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LABORATORY O F ARMOURAND
COMPANY]
SOLUBILITIES OF HIGH MOLECULAR WEIGHT NORMAL ALIPHATIC PRIMARY ALCOHOLS C. W. HOERR, H . J. HARWOOD,
AND
A. W. RALSTON
Received February 28, 19/14
The aliphatic alcohols appear to be molecularly associated, as shown by investigations using several independent methods (1-8). The fact that the alcoliols, like the fatty acids, crystallize in double molecules with their polar groups adjacent (9) is indicative of a tendency toward association in the liquid state and in solution. The relatively high dipole moment of the alcohols (10) also suggests the probability of some form of dipole-dipole coupling. Determination of the molecular weight of hexadecyl alcohol in menthol has shown (2) that in solutions as dilute as 0.001 molal the apparent molecular weight is 17.4% higher than that calculated from the empirical formula. Several investigators (6-8) have suggested that association of the alcohols occurs by hydrogen bonding a t the polar groups, and that some type of interaction occurs between the solvent molecules and the alcohol (7). All of these previous investigators are generally agreed that association increases as the concentration increases, and decreases with increased temperature and increased molecular weight. Several reports have attributed the characteristic solubility curves of longchain compounds to molecular association (11, 12). A typical solubility curve of an aliphatic compound in an organic solvent consists of a steep initial slope, an abrupt change of slope a t moderate dilution, and a relatively flat slope a t higher concentrations. This type of curve is exhibited by the fatty acids (12,13), aliphatic ketones (14), amides, anilides, and T\T ,?j-diphenylamides (15), nitriles (16), primary amines (17), secondary amines (18), tertiary amines (19), and amine salts (20). In order to study the behavior of the alcohols, the solubilities of 1-decanol, 1-dodecanol, 1-tetradecanol, 1-hexadecanol, and 1-octadecanol have been determined in fifteen organic solvents. EXPERIMEKTAL
1-Decanol, 1-tetradecanol, and 1-octadecanol were prepared by catalytic hydrogenation of ethyl caprate, methyl myristate, and ethyl stearate, respectively, which had, in turn, been prepared from highly purified f a t t y acids (13). The freezing points of the a modifications and melting points of the ,8 forms of these esters are listed in Table I. The alcohols obtained from these esters were purified by vacuum distillation. 1-Dodecm o l and 1-hexadecanol were obtained from commercial products. The former was purified by vacuum distillation in a Stedman packed column and the latter was recrystallized from acetone until a constant freezing point was obtained. The freezing points of the alcohols used in this investigation are listed in Table 11. The solubility measurements were made with the equipment and in the manner previously described (16, 20). 267
268
HOERR, HARWOOD, AND RALSTON
TABLE I
FREEZING AND F.P.,
"c.
MELTING POINTS OF PURIFIED M.P.,
"C.
ESTERS
LITERATURE REF.
ESTER
Ethyl caprate
a form
9 , form
-19.50
-18.0
Methyl myristate
18.39
19.0
Ethyl stearate
31.05
33.8
F.P.,
"c.
Y.P.,
-
(P) -19.9 -20.5 -19.96 18.35 18.37 (a) 30.4 (a) 30.56 (01) 31.05
-20.3
-
18.8 (p) 32.9 -
:; :;::)
j;:;
(a)
31.05 30.5 -
"c.
-
(a) 34.0
(cy)
31.7 33.7-34.1
TABLE I1
FREEZING POINTS OF PURIFIED ALCOHOLS ALCOHOL
1-Decanol 1-Dodecanol
NO. OF
c ATOXS
j
F.P.,
"c.
6.88 23.95
1-Tetradecanol
14
38.26
1-Hexadecanol
16
49.62
1-Octadecanol
1
57.98 l8
P.P.,
OC.
(LIT.)
6.4 (1); 5.99 (23). 23.8 (1); 23.87 (23); m.p. 24 (32, 33); m.p. 21-22 (34); 23.6, m.p. 23.8 (35); m.p. 26 (36). 37.62 (23); 37.7 (24, 35); m.p. 37.5-38 (32); m.p. 38 (33); m.p. 39-39.5 (37). 49.27 (23, 28); 49.1 (27); 47.8 (30); m.p. 4949.5 (33,38);49.25 (35);m.p.48.5-49.5 (37); m.p. 49.5 (39); m.p. 49.3 (40); m.p. 48 (41); m.p. 50 (42); m.p. 49.10 (43); m.p. 48-48.2 (44); m.p. 45-46 (45); m.p. 49.149.2 (46); m.p. 49 (47). 57.85 (23); 57.95 (28,35); m.p. 59 (33,48,49); m.p.58-59 (34);m.p.57.60-57.75 (46);m.p. 58 (47,50);m.p.58.5(51);m.p.57-58(52).
RESULTS AND DISCUSSION
The higher alcohols show a behavior in organic solvents similar to the other long-chain compounds investigated. Their solubility curves resemble those of the nitriles and fatty acids, whose polarity is of the same order of magnitude as that of the alcohols. Like the other aliphatic compounds, the alcohols form simple eutectics with the non-polar solvents benzene, cyclohexane, and tetrachloromethane. These systems are shown graphically in Figs. 1-3, respectively, and the compositions and freezing points of the eutectics are listed in Table 111.
WEIGHT PER CENT. ALCOHOL
FIG.1. SOLUBILITIES OF THE ALCOHOLS IN BENZENE. THENUMBERS ON THE CURVESREFER TO THE NUMBER OF CARBON ATOMS
I
l
l
l 20
l
l
l
l
l
l
l
l
l
60
40
l
l
l
l
eo
WEIGHT PER CENT. ALCOHOL.
F I G . 2. SOLUBILITIES OF THE ALCOHOLS I N CYCLOHEXANE 269
l
l 100
270
HQERR, HARWOOD, AND RALSTON
20
0
40
60
100
80
WEIGHT PER CENT. ALCOHOL
FIG.3. SOLUBILITIES OF
THE
ALCOHOLSIN TETRACHLOROMETHANE
TABLE I11 EUTECTICS FORMED BY THE ALCOHOLS NO. OF
c ATOMS
SOLVENT
I L Wt. o/c alcohol . . . . . . . . . Temp., "C.. . . . . . . . . . . .
12
14
16
18
--
35.0 -7.5
23.9 2.5
6.5 5.2
1.7 =5.5
0.5 z5.5
(Wt. % alcohol. . . . . . . . . 29.3 \Temp., "C.. . . . . . . . . . . . -10.8
15.8 -0.9
5.6 4.8
1.4 6.0
0.4 6.5
Wt. yo alcohol. . . . . . . . . 5.7 Tetrachloromethane {Temp., "C., . . . . . . . . . . . -25.2
1.1 -23.3
Benzene Cyclohexane
-23.0 OS1
I
-
-
The solubilities of the alcohols above the melting points of these solvents are listed in Tables IV-VI respectively. The alcohols are most soluble in benzene and least soluble in tetrachloromethane.
27 1
SOLUBILITIES O F ALIPHATIC PRIMART ALCOHOLS
TABLE I V SOLUBILITIES OF -4LCOHOLS I N
NO. OF
BENZENE
G. PER 100 G. BENZENE
c ATOMS
30.0"
40.00
50.00
lo
m
m
m
ca
m
12 14 16
139 14.2 2.8 1.2
1390 74 13.5 4.2
m
m
m
355 73 22.3
m
m
302 98
430
1s
m
TABLE V SOLUBILITIES OF ALCOHOLS IN CYCLOHEXANE NO. OF
G. PER 100 G. CYCLOHEXANE
c ATOMS 20.00
10.0"
10 12 14 16 18
--
1
30.0'
40.0'
50.0'
m
m
m
m
m
125 13.4 2.2 0.6
1290 72 11.0 3.2
m
m
m
350 66 18.1
m
m
285 92
400
m
TABLE V I SOLUBILITIES OF ALCOHOLS IN TETRACHLOROMETHANE NO. OF
c ATOMS
I
G . PER 100 G. TETRACHLOROKETHANE
-20.00
--
9.7 1.3 0.2
10 12 14 16 18
-
0.0'
10.0"
240 18.9 2.0 0.4
