INDUSTRIAL AND ENGINEERING CHEMISTRY
May, 1944
DISCUSSION OF RESULTS
The production of methyl acetoxypropionate from lactic acid, acetic acid, and methanol by the methods described here have the advantage of not requiring the use of acetic anhydride or ketene, but the yields are not so high as those obtained by convereion of lactic acid into methyl lactate followed by acetylation with acetic anhydride, as described in the preceding paper. To. afford a comparison of the relative merits of the two methods, the materials costs of methyl scetoxypropionate prepared by the two methods were calculated. The prices assumed for the intermediate chemicals may not have been exactly correct, but the same prices were used for both methods and therefore the calculated material costs should be adequate for a preliminary comparison. In making the calculations, the cost of sulfurio acid wed a3 catalyst was not included, and it was assumed that a n over-all yield of 85% acetoxypropionic acid could be obtained from lactic acid by treatment of the distillation residues with acetic acid. The other yields assumed in estimating relative costs w-ere: 75% methyl acetoxypropionate and 10% methyl lactate in the esterification of acetoxypropionic acid, 90% ðyl lactate in the esterification of lactic acid, and 96% methyl acetoxypropionate in the acetylation of methyl lactate. All yields were calculated on the basis of unrecovered starting materials. The calculated cost of materials indicated that the acetoxypropionic acid method of making methyl acetoxypropionate is somewhat more expensive (approximately 2 cents per pound) than the previously described methyl lactate method (4). The aretoxypropionic acid method, however, has the advantage of not requiring plants for the manufacture of acetic anhydride or ketene. Owing t o the shortage of alloys and other construction materials, this advantage would be highly important under war-
475
time conditions if large quantities of methyl acrylate were manufactured by the pyrolysis of methyl acetoxypropionate. ACKNOWLEDGMENT
The assistance and cooperation of other members of the Carbohydrate Division of this laboratory are gratefully acknowledged. LITERATURE CITED
'
AnschUtz, R., and Bertram, W., Ber., 37,3971-4 (1904). Auger, M. V., Compt. rend., 140, 938 (1905). Burns, R., Jones, D. T., and Ritchie, P. D., J.,Chem. SOC.,1935, 400-6.
Filachione, E. M., Fein, M. L., Fisher, C. H., and Smith, L. T., Div. Ind. Eng. Chem., A.C.S., Detroit, April, 1943. Fisher, C. H., Ratchford, W. P., and Smith, L. T.. IND.ENG. CHEM.,36, 229-34 (1944). Freudenberg, K., and Markert, L., Ber., 60B,2447-58 (1927). Neher, H. T., IND.ENQ.CHEM.,28, 267-71 (1936). Ritchie, P. D.,Jones, D. T., and Burns, R.,U. 8. Patent 2,265,814 (Dee. 9,1941). Rohm, 0.. Ibid., 1,121,134(Dec. 15,1914). Rohm, O.,and Bauer, W., German Patent 693,140 (June 6, 1940).
Smith, L. T.. Fiaher, C. H., Filachione, E. M., Ratohford, W. P., and Fein, M. L.,Div. Org. Chem., A.C.S., Memphis, April 1942.
Smith, L. T., FisheF: Cf H., Ratchford, W. P.. and Fein, M. L., IND.ENG.CHEM.,34, 473-9 (1942). Starkweather, H.W.,and Collins, A. M., U. 8. Patent 2,218,362 (Oot. 15, 1940). Watson, P.D..IND.ENG.CHEM.,32, 399-401 (1940). Wingfoot Gorp., Brit. Patent 622,981 (July 2, 1940). PRFJBENTED a8 part of the Symposium on Lactic Acid and Derived Productr before the Division of Industrial and Engineering Chemistry at the 106th Meeting of the AMFJRICAN CHFJMICAL SOCIETY, Pittsburgh, Pa.
CLASSIFICATION of TOBACCO Nicotine-Nornicotine Method C . V. BOWEN AND W. F. BARTHEL Bureau of Entomology and Plant Quarantine, s. Department of Agriculture, Beltsvil,e, Md.
HE recent discovery
Of the u.idespread OCcurrence of nornicotine in tobaccos (9) brings up the need for their rapid classification according to the predominant alkaloid. Markwood and Barthel (4) made such a classification based on the melting points of the picrate of the benzene-so1ub1e tobaccos giving picrate melting points above 215' C. were classified as nicotine type, those giving melting points between 175' and 200' C. as nornicotine type, and those between 190' and 215' C. as mixed type. No composition limits corresponding t o these melting point limits were given. Furthermore, i t is now known that some tobaccos contain other benzene-soluble basic materials which influence the picrate melting point. The work has therefore been continued to establish a rough correlation between composition and melting point for known mixtures of nicotine and nornicotine and to check the classification scheme adopted against the melting points of picrates obtained from analyzed samples o f toharro.
T
*
The melting points of the picrates of known mixtures of nicotine and nornicotine indicate that the melting point of .the steam-volatile alkaloid picrate may be used as a means of classifying tobaccos as to alkaloidal type. According to the upper limit of the melting point spread, the tobacco is classified as nicotine type (melting point above 211' C.), mixed nicotine-nornicotine type (melting point 198-211 and nornicotine type (melting point below 198' C.). Six tobaccos of known nicotine and nornicotine content were tested for melting point of mixed picrates, and they were found to agree with the classification.
c.),
RELATION BETWEEN PICRATE MELTING POINT AND COMPOSITION
Known mixtures of standard nicotine and nornicotine solutions were treated with aqueous picric acid solution to obtain mixtures of the coprecipitated picrates. The standard solution of nicotine was prepared from a sample that had been vacuum-distilled, treated with nitrous acid to remove any secondary amines, and then steam-distilled from an aqueous alkaline solution. The nornicotine used in the standard solutions was identical with that
INDUSTRIAL AND ENGINEERING CHEMISTRY
476
TABLE I. MELTINGP O I N T SPREAD OF PICRATES O F KNOWN MIXTURESOF NICOTINE AND XORNICOTINE Nicotine,
%
0 5.2
10.8
13.7 15.7 20.8 30.0 35.6
Nornicotine,
%
100 94.8 89.4 86.3 84.3 79.2 70.0 64.4
M.P. Spread (Cor.), C.
186.9-189.6 167.8-180.4 180.3-184.1 177.8-184.6 175.3-183.1 178.4-182.6 178.4-182.5 177.4-199.9
Nicotine,
%
45.3 52.5 62.4 68.9 81.6 89.9
100
Nornicotine,
%
M.P. Spread (Cor.), O C.
54.7 47.5 37.6 31.1 18.4 10.1
175.5-204.1 180.0-206.2 192.0-208.3 194.5-211.7 204.9-217.5 213.0-219.9 218.7-224.8
0
used by Markwood (S), which had been obtained from the Robinson Medium Broadleaf strain of Maryland tobacco, and formed a picrate melting at 190-191" C. The absence of nicotine was established by treating a sample with nitrous acid and by steam distilling the aqueous solution after making i t basic to phenolphthalein. Upon heating in a capillary tube, each mixture of the alkaloid picrates so obtained melted, not sharply but over a temperature range that varied with the composition. This range or spread, from the temperature of first noticeable softening to that of disappearance of the last crystal, is shown in Table I and Figure 1. The latter point was much more reproducible and will be referred to as the upper limit of the melting point spread. Figure 1 shows that the upper limits of the melting point spread of mixtures rich in nicotine fall on a straight line; those of mixtures rich in nornicotine are approximately alike and definitely lower than the lowest temperature reached by this line. Evidently a eutectic mixture exists. Since this abrupt change in the character of the curve occurs naturally at a composition of two thirds nornicotine and one third nicotine, it furnishes a convenient composition limit for nornicotine-type tobaccos. By analogy, the composition two thirds nicotine and one third nornicotine can be selected as the limit for nicotine-type tobaccos. The fairly rapid change of melting point with composition makes the differentiation easy and definite between a mixture rich in nicotine, and one not so rich. These upper limits of melting point spread of the nicotine-nornicotine picrates serve as a basis for classifying the tobaccos melting below 198' C. as nornicotine type, those melting above 211 O as nicotine type, and those melting between these temperatures as mixed type.
Vol. 36, No. 5
of Markwood and Barthel (4) and by the proposed steamdistillation method (Table 11). According to the Markwood and Barthel classification, based on melting point spread, it is obvious that if their data for tobacco samples had been plotted, the melting point spread would in all cases have fallen within areas A , B, and C in Figure 2. Although this was satisfactory by their procedure for the tobaccos studied, it is evident that samples with part of their spread in area D will be encountered-namely, MarylandConnecticut Broadleaf. Certain known solutions also gave values lying outside the ranges prescribed in their classification. The use of only the upper limit of the melting point spread makes allowance for all possible mixtures. The presence of benzene-soluble basic material, such as the nonsteam-volatile aikaloid in Maryland-Connecticut Broadleaf, precludes the use of benzene extraction of the alkaloids. Since nicotine and nornicotine are volatile with steam, a steam distillation into dilute hydrochloric +id and subsequent concentration of the distillate eliminates the use of benzene and shortens the time required. This method is briefly described as follows: Mix a 2-gram sample of tobacco with 10 grams of sodium chloride and 10 ml. of sodium hydroxide solution (30% by weight) and steam distill into 3 ml. of hydrochloric acid. With the use of an improved steam d!stillation apparatus (I) the distillation can be completed w i t h p 30 minutes. Make the distillate just acid to phenolphthalein, evaporate to a small volume, filter into a small flask, neutralize with sodium hydroxide solution, add 25 ml. of saturated aqueous picric acid solution, and evaporate to 30 ml. Allow to stand to crystallize. If no crystals form, a larger sample of tobacco should be taken for the determination.
ALKALOID PICRATE MELTING POINTS OF ANALYZED TOBACCOS
Previous analyses (2) of several tobaccos for nicotine and nornicotine were compared with the melting points of the alkaloid picrates, as determined both by the benzene-extraction method
Figure 1. Melting Point Spread of Picrates of Known Mixtures of Nicotine and Nornicotine Solid vertical lines show the melting point spread of analyzed mamples of tobacco3 broken lines @howthe composition range of each class of tobaooo.
TABLE 11. RELATION BETWEEN NICOTINE-NORNICOTINE CONTENT AND ALKALOID PICRATE MELTING POINT OF CBJRTAIN TOBACCOS Tobacco5 Nicotiana tobacum Robinson Maryland Medium Broadleaf, sample 1 Cash flue-cured Robihson Maryland Medium Broadleaf, sample 2 Burley, Halley Maryland-Connecticut Broadleaf Nicotiana Tustica 88
Nornicotine in NicotineAnalysis, Yo Nornicotine Nicotine Nornicotine Mixt., o/c
0.34 0.70 0.98 1.23 2.22 4.57
1.71 2.40 2.16 1.41 0.49 0.99
83.4 77.4 8.86 53.4 18.1
17.8
M.P. Spread (Cor.), a C. Benzene extn. Steam distn.
184.6-185.6 173.2-183.6 179.4-196.1 192.0-124.0 215.6-220.9b 215.1-219.3
179.4-184.6 181.6-184.6 180.4-194.1 196.1-205.6 202.5-218.9 214.0-221.9
Classification Type Nornicotine Nornicotine Nornicotine Mixed
g;;;;;
Sample, 1 WES the source of nornicotine used in the standard solution; in the other samples the steam-volatile secondary-amine alkaloid was identified nornicotine by methylation. Due t o an additional alkaloid (approx. 0.2%). not steam volatile, having a melting point spread of 237.1-237.6' C.
b
INDUSTRIAL AND ENGINEERING CHEMISTRY
H.5 1944 100
zao
90
eo
70
I
I
0 UPPCR
eo
PERCENT LIMIT
so
ao
zo
IO
I
I
I
I
NOlNlCOTINE
0
4Tl
The melting point is taken without recrystallization, which would tend to eliminate the minor alkaloid. The presence of picric acid accounts for the spread in the melting points of pure nicotine picrate and pure nornicotine picrate (Table I). Although the picrate melting point is not intended to be a quantitative procedure, the close agreement between the percentage composition and the melting point of the steamvolatile alkaloid picrate obtained from tobaceo with the values obtained from the known solutions is striking. LITERATURE CITED
(1)Bowen, C. V., and Barthel. W. F., IND. ENG. CHEM.,ANAL.ED.,15, 596 (1943). (2) Ibid., 15,740 (1943). (3) Markwood, L.N., J. Assoc. O f l c h l Aor. Chem., 26,283-9 (1943). (4) Markwood, L. N.,and Barthel, W. F., Ibid., 26, 280-3 (1943).
Figure 2. Area of Melting Point Spread Accordin to the Markwood and Barthel Classification iri Relation to Data for known Mixtures in Figure 1
OXIDATION OF LUBRICATING OILS Effect of Natural Sulfur Compounds and of Peroxides N ACTUAL service the oxiG. H. DENISON, JR. present, suah as sulfur comdation of a lubricating oil Standard oilCompany of sm F ~ ~ pounds.~ The most ~ obvious~poinof attack in studying compositakes place in highly complition, a t least for oxidation ret csted systems. For example, in an internal combustion engine, catalysis by metal surfaces and search, consists in determining whether the hydrocarbons or the metal soaps as well as complex variations in temperature and oilnonhydrocarbons control the oxidation characteristics. air agitation throughout the oil stream markedly affect stability. HYDROCARBON FRACTlON T o investigate the mechanism of oxidation in such a complicated There are two general methods by which the composition of a system without adequate knowledge of the oxidation in simple mixture such as lubricating oil can be determined or, more litersystems does not appear sound. The aim of the present paper is ally, approximated. These methods might be termed “analytic” to aid in establishing a basic mechanism of oil oxidation under as and “synthetic”. I n the analytic method the mixture is sepasimple conditions as feasible; when adequate knowledge has rated by physical and chemical processes into its components, been obtained, effect of service variables and catalysts may be which are analyzed and compared with known substances. I n dealt with as perturbations on the reactions taking place in simple the case of lubricating oils this process is exceedingly difficult besystems. cause of the complexity of the mixture. The synthetic method Before lubricating oil oxidation can be discussed, a picture of employs the procedure of preparing compounds similar to those oil constitution must be established. A finished lubricating oil expected to be present in the mixture and comparing the properconsists of a multitude of dzerent hydrocarbons, which make up ties of the synthesized substances and their blends with those of from 80 t o 98% of the stock. I n addition, there are 2 to 2070 the l+ricating oil. This method is simpler than the analytical sulfur compounds, 0.08 to 0.3% nitrogen compounds and some method, but definite proof of composition is never established. oxygen compounds. These materials may so perturb the oxidaBoth of these methods have been applied by Mikeska (7)and by tion of one another as t o mask completely any similarity of the oxidation mechanism to those of the pure, low-molecular-weight many others. I n applying the analytic method to the present problem, the compounds in the literature. The resistance of oil to deterioration varies with the source of technique adopted a t the National Bureau of Standards was followed and the finished lubricating oil separated into narrow the crude and the treatment it receives. Simultaneously, with this variation in stability, the oil varies both in its major fraction, fractions by solvent extraction in a Fenske column, as described by Mair and Schicktanz (6). hydrocarbons, and in the small percentage of nonhydrocarbons
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