PRODUCTION OF GLYOXYLIC ACID W I L L I A M T . B L A C K 1 A N D G E R H A R D A. C O O K Linde Division, Research Laboratory, Union Carbide Carp., Tonawanda, N . Y. Glyoxylic acid may be simply produced by treating an aqueous solution of maleic acid at 15" to 25" C. HOOCCH= with a slight excess over the stoichiometric quantity of ozone required by the equation: 0 3 HCOOH CO2. The reaction is essentially quantitative. The formic acid CHCOOH -+ CHO-COOH and most of the water are distilled off at reduced pressure at 50' C., leaving glyoxylic acid monohydrate (purity greater than 97%) behind. The product may be crystallized to give a solid which melts over the range 36' to 55' C.
+
+
+
astonishing that glyoxylic acid, which is a stable compound having two functional groups in a basically small unit structure, has to date found so few applications. Until recently it was not even listed in the catalogs of organic chemicals. I t has now become available in small quantities, but the price range of $0.60 to $1.90 (1966 prices) per gram of the monohydrate seems to indicate that no lowcost method for making it is currently available. We have confirmed the fact, mentioned in the literature 9s early as 1903, that glyoxylic acid can be made by treating an aqueous solution of maleic acid with ozone, and we have discovered a simple method of isolating the product in fairly high purity. T SEEMS
I organic
Maleic acid dissolved in water is treated at a temperature of 15' to 25' C. with a slight excess over the stoichiometric quantity of ozone calculated from the equation :
O3
+ HOOCCH=CHCOOH
e3
+ H C O O H + COz
CHO-COOH
(1)
The reaction proceeds quantitatively as shown. When the required amount of ozone has been added, the formic acid and most of the water are distilled off under reduced pressure a t 50' C. The product when cooled to room temperature is a colorless, very viscous liquid. A few seed crystals of glyoxylic acid monohydrate are added and the mixture is stirred from time to time. Within 24 hours the sirup usually changes to a crystalline mass which melts over the range 36' to 55' C. The large melting range is believed to be chiefly due to variation in the extent of hydration rather than to the presence of impurities. I t is believed that this method for the laboratory preparation of glyoxylic acid by ozonation of aqueous maleic acid could be developed into an economical commercial method, since both ozone and maleic acid are now available on a large scale at fairly low cost.
e
H I1 Zwitterion I1 then rearranges to give formic acid and carbon dioxide. Historical
The first experiment on the preparation of glyoxylic acid by ozonation of maleic acid dissolved in water was apparently carried out by Harries (4)in 1903, but his yield was poor and he isolated the product only as the phenylhydrazone. H e did not measure the ozone absorbed nor carry the ozonation reaction to completion. H e assumed, but did not verify, that the reaction was: 2/3
+
+ HOOC-C-0-0
HOOC-CHO
0 3
+ HOOCCH=CHCOOH
+
2 CHO-COOH
(2)
The ozonation in aqueous solution was also carried out by Hendricks ( 5 ) . When no more ozone was absorbed, he found that the yield of glyoxylic acid (based on starting maleic acid) was only about half of that indicated by Equation 2. Hendricks assumed (without verification) that half of the original maleic acid remained unchanged in the solution when the reaction with ozone stopped; he concluded that this method of making glyoxylic acid would be of no value unless a practical method were developed for separating glyoxylic acid from the supposedly unchanged maleic acid. Both Hendricks ( 5 ) and Eisenbraun and Purves (3) tried in vain to find a solvent from which glyoxylic acid could be recrystallized. However, if desired, the product may be purified by precipitating it out in the form of one of its metal salts (3, 5 ) , separating the salt, redissolving it in water, removing the metal ions-e.g., by means of an ion exchange resin (3)-and then evaporating off the water.
Mechanism
The mechanism of the reaction has not been studied. Following Criegee as given by Bailey ( I ) , we postulate:
+
HOOC-CH=CH-COOH
0 3 -+
0 3
/ \ C-COOH
HOOC-C-
+
H
H
e € + 0-0 0
I
1
HOOC-C-C-COOH
+
H I 1
350
Present address, 3849 Kenwood Drive, Stow, Ohio. l & E C PRODUCT RESEARCH A N D DEVELOPMENT
Experimental
Forty grams (0.345 mole) of maleic acid was dissolved in 100 cc. of distilled water. Oxygen containing about 4 mole % ozone was bubbled into the solution through a disperser at a flow of about 2 cu. feet per hour. The temperature of the aqueous solution was kept between 15' and 25' C. during ozonation. The ozone was metered by analyzing the gas stream before and after the ozonation vessel by the iodometric method ( 2 ) . The ozone was almost completely absorbed until about 95% of the stoichiometric quantity (Equation 1) had been bubbled into the solution; from this point on, some ozone started to appear in the off-gas. Altogether, about 10% more O 3 than the stoichiometric was fed into the solution; only the stoichiometric quantity was absorbed. The solution was then transferred to a vacuum stripper kept at 50' C. by a heated water bath. The formic acid and water were distilled off. When nothing more came over, a little more water was added and the stripping was continued to remove
the last of the formic acid. The resulting sirup was cooled to 20' C. and seed crystals of glyoxylic acid monohydrate were added. The mixture was stirred from time to time. Within 24 hours the sirup changed to a mass of crystals. X-ray diffraction showed that the product was crystalline and not just an amorphous mass of solid material. No maleic, formic, or oxalic acid was found in the product. The glyoxylic acid was identified by making the semicarbazone ( 6 ) . T h e crystalline product contained 0.336 mole of aldehyde carbonyl (Z), which would correspond to a yield of 97.4y0 if all the aldehyde were glyoxylic acid and if the initial maleic acid were 100.0% pure. ANALYSIS.Calculated for C 2 H 2 0 3H20: . C, 26.09; H, 4.38; CO, aldehyde carbonyl (Z), 30.43. Found: C, 26.1 f 0.5; H, 4.0 f. 0.4; CO, 32.4. These results indicate that a little anhydrous glyoxylic acid was mixed with the monohydrate. Any impurities present are believed to be less than 3y0 of the weight of (crystalline product. No attempt was made a t further purification. Formic acid in the distillate from the vacuum stripping was identified by a Duclaux distillation. The first batch of crystalline glyoxylic acid (used thereafter as a source of seed crystals) was obtained by letting the sirupy monohydrate stand for several days in a flask at room temperature. The walls of the flask were scratched from time to time with a stirring rod, and the crystals finally appeared. Different batches of crystals were found to have slightly different x-ray diffraction patterns; this was probably caused by slight variation in the: proportion of water of hydration. The glyoxylic acid monohydrate was sometimes difficult to crystallize, especially in the summertime. I t was found helpful to keep the sirup with seed crystals in a closed container at a temperature not over about 20' C. while the crystals were growing.
Analytical Determination of Maleic Acid
As an aid in following the course of the ozonation of maleic acid, an analytical method was devised (7) for determining the concentration of maleic acid in the presence of both glyoxylic and formic acids. This method consists in measuring in a spectrophotometer the absorbance of an aqueous solution of known glyoxylic acid content [determined by the method of Smith and Mitchell (a), on the assumption that other aldehydes are absent] at a wavelength of 260 mp, and reading off the maleic acid concentration from calibration curves prepared with solutions containing glyoxylic, formic, and maleic acids in known concentration. (For the present purpose, calibration need be carried out only for solutions in which the molar concentration of formic acid is the same as that of glyoxylic acid.) Safety
Ozone is extremely toxic. The ozonation should be carried out in such a way that no one has to breathe an atmosphere containing more than 0.1 p.p.m. of ozone ( 9 ) . literature Cited (1) Bailey, P. S., Chem. Revs. 58, 927 (1958). (2) Firdsall, C. M., Jenkins, A. C., Spadinger, E., Anal. Chem. 24, 662 (1952). (3) Eisenbraun, A. A , , Purves, C. B., Can. J . Chem. 38, 622 (1960). (4) Harries, C., Ber. 36, 1935 (1903). (5) Hendricks, R. H., Ph.D. thesis, St. Louis University, 1935; Univ. Microfilms, Ann Arbor, Mich., Publ. 183, 1935. ( 6 ) Mohrschulz, W., 2. Ekktrochem. 32, 434 (1926). (7) Moore, I$'. N., Pankhurst, R. G., Linde Division, Union Carbide Corp., unpublished work. (8) Smith, D. M., Mitchell, J., Jr., Anal. Chem. 22, 750 (1950). ( 9 ) Stokinger, H. E., Advan. Chem. Ser., No. 21, 363 (1959).
RECEIVED for review April 25, 1966 ACCEPTEDAugust 15, 1966
ESTERIFICATION RATES OF LONG-CHAIN HYDROCARBON DICARBOXYLIC ACIDS AND T H E STERIC ENVIRONMENT IN T H E VICINITY OF T H E ACID GROUPS R. H. QUACCHIA AND A. J.
D I M I L O
Aerojet-General Corf ., Sacramento, Gal$
long-chain, a,w-dicarboxylic acid hydrocarbons based on polymerization of butadienes are being used almost exclusively for the preparation of the new solid-rocket propellant binders, methods of characterizing these polybutadienes are necessary and are being developed. Reactivity of the acid groups with curing agents is one of the parameters which require close control to ensure reproducible propellant properties. An approach to characterizing the reactivity of the acidterminated polybutadienes was made by the use of esterification rates of these acids with excess 1-butanol in refluxing benzene. While the method was not fully developed as a characterization test for reactivity, the results of the investigation afforded an insight into the nature of the polymer structure in the vicinity of the carboxylic acid groups. ECAUSE
Experimental Rates of Esterification. METHODA. RATE OF WATER FORMATION BY AZEOTROPIC DISTILLATION (4).A 3-liter three-necked flask containing 0.139 equivalent of acid-terminated polymer or aliphatic carboxylic acid, 110 grams (1.53 equivalents) of 1-butanol (Merck, reagent grade), and 1.3 liters of benzene (Matheson, reagent grade) was fitted with a thermometer, a 5-ml. (graduated in 0.1 ml.) Dean-Stark trap (Ace-Glass Co., No. 7735), and a Liebig condenser with drip tip and protected from moisture with a tube containing Drierite. The reaction system was dried overnight by azeotropic distillation using a 3-liter Glas-Col heating mantle with a Variac setting of 55 to maintain a gentle reflux. A 300-ml. flask containing 0.9525 gram (5 X mole) of p-toluenesulfonic acid monohydrate and 200 ml. of benzene was fitted with a Dean-Stark trap and a reflux condenser. The system was dried overnight by azeotropic distillation. VOL. 5
NO. 4 D E C E M B E R 1 9 6 6 351
