508
INDUSTRIAL AND ENGINEERING CHEMISTRY
pH 5.7 to 6.5 gave only a 38% conversion to the amino compound and above pH 7.0 only a 5% conversion. The exact cause for the low yields in these experiments was not determined, but it may be attributed to the dissociation of the nitro hydroxy compound to the nitroparaffin and aldehyde, since it is known that at pH 6.0 and above, the nitroparaffin-aldehyde condensation becomes reversible. I t is believed that feirous chloride or hydrochloric acid may be substituted for ferrous sulfate or sulfuric acid in the iron reduction of nitro hydroxy compounds with equally satisfactory conversions. Horvever, these reductions xi11 yield the hvdrochlorides of the corresponding amino hydroxy compounds which cannot be converted readily to the free amino hydroxy compounds; certainly not so readily as can the corresponding sulfates by the method described herein. In view of this anticipated difficulty, the use of ferrous chloride or hydiochloric acid in the iron reduction of nitro hydroxy compounds was not studied. The nitro hydroxy compounds studied herein have been reduced with hydrogen in presence of Raiiey nickel ( 1 2 ) . Because of the instability of nitro hydroxy compounds in basic media, the conversions in these reductions are lower and the isolation of products in a high state of purity is much more difficult. The lower yields in the hydrogenation are balanced by the higher materials cost in the iron reduction, so that the cost of production of amino hydroxy compounds by the two methods is about the
Vol. 40, No. 3
same-for example, the materials cost for 2-amino-2-methyl-lpropanol is 50 cents per pound by each method. ACKNOWLEDGMENT
The plant iron reductions were carried out in cooperation with H . A I . F. Fischer, nitroparaffin derivatives plant manager, Commercial Solvents Corporation. LITERATURE CITED (1) Bechamp, A., A m . , 92, 402 (1854). (2) Davis, C. W., U.S. Patent 1,663,473 (1928). (3)
Dunstan, W. R., and Dymond, T. S.,J . Chem. Soc., 59, 410-33 (1897).
Girsewald,C. von, German Patent 281,100 (1914). ( 5 ) Henry, L., Bull. mad. TOY. BeZgique (a), 38, 584-606 (1900). (6) Johnson, K., and Degering, E. F., J . Am. Chem. Soc., 61, 3194-5 (4)
(1939).
(7) Krause, H., Chem.-Ztg., 40, 810 (1916). (8) Lippincott, S. B., J . Am. Chem. Soc., 62, 2604-6 (1940). (9) Meldola, R., J . Chem. SOC.,93, 2214-57 (1908). (10) Moore, T. S., British Patent 155,319 (1919). (11) Preibisch, R., J . prakt. Chem., 8 ( 2 ) ,309-27 (1874). (12) Yanderbilt, B. M.,and Hass, H. B., ISD.ENG.CHEX.,32, 34-8 (1940). (13)
Worstall, R. d.,Am. Cliem. J . , 21, 210-39 (1899).
RECEIVED -lpril 9, 1947. Presented before the Division of Industrial and CHEMICAL Engineering Chemistry a t the 111th Xeeting of the AXERICAN SOCIETY, Atlantic City, S . J.
Liquid Sulfur Dioxide in Sdfonation of LEE LEISERSON, R. W. BOST,
ROBERT LEBAROIV]
University of .Torch Carolina, Chapel Hill, >Y.C .
A technique is described, for the preparation of aromatic sulfonic acids in substantially quantitative yields, with sulfur trioxide as the sulfonating agent and sulfur dioxide as the solvent. The method was evaluated with benzene as a typical hydrocarbon. The procedure was \aried in regard to solvent, sulfonating agent, addition and ratio of reactants, reaction time, and purity of the benzene. #
T
'
HE purpose of this paper is to describe a simple method for the preparation of aromatic sulfonic acids bv use of sulfur trioxide in sulfur dioxide. The method is evaluated vith benzene as a typical hydrocarbon. The use of sulfur trioxide as a sulfonating agent has long been known ( I ) , and the mechanism of its addition to a hydrocarbon through an electrophilic attack has been given (b'j, but the technique required for its direct application, the products, and the yields obtained have been obscure. Detailed procedures for the sulfonation of benzene have been given by Groggins ( d ) , Xeyer ( 6 ) , and Tanasescu and Macarovici (8). The direct addition of sulfur trioxide to benzene using sulfur dioxide as a solvent is described in a basic patent issued to Grob and Adams ( 3 ) in 1922. Courtot and Bonnet ( 2 ) successfully used sulfur trioxide in chloroform to ,prepare several aromatic sulfonic acids. Ross and co-workers ( 7 ) give a preparation for benzenesulfonic acid using chlorosulfonic acid as the sulfonating agent and liquid sulfur dioxide as the solvent. Hovever, there has been no critical evaluation of the sulfur trioxide methods to 1
Present address, Virginia Smelting Company, West Nolfolk, Va.
determine thk products and yields. The results of such an investigat,ion follow in this report. PROCEDURE
-4simple procedure for the direct preparation of pure bcnzcncsulfonic acid and sodium benzenesulfonate is given in a later section of this paper. This procedure has been varied in regard to purity of the benzene, solvent, sulfonating agent, addition and ratio of reactant's, and reaction time. The yield of crude benzenesulfonic acid using sulfur dioxide and sulfur trioxide ran better than 9570, and the product melt,ed close to 60" C. When chloroform mas used as a solvent the yield v a s 91%, and the melting point of the product was 53-58' C. Chlorosulfonic acid, when used as the sulfonating agent, gave a crude semicrystalline product in 88% yield. A product containing some diphenylsulfone is produced in direct sulfonation of benzene. It is easily separated from the sulfonic acid by dissolving the latter in water and filtering off the insoluble material, which has a melt'ing point of 124-125" C. The quantity obtained in this way is dependent on the q u a h y of t,he benzene used. The crude product, obtained Lvith a purified benzene to be described contains about 1% sulfone. With C.P. benzene 5% of sulfone was obtained. This result confirms the report of Tanasescu and Macarovici (8),who sulfonated nith sulfuric acid at room temperature. There was a notable difference in color between the reaction mixtures when two benzenes of different quality were used. C.P. benzene gave colorless or faintly colored solutions and products
I N D U S ~ R I A LA N D E N G I N E E R I N G C H E M I S T R Y
March 1948
509.
TABLEI. SULFONATION OF BENZENE Experiment No.
Ma,nner of addition
Reaction time after addition, hr. Reaction completed a t room temp. Crude CeHsSOaH Grams Yield, % hIeltinp: ' C. - point, .
1
2
3
SOa added
CeHe added to dilute so3 soln. in 15 min.
ClSOsII added to dilute CeHs soln. in 16 min.
to dilute CeHa s o h . in 15 min.
4
ClSOaH added to dilute CeHa soln. open Dewar in 15 min.
5
7
6
8
9
LO
+
Add SOa & CeHe added Add SO, & Add SO8 & Add SO3 & Add SOa CcHsin 15 CqHein 15 CqHein 15 CqHein 15 CqHain 15 to dilute min. min. min. nun. min. in SO815 soln. min. simul. simul. simul. simul. simul.
2
2
1/2 ,-
I/.
I/'
4
2
2
2
2
KO
NO
Yes
Yes
Yes
No
No
Yes
Yes
No
Crude CnHa(S0aH)z 28 94 Liquid
38 5 97.5 59-61
38 96.5 57-59
35 88.5 Semi. . , . : , , . . 4 " . . " . crystalline .
59 74.6. Semicrystalline
CaHeSOrCsHa Grams brams 0.8 0.8 0.4 6 7.5 12.7 % of total product 2.08 1.0% 17.1 CsHsSOsNa n r a mP 39 31 20 Grams 29.5R 46.5 65.6 51.7 Yield, % 69 44.5 a Constant boiling main fraction of J. T. Baker Co. purified benzene. b J. T. Baker Co. C.P. benzene. Neutral equivalent of product corresponds exactly to yield of benzenesulfonic
throughout the procedure. The distilled purified benzene produced an amber-colored reaction mixture, and a light tan sulfonic acid which gave a q e e n aqueous solution. Treatment with activated carbon removed the color, leaving a pale yellow solution. The yields and constants of the sulfonic acid from both materials were the same. Benzenesulfonic acid crystallizes out in a complex with sulfur dioxide when the latter is used as a solvent. The highegt melting crude product (m.p. 60-61' C.) was obtained when the reactants, benzene and sulfur trioxide, were added simultaneously to the stirred liquid sulfur dioxide. The color of the reaction mixture was lightest under these conditions. The percentage of diphenylsulfone in the crude product was 1.9% as compared with 1% when benzene was added to a solution'of sulfur trioxide in liquid sulfur dioxide. When the sulfur trioxide was added to a benzene solution, 2.1% of the product was sulfone. The simplest procedure for carrying out the reaction-addition of hydrocarbon to a sulfur dioxide bath containing sulfur trioxide a t a rate sufficient to maintain rapid refluxing-is also the condition for low sulfone formation. With compounds that are more reactive than benzene, sulfone formation is not a problem, but oversulfonation is. Then it is desirable to add the sulfonating agent to a solution of the hydrocarbon. The reaction is not instantaneous. I n a run where the addition took 15 minutes and the evaporatiqn of the solvent took 15 minutes, free sulfur trioxide was present. The resultant liquid mixture finished reacting while stored in a vacuum desiccator overnight. Experiments with 2- and 4-hour reaction periods gave identical results. An indication of complete reaction is the appearance of crystals on the sides of the flask above the surface of the liquid. These appear in about 2 hours. The molar ratio of benzene to sulfur trioxide was varied as follows: 1to I, 2 to 1,and 1to 2. The use of an excess of benzene had no advantage, and results were identical with the use of equimolar ratio except that there was a somewhat greater percentage of sulfone formed. An excess of sulfur trioxide 'greater than that required for monosulfonation produced a liquid product containing free sulfur trioxide. This indicates that the sulfonation of benzene takes place stepwise. The benzenesulfonic acid first formed will slowly react at room temperature with sulfur trioxide to form some benzenedisulfonic acid.
..
37.5 95 57-60
36.5 92.5 60-61
37 93.6 58-60
1.7 4.5
0.7 1.92
1.1 2.97
27.5 61
29.5 65.6
30 66.6
Negligible
'
... .. .. ..
36 91 53-58
38 96.3 57-59
0.8 2.2
1.9 5.0
29 64.5
31 69
acid.
The data on the several experiments are summarized in Table I All the experiments were made with 0.25 mole of sulfonating agent except when an attempt was made to repeat exactly the work of Ross et aE. (7). Then 0.5 mole of chlorosulfonic acid and 0.77 mole of benzene were used, and the sulfur dioxide was simply allowed to evaporate. Control of the reaction was assured by the use of a sulfur dioxide bath a t normal pressures the heat of reaction being dissipated by the boiling solvent. Wken chloroform was used as a solvent, the reaction was cooled by means of an ice bath. The work was done on a constant boiling middle fraction (b.p. 80 0.5' C.) of J. T. Baker Company's purified benzene except when Baker's C.P. benzene was used for comparison. The sulfur trioxide was obtained by distilling it from 20-30% fuming sulfuric acid through an 8-inch Vigreux column in an all-glass apparatus. Liquid sulfur trioxide is easily measured and transferred by means of a pipet filled by suction applied by a rubber bulb. This material should be handled with the same precautions as fuming sulfuric acid. PREPARATION O F BENZENESULFONIC ACID
Two hundred cubic centimeters of refrigerant-grade liquid sulfur dioxide, drawn from a n inverted cylinder in a hood, are introduced into an all-glass apparatus. This consists of a three-necked 500-cc. flask equipped with a mechanical stirrer lubricated with silicone stopcock grease, a dropping funnel, and a reflux condenser; the well of the latter is fdled with a dry ice-acetone mixture and is open to the air through a calcium chloride tube. A thermometer inserted during the reaction will show that the temperature of the refluxingsulfur dioxide bath after the addition of reactants will rise to -6' C. and then fall to -8' C. The refluxing bath serves to control the temperature of the reaction closely. The operation is best conducted in a hood. To the vigorously stirred solution are added 20.4 grams (10.4 cc., 0.25 mole) of liquid sulfur trioxide which has been distilled from fuming sulfuric acid. Then 19.5 grams (22.23 cc., 0.25 mole) of benzene are added to the dropping funnel, dropwise above the surface of the liquid, in a period of 10 minutes. The reaction mixture is allowed to reflux for 2 to 4 hours after the addition. The reaction is complete when benzenesulfonic acid begins to crystallize just above the solution. The dry ice condenser and dropping funnel are removed, and one of the necks of the flask is stoppered. The other is connected to a gas absorption column or to the hood. The removal of the
INDUSTRIAL A N D ENGINEERING CHEMISTRY
.s10
solvent is facilitated by vigorous stirring and by the installation of a hot plate several inches from the flask. The hot plate is removed before the sulfur dioxide is completely evaporated. The crystalline product is broken up with a glass spatula before it freezes to a hard cake, and the flask is placed in a vacuum desiccator over sulfuric acid. The desiccator is evacuated to remove the remaining sulfur dioxide. Thirty-eight grams (967, yield) of crude sulfonic acid are obtained, melting at 5759" C. The crude product is dissolved in 150 cc. of vmter and the diphenylsulfone removed by filtration. The solution is treated with activated charcoal to remove color and then concentrated under reduced pressure on a steam bath. -4fter boiling has completely stopped, the flask is cooled. Thirty-five grams (79.5% yield) of crystalline product (benzenesulfonic acid monohydrate) are obtained, melting at 46-49' C. This material may be distilled from a 100-cc. distilling flask (all-glass apparatus) under reduced pressure. KOattempt is made to distill the liquid until it is completely degassed. Water appears as condensate in the dry ice trap. After degassing at about 1 mm., the product is distilled a t a pressure of less than 1 mm. maintained by a Cenco-Hyvac pump. A forerun of about 2 grams is collected, and then the main product distills a t 130' at less than 1 mm. Twenty-two grams (56% yield) of pure white benzenesulfonic acid are collected, melting at 60-61' C. There is no apparent gassing during distillation. The residue is a,ll water soluble.
dried in an oven at 105" C. to produce 31 grams (69% yield) of pure white sodium benzenesulfonate. Evaporation of the neutral solution to dryness mill give 35.5 grams (797, yield) of sodium benzenesulfonate with an off-white color. CONCLUSIONS
1. I t is possible to prepare aromatic sulfonic acids and their salts by a simple method using equivalent quantities of aromatic hydrocarbon and sulfur trioxide. 2. Sulfur trioxide is an ideal sulfonating agent for this purpose, for it adds directly to the hydrocarbon without producing side reactions. Chlorosulfonic acid does not have this advantage, and it liberates hydrogen chloride as a corrosive gas. A complex process is always required for the removal of sulfuric acid. 3. Sulfur dioxide as a solvent is unique in acting as a catalyst and as a refrigerant, and therefore affords an easy means of temperature control; it is readily removable and recoverable from the reaction mixture and consequently enables the isolation of pure products. Chloroform may be used as a solvent, but it does not possess these advantages. 4. A small amount of diphenylsulfone is produced as a byproduct in the reaction. The use of very pure benzene, C.P. grade low in sulfur, enhances the yield of this material. 5. The sulfonation procedure given has the following advantages: (a)The reaction is readily controlled, (5)the sulfur trioxide is completely consumed, ( c ) the reaction is complete in a reasonable period of time, ( d ) the products are not contaminated with inorganic salts, are of light color, and may be easily purified and ( e ) there is a large process economy in the amount of acid and alkali required if neutral salts are desired.
PREPARATION OF SODIUM BENZENESULFONATE
Crude benzenesulfonic acid prepared as described is dissolved in 150 cc. of water. The aqueous solution is boiled to remove sulfur dioxide. After treatment with activated charcoal to remove color, the aqueous solution is filtered, neutralized with 15 grams (0.121 mole), the theoretical amount, of sodium carbonate monohydrate. The solution is concentrated on a steam bath under reduced pressure until crystallization begins. The mixture is cooled to 0" C. and filtered. The mother liquor is treated again in the same manner. The combined product is
Vol. 40, No. 3
LITERATURE CITED
Armstrong, A'atuw, 138, 26 (1936). Courtot and Bonnet, Compt. rend., 182, 855 (1926). Grob and Adams, U. S.Patent 1,422,654 (1922). Groggins, "Unit Processes in Organic Synthesis," p. 212, New York, McGraw-Hill Book Co., Inc., 1935. (5) Luder and Zuffanti, Chem. Revs., 34, 349 (1944). (6) Meyer, Ann., 433, 330 (1923). (7) ROSS et d., IND. ENG.CHEM., 34, 924 (1942). (8) Tanasescu and Macarovici,BUZZ.SOC.Chim., 5, 5, 1126 (1938).
(1) (2) (3) (4)
RECEIVED February 7, 1947.
Zirconyl and
irconyl Compounds in Acid Dyestuffs r! -
J
J
WARREN B. BLUNIENTHAL, The Titanium Alloy Manufacturing Co., Niagara Falls, N . Y . Zirconyl and basic zirconyl salts are found to be precipitants for many acid dyestuffs and it is believed that they will precipitate the entire class of acid dyestuffs. The compounds which form are salts of the cations ZrO+', ZrtOs++, and Zr609++ with the dye anions. Techniques are described for forming these compounds under such conditions that they fulfill the requirements of pigment toners of good quality.
L
AKE pigments prepared by precipitating acid dyestuffs
onto suitable substrates have long been of great commercial importance as well as academic interest (2). The substrate is usually a hydrous metal oxide, such as alumina hydrate, and it may or may not be extended with other insoluble materials such as blanc fixe, China clay, and whiting ( 1 ) . Barium, calcium, and aluminum salts are commonly used as precipitating agents for fixing the dye on the substrate. Pigments of this type have a marked limitation in the color intensity which can be developed, due to the large proportion of noncolored material in the compositions.
The acid dyestuffsare usually azo or quinoid compounds, containing one or more sulfonic or carboxylic acid groups, or both. The precipitating cations (barium, calcium, aluminum, etc.) do not generally form insoluble compounds with the dye (4,but are absorbed by the alumina liydrate (or other substrate), increasing its electropositive charge and causing it to absorb large quantities of the electronegative dye anions. The resulting lake is a composite of alumina hydrate, metal cation, and dye anion. Laboratory studies of many metals have been undertaken by numerous investigators, who have studied their properties both as substrates and as fixatives, and vast numbers of lake compositions have been reported. However, commercial lake pigments of acid dyes have been generally limited to those lakes formed on alumina hydrate and fixed with barium, calcium, and aluminum salts, a consequence of the soft texture of alumina hydrate and of the low cost of these materials. Since zirconium salts have become available in commercial quantities, many investigators have examined their properties in lake compositions. Because of the hard texture of zirconia hydrate, lakes containing this substance as a substrate are gen-
