(15) Reinking, N. H. (to Union Carbide Gorp.), u. s. Patent 2,951,822 (Sept. 6, 1960). (16) Reinking, N. H.. Barth. B. P., Castner, F. J. (to Union . Carbide Gorp.), Ibid:,2,951,'825 (Sept. 6, 1960). (17) Reynolds, H. C. (to Merck and Co.), Zbid., 3,014,895 (Dec. 26, 1961). (18) Rocklin, A. L. (to Dow Chemical Co.), Ibid., 2,829,164 (April 1, 1958). (19) Union Carbide Plastics Co., brochure, ''Filament Winding and Reinforced Plastics Resin: Bakelite Epoxy ERL-0500."
(20) Wismer, Marco (to Pittsburgh Plate Glass Co.),U. 3,016,362 (Jan. 9, 1962).
s. Patent
RECEIVED for review May 31, 1966 ACCEPTED August 3, 1966 Division of Organic Coatings and Plastics Chemistry, 152nd Meeting, ACS, New York, N. Y., September 1966.
HYDROXYMETHYL REPLACEMENT REACTIONS
OF TETRAKIS(HYDR0XYMETHYL)PHOSPHONIUM CHLORIDE W I L L I A M J. VULLO Research Center, Hooker Chemical Corp., Niagara Falls, N.Y.
In the presence of approximately an equivalent amount of base, tetrakis(hydroxymethy1)phosphonium chloride reacts with an a$-unsaturated nitrile, acid, amide, and an epoxide by way of hydroxymethyl group replacement. Acrylonitrile gave tris(2-cyanoethyl)phosphine, acrylic acid gave 2-tris(hydroxymethyl)phosphinopropionic acid betaine, acrylamide gave a methylolamide resin, and ethylene oxide gave, prechloride. Hydroxymethyl replacement is believed sumably, tris(2-hydroxyethyl)hydroxymethylphosphoni1~m to proceed through conversion of hydroxymethylphosphonium salt to tertiary phosphine, and reaction of the tertiary phosphine with the active double bond or epoxide ring. The sequence repeats itself in cases where basic species are generated, leading to the replacement of more than one hydroxymethyl group.
u
recently the chemistry of tetrakis(hydroxymethy1)phosphonium chloride (Tetrakis) has been primarily concerned with oxidation at the phosphorus atom or reactions of the hydroxyl group. Oxidation with a variety of agents under mild conditions gives tris(hydroxymethy1)phosphine oxide and under more drastic alkaline conditions gives bis(hydroxymethy1)phosphinic acid ( 7 7 ) . The best example of Tetrakis functioning as an ordinary poly01 is its conversion to tetrakis(chloromethy1)phosphonium chloride by reaction with phosphorus pentachloride (77) or thionyl chloride (70). Similarly, esters are said to result from reaction with carboxylic acids and anhydrides (75), carbamates from reaction with isocyanates (23), ethers from reaction with epoxides (7-4) and aziridines (75), and acetals from reaction with certain aldehydes (24). Products of these reactions, however, were characterized inadequately, since oxidation and polymerization reactions also occurred. Tetrakis functions as an active alcohol-e.g., like an N-methylolamine or methylene glycolin its reactions with amines, amides, and phenols (75). The simplest example of such condensation reactions is the reaction of Tetrakis with secondary amines, giving tris(dialky1amino)phosphines in good yield (5). Very few examples exist where Tetrakis has undergone reactions which resulted in the formation of new carbon to phosphorus bonds. Several workers have accomplished this by reaction of Tetrakis with base, which apparently generates tris(hydroxymethy1)phosphine (7), followed by reaction with alkyl halide-e.g., Equations 1 and 2 (8-70, 73). NTIL
(HOCH2)dPCl
+ NaOH
--f
+
(HOCHZ)~P HCHO
+ RX
(HOCHz)3P 346
--f
+ NaCl + HzO
(1)
(HOCHZ)~$RX
I&EC PRODUCT RESEARCH A N D DEVELOPMENT
Such a reaction sequence may be called hydroxymethyl replacement, since the net result is the replacement of one of the hydroxymethyl groups of Tetrakis with an alkyl group. Hellman (70) and Petrov (73), by successive reactions with base and alkyl halide, have synthesized mixed tertiary phosphines and polyalkylphosphonium salts from Tetrakis. The author has been interested in finding new examples of hydroxymethyl replacement reactions of Tetrakis, and in particular those in which more than one new carbon to phosphorus bond are formed. The present paper discusses the author's results concerning the reactions of Tetrakis with acrylonitrile, acrylamide, acrylic acid, and ethylene oxide. Experimental
Preparation of Tris(2-cyanoethy1)phosphine. To a solution of 79.3 grams (0.333 mole) of 80% aqueous Tetrakis, in 75 ml. of denatured alcohol, was added a solution of 19.6 grams (0.301 mole) of 8670 potassium hydroxide in 20 ml. of distilled water while stirring, cooling to below 30' C., and maintaining a nitrogen atmosphere. Next 58.2 grams (1.10 moles) of acrylonitrile was added slowly while cooling to 35' to 40' C. After stirring overnight at room temperature, the reaction mixture was poured into ice water and the precipitate collected, washed with cold water, and dried. The yield of dry tris(2-cyanoethy1)phosphine of melting point 95.8-97' C . and equivalent weight (iodine) 97 was 49.8 grams, 84% of theory based on potassium hydroxide and 78% based on Tetrakis [literature melting point 98-99' C. ( 7 4 , equivalent weight calculated for C ~ H I ~ N is 96.51. ~P A portion of the tris(2-cyanoethy1)phosphine was oxidized with hydrogen peroxide in acetic acid to give a 45% yield of tris(2-cyanoethy1)phosphine oxide [m.p. 165-68' C. ; literature m.p. 171-173' C. (74)]. Yields of tris(2-cyanoethy1)phosphine were lower, and proportional to the amount of base, when Tetrakis (1 mole), base,
and acrylonitrile (3 moles) reacted in water in open beakers. Under these conditions a maximum yield of 59% was obtained when the ratio of sodium hydroxide to Tetrakis was 1.5 to 1. When a solution of Tetrakis and acrylonitrile (mole ratio 1 to 3) in alcohol-water was allowed to stand overnight a t room temperature and then distilled a t 1 atm., the acrylonitrile was recovered essentially quantitatively as the water azeotrope.
Reaction of Tetrakis and Acrylamide. A solution of 38.1 grams (0.200 mole) of crystalline Tetrakis in 50 ml. of denatured ethanol was neutralized under a nitrogen atmosphere with a solution of 11.8 grams (0.182 mole) of 8670 potassium hydroxide in 10 ml. of distilled water. The supernatant liquid was decanted from the potassium chloride precipitate (dry weight 12.7 grams, 94y0 of theory) and combined with alcohol extracts of the salt. T o this alcoholic solution was added, under nitrogen, a solution of 39.0 grams (0.55 mole) of acrylamide in 50 ml. of distilled water while cooling in order to maintain the temperature in the range of 25' to 42' C. T h e turbid reaction solution was stirred for 8 hours a t room temperature and then let stand for a n additional 9 hours under nitrogen without stirring. Concentration on a rotating evaporator a t 20 mm. and 45' C. gave 81 grams of a medium viscosity amber oil. This material was soluble in water, acetic acid, and methanol and insoluble (forming gummy white solids) in acetone, ethyl alcohol, isopropyl alcohol, and dioxane. T h e oily product was selfextinguishing and intumescent (phosphorus, 6.0% equivalent weight, 1148 by titration with iodine). Upon further concentration a hygroscopic, tacky solid is obtained which is soluble in cold water but only slightly soluble in warm methanol. When carried out in water solvent, the reaction of Tetrakis (1 mole) with acrylamide (3 moles) and base (somewhat less than 1 mole) is exothermic and is best controlled by mixing the components simultaneously so as to maintain the pH about 8 and cooling to keep the reaction temperature below 40' C. Upon long standing such reaction solutions gel.
Preparation of 2-Tris(hydroxymethy1)phosphinopropionic Acid Betaine. A solution of 9.50 grams (0.050 mole) of anhydrous Tetrakis in 55 ml. of anhydrous ethanol was stirred under a nitrogen atmosphere, cooled to about 20' C., and neutralized by the addition of 2.80 grams (0.043 mole) of 86% potassium hydroxide pellets dissolved in 45 ml. of anhydrous ethanol. The mixture was stirred a few minutes and filtered by suction to remove the potassium chloride (dry weight 2.95 grams, 9270 of theory), and the filtrate (pH 6) was returned to a nitrogen atmosphere and cooled in an ice-water bath. T o this was added, rapidly, a solution of 3.24 grams (0.0450 mole) of acrylic acid in 10 ml. of anhydrous ethanol. T h e reaction mixture was stirred a total of 2 hours, during which the temperature was allowed to rise to room temperature. T h e white precipitate which gradually formed during this period was collected, washed with cold alcohol, and dried in vacuo a t 65' C. The yield of betaine was 6.9 grams, 82% of theory based on potassium hydroxide and 78% based on Tetrakis. This melted a t 145-48' C., after softening at 139' C . [literature m.p. 148-49'C. (78)]. Analysis. Calculated for C6H130SP: P, 15.79; C1, 0; molecular weight, 196.14. Found: P, 15.62; C1, 1.4; equivalent weight 104 (iodine). The equivalent weight., phosphorus content, and chlorine content indicated the betaine product to be contaminated with about 4y0 of potassium chloride.
Reaction of Tetrakis and Ethylene three-necked flask was fitted with a gas containing a thermometer and a vented addition funnel, and a second addition
Oxide. A 1-liter, bubbler, a Y tube pressure-equalizing funnel maintained
under a slight positive pressure of nitrogen. The reaction flask contained two portholes through which a glass and a calomel electrode were inserted tightly. Stirring was accomplished magnetically and cooling by means of an ice bath. The entire reaction setup was placed on a large balance. To the reaction flask were added 238 grams (1.00 mole) of 80% Tetrakis and 100 grams of previously boiled water. A solution of 53 grams (0.81 mole) of 8670 potassium hydroxide pellets in 150 grams of previously boiled water was placed in the pressure equilibrated addition funnel. A solution of 97 grams (1.00 mole) of concentrated hydrochloric acid and 97 grams of previously boiled water was placed in the second addition funnel under a slight positive pressure of nitrogen. T h e system was flushed with nitrogen and the base solution was added during stirring and cooling. Ethylene oxide, 4.17 moles, then was swept into the reaction mixture with the aid of nitrogen. Cooling was necessary during the first half of oxide addition in order to maintain the temperature in the range of 23' to 42' C. T h e pH was maintained in the range of 8 to 9 during the oxide flow by portionwise addition of hydrochloric acid, and finally adjusted to 7; total acid employed was 1.07 moles. After the oxide addition was complete, excess oxide was removed by purging with a rapid stream of nitrogen and it was determined by weight difference that 3.44 moles of ethylene oxide had been absorbed. Analysis of aliquots of the reaction mixture by titration with aqueous iodine and precipitation of formaldehyde in the oxidized aliquots as the dimedone derivative indicated the presence of 0.956 mole of oxidizable phosphorus and 3.58 moles of formaldehyde. By analogy with Tetrakis (7) the iodometry is believed to obey the following stoichiometry :
+
+
+ Iz O=P(CH&H20H)3 + H C H O + 21- + 3H+
H O C H ~ P ( C H ~ C H Z O H )H20 ~
4
The reaction mixture was taken up in anhydrous alcohol, filtered to separate from potassium chloride (dry weight 58.7 grams), and concentrated in water aspirator vacuum to 85% dryness, yielding 254 grams of a yellow mobile liquid. A 10.12-gram portion of this liquid upon further concentration to constant weight a t 60' to 70' C. and 0.2 mm. yielded 8.68 grams of crude tris(2-hydroxyethyl)hydroxymethylphosphonium chloride as a viscous amber oil. Analysis. Calculated for C ~ H I S O ~ P C P. I : 13.32; molecular weight, 232.65. Found: P, 13.33; 124 grams per equivalent by aqueous iodine; 242 grams per mole by tetrabutylammonium hydroxide; 260 grams per mole by perchloric acid with mercuric acetate. A similar product prepared in another run was found, upon oxidation with iodine and treatment with dimendone, to release 0.96 mole of formaldehyde per mole of oxidizable phosphorus. The infrared spectrum (neat) of the phosphonium chloride was very similar to that of Tetrakis (strong primary hydroxyl) at 3.03 and 9.50 microns, except that the hydroxyethylated product contained weak bands a t 8.65 microns (possibly P=O), 9.85 microns (possibly P O H or POC), and 10.48 microns (possibly P O H or POC), and was missing a weak band a t 10.86 microns which was present in Tetrakis. The tetraphenylboron derivative was prepared in water from 1.37 grams of the 85y0 solution of phosphonium chloride and 1.71 grams of sodium tetraphenylboron. The yield of dry derivative of melting point 143-45' C. was 1.3 grams, 74y0 of theory. Analysis. Calculated for CalH3804PB: C, 72.10; H, 7.42; P, 6.00; B, 2.10. Found: C, 71.75; H, 7.26; P, 5.86; B, 2.10. Results and Discussion
Reaction of Tetrakis with Acrylonitrile. Tetrakis, in the presence of base, reacts rapidly and exothermically with VOL. 5
NO. 4 D E C E M B E R 1 9 6 6
347
acrylonitrile to give tris(2-cyanoethy1)phosphine. The base acts as a reactant, since the yield of the phosphine is related directly to the base to Tetrakis mole ratio. With a constant mole ratio of acrylonitrile to Tetrakis of 3 to 1, and operating under less than optimum reaction conditions-e.g., open beakers-the yields of tris(2-cyanoethy1)phosphine were 0, 12, 24, 57, and 5970 when the mole ratio of base to Tetrakis was 0 to 1, 0.25 to 1, 0.5 to 1, 1 to 1, and 1.5 to 1, respectively. I n the absence of base, no reaction occurred between the Tetrakis and acrylonitrile on standing for 24 hours at room temperature or upon subsequent recovery of the acrylonitrile by distillation; the recovery was quantitative. An 85% yield of this tertiary phosphine was isolated when the reaction was performed in a nitrogen atmosphere. The stoichiometry of the reaction is: (H0CHz)aPCl
+ M O H + 3CH-CHCN P(CHzCH2CN)a + 4HCHO + Hz0 + MC1 -+
Tris(2-cyanoethy1)phosphine has been prepared by others in yields of about 80% from acrylonitrile and phosphine in the presence of base (74) or heavy metal catalyst (79) and from acrylonitrile and tris(hydroxymethy1)phosphine (20). Reaction of Tetrakis with Acrylamide. I n the absence of added base, Tetrakis and acrylamide did not appear to react on standing at room temperature, although they reportedly do react upon continued reflux (77). Also, no reaction appeared to occur when an aqueous solution of Tetrakis and acetamide and an aqueous solution of tris(hydroxymethy1)phosphine oxide and acrylamide were made mildly alkaline. However, when an aqueous solution of Tetrakis and acrylamide (mole ratio 1 to 3) \%asbrought to p H 8 by addition of slightly less than 1 mole equivalent of sodium hydroxide, after a brief induction period, an exothermic reaction occurred characterized by a gradual rise in p H to over 11. Hydrogen evolution occurred during the latter stages of the reaction and during solvent removal, and on long standing reaction solutions gelled. Much less heat was evolved when nonaqueous solvents were employed. The exact nature of the base-initiated reaction of Tetrakis with acrylamide is not known for certain, because of the instability of the reaction product, which appears to be a mixture of poly(n'-rnethylolcarbamoylethy1)phosphonium hydroxides, such as compound I, and phosphine oxides, such as compound 11, and their low molecular weight condensation polymers. OH
+ MOH + 3CHz=CHCONH2 P(CHzCHzCONHz)3 + 4HCHO + HzO + MCl I P(CHzCHzCONHz)3 + 4HCHO + HzO (HOCHz)4PCl
I
HOCH&(CH2CH&ONHCHzOH)3 -OH
I1 By analogy to the acrylonitrile reaction, the first stage of the reaction of Tetrakis with acrylamide probably involves hydroxymethyl abstraction (Equation 3). The resulting tris(2-carbamoylethy1)phosphine can react then with the byproduct formaldehyde both through the amide groups and at the phosphorus atom (Equation 4). The increase in alkalinity which is observed may be due to the greater basicity of the phosphorus atom in the carbamoylethylphosphine, compared to tris(2-~yanoethyl)phosphine, which permits reaction with formaldehyde and water to give a hydroxymethylphosphonium hydroxide. 348
I & E C P R O D U C T RESEARCH A N D D E V E L O P M E N T
(4)
I1 The major portion of the exotherm and the gas evolution observed when the p H passes 10 are due undoubtedly to the well known hydroxide-catalyzed oxidation of hydroxymethylphosphonium compounds-e.g., compound 11-to the corresponding phosphine oxides (9). I n the related prior literature Tetrakis has been reported to give a water-soluble resin which is useful in flameproofing plywood (77) when boiled with aqueous acrylamide (no base or only catalytic amounts). The same workers include acrylamide in a series of polyamines and amides which, upon polymethylolation with formaldehyde, react with Tetrakis to give polymers and solutions useful in flame-retarding textiles (76). Tris(hydroxymethy1)phosphine has been reported to give a water-soluble quaternary phosphonium hydroxide, isolated as an oil, when reacting with an equimolar quantity of acrylamide (78,22). Reaction of Tetrakis with Acrylic Acid. A fully neutralized solution of Tetrakis was found to react with acrylic acid to give in good yield 2- [tris(hydroxymethyl)phosphino]propionic acid betaine. The reaction fits the stoichiometry shown in Equation 5.
+ M O H + CHz=CHCOOH (HOCHz)3PCH&HzCOO + H C H O + H20 + MC1
(HOCH2)4PCl
+
(5)
The synthesis was performed by neutralizing an alcoholic solution of Tetrakis with an approximately equal molar quantity of potassium hydroxide dissolved in alcohol, filtering off the precipitated potassium chloride, and then adding an approximately equal molar quantity of acrylic acid in alcohol. The betaine gradually precipitated out of the reaction solution. The yield of crude product (96% purity) was 82% based on potassium hydroxide or 70% based on Tetrakis. This betaine has been prepared previously from the reaction of tris(hydroxymethy1)phosphine and acrylic acid (78, 27). However, Tetrakis was reported to react with potassium acrylate by way of metathesis ( 6 ) (Equation 6).
+ CHz=CHCOOK
-+
0
I1
(HOCHz)rPOC-CH=CHz O=P(CHzCHzCONHCHzOH)3
(3)
-+
(HOCHz)4PC1
+
HOCH~P(CH~CHZCONHCH~OH)~
+
+ KC1
(6)
Reaction of Tetrakis with Ethylene Oxide. I n the presence of a t least enough aqueous base to raise the p H to about 5, Tetrakis was found to react rapidly, exothermically, and in good yield with ethylene oxide. The reaction is characterized by a moderate exotherm, an increase in pH, the predominant retention of phosphorus in the reduced state, and the release of formaldehyde. Vsing over 4 moles of oxide per mole of Tetrakis, approximately 3 moles of ethylene oxide were absorbed, approximately 1 mole of phosphonium hydroxide was formed, and the sum total of free and phosphoniumbound formaldehyde (the analytical method employed does not distinguish between these) approached 4 moles per mole of Tetrakis; maximum actually observed v a s 3.58. The reaction is believed to be:
0
/\
(HOCHz).iPCl
+ MOH + 3CH2CHz
+
-OH
HOCHz$(CHzCHzOH)3
+ MCl + SHCHO
The reaction was best conducted in a p H range of about 8 to 9 accomplished by continuous addition of dilute acid, since above p H 10 oxidation of trivalent phosphorus occurred a t the expense of hydroxyethylation, and a t p H below 6, the conversion of oxide slowed down considerably. T h e hydroxyethylated phosphonium product, which was isolated as a viscous pale yellow oil following neutralization of the reaction mixture with hydrochloric acid and removal of salt and volatile components, is believed to be mainly tris(2-hydroxyethyl)hydroxymethylphosphonium chloride contaminated by a small amount of phosphine oxides. This structure was assigned on the basis of the previously described stoichiometry of the reaction and the following information. The phosphorus content agreed closely, and the equivalent weights (by iodine oxidation and by titrations as a weak acid and as a phosphonium salt) agreed fairly closely with the calculated values. T h e ratio of formaldehyde (released by iodine oxidation and determined by the dimedone derivative) to moles of oxidizable phosphorus was found to be very nearly 1.O. The infrared spectrum agreed with a hydroxyalkylphosphonium salt contaminated by small amounts of compounds containing P=O, and P-0-C or P-0-H. The crystalline tetraphenylboron derivative, isolated in good yield, gave acceptable analyses for all of the elements, although the similarity of analyses made impossible the exclusion of the compound containing tlvo hydroxymethyl and two hydroxyethyl groups. A search of the literature revealed a few instances where Tetrakis reacted with epoxides. Reaction products were not characterized well and were thought to be hydroxyethyl ethers arising from hydroxyl addition to the epoxide group (7-4, 72). Tris(hydroxymethy1) phosphine has been reported to react with an equal molar amount of alkylene oxide (ethylene oxide, glycidol, and epichlorohydrin) to give water-soluble oils, presumed to be tris(hydroxymethyl)2-hydroxyalkylphosphonium hydroxides (78, 22). Hydroxymethyl Replacement Reactions of Tetrakis. The above described conversions to phosphines and phosphonium compounds via hydroxymethyl group replacement all probably proceed through the same first step, the formation of tris(hydroxymethy1)phosphine (Equation 1). Subsequent reaction of the tris(hydroxymethy1)phosphine with alkyl halide or with the double bond of acrylic acid stops with the replacement of only one of the hydroxymethyl groups of Tetrakis because of the low basicity of the anions produced, halide ion and carboxylate, respectively. I n the case of reaction with acrylonitrile, acrylamide., and ethylene oxide, however, basic
species are generated-e.g., carbanions from acrylamide and alkoxides from ethylene oxide. These basic species are able to propagate the reaction, as illustrated for acrylonitrile, by converting hydroxymethylphosphonium intermediates to the corresponding phosphine plus formaldehyde. Ultimate products are tertiary phosphines or, when the phosphines are sufficiently basic to react with by-product formaldehyde, trialkylmonohydroxymethylphosphonium hydroxides. (HOCH2)sP
+ CHFCHCN
--$
(HOCHJ~~HZ-CHCN
( H O C H J 3 k H 2 C H 2 C N -OH
--(+ 1 internal
mechanism’
+CHz=CHCN -HCHO (HOCHZ)ZPCH~CH~CN
HOCH2P(CHzCH2CN)
-H20
+
(HOCHZ)z P C H ~ C H ~ C N H C H O I
HOCHzP(CHzCH&N)2
+ C ! ~ ~ ~ NP(CH2CH2CN) +
literature Cited (1) Rullock, A. L., Reeves, W. A., Guthrie, J. D. (to United States of America), U. S. Patent 2,830,964 (April 15, 1958). ( 2 ) Bullock, A. L., Reeves, W. A., Guthrie, J. D. (to Albright and Wilson), Brit. Patent 816,069 (July 8, 1959). (3) Bullock, A. L., Reeves, W. A., Guthrie, J. D. (to Albright and IVilson), Can. Patent 686,637 (1964). (4) Bullock, A. L., Reeves, W. A., Guthrie, J. D. (to United States of America), U. S. Patent 2,916,473 (Dec. 8, 1959). (5) Coates, H., Hoye, P. A. T. (to Albright and Wilson), Brit. Patent 842,593 (July 27, 1960). (6) Fekete, F. (to Pittsburgh Plate Glass Co.), U. S. Patent 2,831,838 (April 22, 1958).
( 7 ) Fodor, L. M., Ph. D. thesis, Cornel1 University, 1963; Microfilm Order Number 64-3627. (8) Grayson, M. (to American Cyanamid Co.), Brit. Patent 934,895 (1963); German Patent 1,151,255 (July 11, 1963). ( 9 ) Grayson, M., J . Am. Chem. SOC. 85, 79 (1963). (10) Hellman, H., Schumacher, O., Angew. Chem. 72, 211 (1960). (11) Hoffman, A., J . Am. Chem. Soc. 52,2995 (1930). (12) Kindley, L. M., Glekas, L. P., Ritt, P. E., Tu!@ 44 ( l o ) , 185A 119611. (13) Petrov, K.A., Parshina, V. A., Luzanova, M. B., Zh. Obshch. Khzm. 32, 553 (1962). (14) Rauhut, M. M., Heckenbleikner, I., Currier, H. A., Schaefer, 81,1103 (1959). F. C., Wystrach, V. P., J . A m . Chem. SOC. (15) Reeves. TY. A., Guthrie. J. D.. Znd. Ene. Chem. 48. 64 11956). (16) Reeves; W.A.; Guthrie; J. D.’(to Unired States df America), U. S. Patent 2.809.941 1Oct. 15. 1957’1. (17) Zbid., 2,927,’050’(March 1, 1660); ito Albright and Wilson), German Patent 961,658 (April 11, 1957). (18) Reuter, M., Orthner, L., Jakob, F., Wolf, E. (to Farbwerke Hoechst), U. S. Patent 2,937,207 (May 17, 1960). (19) Reuter, M., Wolf, E., German Patent 1,078,574 (March 31, 1960). (20) Reuter, M., Wolf, E. (to Farbwerke Hoechst), Zbid., 1,082,YlO (June 9. 1960). (21) Reuter, M.; Wolf, E., Orthner, L., Jakob, F., Zbid., 1,045,401 (Dec. 4, 1958). (22) Zbid., 1,042,583 (Nov. 6, 1958). (23) Taylor, J. H. (to Imperial Chemical Industries), Brit. Patent 925,570 (May 8,1963). (24) Temin, S. (to Koppers Co.), U. S. Patent 3,037,950 (June 5, 1962).
RECEIVED for review July 18, 1966 ACCEPTEDSeptember 16, 1966
VOL. 5
NO. 4
DECEMBER 1 9 6 6
349
