Industrial Uses for Cane Sugar 11. Properties of Alkyl Esters of Levulinic Acid' GERALDJ. Cox AND MARYL. DODDS Multiple Fellowship of t h e Sugar Institute, Inc., at Mellon Institute of Industrial Research, Pittsburgh, Pa.
0
NEdof the products of the action of hot, dilute hydrochloric acid on cane sugar is levulinic acid, 0
0
CH~-&--CH~-CH~--C--OH
//
Practical properties of thirteen aliphatic esters of levulinic tzcid are given: boiling point, weight per gallon, solubility of the esters in water, solubility of water in the esters, stability of the esters to water, solubility of gums and resins, miscibility with organic solvents, and dilution ratios.
fication of PentasoL2 a commercia1 mixture of amyl alcohols. The data given in the communication with the preparation of these esters ( 2 ) are v a p o r p r e s s u r e , boiling point, specific gravity, surface tension, and index of refraction. Herein are given data of solubility relations to water, organic solvents, and resins, of stability of the esters to water, and also some general observations.
As Thomas and S c h u e t t e (7) have shown that as much as 42 per cent of the theoretical yield of pure levulinic acid-i. e., 285 grams per kg. of cane sugar-can be obtained by conducting the reaction a t 162" C., commercial production of the acid and its esters becomes a promising possibility. Furthermore, it has been shown elsewhere (2) that substantially higher yields of the esters of levulinic acid can be obtained by esterification of crude levulinic acid and purification than by a succession of more tedious operations-isolation, purification, and esterification of levulinic acid. The reaction of sucrose and hydrochloric acid yields, in addition, formic acid equivalent to the levulinic acid and about 22 per cent of the original weight of the sugar as the so-called artificial humic acid. Recovery and utilization of these by-products are essential to commercialization of the levulinic acid reaction. Some of the difficulties which lie in the path of development of levulinic acid production are the still comparatively low yield of the acid, difficulties in distillation owing both to high boiling points and to the accumulation of "tars," and the corrosive action of the mixtures a t the high temperatures and pressures necessary for the reaction. Recent reports on levulinic acid esters have been those of Sah and Ma ( 5 ) , Schuette and Cowley (6), Cowley and Schuette ( I ) , and Cox and Dodds ( 2 ) . Authors to date have concerned themselves with the physical and chemical constants of the esters and not with useful applications. The objective has been the development of uses for these esters and, as means to that end, certain practical properties of the levulinic esters have been examined. The esters studied are twelve in number, as described in another paper ( 2 ) , and the mixed esters derived from esteri-
The alkyl esters of levulinic acid, up to the hexyl series, are colorless liquids boiling in the range 196.0' (methyl) to 253.4" C. (N-amyl). The lower esters (methyl, ethyl, and propyl) have pleasing melon-like odors; the butyl and amyl series have only faint, but still pleasant odors. The taste of the esters is intensely burning and bitter. The boiling points shown in Table I are those observed by Cox and Dodds ( 2 ) in the vapor pressure apparatus of Ramsay and Young (4) a t exactly 760 mm. pressure. The boiling point of the mixed amyl levulinate was determined in the same way. The indexes of refraction (Table I) are those given by Cox and Dodds ( 2 ) . The weights per gallon of the esters are derived from the specific gravities reported in the same paper. The solubility of the esters in water was determined by adding water with shaking to a measured amount of the ester until opalescence just disappeared. The solubility of water in the esters was determined by the reverse operation. The data relating t o water solubilities are given in Table I. The stability of the esters toward water has been observed by determining the increase in free acidity produced by exposure of the esters to an excess of water. Specifically, free acidity in the technical ester was first determined. Then one cc. was boiled for one hour with 50 cc. of water and the free acidity redetermined. A second one-cc. sample was heated for 5 days a t 40' C., and the increase in free
1 The first paper of this series appeared in IND. ENQ. CHEM.,News Ed., 10,149 (1932).
* Pentasol and alcohols of the amyl series were supplied by the Sharplea Solvents Corporation.
PROPERTIES OF ESTERS OF LEVULINIC ACID
TABLEI. PHYSICAL ANI) CHEMICAL PROPERTIES OF ALKYLLEVULINATES ALKYLLEYULINATE
B. P .
760 MY. Hg (OBSD.) AT
INDEXOF REFRACTION AT 20' C.
SP. GR., 2Oo/4O C.
WT. PER GAL.
c. Methyl Ethyl N -propyl Isopropyl N-butyl Iaobutyl sec-Butyl N-smvl
196.0 205.8 221.2 209.3 237.8 230.9 225.8 253.4 248.8 239.6 239.0 247.2 246 (approx.)
Lb. 1.42333 1.42288 1.42576 1.42088 1.42905 1.42677 1.42499 1.43192 1.43102 1.42808 1.42890 1.43100
.. . ..
1.0495 1.0111 0,9896 0.9782 0.9735 0.9677 0.9670 0.9614 0.9603 0.9557 0.9591 0.9607 0.9589
8.74 8.42 8.24 8.15 8.11 8.06 8.06 8.01 8.00 7.96 7.99 8.00 7.99
967
SOLUBILITY Ester in Water in water ester cc. urn I00 cc.
STABILITY TO WATER ACIDITY AFTER: Boiling 6 dags at for one hr. 40 C.
INITIAL ACIDITY
%
% ..
%
$17
7.4 4.3 0.9 1.2 1.6 2.8 2.9 1.0 1.2 3.3 3.7 0.9 1.2
7.9 6.0
2.6 0.2 0.5 0.9 1.5 2.3 0.4 0.6 3.1 3.5 0.4 0.8
0.9
1.1 2.0 2.9 3.2 1.0 1.0
3.3 3.7 1.1 1.2
INDUSTRIAL
968
AND ENGINEERlNG CHEhlISTRY
acidity measured. These data of initial free acidity and also the results of hydrolysis a t 100" and a t 40" C. are shown in Table I. The qualitative solubilities of some resins and gums in levulinic acid esters have been observed by treating approximately 0.5 gram of the substance with the 5-cc. portions of the esters. As these solubilities are similar for each group of isomers, the esters (Table 11) are grouped in their respective series-methyl, ethyl, the propyl (G),butyl (C4), and amyl (C,) esters. TABLEI1 AND
QUALITATIVE SOLUBILITIOF COMMERCIAL GVMS RESINSIlc; THE ESTERSO F LEVULINIC ACID
RESIT MET AIL^ E T H ~ L Cj C1 Cn x-Manila x x Montol X i + + + Kauri x x xxx x Pontianac chips Rosin Bone-dry shellac Gele Gels Bakelite (VIECOUB) Rezyl + + T + Sarpee Ester gum unoxidized Ester gum: oxidized X Albertol copal X + + + T Albertol X + + + t Amberol x x + Cumar Dammar x Varnieh type glyptal X Gels Gels Gels Gele Gels Vinylite 80 Urea formaldehyde = completely soluble; - = insoluble; X = partially soluble
+
+
++
+
+
+
+
+
+
+
+
+
+ ++
+
+
+
+
+
+ ++ +
+
I n general, it was found that the esters are completely miscible with the simple alcohols, immiscible with ethylene glycol and glycerol, and miscible with ethers, aldehydes, ketones, esters, acids, chlorinated aliphatic hydrocarbons, aromatic hydrocarbons, the Cellosolve group, and fatty oils. Methyl levulinate differs from the above generalization in being completely miscible with ethylene glycol and immiscible with fatty oils. Ethyl levulinate is also immiscible with ethylene glycol. The tolerance of levulinic acid ester solutions of 1 2 second nitrocellulose for dilution with (1) toluene, ( 2 ) S-butyl alcohol, and (3) Kemsoline (a commercial petroleum-dis-
Vol. 25, No. 9
tillate diluent) have been determined by the Hercules Powder Company's method for dilution ratios ( 3 ) . These data are given in Table 111. TABLE
111. DILUTIOSRATIOSO F
SOLUTIOKS O F
NITROCELLULOSE
.4LKlL LEYULIN4TE
TOLUENE Diln. % Nitroratio cellulose Methyl 2.40 7.8 7.2 Ethyl 2 85 .V-DrODVl 3 on 7.3 Isdprip-yl 2 80 7.8 "butyl 3 15 7.7 Isobutyl 2 95 8.0 sec-Butyl 2 75 7.7 7.4 N-amyl 3 25 Isoamyl 3.00 8.2 Methylpropylcarbinol 2 . 8 0 9.7 Diethylcarbinol 3.10 7.9' 2-Methylbutyl 3 00 8.0 Mixed amyl 2.80 8.0
BUTYLALCOHOL Diln. % Nitroratlo cellulose 2.35 8.2 3.25 7.4 3.85 8.0 5.05 6.1 6.40 6.4 6.00 6.8 5.55 6.5 7.50 7.2 7.50 7.6 7.75 6.5 8.00 6.5 7.5 7.85 7.5 7.25
1/2 SECOXD
KEMGOLI\E Diln. % ' Nitroratio cdlulone Immiscible 0.45 6.9 0.75 5.9 0.60 6.3 1 .o 5.3 0.85 5.6 0.85 5.7 1.15 5.1 1.0 5.3 0.93 5.5 0.85 5.6 1.0 5.3 1.1 5.0
DISCCSSIOSOF RESULTS An examination of the various data pertaining to the propeities of the esters of levulinic acid reveals that the better characteristics for most present commercial uses of such materials are found in the members of the butyl and amyl series. Generally these esters are more stable toward water, have lower solubility relations t o water, and better dilution ratios of nitrocellulose solutions than the lower homologs. Their solvent powers seem to be as good as those of the lower esters. LITERATURE CITED (1) C o d e y and Schuette, J . Am. Chem. Soc., 55, 387 (1933). (2) Cox and Dodds, I b i d . , 55, 3391 (1933). ( 3 ) Gardner, "Physical and Chemical Examination of Paints, Varnishes, Lacquers, Color," 5th ed., p. 730, Institute of Paint and Varnish Research, Washington, 1930. (4) Ramsay and Young, J . Chem. Soc., 4 7 , 4 2 (1885). (5) Sah and Ma, J . Am. Chem. Soc., 52,4880 (1930). (6) Schuette and Cowley, Ibid., 53,.3485 (1931). (7) Thomas and Schuette, I b i d . , 53, 2324 (1931). RECEIVEDMarch 29, 1933. Presented before t h e Division of Orpsi-ic Chemietry a t t h e 85th Meeting of the American Chemical Society, JVashington, D . C., March 26 t o 31, 1933.
111. Technology of Sucrose Octaacetate and Homologous Esters GERALD
T
J. cox, JOHN H. FERGUSON, h?;D
31.4RY
L. DODDS
A simplijied conrenienf mefhodfor thepreparaof s i m i l a r compoullds of H E fact that sucrose has tion of sucrose ocfaacefafe in high yield is desucrose* been considered primaThe investigation to be rerily as a food, condiment, scribed, together with analogous processes for ported, therefore, is concerned or confection by the layman, making octapropionate and with some of the phases of proor as an example of an abundant disaccharide by the chemist, octabufyrafe. Properties of wdue in the indusduction of the most promising m e m b e r of t h e series-i. e., has in most cases f a r o v e r trial application of the,ye esters of Sucrose are s u c r o s e octaacetate-together shadowed its possible use as a gio,en. with the properties that might polyhydric alcohol. The proapply commercially to its use. d u c t i o n of esters from this compound, utilizing as it does these same alcoholic properties, Mention is also made of the properties of the two nest therefore seemed to offer a starting point for the development highest members of the homologous series-i. e., sucrose octapropionate and sucrose octabutyrate. of a group of industrially useful organic products. Schutzenberger ( 3 ) was the first to acetylate sucrose but The comparatively low cost and high available tonnage of sucrose obtainable in such a high state of purity as is was able t o obtain only a gummy mass from the process. commonly found upon the consumer's table also contributed Later Herzfeld ( 1 ) was able t o obtain a crystalline product to the belief that such a source material or some of its de- and likewise listed some of its physical characteristics. rivatives could be used both extensively and advantageously The octapropionate and octabutyrate are new compounds. in industrial processes. SUCROSE OCT.4hCETATE With this idea in mind, and cognizant of the extensive LARGE-SCALE LABORATORY PRODUCTIOK I N GLASS. The commercial use of the esters of allied substances-for example, cellulose a c e t a t e t h e lower saturated alipliatic preparation of sucrose octaacetate in 6- to 8-pound lots acids were considered as possible reactants for the produvtion was carried out, using the apparatus shown in Figure 1.
