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Formation and Cleavage of Dihydroxydiarylmethane Derivatives.

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In all cases without solvent, addition of pyridine causes
a quantitative reduction of the 1,Zdiketone to the
monoketone (4). The latter is likewise obtained in
almost quantitative yield by working with methanol/
morpholine or with dimethylformamide/aniline. Methanol/piperidine gives a conversion of only 33 % after 7 h.
Without addition of amine, or in the presence of a
primary amine, no reaction occurs in methanol.
In a peculiar way, hydrogen sulfide in carefully purified
dimethylformamide can reduce the 1,2-diketone quantitatively to the monoketone (4) without addition of an
amine, whereas in the presence of a secondary amine,
only the hydroxyketone ( 5 ) is formed.
With piperidine, quantitative reduction to ( 5 ) is
complete after only 1 h ; in the presence of morpholine
a mixture of both reduction products (4) and ( 5 ) is
obtained after 4 h. In the absence of solvent, only
pyridine, morpholine, and piperidine catalyse the
reduction.
Reduction of 1,2-Diketonrs with Hydrogen Sul’de:
Hydrogen sulfide is passed for up to 4 h into a solution of
0.2 mole cf the 1,2-diketone and about 30 ml of amine in
methanol or dimeth>lformamidc, the solution being cooled
with ice; separation of elemental sulfur occurs during the
process. The mixture is acidificd with dilute hydrochloric
acid, the resulting precipitate filtcred off with suction, roughly
separated from sulfur by warming gently with methanol, and
the reduction product, dissolved by the methanol, purified by
recrystallization. Liquid reduction products resulting from
acidification are extracted with cther and, after being dried
over sodium sulfate, distilled.
Examples:
Benzoin from benzil: Reaction in pyridine/dimethylformamide; HzS passed in for 1 h; yield quantitative. Identification by analysis, mixed melting-point, 2,4-dinitrophenylhydrazone, and comparison of infrared spectra.
Deoxybenzoin f r o m benzil: Reaction in pyridine/methanol;
H2S passed in for 4 11; yield quantitative. Identification as
above.
Received, January 7th, 1963
[A 287/82 IE]
German version: To appear in Angew, Chem. 75, No. 16 (1963).
Formation and Cleavage of Dihydroxydiarylmethane Derivatives
BY DR. H. SCHNELL AND DR. H. KRIMM
FARBENFABRIKEN BAYER AG., WERK UER DINGEN (GERMANY)
Dihydroxydiarylmethane derivatives are formed by condensation of aromatic hydroxy and
carbonyl compounds in the presence of acidic condensing agent3 at low temperatures or in
the presence of bases at elevated temperatures. This article deals with formation and cleavage
mechanisms in acid and basic media. As a result of the investigations reported, new methods
of preparing unsymtnetric dihydroxydiarylrnethane derivatives und p-alkenylphenols have
been developed.
1. Preparation of Dihydroxydiarylmethane
Derivatives [*]
Bisphenol A started only after cpoxy resins were developed
from Bisphenol A and epichloiohydrin in 1938 [4]. This
application does not require Bisphenol A of high purity;
however, highly purified material is used in the production of
aromatic polycarbonates [ 5 ] .
The parent compound of the dihydroxydiarylmethane
was first prepaseries, 4>4’-dihydroxydiphenY1methane,
red in 1878 by Beck [I]. The method used involved
alkaline fusion of the corresponding disulfonic acid.
Nolting and Herrberg {Z] also prepared it in low yields
from phenol and formaldehyde in the presence of dilute
mineral acids. In 1891, Dianin [3] synthetized 2,2-bis-
Besides Bisphenol A, a few 4,4’-dihydroxydiarylmethane
derivatives bearing alkyl substituents on the aromatic radicals have also found application; they are used as nonstaining antioxidants for natural and synthetic rubber, polyvinyl compounds, and mineral oils [6]. 4,4’-Dihydroxydiphenylmethane derivatives have also been proposed as intermediates for the preparation of phenolic resins and tanning
(p-hydroxyphenyl)propane in good
from
and acetone in the presence of strong mineral acids.
2,2-Bis-(p-hydroxyphenyl)propane possesses estrogenic activity [7]. Other representatives of this class of compounds
For a long time, this readily obtainable substance, also
referred to as bisphenol, Bisphenol A or Dian, found no
significant industrial application. Large-scale production of
[*] Dihydroxydiarylmethane derivatives imply compounds in
which two equal or different hydroxyaryl groups are linked to the
same carbon atom. This atom can be substituted with hydrogen
or an aliphatic or aromatic radical or be a member of a cycloaliphatic ring.
[ l ] C. Beck, Liebigs Ann. Chem. 194, 318 (1878).
[2] Nolting and Herrberg, Chemiker-Ztg. 16, 185 (1892); see also
N . Caro, Ber. dtsch. chem. Ges. 25, 947 (1892).
[3] A . Dianin, J. russ. physik. Ges. 1891,488,523,601 ; Ber. dtsch.
chem. Ges. 25, Ref. 344 (1892).
Angew. Chem. internat. Edit. / Val. 2 (1963) NO.7
-
[4] Swiss Pat. 211 116 (1940), Gehr. de Trey A.G., inventor: P.
Castan; see also A. M. Paquin: Epoxydverbindungen und Epoxydharze. Springer, Berlm-Gottlngen-Heidelberg, 1958.
[ S ] H. Schnell, Angew. Chem. 68, 033 (1956); Ind. Engng. Chem.
51, 157 (1959); Plast. Inst., Trans. and J. 28, 143 (1960).
[6] US.-Pat. 2515906 (1950), Gulf Res. and Development Co.,
inventors: D. R. Stevens and A. C. Dubbs; US.-Pat. 2559932
(1951), I. C . I. Ltd., inventors: A. S. Bfiggs and J . Haworth;
US.-Pat. 2894004 (1959), Dow Chem. Co., inventor: A. J.
Dietzler; US.-Pat. 2917550 (1959, Dow Chem. Co., inventor:
A. J . Dietzler; US.-Pat. 2877210 I19-59), Hercules Powder C O . .
inventor: R. A. Bankert.
[7] G. Bornmann and A. Loeser, Arzneimittel-Forsch. 9, 9 (1959).
373
are active against poultry coccidiosis [8]. 4,4'-Dihydroxydiphenylmethane derivatives which are substituted with
quinoline or isoquinoline residues on the central carbon
atom have a laxative action [9].
a) Synthesis from Aromatic Hydroxy Compounds and
0 x 0 Compounds by Acid-Catalysed Condensation
The condensation of aromatic hydroxy compounds
with 0x0 compounds proceeds with elimination of
water. Unless this water is bound o r otherwise removed,
the Condensation stops after low conversions.
The reaction is catalysed by acid condensing agents such
as hydrogen chloride, hydrogenbromide, hydrogen fluoride, phosgene, boron trifluoride, aluminum chloride,
phosphorus halides, phosphorus pentoxide, phosphoric
acid, concd. hydrochloric acid, sulfuric acid, mixtures of
glacial acetic acid with acetic anhydride, hydrogen
chloride, or sulfuric acid, mixtures of hydrochloric acid
with sulfuric acid, and appropriate cation exchangers.
Acid condensation catalysts, such as cation exchangers,
that are unable to combine with water give high yields
only if the water is removed, for example, by azeotropic
distillation, or combined with chemical agents such as
CaC12.
By treating phenol with formaldehyde, paraformaldehyde, trioxane, or methylal in the presence of acid
condensing agents such as hydrochloric acid at low
temperatures, in addition to 4,4'-dihydroxydiphenylmethane, other isomers, mostly 2,Y- and 2,4'-dihydroxydiphenylmethane, and resinous polycondensation
products are obtained. Resin formation is minimized by
the use of a large excess of phenol or of dilute mineral
acid as solvent. However, the yields of isomeric dihydroxydiphenylmethanes are about 70 % at the best,
35 % of this being 4,4'-dihydroxydiphenylmethane [lo],
based on phenol.
Better yields of dihydroxydiphenylmethane derivatives
are sometimes obtained when other aliphatic and
aromatic aldehydes, e.g., acetaldehyde, n-butyraldehyde,
isobutyraldehyde, chloral [111, pyridine-aldehyde [ 121,
or benzaldehyde [13] are condensed with phenol in the
presence of acid condensing agents, such as hydrochloric acid or sulfuric acid with a maximum concentration of 70% HzSO4. Substantially higher yields of
well-defined dihydroxydiphenylmethane derivatives are
obtained on acid condensation of 4-, 2,3-, 2,4-, 2,5-,
2,6-, 2,4,5-, or 2,3,4,6-substituted phenols with formaldehyde or other aldehydes [14]. Treatment of un[8] US.-Pat. 2535015 (1950) and 2538725 (1951), Dow Chem.
Co., inventors: J. E. Johnson and D. R. Mussel.
[9] US.-Pat. 2753351 (1956), Dr. Karl Thomae G.m.b.H., inventors: A . Kottler and E. Seeger.
[lo] US.-Pat. 2812364 (1957), Union Carbide Corp., inventors:
A. G . Farnham and F. P. Klosek; US.-Pat. 2792429 (1957),
Union Carbide Corp., inventor: J. M . Whelan, Jr.
1111H. Paulyand H.Schranz,Ber.dtsch.chem.Ges.56,982(1923).
1121 Belg. Pat. 518457 (1953), Dr. Karl Thomae G.m.b.H.
1131 J. Gronowska and B. Szpilewski, Roczniki Chem. 34, 289
(1960).
[14] N. J. L . Megson and A . A. Dummond, J. SOC.chem. Ind. 49.
394 (1930); US.-Pat. 2435593 (1948), Burton T. Bush Inc., inventors: M . Luthy and W. S. Gump; US.-Pat. 2616932 (1952),
374
saturated aldehydes, e.g., acrolein, with phenols in the
presence of acid condensing agents at low temperatures
yields bis(hydroxypheny1)alkenes. At temperatures of
about 100°C, these compounds add on more phenol
across their double bond so that, depending on molar
ratios used, tri- or polyphenols are predominantly
formed 1151.
Ketones give better yields of well-defined condensation
products than aldehydes do. The preferred acid condensing agents are hydrogen chloride, concd. hydrochloric
acid, and sulfuricacid having a maximum concentration
of 70%. The most efficient would be concentrated
sulfuric acid, but its use is precluded by the fact that it
causes sulfonation of aromatic hydroxy compounds and
dihydroxydiarylmethane derivatives. The 70 % sulfuric
acid is less efficient than concd. hydrochloric acid, and
the latter less than hydrogen chloride. Other acid
condensing agents such as BS/formic acid used in conjunction with calcium chloride as water acceptor [16],
or cation exchangers such as sulfonated, crosslinked
polystyrenes [171 have not found any industrial application so far.
The most reactive ketones are acetone [3] and alicyclic
compounds such as cyclohexanone [18]. The condensation activity of dialkyl ketones decreases with increasing length of the alkyl radicals [19]. Alkyl aryl
ketones and diary1 ketones condense at a slower rate
than dialkyl ketones [20].
Ketonic carboxylic acids, e.g., levulinic acid, and
aromatic hydroxy compounds can be condensed to give
bis-(p-hydroxyaryl) compounds in which a carboxyl
group is attached to the alkyl radical [21]. Mercaptals
undergo condensation much more readily than the
corresponding ketones [22].
Surprisingly, acylnitriles such as phenylglyoxylonitrile
also undergo condensation with hydroxy compounds in
the presence of strongly acid condensing agents, to give
Dow Chem. Co., inventors: C. L. Moyle and P . A. Wolf; US.Pats. 2796444,2796445 (1957), American Cyanamid Co., inventor: F. A . V. Sullivan; US.-Pat. 2798079 (1957), Universal Oil
Products Co., inventor: C. B. Linn; US.-Pat. 2932671 (1960),
Alco Oil and Chemical Corp., inventors: 0. B. Hager and B. Coe;
US.-Pat. 2919294 (1959), Monsanto Chem. Co., inventors: D . J.
Beaver and R . 0 . Zerbe; US.-Pat. 2912463 (1959), Monsanto
Chem. CO., inventors: D. J. Beaver and R . 0 . Zerbe; Brit. Pat.
711 122 (1952), N.V. de Bataafsche Petroleum Mij., DDR-Pat.
14472 (1958), inventors :F. A d r e a s , H . Ber tho ld, and W.Heidingsr .
1151 German Printed Patent Application 1061791 (1959), Union
Carbide Corp., inventor: A . c'. Farnham.
1161 Belg. Pat. 601797 (1961), Alpine Chemische A.G.
1171 French Pat. 1237656 (1960), Union Carbide Corp., inventors: F. N . Apel, L . B. Conte, Jr. and H. L . Bender; French
Pat. 1244533 (1960), Union Carbide Corp., inventors: F. N.
Apel, P . Farevaag, and H . L . Bender; Belg. Pat. 589727 (1959),
Ciba, S. A.
[IS] US.-Pat. 1760758 (1930). General Aniline Works Inc., inventor: E. Korten; US.-Pat. 2069560 (1937), E. I. duPont de
Nemours Co., inventor: H. S. Rothrock; US.-Pat. 2069573
(1937), E. I. duPont de Nemoiirs Co., inventor: E. K . Bolton.
[19] F. V . Morris, G . F. Bech//e, and T. J. Byerle, J. Amer. Oil
Chemists' SOC.37, 646 (1960).
[20] A. Miiller, Chemiker-Ztg. 45, 632 (1921).
[21] US.-Pats. 2907736,2907737 (1959), S. C. Johnson and Son
Inc., inventor: S . 0. Greenler; US.-Pat. 2933520 (1960), Pittsburgh Plate Glass Co., inventor: A. R . Bader.
1221 US.-Pat. 2602821 (1952), Shell Development Co., inventors:
D. B. Luten, S. A . Ballard, and C. G . Schwarzer.
Angew. Chem. internat. Edit. Yol. 2 (1963) No. 7
bis-(p-hydroxyary1)arylacetonitriles [23]. The reaction is
accelerated by catalytic amounts of ionizable compounds
of divalent sulfur such as sulfur dichloride, sodium
thiosulfate, hydrogen sulfide, sodium sulfide, thiols,
thiophenols, thioacetic acid, thioglycollic acid, mercapto alkyl sulfonic acid or hydroxyalkylthiols [24].
Less pronounced accelerating effects are exhibited by
hydrogen selenide and hydrogen telluride [25], ferrous
chloride [20], and acid-soluble boron compounds such
as boric acid [26,27]. Ultraviolet and y-radiation are
also reported to catalyze the reaction [28]. The reaction
is carried out with undiluted reactants [29] or their
solutions in inert solvents such as aromatic hydrocarbons [30], chlorinated aliphatic hydrocarbons [3 11,
or glacial acetic acid [3]. High yields result when the
molar ratio of aromatic hydroxy compound to ketone
is at least 3.7:l [22]. The condensation should be
carried out at the lowest temperature possible, and
always below 80 "C, since the formation of by-products
increases with increasing temperature [32,33]. The
temperature at which the reactants cease to form a
homogeneous liquid phase represents a lower limit for
condensations carried out in the absence of solvents.
Many aromatic hydroxy compounds react with ketones
to form crystalline, sharp-melting addition compounds
of defined composition [34].
2,2-Bis-(p-hydroxyphenyl)propane(Bisphenol A) may
be prepared by condensation of phenol and acetone
below 70°C in the presence of sulfuric acid of 70%
maximum concentration ; thiols or thiocarboxylic acids
are added as accelerators. Bisphenol A obtained in this
manner must be purified by cumbersome methods which
depress the yield considerably.
As a result of increased purity requirements, the use of
hydrogen chloride, especially in condensations carried
out in indifferent solvents, or of concd. hydrochloric
acid is preferred [35]. The acid-catalysed condensation
of acetone with phenols yields Bisphenol A ( I ) plus
[23] German Pat. 1075631 (1960), Farbenfabriken Bayer A.G.,
inventors: H. Schnell and G . Buchwald.
[24] US.-Pat. 2359242 (1944); Dow Chem. Co., inventors: R. P.
Perkins and F. Bryner; US.-Pat. 2468982 (1949), G. F. Goodrich
Co., inventor: J. E. Jansen; US.-Pat. 2730552 (1950), 2730553
(1956), 2775620 (1956), N.V. de Bataafsche Petroleum Mij., inventor: G.T. Williamson; US.-Pat. 2923744 (1960), SOC. des
usines chimiques Rh6ne-Poulenc, inventors: I. Scriabine and P.
M . Bonnart; French Pat. 1234620 (1960), Feldmiihle Papier- und
Zellstoffwerke A.G.
[25] US.-Pat. 2762846 (1956), Technical Tape Corp., inventors:
E. J. Reiner, H . S. Schultz, J. G. Schumann, and M . Silberberg.
I261 US.-Pat. 1977627 (1934), I. C. I. Ltd., inventor: R. Greenhalgh.
[27] US.-Pat. 1986423 (1935), E. I. duPont de Nemours Co., inventor: J. A. Arvin.
[28] US.-Pat. 2936272 (1960), Union Carbide Corp., inventors:
H. L. Bender, N . Apel, and L. B. Conte, Jr.
[29] US.-Pat. 1978949 (1934), Rohm and Haas Co., inventors:
S . Kohn and E. Schub.
[30] Brit. Pat. 428944 (1935),Resinous Products and Chem.Comp.
[31] Brit. Pat. 557976 (1943), Distillers Comp. Ltd., inventors:
H . M. Stanley, J. D . Morgan, and W. L. Pritchard.
[32] US.-Pat. 2191831 (1940), Dow Chem. Co., inventor: R . P.
Perkins.
[33] US.-Pat. 1977624 (1934), I. C. I. Ltd., inventor: R . Greenhalgh.
[34] J. Schmidlin and R. Lung, Chem. Ber. 43, 2806 (1910).
[35] Petroleum Refiner, Nov. 1959, 225.
Angew. Chem. internat. Edit. / Vol. 2 (1963) / No. 7
compounds (2) to (4a) as by-products [36]. Small
amounts of p-isopropylphenol and resinous products
are also obtained.
These by-products, consisting mainly of (2), may
amount to 40% or more. Greater amounts are obtained
at higher temperatures.
hl I
The amount of by-products is substantially lowered if
the condensation is carried out so that Bisphenol A or
its addition compound with 1 mole of phenol is allowed
to crystallize out of the reaction mixture [37]. Condensation of saturated phenol solutions in concd. hydrochloric acid, from which the crystalline addition compound separates out as fast as it is formed, yields Bisphenol A containing less than 2 % by-products [38].
Since acid cleavage of cumene hydroperoxide yields
phenol and acetone, the use of acids such as hydrogen
chloride or hydrochloric acid permits its direct conversion to Bisphenol A. To maintain the proper molar
ratio of reactants in the reaction mixture, acetone is
removed by distillation or phenol is added [39].
Isolation of pure bis-(p-hydroxyary1)alkanes is achieved
by neutralizing the reaction mixture and removing
starting materials as well as by-products and solvent.
The simplest process involves neutralization of the
mineral acids with alkali or preferably with sodium
carbonate or bicarbonate solutions, in which phenol and
bis-(p-hydroxyary1)-alkanes are insoluble, and then
washing of the organic phase until free from electrolytes
and fractional distillation in V ~ C U Oof the products [40].
This procedure is unsatisfactory, however, because
decomposition of bis-(p-hydroxyary1)alkanes at high
temperatures is accelerated by alkaline impurities and
[36] W. F. Christopher and D. W. Fux: Polycarbonates. Reinhold
Publishing Corp., New York 1962, p. 12.
[37] German Pat. 1027205 (1958), Farbenfabriken Bayer A.G.,
inventors: K . H. Meyer and H . Schnell.
[38] Belg. Pat. 480053 (1961), Farbenfabriken Bayer A.G., inventors: H . Ruppert and H . Schnell.
[39] French Pat. 1060888 (1954), N.V. de Betaafsche Petroleum
Mij., inventors: H. I. Watermann and J. P . Fortuin; US.-Pat.
2669588 (1954), Shell Development Co., inventors: P. H. Deming
and H. Dannenberg; US.-Pat. 27 13072 (1955), Shell Development Co., inventor: H. Dannenberg; French Pat. 1037 198 (1953),
SOC.des usines chimiques RhAne- I'oulenc.
[401 Brit. Pat. 794476 (1958), CJnion Carbide Corp., inventors:
R . I, Hoaglin, C. W . Plummer, and H. C . Schultze; US.-Pat.
2 182308 (1939), Dow Chemical Co., inventors: E. C. Brifton and
F. Bryner .
375
metal ions. Moreover, isomer separation by distillation
is not possible. Thermal decomposition can be markedly
reduced by the use of additives such as secondary or
tertiary alkaline earth phosphates which inactivate alkaline impurities and bind metal ions [41].
Following removal of unreacted starting materials, e.g.
by steam distillation, purification can also be accomplished by dissolving the reaction product in alkali and
reprecipitating it by acidification. This process is not
very effective [42].
More thorough purification is achieved if the condensation product is dissolved in boiling dilute alkali and
allowed to crystallize out on cooling. The alkali should
neutralize only about 1/20 of the aromatic hydroxyl
groups [43]. The disadvantage of both methods lies in
the sensitivity of alkaline solutions of bis(hydroxypheny1)alkanes to atmospheric oxygen.
Decomposition is minimized if bis-(p-hydroxyary1)alkanes or their addition compounds with aromatic
hydroxy compounds are purified by crystallization from
organic solvents such as benzene, toluene, chlorotoluene,
or dichloroethylene. Another suitable solvent is phenol,
the crystalline phenol-bis(p-hydroxyary1)alkane addition
compound precipitating out from this on cooling [44].
More suitable is a phenol-water mixture which yields
addition compounds of high purity [37]. Removal of
the phenol by distillation constitutes the best method of
cleaving these compounds.
It has also been proposed to extract the condensation
product with solvents such as heptane which dissolve
only the by-products 1451.
b) Synthesis by Alkaline Condensation of Aromatic
Hydroxy and 0 x 0 Compounds
The preparation of dihydroxydiarylmethane derivatives
by alkaline condensation of aromatic hydroxy compounds with 0x0 compounds has only slight practical importance. Treatment of unsubstituted aromatic hydroxy
compounds with formaldehyde in the presence of alkali
gives mixtures of ring substituted mono- and polyhydroxymethyl aromatic hydroxy compounds from
which well-defined products either cannot be isolated at
all or are obtained only with difficulty. These hydroxymethylphenols react further to give resols [46]. In this
reaction, dihydroxydiarylmethane derivatives, among
other compounds, are formed as intermediates.
The reaction of solutions of 2,4- or 2,6-dialkylphenols
with aliphatic or aromatic aldehydes in the presence of
[41] Belg. Pat. 469518 (1960), Farbenfabriken Bayer A.G., inventors: G. Fritz and H . Schnell.
[42] US.-Pat. 2806068 (1957), Koninklijke Zwavelsuurfabriek
N.V., inventor: J. P . Abrrrhams.
[43] Belg. Pat. 611082 (1962), Farbenfabriken Bayer A.G., inventors: H , Heller, L. Bottenbruch, and H. Schnell.
[44] US.-Pat. 2791 616 (1957), Shell Development Co., inventor:
D . B. Luten, Jr.
[45] US.-Pat. 2845464 (1958), Shell Development Co., inventor:
D . B. Luten, Jr.
[46] K . Hultsch: Chemie der Phenolharze. Springer, Berlin-Gottingen-Heidelberg 1950.
376
alkali metal hydroxide as condensing agent gives useful
yields of dihydroxydiphenylmethane derivatives 1471.
Alkaline condensation of hydroxymethyl-substituted
phenol derivatives (obtaina ble from disubstituted phenols
such as 2,4-dimethylphenol) with other 2,4- or 2,6-disubstituted phenols leads to unsymmetric dihydroxydiphenylmethane derivatives [48].
Alkaline condensation of aromatic hydroxy compounds
with aldehydes is carried out in the absence of water,
mostly in aliphatic alcohols, at temperatures up to
130 "C.
Dihydroxydiphenylmethane derivatives are obtained in
good yields on treatment of saturated ketones such as
acetone and cyclohexanone or acetophenone with phenol
or 2- or 2,6-substituted phenols. The reaction is carried
out in the presence of an alkali or alkaline earth phenoxide at 100-200°C. Here, too, the formstion of 4,4'dihydroxydiarylmethane derivatives is favored by an
excess of the aromatic hydroxy compound (3-7 moles
per mole of ketone); 1.0-2.5 moles of alkali or alkaline
earth phenoxide should be used. Larger amounts of
phenoxide cause increased formation of resinous byproducts [49].
The high reaction temperatures (160-180 "C) and relatively extended reaction times are disadvantageous
since, under alkaline conditions, they promote attack
by oxygen on the phenols and bisphenols.
2. Other Preparative Methods
a) Reaction of Alkenylphenols with Aromatic Hydroxy
Compounds
Compounds with a hydroxyaryl radical attached to a
carbon atom which is also linked to another radical by
a double bond readily add on aromatic hydroxy compounds to give dihydroxydiarylmethane derivatives. This
reaction is exothermic and is catalyzed by acids at low
temperatures or by bases at elevated temperatures [SO].
Suitable alkenylphenols include 1 -(p-hydroxypheny1)-1propene, 2-(p-hydroxyphenyl)- 1-propene, 2-(p-hydroxypheny1)-1-butene, 1-(p-hydroxypheny1)-1-phenylethylene, and 1-(p-hydroxypheny1)-I-cyclohexene.
Aromatic hydroxy compounds which undergo the addition are phenol, and alkyl-, aryl-, aralkyl-, cycloalkyl-,
halogeno-, alkoxy-, and nitro-substituted phenols and
naphthols, provided that they still contain labile hydrogen atoms on the aromatic ring.
In the presence of acid catalysts such as hydrogen chloride, hydrochloric acid, sulfuric acid, p-toluenesulfonic
acid, phosphoric acid, BF;3, ZnCl2, AIC13, SnC14, or ionexchange resins with strongly acidic groups, the reaction
[47] US.-Pat. 2807653 (1957). Ethyl Corp., inventors: A . H . Filbey and T. H . Coffield; M . A'. Klzrrrrrsch and B. s. Joshi, J. org.
Chemistry 22, 1435 (1957).
[48] Brit. Pat, 719101 (1954), I. C. 1. Ltd.; Belg. Pat. 593606
(1961), Shell Int. Res. Mlj., inventors: R . C. Morris, A . L. Rocklin, and R . E. Vincent.
[49] US.-Pat. 2858 342 (1958), Unlon Carbide Corp., inventors:
H . L. Bender, L. B. Conte, Jr., and F. N . Ape].
[SO] Belg. Pat. 487307 (1962), Farbenfabriken Bayer A.G., inventors: H . Krimm, H . Ruppivt, and H . Schnell.
Argew. Chem. intrmut. Edit.
Vol. 2 (1963) I No. 7
takes place at a satisfactory rate even at or below room
temperature. By-product formation increases with rising
temperature.
If basic catalysts such as alkali phenoxides, alkoxides,
carbonates, or alkali salts of aliphatic or aromatic carboxylic acids are used, the reaction must be carried out
at 100-160 "C.
To achieve high yields (> 80 %), it is advantageous to
use an excess (1-3 moles) of the aromatic hydroxy compound. The same by-products are formed as in the condensation of aromatic hydroxy compounds with 0x0
compounds. For example, 3 moles of phenol and 1 mole
of p-isopropenylphenol react together in the presence of
0.006 mole of p-toluenesulfonic acid at 20 "C, or of 0.1
mole of sodium phenoxide at 150 O C , to give in a short
time 2,2-bis-(p-hydroxyphenyl)propane in yields exceeding 80 %.
H O - ( - J ~ ~ O H
-
CH3-
The reaction mixture is best worked up by neutralizing
the catalyst, distilling off the excess of hydroxyaryl compound and purifying the resulting product by crystallization or distillation. Acidic and basic catalysis generally give identical results, but in some cases characteristic
differences are noted. Thus the reaction of alkenylphen01s with halogenated phenols in the presence of acid catalysts is slow and gives poor yields, whereas a smooth reaction occurs when basic catalysts are used.
Di-, tri-, and polyalkenylphenols also undergo additions
with aromatic hydroxy compounds in the presence of
acidic or basic catalysts to give dihydroxydiarylmethane
derivatives.
The particular advantages of this method lie in the facts
that only catalytic amounts of acidic or basic substances
are used, that the reaction can be carried out under anhydrous conditions, and that it provides a simple route
to well-defined, unsymmetric 4,4'-dihydroxydiarylmethane derivatives.
and enol esters such as isopropenyl acetate [54] also
react with phenol in the presence of strong mineral acids
to yield the corresponding 4,4'-dihydroxydiphenylmethane derivatives.
3. Mechanism of Formation of
Dihydroxydiarylmethane Derivatives
On the basis of his investigations of the thermal cleavage
of 4,4'-dihydroxydiphenylmethane derivatives, v. Braun
[55] has already postulated that p-isopropenylphenol is
formed as an intermediate when phenol and acetone react together in the presence of mineral acid to give 2,2bis-(p-hydroxypheny1)propane.
Since it has been shown in the meantime that alkenylphenols actually do add on aromatic hydroxy compounds in the presence of acid and basic catalysts to
yield dihydroxydiarylmethane derivatives, and that the
by-products formed in this process are the same as those
obtained in the condensation of 0x0 compounds with
aromatic hydroxy compounds, the two-step reaction
mechanism postulated by v. Braun becomes quite
probable. The acid-catalyzed condensation of acetone
with phenol to give 2,2-bis-(p-hydroxyphenyI)propane
is represented in Scheme 1.
CH,
(54
"i.-C$
CII,
L
b) Reaction of Olefins with Aromatic Hydroxy
Compounds
derivatives are also
formed when hydroxyaryl derivatives are allowed to
react with compounds which are capable of yielding
alkenylphenols under the reaction conditions used. Thus,
in the presence of acid catalysts, 1,I-bis-(p-hydroxyphenyl)ethane is obtained from acetylene and phenol
[51], and 2,2-bis-(p-hydroxyphenyl)propanefrom allene
or methylacetylene and phenol [52]. Halogenated alkenes such as 2-chloropropene or 1-chlorocyclohexene 1531
I
4,4'-Dihydroxydiarylmethane
[51] J. Furukawa, T. Omae, T.Tsuruta, and S . Nukushio, J. chem.
SOC.Japan, ind. Chem. Sect. 60, 803 (1957); Chem. Abstr. 53,
10121f (1959); W . L . Wajsser and W . D . Rjabow, Dokl. Acad.
Nauk SSSR 121, 648 (1958); Erdol u. Kohle 12, 657 (1959).
[52] US.-Pat. 2884462 (1959), Union Carbide Corp., inventor:
J. P. Henry.
[53] US.-Pat. 2602822 (1952), Shell Development Co., inventors:
C. G . Schwarzer and D . B. Luten.
Angew. Chem. internat. Edit. VoI. 2 (1963)
No. 7
i9)
(11)
Scheme 1. Course of the condensatioii of acetone with phenol to give
2,2-bis-(p-hydroxyphenyl)propane.
A proton adds onto the oxygen of the mesomeric limiting structure (Sa) of acetone, thereby stabilizing the
carbonium structure (6). The quinonoid limiting structure (7a) of phenol, with its nucleophilic electron pair
in thepara position, then adds onto the electron-deficient
1541 Brit. Pat. 794476 (1958), Union Carbide Corp., inventors:
R. I. Houglin, C . W . Plummer, and H . C . Schultze.
[ 5 5 ] J . v. Braun, Liebigs Ann. Chem. 472, 1 (1929); E. Leibnitz and
K. Nautnann, Chem. Techn. 3 , 5 (1951).
377
carbonium ion of the acetone. A protonated carbinol(8)
is formed which immediately loses water in the acidic
medium, yielding a carbonium ion (Ya), i.e. protonated
p-isopropenylphenol. This intermediate is a phenylene
homologue of protonated acetone. It also appears as an
intermediate in the acid-catalysedreaction of isopropenyl
phenol (9) with phenol. Reaction with another phenol
molecule then gives, in analogy with the first reaction
step, an addition compound ( l o ) , which undergoes aromatization to 2,2-bis-(p-hydroxyphenyl)propane (11) by
elimination of a proton. The deep red-brown transient
color of the reaction mixture, observable during acid
condensations of phenol with isopropenylphenol or acetone, is most probably caused by the carbonium ion (Ya).
The first of the two reaction steps (condensation of acetone and phenol with elimination of water, and addition
of the protonated p-isopropenylphenol onto phenol) is
rate-determining. The second step is fast and quite exothermic.
Scheme 1 also readily explains the formation of byproducts in the condensation of phenol with acetone.
Addition of (9a) at the o-position of phenol leads to 2(o-hydroxyphenyl)-2-~-hydroxyphenyl)propane; addition at the 0- and p-positions gives 2,4-bis-(p-hydroxycumy1)phenol (3). Chroman derivatives may arise as a
result of ring closure of the dimeric product from two
molecules of o-isopropenylphenol [56]or from one mole
each of 0-and p-isopropenylphenol:
o-Isopropenylphenol does in fact form 2'-hydroxy-2methyl-4,4-dimethylflavan (m.p. 97 "C) readily in the
presence of acid catalysts; an equimolar mixture of oand p-isopropenylphenols yields 4'-hydroxy-2-methyl4,4-dimethylflavan (4a), m.p. 133 "C. 2,2-Dimethyl-4(p-hydroxy)phenyl-4-methylchroman (4) is very probably formed by condensation of phenol with mesityl
oxide formed in the reaction mixture from acetone.
Treatment of mesityl oxide with phenol in the presence
of hydrogen chloride readily gives (4) in good yields [57].
The base-catalysed condensation mechanism is illustrated in Scheme 2.
The quinonoid limiting structure of the phenoxide ion
(13a) is stabilized by salt formation and adds onto the
electron-deficient position in the resonance hybrid (12a)
of acetone which has a degenerate double bond yielding
the p-hydroxyphenylisopropanol anion (I4a). This alcohol is also readily obtained from p-hydroxyacetophenone and methylmagnesium iodide. It is unstable
under the basic condensation conditions and loses the
elements of water above 100 "C to yield p-isopropenylphenol. In the next step, p-isopropenylphenol reacts in
the form of a polarized carbonium phenoxide (15b)
with another phenoxide ion (13a) to give (16), which
undergoes aromatization via proton and electron shifts
[56] W . Baker, R . F. Curtis, and J. F. W . McOmie, J. chem. SOC.
(London) 1952, 1774.
1571 A. Dianin, Zhurn. russ. fiz.-khim. Obshch. 46, 1310 (1914).
378
,c
o=c,
11,
(12)
CH,
1
t!
'cI<,
i
0110
Scheme 2. Base-catalysed condcnsation of acetone with phenol to give
2,2-bis-(p-hydroxyphenyl)propane.
to form the anion of 2,2-bis-(p-hydroxyphenyl)propane.
Here, too, the same reaction products are obtained as in
the base-catalysed condensation of p-isopropenylphenol
(15) with phenol. The fundamental difference between
acidic and basic condensation is that the intermediate
products with carbonium ion structures such as (6) or
(Ya) are more reactive than the quinonoid limiting
structures of the phenoxide ion which have a carbanion
structure, e.g. (13a).
4. Properties and Analysis of
Dihydroxydiarylmethane Derivatives
4,4'-Dihydroxydiarylmethane derivatives are crystalline,
high-melting substances; they are insoluble in water but
soluble in oxygenated solvents such as alcohols, ethers, and
ketones and in hydrocarbons such as cyclohexane, benzene,
toluene, and xylene. When undiluted or in acid solution, they
are quite stable towards atmospheric oxygen; alkaline
solutions discolor in the presence of oxygen. Their watersoluble ammonium salts give off ammonia slowly at room
temperatures and rapidly at elevated temperatures.
Quantitative analysis of dihydroxydiarylmethane derivatives
can be accomplished by hromometric and potentiometric
titration. Their purity can be tested by melting and solidification point determinations. Paper and thin-layer chromatography can be used to separate bis-(phydroxypheny1)alkanes
from their by-products. Many of them can be characterized
by their colors on coupling with diazonium salts and identified by their infrared spectra.
5. Cleavage of Dihydroxydiarylmethane
Derivatives
4,4'-Dihydroxydiarylmethane derivatives undergo thermal and hydrolytic cleavage [55]. On heating above
Angew. Chem. intcmat. Edit. I Vol. 2 (1963)
NO.7
250'C at normal pressure or under reduced pressure,
they give rise to aromatic hydroxy compounds, alkenyland alkyl-substituted aromatic hydroxy compounds,
and non-distillable resinous products. Thermal cleavage
of Bisphenol A gives phenol, p-isopropylphenol, and
resinous substances. The isopropylphenol is produced
by disproportionation of the isopropenylphenol initially
formed. On the other hand, thermal cleavage of 1,l-bis(p-hydroxypheny1)cyclohexanealso yields the substantially more stable olefin 1-(p-hydroxypheny1)-I-cyclohexene in addition to phenol [55].
Acidic and basic compounds markedly reduce the temperature of decomposition. In the presence of acid compounds such as sulfuric acid, p-toluenesulfonic acid, zinc
chloride, potassium bisulfate, or acidic Fuller's earth,
bis-(p-hydroxyary1)alkanes undergo cleavage at temperatures just above 150"C, even under completely anhydrous conditions. Approximately 1 mole of the corresponding aromatic hydroxy compound is formed per
mole of Bisphenol A together with alkenylphenols [58],
their polymerization products, alkylphenols, and indeterminate resinous products. Particularly stable alkenylphenols such as l-(p-hydroxypheny1)-I-cyclohexene can be obtained in useful yields.
The mechanism of acid cleavage is best illustrated by
Scheme 3.
Scheme 3. Acid cleavage of 2.2bis - (phydroxypheny1)propane.
Addition of a proton or a Lewis acid to the phenolic
hydroxyl group weakens the bond with the central
carbon atom. Ion stabilization after cleavage gives p-isopropenylphenol and phenol. At the same temperature,
p-cumylphenol is correspondingly cleaved into a-methylstyrene and phenol. In the cleavagewith acid the protons
attack not only the free hydroxyl groups but also the
ester and ether groups. Thus the monoacetate of Bisphenol A is cleaved into phenyl acetate and p-isopropenylphenol, the diacetate into phenyl acetate and (p-isopropeny1)phenyl acetate, and (p-cumy1)phenyl acetate
into phenyl acetate and a-methylstyrene. In all these
cases, the cleavage temperature is below 200 "C.
Cleavage with base of 4,4'-dihydroxydiphenylmethane
derivatives above 170 "C takes place much more readily,
giving well-defined products in high yields [59]. In this
reaction, only equimolar amounts of alkenylphenols and
phenols are generally obtained. Since basic catalysis promotes side reactions such as alkenylphenol disproportionation and polymerization to only a minor degree,
alkenylphenols can be isolated in yields of over 90%.
[58] B. B. Corson et al., J. org. Chemistry 23, 544 (1958).
[59] Belg. Pat. 503367 (1960), Farbenfabriken Bayer A.G., in-
ventors: H . Krimm and H . Schnell.
Angew. Chem. internat. Edit. 1 Vol. 2 (1963) / No. 7
This represents a simple route to a large number of p
alkenylphenols. A typical example is the alkaline cleavage of Bisphenol A, described below.
Bisphenol A is heated to 170 230°C at 15 mm Hg in the
presence of a basic catalyst (0.01 1.0 '% sodium hydroxide,
carbonate, phenoxide, or acetate). A mixture of p-nopropenylphenol (b.p. 120"C/10 mm Hg) and phenol distils
over, and is then separated by fractional distillation. The
yield of p-isopropenylphenol (m. p. 84 "C) exceeds 90 %.
Scheme 4. Alkaline cleavage of 2.2-bis-(p-hydroxyphenyl)~ro~ane.
The mechanism of the cleavage with base is illustrated
in Scheme 4.Abstraction of a proton from one hydroxyl
group of Bisphenol A facilitates the formation of a
quinonoid limiting structure by electron displacement.
As a result, the bond between the central carbon atom
and the other aromatic residue is weakened. Finally,
phenol is split off in the form of an isomeric phenoxide.
The quinone methide, which is also formed, and the
carbonium phenoxide represent resonance hybrids of p isopropenylphenol, which arise from the latter by proton
displacement.
In agreement with this mechanism, the monoacetate of
2,2-bis(-p-hydroxyphenyl)propaneundergoes cleavage in
the presence of base to give phenyl acetate andp-isopropenylphenol, whereas the diacetate is stable under these
conditions. p-Cumylphenol and (p-cumyllphenyl acetate
are stable in the presence of basic catalysts upto 300 "C.
In the presence of aqueous alkali hydroxide at high
temperatures, 44'- dihydroxydiphenylmethane derivatives are not hydrolysed to the alcohols but, instead, to
ketonic compounds and phenols [60]. Heating 2,2-bis(p-hydroxy-pheny1)propanewith aqueous sodium hydroxide at 240°C under pressure gives acetone and phenol
in good yield.
The reductive cleavage of 4,4'-dihydroxydiphenylmethane derivatives with heavy metal catalysts leads to palkylphenols and phenols. Thus, on hydrogenation in
the liquid phase [61] at 160 "C with a nickel-containing
bismuth catalyst, or in the vapor phase [62] at 330°C
with nickel-copper sulfide catalysts on chromic oxidealumina carriers, 2,2- bis - (p - hydroxypheny1)propane
gives p-isopropylphenol and phenol in high yields.
Received, June 14th, 1962
[A 273/84 IEI
German version: Angew. Chem. 75, 662 (1963).
[60] German Patent 1094759 (19601, Farbenfabriken Bayer A. G.,
inventors: K . H . Meyer and H . Schnell.
[61] German Patent 467640 (1928), Schering-Kahlbaum A.G.,
inventor: H. Jordan; German Patent 479352 (1929), ScheringKahlbaum A.G., inventor: H . Jordan.
[62] German Patent 1 105428 (1961), Farbenfabriken Bayer A.G.,
inventors: G. v. Schuckmann and E l . Schnell.
379
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