diffusion of which is slow coinpared with the rate of polymer chain growth. 4. Employing a model based on this concept, it is calculated that gelation can only occur after
[CONTRIBUTION FROM
THE
these swollen niolecules have filled 13-23% of the reaction mixture. Experimental results indicate 2546% in fair agreement with calculation. PASSAIC, NEWJERSEY RECEIVED OCTOBER 27, 1944
RESEARCH LABORATORIES OF THE STANDARD OIL COMPANY (INDIANA)]
The Acidic Constituents of Degras. A New Method of Structure Elucidation’ BY A. W. WEITKAMP
Introduction Because of the unique complexity of degras (wool fat, wool wax) the identities of the individual acidic constituents have remained obscure. Early investigator^^^^^^ recognized the presence of two types of acids: (a) hydroxy acids ( C , , H z n 0 3 ) and (b) acids of normal oxygen content (CnH2,,0,). Attempts to resolve the mixture by ester distillation were unsuccessful. Kuwatab obtained about 77, of impure C & s O 3 by selective extraction with 90% methanol, followed by fractional distillation of the methyl esters of the extract. This acid was shown to be a “stereoisomer of synthetic a-hydroxyhexadecanoic acid.” The structures of the acids of normal oxygen content have been variously postulated as b r a n ~ h e or d ~even ~ ~cyclic,1o ~ ~ ~ but ~ ~ there ~ is no evidence that any such acids were isolated or identified. The ester distillation method seemed to us to offer greater possibilities than solvent extraction as a means of separating the individual constituents, particularly since recent advances in column p a c k i n g ~ ‘ ~have J ~ made possible the construction of highly efficient laboratory stills. The greatest deficiency of the ester distillation method as applied to this problem is that the methyl esters of the hydroxy acids are thermally unstable. hfembers of the 2-hydroxy series above C 1 6 H a O 3 have not been recovered. The laboratory vacuum still used in this investigation was identical with one described in an earlier paper14 except for the substitution of a more efficient, spiral-conical-pattern, wire gauze packing.15 The packed section was 44 inches in (1) Presented before the Division of Organic Chemistry, New York meeting of the American Chemical Society, Septemher 14. 1944. (2) Chevreul, C o m p f .rend., 42, 130 (1856). (3) Lewkowitsch, J . SOC.Chcm. I n d . , 11,136 (1892); 16,14 (1896). (4) Darmstaeder and Lifschutz, Ber.. 28, 3133 (189.5); 29, 618, 1474, 2890 (1896); 81, 97, 1122 (1898). ( 5 ) Kuwata, TRISJOURNAL, 60,559 (1938). (6) Busine, Wagncrt Jahrcsbcr.. SO, 1189 (1884). (7) Herbig, J . SOC.Chnn. Ind., 15, 138 (18’36). (8) Rohmann. Biochcm. 2.. 77, 298 (19lfi). (9) Drummond and naker, J . Sm. Chrm. I n d . , 48, 232T (1929). (IO) Abraham and Hilditch, ibid.. 54, 308T (1935). (11) Kuwata and Ishii, J . SOC.Chcm I n d . . Japan, SB, 317B, 318B, 3680 (1936). (12) Bragg. I n d . E n g . Chrm., A n a l . E d . , 11, 283 (1939). (13) Lecky and Ewell, ibid.. 12, 544 (1940). (14) Weitkamp and Brunstrum, Oil &+ Soap, 18, 47 (1941). (15) Weitkamp and Oblad (to Standard Oil Co. (Ind.)), U. S Patent 2.325.818.
length by one inch inside diameter. The over-all efficiencywas approximately 100theoretical plates. The specimen of degras used in this study was taken from a commercial lot purchased in 1941 from Arlington Mills, 80 Chauiicy St., Boston, Mass., under the brand name, “Centrifuged Degras.” Its composition was as follows: COMPOSITION OF DEGRAS, WT. % 1.2 11.0 44.0 46.1
Moisture Free acids Combined acids Unsaponifiable (sterols, etc.)
The work reported in this paper was restricted to those acids originally present as sterol esters because of the possibility that the free acids might include extraneous acidic material, originating from the detergents used for scouring the wool. Altogether 32 acidic constituents have been isolated. These are distributed among four homologous series: (I) normal fatty acids, (11) optically active 2-hydroxy acids, (111) is0 acids (methyl side chain in the penultimate position) and (IV) dextrorotatory anteisole acids (methyl side chain in the antepekltimate position). I CHa-(CHz)z,r-COOH I1 CHa-(CHz)z,-i-CH-COOH
I
n = 4 to 12 incl. n = 6.7
OH I11 CHs-CH-(CHz)zn-COOH
I
n = 3 t.o 11 incl.
CH:
IV CHa--CHr-CH-(CHz)zn-COOH
I
n = 2 to 13 incl.
CHa
Isolation of Constituents The free acids (110 g.) were extracted with alkaline 60% ethanol from a petroleum ether solution of degras (1000 g.). The sterol esters (878 g.) were saponified with potassium hydroxide and separated with petroleum ether and OOyo ethanol into sterols (461 g.) and acids (440 g.). These acids were esterified with methanol and dry hydrogen chloride and finally filtered in pctrolcurii ether solution through Attapulgus clay. T h e yield of neutral, straw-colored esters was 40.5 p. or 887, of the theoretical based on a11 average (16) Apparently there has been no name comparahle to r * n . ~ p p l i ~ l to the series of compounds having a methyl group at the third car bon atom. To 611 this need the term. anlerro. was coined
TABLEI ACIDICCoNSITUlENTS UF
Kame of acid
Melting point of acid, ' C . , cor.' From literature Found
DECRAS
Melting point of amide, "C., cor.Found
Formula
Neutralization equivalent Calcd Found
n- Decanoic, Capric n-Dodecanoic, Lauric n-Tetradecanoic, Myrktiv n-Hexadecarioic, Palmitic n-Octadecanoic, Stearic a-Eicosanoic, Arachidic n- Docosanoic, Behenic n-Tetracosanoic, Lignoceric n-Hexacoianoic, Cerotic 2-Hydroxytetradecanoic, a-OHmyristic 2-Hydroxyhesadecanoic, n-OHpalmitic
Methyl esters B. p . , uncor. a t Per c e n t . 1.95 mm. present
79 104.5 128 5 150 170
0.3 .i 2 8 2 8
1x8
205.5 222 237
.6 0.4 1.2 0 8
146.5
0.2
75 100.5 124.5 146.5 166.5 185 202.5 219 234 248
0.1 .4 2.8 5.8 4.0 5.0 4.0
us
Is0 Series 8-Methyliio1ia11oic.Isocapric 10-Methylundecanoic, Isolauric 12-Methyltridecanoic, Isomyristic 14-Methylpentadecanoic, Isopalmitic 16-Methylheptadecanoic, Isostearic 18-&1ethylnonadecanoic, Isoarachidic 20-Methylheneicosanoic, Isobehenic 22-Methyltricosanoic, Isolignoceric 24-Methylpentacosanoic, Isocerotic 26-Methylheptacosanoic, Isomontanic
.. 41.9 50.5-51 . # Y e 53.3 ti1.8-ti2.426 62.4 t i 7 , 6 4 8 .Y 6 6 9 . 5 75.3 79.1 83.1 86.9 89.3
103.1 108 , 0 107.?J 102.1 107,3 105.1 108.4 110.5 112.1
172.26 200.31 228.36 256.42 284.47 312.52 340.57 368.62 396.68 424.73
, ,
.
200.8 228.5 256.1 281.2 312.6 340.4 370.4 396.9 ,
..
158.23 ... 60 6-Methyloctanoic 186.29 190.2 88 8-Methyldecanoic 10-Methyldodecanoic 214.34 214.5 112.5 242.39 242.3 136 12-Methyltetradecalloic 14-llethylhexadecanoic 270.44 270.7 156.5 298.49 299.4 176 16-JIethyloctatiecanor 18-Methyleicosanoic 326.55 326.1 194 LI)-~lethyldecozari~i~ 354.60 353.8 211 22-hIethyltetracosaiioic 382.65 382.3 227 24-hIethylhexacosanoic 410 70 410.6 211 5 28- Methyltriacontanoic 266 466.81 ... Temperatures of complete melting were determined by the niethod of Francis and Piper.*" &-Isomer. C19 and Ca0fractions from which pure acids were not isolated.
molecular weight of 300 for the acids. The 12y0 loss was due mainly to adsorption of colored constituents on the clay. Fractional distillation of the mixed methyl esters yielded 328 g. (8lyO) of distillate and 53 g. ( Inf&) of residue, leaving 24 g. (6%) not recwered. This SY0 loss (material not condensed by a water-cooled condenser) probably represents cktensive decomposition of the methyl esters of oxygenated acids, in view of the fact that the iiiethyl esters of acids of normal oxygen content .ire thermally stable and distill without decomposition. The boiling points (uncorrected) a t 1.95 1~1111.pressure and an estimate of the relative pro-
2.8 3.6
0.8
e
0.1 .6 1.0 4.8 3.6 4.8 5.6 3.6 7.0 5.2 l.oc Includes
portions of the various methyl esters in the SlSZ, distillate are listed in Table I. The proportions are expressed volumetrically and are uncorrected for the presence of volatile products of decomposition. The differences in the boiling points of the various methyl esters are due chiefly to differences in molecular weight and to a smaller extent t o structural differences. The mixture was initially separated by distillation into a series of fractions differing from each other by one -CHtunit. Fractions corresponding to acids of odd carbon content each yielded an anteiso acid. Fractions corresponding to acids of even carbon content
March, 1945
THE
10
11
12
ACIDICCONSTITUENTS O F DECRAS
Carbon content of CnHt.Og acids. 13 14 16 18 20 21 28
449
46
I 1 I I I I I I111111111 IIlIIl I
Fig. 1.-Melting
0.00A
0.003 0.003 0.001 0 l/mol. w t . points of fatty acids: 0-0, anteiso acids; e--., is0 acids; o - ~ , normal acidsz0i21;A-A, stereoisomeric 2-hydroxy acids; .--., synthetic 2-hydroxy a ~ i d s . ~ ~ ~ ~ ~
0.006
0.004
each yielded a normal acid, an is0 acid and in two instances a %hydroxy acid with two fewer carbon atoms. In order effectively to separate the corresponding normal and is0 acid esters, by means described below, i t was necessary to remove the %hydroxy acids. This was done by fractional crystallization of the free acids from petroleum ether, in which the 2-hydroxy acids are nearly insoluble. Final traces of the 2-hydroxy acids were destroyed by oxidation with potassium permanganate, after which the residual normal acid and is0 acid were reesterified. As a means of improving the separation of binary inixtures o f fatty :icicls by distiIl:itiot~,Axc
and Bratton" suggested extending the mixture with a hydrocarbon diluent. This procedure has been successfully applied to the purification and/or separation of the methyl esters of all of the d e g a s acids except the 2-hydroxy acids. Methyl esters have the advantage of co-distilling with the hydrocarbon diluent a t their normal boiling points, whereas the fatty acids form minimum boiling azeotropic mixtures with hydrocarbons. The boiling points of the methyl esters of the normal acids are only 3-4' higher than the boiling points of the methyl esters of the is0 acids. Their separation is further complicated by the fact that ( 1 7 ) 4xe and nralton, Tins
JOURNAL,
69, 1424 (1937).
450
Vol. 67
A. W. WEITKAMP
some of the normal acids are present in very small proportions. By means of the technique of estended distillation it has been possible to isolate both the is0 and normal acids, although in some cases the latter have not been obtained in completely pure condition. The various acids were recovered from the purified ester fractions and recrystallized to constant melting point from acetone or petroleum ether.
houettes for the identification of substances. The profile angle of the normal fatty acids is unrelated to chain length but is a characteristic property of the even or odd members of the series. Thc normal fatty acids crystallize in the monoclinic system.23 Optically Active 2-Hydrogy Acid Series.Only the and Cl6 members were isolated. Higher homologs, if present, did not survive distillation of the methyl esters. Kuwata6 found the CIS member, 2-hydroxyhexadecanoic acid, to be levorotatory, [a]D - 1.0 (c, 5.2 in alcohol), and identified it by oxidation to n-pentadecanoic acid as an optical isomer of dl-2-hydroxyhexadecanoic acid. Similarly, oxidation of our 2-hydroxyhexadecanoic acid yielded n-pentadecanoic acid, in. p. 52.4O; Meyer and Reid,2152.26'. Oxidation of our 2-hydroxytetradecanoic acid yielded n-tridecanoic acid, m. p. 41.3'; Meyer and Reid,2141.55'. Optical rotations were not determined. However, the melting points in the following tabulation indicate that these acids are distinct from the synthetic acids and hence must be optical isomers.
Identification and Proof of Homology Each of the acidic constituents falls naturally into one of four groups characterized by a distinctive crystal habit (Plates 1-IV).l8 In addition, the boiling points of the methyl esters (Table I) and the melting points of the fatty acids (Table I) of the members of each group lie on smooth curves when arranged in order of increasing molecular weight. Above C ~ in O the fatty acid series it appears that molecular weight is the major variable affecting the melting points (Fig. 1). The melting point curves are nearly linear with respect to reciprocal molecular weights and converge a t infinite molecular weight a t about %Hydroxyhexadecanoic 2-Hydroxytetra136.5'. acid decanoic acid PresPresIt has not been feasible separately to identify ent Synent Syneach individual constituent, but rather to deterRuwatab study thetic" study thetic*$ mine the identity of a t least one member of each bl. p. o f acid, ' C . 86437 9 3 . 6 86.16 * 8 8 . 5 81.5-82 0.05 group and establish the homologous relationship p. o f methyl within each group by a determination of the ac- M ,ester, '(2. 45-46 45.A 5 7 . 5 ( S . P . ) ... ... tual relationship between two or more adjacent Neut. eq. of acid . 272.5 172.4 246.4 2 4 4 . 4 members. (calcd.) (calcd.) Normal Fatty Acid Series.-This series conThe 2-hydroxy acids crystallize in clusters of tained all even members from CIOto c26. dl but C14and CIS are minor components. Both identity radiating fibers. Photomicrographs are shown and homology followed from a direct comparison, in Plate 11. Homology in this series is such that higher by means of mixed melting points, with authentic specimens.lS Because of the relative diEculty of homologs cannot be derived from lower homologs isolation, the melting points (Table I) are lower by known chain building processes involving the by 0.3-1.7' than the best reported values.20*?*carboxyl group. The question arises as to whether The normal acids crystallize in characteristic thin these hydroxy acids might be intermediates in the plates appearing as equilateral parallelograms biosynthesis of normal acids or vice versa. Is0 Acid Series.-All even members from with an acute angle of approx. 55'. Representative photomicrographs are shown in Plate I. Cl0 to C28 were isolated. Their melting points SheadZ2established the suitability of the angular (Table I) lie very close to the melting points of the constants of microcrystalline profiles arid sil- corresponding normal acids. However, mixed inelting points with normal acids are depressed (18) The photomicrographs were made at 860 diameters with 10-15°. Furthermore, the crystal habits of the cardioid illumination. Crystals were prepared by dissolving sufficient fatty acid in Mineral Seal Oil (Viscosity at 100"F., 5 . 2 Centinormal and is0 acids are dissimilar. The latter stokes) for slight crystallization t o occur at room temperature. Cryscrystallize in thin plates appearing as elongated tals of the normal and is0 acids were prepared in small beakers and parallelograms with a characteristic profile angle transferred to slides for observntion. The 2-hydroxy and onleiso of approsimately 75O (Plate 111). The ratio of acids were prepared for observation as follows: A drop of the crystal slurry was placed on a slide, and as the cover glass was pressed length to width increases greatly as the series is down, a concentration gradient was produced, assuring that some ascended so that the higher members appear to part of the slide would have optimum density. The acid was then the naked eye as fine needles. redissolved by warming. By means of a movable stage crystallizaFordyce and Johnson28synthesized a series of tion could be followed from the center outward. In addition to the still photographs shown here, action photographs of the crystallizais0 acids but did not give sufficient physical data tion of the anteiso acids were made. for a rigorous comparison. (19) Authentic normal acids were obtained as follows: Ciz from 128) hluller. .Vnlure, 116, 45 (1925). coconut oit. Cu to Czr from hydrogenated sardine oil. ,
(20) Francis and Piper, Tms JOURNAL, 61, 577 (19351) (21) Meyer and Reid, ;bid., 66, 1577 (1933). 1:'2> S h e d I w d F n r Chrrii , A n n 1 E ? , 29. iOfi / 1 ( 2 7 7 '
f24) hlendel and Coops, Rrc. Irao. chim., 68, 1133 (1989). 1%) 1.e Sueur, J . Chem. Soc., 8'7, 1903 (1905). ' 2 6 ) FOrdScc? an'! Johnqnn, THISJOTlRNAl., 66. 3368 (1983)
Myristic
Ligrioceric
Palmitic Plate I.-Normal
acids
2-Hydroxymyristic
%Hydroxypalmitic Plate 11.-Hydroxy
acids.
1, Isolaurie 2. Isomyrirtic
4, Isostearic 5. Iroarachidic
7. Isolignoeeric
3, Isopalmitic
6, Irobehenic
9. 17-Mcthyloctadecanoic
Plate 11I.-Iro acids
8, Ismerotic
March, 1945 Acid
Isomyrist~c Isopalmitic Isostcaric
4,il
THE .%CIDIC CUNSTLTUENTS OF DEOKAS Melting point, O C . Synthetic28 From degrds
50 5-51.5 61.8-62.4 67.6-68.2
53.3 63.4
69.5
Recently Cason" undertook the synthesis of a series of methyloctadecnnoic acids. The first member of this series to be reported was the iso acid, 1 'i-niethyloctadecanoic acid. By application of the nitrile synthesis to the Cis acid, in. p. (i9.5' from degras, a C19acid was obtained which proved to be identical with Casori's 17-methyloctadecanoic acid. hkied melting puints of the acid and derivatives were not depressed. Melting poinl.
Acid Amide Tribromoanilide
I
OC.
Cason's iso-C10*7
c i 9 from degras Cia
67.3-67.8 100.2-101 3 112-112 5
66.9 101.2 112.1
1
I
25 5(J 75 100 Per cent. isopalmitic acid. Fig. il.--Solidification point ctirve; 14-methylpentadecanoic (isopalmitic) acid-hexadecanoic (palmitic) acid.
0
The homologous relationship of adjacent mem- which the carbon chain is represented as a cobers was established by obtaining isostearic acid planar zigzag.aoJ1 The next higher normal acid from the Cl6 member by twice applying the will not fit into the available space. This is nitrile synthesis. The intermediate 15-methyl- illustrated by the binary solidification point hexadecanoic acid melts a t 60.2' ; the corre- curves (Fig. 3). The lower pair involve isosponding amide melts a t 99.3'. stearic acid which is known to be branched a t the An easier clue to homology, and incidentally to 16th carbon atom. The systems with heptastructure, was found in the behavior of binary decanoic acid and hexadecanoic (palmitic) acid i mixtures of the is0 acids with normal acids. The well-known fact that solidification point curves of binary mixtures of adjacent even-numbered normal fatty acids exhibit two transitions has been explainedz8on the basis of intermolecular compound formation. The solidification pointz9curve 70 for mixtures of palmitic acid and isopalmitic acid exhibits only one transition (Fig. 2). The nonoccurrence of compound formation in this case must be attributed to interference from the ci 65 methyl side chain of isopalmitic acid. However, d such interference does not occur if the chain 5 Y length of the normal acid does not exceed the b length of the unbranched portion of the is0 acid. e 8 60 This can be illustrated by a simple diagram in ci
55
(27) Cason, THIS JOURNAL, 64, 1106 (1942). (28) Francis, Collins and Piper, Proc. Roy. SOC.(London), 8158, 710 (1937). (29) B y using a thermometer with a short bulb and a 60-ml. beaker with a valley pressed in the side-wall, solidification points reproducible to 0.1' can he determined with as little as 0.1 g. of fatty acid. The rate of cooling is controlled by proximity to a low-heat hot-plate. The specimen is stirred by rotating the thermometer. For a series of determinations 0.1 to 0.2 g. of an acid is weighed into the modified beaker and incremental additions of the other acid are made. Thorough mixing is assured by adding and carefully evaporating a few drops of acetone after each addition. A n y acid adhering to the thermometer is rinsed into the heaker with acetone. T h e volatility of acids below CIC may introduce appreciable mor.
25 50 75 100 Weight per cent. is0 acid. Fig. 3.--Solidification point curves: A-A, 18-methylnonadecarioic (isoarachidic) acid-nonadecanoic acid; 0-0, 18-methylnonadecanoic acid-octadecanoic (stearic) acid ; 0-0, 16-methylheptadecanoic (isostearic) acidheptadecanoic (margaric) acid; V-V, 16-methylheptadecanoic acid-hexadecanoic (palmitic) acid.
0
(30) Piper, Malkin and Austin, J . Chcm. Sac., 2310 (1926). (31) Mtiller and Shearer,ibid., 148, 3159 (1923).
exhibit, respectively, one and two transitions. The upper pair of curves involve the C Zbranched ~ acid. Its systems with nonadecanoic acid and octadecanoic (stearic) acid exhibit, respectively, one and two transitions. Hence, the CZOacid is branched a t the lSth carbon atom and must be 18-methylnonadecanoic (isoarachidic) acid. Dextrorotatory Anteiso Series.-The unique feature of this series is that the members contain odd numbers (C9-C31) of carbon atoms. The c~lzteisoseries differs from the is0 series in that the end group is s-butyl instead of isopropyl.
1
I
I
by determination of the optical rotations32tabulated below. Acid 12-methyltetradecanoic 14-methylhexadecanoic 16-methyloctadecanoic
Concn.,g./lOO ml. 8 8 . 2 (pure subs.) 20.04 (inucetone)
2 0 . 4 0 (in acetone)
Obs. rotation 2-dm. tube
+28.9
[a]2%
* 0.15'
+4.V
+ 6 . 8 *0.15' + 5 . 4 0.16'
+5.0° +4.G0
i.
According to the rule of the absolute configuration of these acids must be the same as the absolute configuration of levorotatory d-2inethylbutanol-1 from fusel oil, i. e., the d-configuration. This is further substantiated by the fact that the acids obtained from levorotatory d-2-methylbutanol-1 by oxidation and by the nitrile synthesis are dextrorotatory. Molecular rotations, except for the lowest homolog in which the carboxyl group is attached directly to the asymmetric carbon atom, are strikingly uniform. The rotations of the C1, and Clo anteiso acids are not strictly comparable since these were measured in acetone solution. MolecuIar Acid
d-2-Methylbutanoic34 d-3-Methylpentanoics6 d-4-Methylhexanoica6 d-12-Methyltetradenoic
25 50 75 100 Weight per cent. anteiso acid. Fig. 4.--Solidification point curves: -0, d-18methyleicosanoic acid-nonadecanoic acid; A- A, d18-methyleicosanoic acid-octadecanoic (stearic) acid; V--V , d- 16-methyloctadecanoic acid-heptadecanoic d-16-methyloctadecanoic acid(margaric) acid; hexadecanoic (palmitic) acid. 0
c]-a,
Binary solidification point curves with normal acids (Fig. 4) show that the Cle and Czl members are branched a t the 16th and 18th carbon atoms, respectively. The possible structures for the Clo member are (I) d-, I-, and dl-16-methyloctadecanoic acid I CHI-CH-CH-(CH&-COOH
I
CHa
and (11) 16,16-dimethylheptadecanoic acid. CHa
I1
I CHrCI
(CHi)u-COOH
CHs
The optically inactive possibilities were eliminated
Specific rotation
[e]D
+17.5"
+ [aI2"D + 8.44" (a]D
S.%?O
[ a ] * 6f~ 4 . 7 "
rotation
+17.85"
+10.35" +10.98' f11.37"
The asymmetry of the natural anteiso acids is reflected in their curious crystal habit (Plate IV). These acids crystallize from solution in mineral oil in a tubular form which is generated by the counterclockwisespiral growth of a very thin and quite narrow ribbon. The diameter of the tubes is on the order of one micron. A frequent variation of the tubular form is an open helical coil appearing in some of the photomicrographs as parallel rows of alternating dashes. A rare modification appears as a ribbon twisted along its .. major axis. Comparison of dl- and d-16-Methyloctadecade Acid.-Gason and Prout'' synthesized and characterized d-16-methyloctadecanoic acid. Close similarity with d-16-methyloctadecanoic acid is suggested by the following comparison. 16-Methyloctadecanoic dl d
49.9" 46.8 Acid, m. p., "C. 48.6" 46.8 Acid, s. p., "C. 93.3 Amide, m. p., "C. 92.5-93.0" Tribromoanilide, m.p., "C. 106.2-106.9s7 108.4 1 440057 1.44M Acid, nK6D a Specimen supplied by Cawn. * Determined by Cason. (32) Optical rotations were determined by Dr. W. E. Militzer. University of Nebraska, using a Bates type saccharimeter. (33) Boys, Proc. Roy. SOC.(London), A l U , 655, 675 (1934) (34) Marckwald, Ber., 39,1093 (1899). (35) Marckwald and Nolda. ibid., 19, 1590 (1909). (36) Welt, Compt. r e d . , 119, 855 (1894). (37) -son and Prout, T m s JOURNAL, 66,49 (1944).
March, 1945
THEACIDICCONSTITUENTS OF DEGRAS
Mixed melting points were not noticeably depressed. Crystal habits, however, are distinctly different (Plate IV).
453
the first &ect of a normal acid on the dl acid is to cause dissociation of the dl compound. The resulting mixture of stereoisomers is almost indistinguishable from the dextrorotatory acid in behavior with normal acids. Amides of Fatty Acids.-In order to more completely characterize the new fatty acids reported in this paper the amides have been prepared. Melting points are listed in Table I. The melting points of the is0 amides and anteiso amides, plotted against the number of carbon atoms in the molecule, have been observed to lie on parallel curves which exhibit minima approximately a t
" 1
l l l l l l l l l i l l l l l l l l l
1
0 20 40 60 80 100 Per cent. added d-16-methyloctadecanoic acid. Pig. 5.-Solidification point curve: d-16-methyloctadecanoic acid-d2-16-methyloctadecanoicacid.
The binary solidification point curve of the dl and dextro acids (Fig. 5) shows that the dl acid exists as a dl compound. Further compound formation of the type d31 or dzl is evident in the mid-portion of the curve. From the flatness of. the curves it can be concluded that the compounds are largely dissociated.
85
! l l l i l ! l l l l l l l l ! l l
11 13 15 17 19 21 23 25 27 31 Carbon content. Fig. 7.-Melting points of amides: -0, amides of is0 acids, from degras acids except CS,Levene and Alle11,~8 amides of normal acidsag; A-A, in. p. 114'; 0-0, amides of dextrorotatory anteiso acids.
9
each fifth carbon atom (Fig. 7 ) . associates periodic minima in the homologous series with a spiral the carbon atoms in the chain.
0 20 40 BO 80 100 Weight per cent. IS-methyloctadecanoic acid. Fig. G.--Solidification point curves: 0-0,dl-16iiicthyloctadecanoic acid-heptadecanoic (margaric) acid; -0, dl-16-inethyloctadecanoic acid-hexadecaiioic (palmitic) acid; 0 --0, d-16-methyloctadecmloir acid-heptdclecmoic acid: i> -0, d-16-methyltxtadecaiioic acitl-herd tlecauoic acid
Binary solidification point curves of the dl acid with normal acids (Fig. 6) offer a further test and verification of the validity of the new method of locating a side chain. Quantitative interpretation of the curves is limited by the non-ideal 1i:iturr of fatty acid mixtures. It appe:m that
Tirnmermans4" properties of an arrangement of The occurrence
--
I 10 I) 25 5ll I *I Weigh t per ceiit . 16-nirtIiyloc taciecauoamidr Pig. 8.-Solidificatiori point curves: -0,d-16-methyloctadecanoamide-heptadecaiioamide; A- A, d-16-methyloctadecaiioaniide-. hexadecarioamide. - -~ (38) I.evene and Allen. J. Hid. C/re?n.,97, -1.13 (1016). (39) Robertson. J. C h r m . . S ~ K . .116, 1210 (1919). ( I n ) 7'irnrnrrrnxns. / O i l 1 w r r h i m
H I / P , S6, 282, I 121; [ 1!12Ii)
4-54
D ERR ELL L. HILL,GERALDE. IS.BRANCH A X D MORRISPATAPOFF
oi periodic repetition of melting point minima is ~nprecedented,~~ It is of interest that the amides associate in the same manner as the fatty acids and may be used in place of the fatty acids for the determination of structures. Solidification point curves are shown in Fig. 8 for the amides of the fatty acids whose solidification point curves appear as t.he lower pair in Fig. 4. Acknowledgment.-The writer is indebted t o 1.h. James Cason, Vanderbilt University, for generously supplying samples of dl-16- and 17methyloctadecarioic acids and derivatives, and t o Ilr. W.E. Militzer, University of Nebraska, for determining optical rot at ions. ‘ ( 4 I ) Giiman, “Or&anie Chemistry ,” 211 ed., John \\‘ilcy X: Sons.. Itic.. h’ew York. \T Y..l94:3. \ ‘ t i l . 11, 13 1730.
Vol. 67
Summary Thirty-two of the acidic constituents of degras have been isolated and identified. These include: (1) nine normal fatty acids, (210 to c26; (2) two optically active 2-hydroxy acids, CM and Cl6; (3) ten is0 acids, C ~ to O (228; (4) eleven dextrorotatory anteiso acids, Cs to C2, and (231. Dark field photomicrographs of representative nienibers of each of the four series have been prepared. X new method of structure elucidation applicable to acids or amides with simple branched chains is based on the number of transitions appearing in the solidification point curves of binary mixtures of the branched acid or amide with normal fatty acids or amides. WHITIXG, INDIANA
RECEIVED OCTOBER19. 1944
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[ C O V T R I D U T I O K FROM THE CHEMICAL
LABORATORY O F TIIE
UNIVERSITY O F C A L I F O R N I A ]
A Spectrophotometric Study of the Anhydro Base of Viridine Green BY TERRELL 1,. HILL,’C:ER.\I,DE. K. BRANCH AND MORRISPATAPOFF Since we had a method of analyzing the red solid for anhydro baFe the colorless pseudo bases present were not objectionable. The anhydro base polymerizes or resinifies slowly when dissolved in a solvent with which it I (Ce,HsNHCsHa) ( C ~ H O C=Cs&=N&HCsH, ) cannot combine to form an ether. It is much I1 (C~H~NHC~,HHI)(C~HJ)C=C~H,=NCBHS more stable as the red solid, though even in this I11 (CgHsN+H&H,) (CgH5NHCsHd(CgH5)COCHz form i t gradually deteriorates. IV (CeHsNHCeHd2(CsHs)COCH3 The anhydro base was first prepared by Baeyer I1 is the conjugate base of 1. I t is called the and Villiger2 by evaporating a brown ethereal Honiolka base, or better the anhydro base, since solution obtained by shaking a salt of the dye it is the anhydride of the color base. IV is the with a mixture of aqueous sodiuin hydroxide and pseudo base of I in the methanol system, just ether. Prepared in this way it is coiitaininatrd as the carbinol is the pseudo base in the water sys- with colored polymcrs or resins. These iinpuritem. It is a methyl ether. I11 is the conjugate ties are to a great extent avoided when the anhydro base is formed in a methanol solution of thc acid of 11’. Equilibria between I and 11, and between I11 dye, transferred by extraction methods to an inert and IV are very rapid, since the reactions are solvent from which it can be precipitated without simple neutralizations. But the reversible reac- concentrating the solution. Such methods allow tions of I or 11 to 111 or IV are slower. I is stable the formation of pseudo bases much more than with respect to 111, and IV is stable with respect the method of Baeyer and Villiger does. to 11. Hence I1 and I11 are metastable comPreparation and Analysis pounds, and they can exist in appreciable concenThe chloride of thc dye was prepared in a way that trations only because they are formed by reac- essentially that first used by Meldola.8 Diphenylamine and aluminum chloride in the ratio d tions that are faster than those by which equilib17 to 13 by weight were mixed in a large container. Ai, ria are achieved. of benzotrichloride equal t o half of the diphenylI is green, I1 is red, and I11 and 1V are color- amount amine in moles was added. When this mixture w a s less. Helice many of the reactions between thew warmed the reaction started and proceeded to completion with some violence. T h e reaction product was washed compounds can be studied colorimetrically. I n our work we started with a solid prepdra- with warm dilute aqueous hydrochloric acid, and then dried hot toluene. The residue was dissolved in methyl tion of the bases. This solid contained a much with alcohol, and aqueous sodium hydroxide, carbon tetralarger proportion of the anhydro base than chloride and water were added in the order given. The red corresponds to equilibrium. This material we carbon tetrachloride layer was repeatedly washed with shall call the red solid in the rest of this article. water and dried with sodium sulfate. From this solution
Introduction In a solution of N,N’-diphenyl-p,p’-diaminotriphenylmethyl chloride in methyl alcohol the following triphenylmethane derivatives can exist
IC
the chloride was precipitated with a little leas hydrochloric
(1) This paper h a s been constructed from portions of li Thesis presented by T. L. Hill, in partial fulfillment of l h r rcqiiircinrnts lor t h e Ph.D. degree a t t h e I.niver.;ity o f ( T r t l i f n m i n
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( 2 ) Baeyer and Villiger, /;e,., 37, 2XtiG (lOU4). ( 3 ) \ r r i 8 i o i n . .r r h r , n xt,r . 41, i w i i ~ w
