydrin using known techniques to give the corresponding epoxy 
resins, or with polyisocyanates to form polyurethanes, or can be employed 
in other reactions requiring reactive hydroxyl groups. The compounds are 
useful as flame retardants due to their bromine content. 
DETAILED DESCRIPTION OF THE INVENTION 
The process of the present invention advantageously employs bromine, a 
liquid reaction medium, a tetraalkyl dihydroxydiaromatic 
polymethylene-bridged compound (hereinafter TDDPC) having terminal para 
hydroxyl moieties and, optionally, a bromination catalyst. 
Preferred TDDPC's are represented generally by the formula: 
##STR1## 
wherein n is zero or a positive integer, each R.sub.a independently is H 
or alkyl of up to about 12 carbon atoms, and each R independently is a 
primary or secondary alkyl moiety of up to about 6 carbon atoms. 
Preferably, n is zero or a positive integer of up to about 12, each 
R.sub.a independently is H or alkyl of up to about 6 carbon atoms, and 
each R independently is alkyl of up to about 3 carbon atoms. R most 
preferably is methyl, R.sub.a most preferably is H, and n most preferably 
is zero. It should be noted that the process of the present invention can 
be employed to put additional bromine atoms on partially brominated 
TDDPC's. 
A brominating agent is employed in the practice of the present invention. 
While it may be possible to employ known brominating agents which are 
useful for the bromination of aromatic rings, bromine is the preferred 
brominating agent when high purity products are desired. The amount of 
bromine to employ depends upon (1) the amount of bromine in the product 
desired, and (2) whether a catalyst is employed. In general, less bromine 
is required when a catalyst is employed. For example, if the 
dibromo-product is desired, then stoichiometry would indicate that at 
least about 2 moles of bromine atoms are required per mole of substrate 
compound to be brominated. Typically, with a catalyst, a stoichiometric 
excess of bromine ranging from about 0 to about 25 percent or more is 
employed; preferably, a stoichiometric excess ranging from about 5 to 
about 15 percent is employed. Typically, up to about 12 moles of bromine 
are employed per mole of TDDPC in the production of tetra-brominated 
products when operating without a catalyst. Smaller excesses of bromine 
typically require longer reaction times. Similarly, if a brominating agent 
is employed which is not bromine, the amount of said agent to be employed 
should provide bromine in the quantities stated hereinabove. 
A bromination catalyst is optionally employed in the process of the present 
invention. Friedel-Crafts catalysts are preferred, and are well known. 
Examples of bromination catalysts include the halides of metals such as 
iron, aluminum, and tin. Examples of preferred catalysts include aluminum 
bromide and aluminum chloride, with aluminum chloride being most 
preferred. The catalyst is employed in catalytic quantities. Preferably, 
the amount of catalyst employed ranges from about 0.1 to about 5 weight 
percent of catalyst based on the mass of aromatic compound employed. 
Larger amounts of catalyst may be employed, but may be economically 
impractical. The catalyst may be employed in a variety of forms. 
A reaction medium advantageously is employed in the process of the present 
invention. The reaction medium functions to solubilize the reactants and 
reaction products, and to aid in heat transfer. While the amount of 
reaction medium employed may range widely, the amount of reaction medium 
to be employed generally is indicated by practical considerations, and 
typically ranges from about 8 to about 20 moles of reaction medium per 
mole of aromatic compound. Preferably, from about 10 to about 15 moles of 
reaction medium are employed per mole of aromatic compound. Typical 
solvents include the perhalogenated lower alkanes. However, it is to be 
noted that carbon tetrachloride is the preferred solvent due to its 
physical properties. 
The order of addition of the reactants is not critical. However, according 
to a preferred process of the present invention, a brominating agent is 
slowly added to a mixture comprising a reaction medium, a TDDPC, and, 
optionally, a bromination catalyst. When the addition of the brominating 
agent is complete, the resulting reaction mixture typically is brought to 
elevated temperature until the reaction is completed. 
The initial addition temperature, i.e., the temperature of the reaction 
mixture during the period of addition of the brominating agent thereto, 
typically is a temperature at which the reaction mixture is a liquid. 
Preferably, the initial addition temperature is up to about 30.degree. C. 
More preferably, the addition temperature is from about 20.degree. C. to 
about 30.degree. C. Most preferably, for the sake of convenience, ambient 
temperature is employed. 
As stated hereinabove, when the addition of the brominating agent to the 
reaction mixture is complete, the total reaction mixture can be heated to 
elevated temperature in order to assure complete bromination. Typically, 
the total reaction mixture is heated to reflux temperature and said 
temperature is maintained until the reaction is complete. Completion of 
the reaction can be observed by following the rate of evolution of 
hydrogen bromide from the reaction mixture, i.e., the reaction is complete 
when the rate of hydrogen bromide evolution falls to zero. Ordinarily, the 
reaction will proceed at atmospheric pressure or higher, but 
subatmospheric pressure can be employed if desired. 
The total reaction time of from about 1 to about 100 hours, depending 
primarily on the aromatic reacting, is generally adequate for complete 
reaction under the conditions of the invention. Typically, a total 
reaction time of up to about 20 hours will be sufficient to produce high 
yields of high assay products. In some cases, bromination may be complete 
in 3 hours or less. It is desirable to add the brominating agent to the 
reaction mixture at a sufficiently slow rate to minimize loss of bromine 
and reaction medium, and to permit the desired low addition temperature to 
be maintained under conditions of control and safety. 
When the reaction is carried out as described hereinabove, a brominated 
TDDPC will be formed. Preferred brominated products of the present 
invention are represented generally by the following formula: 
##STR2## 
wherein n, R, and R.sub.a are as described hereinabove, and wherein each X 
independently is Br or H. Preferably, at least one X moiety is Br. Most 
preferably, two or three X moieties are Br. 
The reaction mixture resulting from carrying out the process of the 
invention can be processed by a variety of known work-up procedures to 
isolate the brominated products. The crude reaction mixture, which may 
contain the brominated products, excess reaction medium and excess 
catalyst, can, for instance, be subjected to stripping either at 
atmospheric pressure or preferably under reduced pressure to the point of 
constant weight of the residue. The crude product which is thus isolated 
may be further purified, for instance, by recrystallization or by 
digestion with a recovery medium such as acetone, toluene, or dilute 
hydrochloric acid. This isolation method by stripping is fast, simple and 
gives reliable yield data and relatively pure product. It is preferred to 
employ a work-up method which neutralizes bromine. The yield of pure 
product, i.e., the numerical product of conversion of TPPDC, selectivity 
to the desired product, and purity of the desired product, typically is at 
least about 50 mole percent. Preferably, the yield is at least about 60 
mole percent, and more preferably, the yield is at least about 75 mole 
percent. 
It is generally possible to predict the product(s) which will result from 
application of this perbromination process under optimum reaction 
conditions to any particular starting material. The general rule is that 
every nuclear hydrogen atom of the aromatic compound will be replaced by a 
bromine atom if the reaction is carried to completion, that is, until the 
evolution of hydrogen bromide has stopped. This level of bromination may 
be reached by proper adjustment or reaction temperature, catalyst 
concentration and reaction time. The bromination process is continued 
until such time as the sampling indicates that the desired degree of 
bromination has been reached, or the bromination reaction may be continued 
until evolution of hydrogen bromide has substantially ceased. 
SPECIFIC EMBODIMENTS 
The following Examples and Comparative Experiments are given to illustrate 
the invention and should not be construed as limiting its scope. All parts 
and percentages are by weight unless otherwise indicated.

EXAMPLE 1 
Preparation of 4,4'-(1,2-Ethanediyl)bis(3-bromo-2,6-dimethylphenol) 
(Dibromotetramethylbisphenol E) 
A 20.0 g (0.074 mole) portion of tetramethylbisphenol E is suspended in 75 
ml of CCl.sub.4. A 4.2 ml portion of bromine (0.082 mole) is added at 
23.degree.-25.degree. C., and the mixture is heated to reflux. All of the 
bromine has reacted by this time. Analysis by gas chromatography (GC) and 
NMR indicates the following composition: 42 area percent starting 
material, 14 area percent monobromotetramethyl-bisphenol E, and 43 area 
percent dibromotetramethylbisphenol E. After adding 4.2 more ml of 
bromine, the mixture is refluxed for 1.5 hrs and analyzed by GC; the 
following composition is obtained: 2 area percent starting material, 7 
area percent monobrominated product, 90 area percent dibrominated product, 
and 1 area percent tribrominated material. Cooling of the slurry to 
25.degree. C. and filtration of the insoluble solid gives 29.2 g of a 
brown solid which melts at 191.degree.-194.degree. C. Recrystallization 
from toluene gives a solid which melts at 194.degree.-197.degree. C. and 
has the following composition: 5 area percent monobromo, 93 area percent 
dibromo, and 2 area percent tribromotetramethylbisphenol E. The NMR 
spectrum is consistent with the proposed structure: .sup.1 H NMR (acetone 
d.sub.6) .delta.: 2.20 (s, 6H, --CH.sub.3), 2.36 (s, 6H, --CH.sub.3), 2.86 
(s, 4H, --CH.sub.2 --), 6.88 (s, 2H, --CH), and 7.35 (s, 2H, --OH). 
EXAMPLE 2 
Preparation of 
3,5-Dibromo-4-(2-(2-bromo-4-hydroxy-3,5-dimethylphenyl)ethyl)-2,6-dimethyl 
phenol (Tribromotetramethylbisphenol E) 
A 12.5 g (0.046 mole) portion of tetramethylbisphenol E is suspended in 100 
ml of CCl.sub.4, and 12.0 ml (0.234 mole) of bromine is added at 
23.degree.-25.degree. C. After refluxing the mixture for 1.0 hr, the 
following composition is observed: 16 area percent dibromo, 77 area 
percent tribromo, and 7 area percent tetrabromotetramethylbisphenol E. The 
unreacted bromine is removed by distillation. More CCl.sub.4 is added (50 
ml), and the slurry is cooled to 25.degree. C. Filtration of the insoluble 
solid affords 18.2 g of a brown solid which melts at 
249.degree.-255.degree. C. Recrystallization from toluene affords a 
gray-brown solid which melts at 257.degree.-262.degree. C., and has the 
following composition: 6 area percent dibromo, 78 area percent tribromo, 
and 16 area percent tetrabromotetramethylbisphenol E. It has the following 
NMR spectrum: .sup.1 H NMR (DMSO d.sub.6) .delta.: 2.12 (s, 3H), 2.28 (s, 
9H), 3.20 (s, 4H), and 6.90 (s, 1H). 
EXAMPLE 3 
Preparation of 4,4'-(1,2-ethanediyl)bis(3,5-dibromo-2,6-dimethylphenol) 
(Tetrabromotetramethylbisphenol E) 
A 27.1 g (0.1 mole) portion of tetramethylbisphenol E is suspended in 100 
ml of CCl.sub.4. A 60 ml (1.17 mole) portion of bromine is added dropwise 
while keeping the temperature below 30.degree. C. using a water bath for 
cooling. Immediate evolution of HBr is observed. The mixture is brought to 
reflux for 2 hrs. The excess bromine is removed by distillation with the 
aid of 200 ml of CCl.sub.4. The mixture is cooled to 25.degree. C., and 
the insoluble solid is filtered. This affords 52.0 g of brown solid which 
melts at 290.degree.-297.degree. C. Purification of the insoluble solid 
involves suspending it in 100 ml of acetone, refluxing for 1.0 hr, cooling 
to 25.degree. C., and filtering the insoluble solid. A white solid is 
obtained, 46.0 g, which melts at 295.degree.-297.degree. C. and has the 
following composition: 75 area percent tetrabromo and 25 area percent 
tribromotetramethylbisphenol E. The .sup.1 H NMR spectrum (DMSO d.sub.6) 
has a small singlet at 2.12 .delta. and 2 major peaks, a singlet at 2.26 
.delta., and a singlet at 3.20 .delta., in a ratio of 3 to 1. This 
spectrum is consistent with the proposed structure. 
EXAMPLE 4 
Bromination Using A Friedel-Crafts Catalyst 
A 136 g (0.5 mole) portion of tetramethyl bisphenol E is suspended in 1,400 
ml of CH.sub.2 Cl.sub.2. Following the addition of 2.0 g of FeCl.sub.3, 86 
ml (1.65 mole) of bromine is added at 20.degree.-24.degree. C. After 
refluxing the mixture for 2.0 hr all of the bromine had reacted. A portion 
of the solvent, 300 ml, is removed by distillation, and the slurry is 
cooled to 25.degree. C. Filtration of the insoluble solid affords 262 g of 
a light brown solid which has the following composition: 8 area percent 
dibromo, 58 area percent tribromo and 34 area percent tetrabromo 
tetramethyl-bisphenol E. The .sup.1 H NMR spectrum is consistent with this 
composition. 
COMATIVE EXPERIMENT 1 
Not an embodiment of the present invention 
Bromination of Tetramethylbisphenol F 
A 25.6-g portion of tetramethylbisphenol F (0.1 mole) is suspended in 125 
ml of carbon tetrachloride, and the slurry is cooled to 5.degree. C. A 
6-ml portion of bromine (0.12 mole) is added dropwise, and the mixture is 
stirred for 15 minutes. All of the bromine reacts. Analysis of the mixture 
by gas chromatography indicates that &gt;90 percent of the starting material 
reacts. The major product formed is 4-bromo-2,6-dimethylphenol, which is 
identified by comparison with an authentic sample; a number of other 
cleavage products are formed. Addition of 6 more ml of bromine gives 
complete cleavage of the tetramethylbisphenol F. 
COMATIVE EXPERIMENT 2 
Not an embodiment of the present invention 
Bromination of Tetramethylbisphenol A 
A 14.2-g portion of tetramethylbisphenol A (0.05 mole) is suspended in 100 
ml of carbon tetrachloride, and the slurry is cooled to 5.degree. C. A 
3-ml portion of bromine (0.06 mole) is added dropwise, and the reaction is 
analyzed by gas chromatography. More than 60 percent of the starting 
material reacts, forming two major products, one of them being 
4-bromo-2,6-dimethylphenol. After stirring at 25.degree. C. for two hours, 
the insoluble product is filtered, 5.5 g, and is identified as 
tetramethylbisphenol A. The carbon tetrachloride solution has 
4-bromo-2,6-dimethylphenol as the main component, as identified by gas 
chromatography and nuclear magnetic resonance, and by comparison with an 
authentic sample. 
The preceding Examples and Comparative Experiments surprisingly indicate 
that TDDPC compounds having a polymethylene-bridge can be brominated on 
the aromatic rings, whereas similar compounds having only one linking 
carbon atom do not ring-brominate.