T H E NATURE OF SECONDARY VALENCE. PART IV BY HOMER W. SMITH
Partition Coefficients in the System Glycerine : Acetone i 1. Introduction
In the experimental work thus far presented, water has always been used as one of the solvents. Since water is unique in its physical properties, it seemed possible that the results obtained in these systems might be modified to a great extent in systems composed of non-aqueous liquids. For this reason, a large amount of work has been done in the system glycerine : acetone. Glycerine takes the part of water and acetone the part of the organic solvent. In preliminary experiments, a commercial grade of glycerine was heated in a distilling flask a t 140" C for two hours. This sample on trial gavk the same results as did the original material and consequently the original was used with out preliminary heating.l It furthermore checked in a satisfactory manner other lots from the same and other sources so that it is improbable that any systematic error entered from this direction. The acetone was carefully redistilled from a mixture of equal parts of calcium oxide and calcium chloride. Since the acidlacetone was repeatedly recovered in this manner, it is certain that the product was anhydrous and free from serious contaminations. The acid phthalate salts were made by mixing standardized solutions of phthalic acid on the one hand, and the , desired amine on the other, in the proportions of two to one. It was assumed that the remaining titratable hydrogen of the phthalic acid represented one molecule of the amine acid-salt. It was necessary to design a special container for this study, since the glycerine cannot be measured from one Eastman Research Lab. Practical.
Homer W . Smith
722
flask to another with any accuracy. A number of glass, pistol-shaped flasks were devised. Each consisted of a bulb of definite volume (corresponding to the pistol grip) opening a t an angle of 75" into a tube of larger volume (corresponding to the pistol barrel). The neck between the bulb and cylinder was made small, and so graduated that each bulb held exactly the same volume of liquid ( 3 3 . 2 cc * .05 cc). The glycerine was run directly from a gravity bottle into the bulb by means of a suitable delivery tube, thus facilitating the accurate delivery of a given volume of glycerine. An equal volume of +e acetone solution of known titer was then added, the cylinder mouth stoppered and shaken for a few moments to secure an initial mixing. The mixture was then brought to the desired temperature and shaken for two or three minutes. (It is
1
I
II
II
I
I I
I
I
I
I
I
I
I
1
I I
L I
I
, 1
I
Fig. 1 The Partition Coefficients (CZ=1 m / L ) in the System Acetone: Glycerine
T h e N a t u r e of Secondary Valence
723
probable that a half-minute’s shaking brings the mixture to equilibrium.) After shaking, the acetone, being the liquid of lesser density, can be drawn directly into a pipette inserted through the cylinder mouth. All solutions were made in acetone and titrated with standard aqueous acid or alkali. The concentration in the glycerine was determined by difference. §
2. General Considerations
The general picture is the same as i t was in the previous systems. It is therefore not necessary to describe it in detail. This system puts the method of correction to a much more severe test, however, because after shaking equal volumes of acetone and glycerine together, the acetone layer loses about 17% in volume, the glycerine increasing 15%, and the total volume decreasing 2%. Thus we are not determining the partition coefficient of the solute between pure acetone and pure glycerine, but between two mixtures of acetone and glycerine. Since the concentration in the glycerine is determined by difference, and on a volume basis, i t might be expected that the change in volume which occurs when the two liquids are mixed would introduce a serious complication. The decrease in volume of the acetone layer would necessitate an increase in concentration of the solute, were the solute unable to pass into the glycerine layer. We will see that this actually does take place in some instances. But, where partition does take place, if we deal with concentrations per unit volume of solvent, the facts show that the relative results are not modified. It is probable, however, that the absolute value of the series constants are modified, but this point will not be treated in detail until we consider the relations between the series constants in various systems. One of the most important points brought out by the data in Table I is the fact that the absolute values of the series constants for the amines and the acids are identical in the system glycerine ; acetone. Consequently the amine and the acids have been considered together in the following tables.
Homer W . Smith
724
TABLE I Partition Coefficients of the Amines and Acids in the System Glycerine : Acetone
l a
Series number
Benzilic acid Benzoic acid a -p-Dinitropropionic acid 2.4-Dinitrobenzoic acid Salicylic acid 2.4.6-Trinitrobenzoic acid n-Valeric acid 1.414 1.45154 Formic acid a-Bromopropionic acid iso-Valeric acid 1.o -I-1.30103 Chloroacetic acid %-Butyric acid .8 1.20412 Acetic acid Thiacetic acid Propionic acid Dichloroacetic acid Sec-Butyric acid .7 -I-1.14613 Propionic acid .6 1.07918 Bromoacetic acid .5 1.00000 Ethyl amine a-Bromopropionic acid .4 + O s 90309 Thiacetic acid .3 + O . 77815 Ethyl amine Dimethyl amine Dichloroacetic acid .2 + O . 60206 Dimethyl amine .1414 +O .45154 Trichloroacetic acid .1 +O .30103 Trichloroacetic acid .os +O .20412
+
+
+ +
These compounds pass completely into the acetone layer.
41.5 1 1.36 05.8 10 6 . 2 29.5 1 0 . 0
1.39 6.4 0.7
78.0 07.8
3.99 2.52
1 3.90 1 2.70
64.0 1 73.6 10 85.3 1 97.2 10 07.3 1
1.85 2.65 4.20 7.0 9.68
1.86 2.69 4.22 6.67 9.83
85.3 10
3.55
3.69
1 3.13
3.58
64.6 10 1.20 05.8 1 5.80
1.20 5.80
1.45
1.35
84.5
73.6
1
64.6 1 0.71 0.716 66.3 10 0.671 0.764 97.2 1 2.50 2.50 66.3
1 0.50
0.502
19.5 10
2.65
2.77
1
1.95
1.96
19.5
The Nature of Secondary Valence
l a
Series number
Anthraailic acid .07
3 obs
-
2.92
725 E calc. 2.84
4-0.14613 Fumaric acid Triethyl amine
.06
12.6 10 52.6 10
1.02 g.9
1.05 4.89
.09.3 10 -12.6 1 3 1 . 5 10
3.81 3.89 3.75
0.795 0.888 4.02
97.8 1 3.44 L35.0 1 1.80
0.427 1.78
0.42 0.45 0.60 0.99 1.26 2.05
0.398 0.452 0.600 1.02 1.38 2.06
$0.07918 Diethyl amine Fumaric acid Dipropyl amine
-05
1 cz .35.0 10 v m
-
0.00000
j=
Malonic acid Anthranilic acid
.04 .03
4.09691 -0.22185 Diethyl amine Maleic acid Succinic acid n-Methylpiperidine Bromosuccinic acid Mandelic acid
-0.39794 Piperidine Dipropyl amine Triethyl amine .01414 -0.54846 o-Phthalic acid .Ol -0.69897 Malic acid Gallic acid .008 4.79588 .007 -0.85387 .006 -0.92082 Hippuric acid .005 -1.00000 .004 -1.09691 Tartaric acid .0001414 -2,54846 Dimethyl amine-acid-phthalate .00007 -3.85387 Trimethyl amine-acid-phthalate .00003 -3.22186 Piperidine-acid-phthalate Diethyl amine-acid-phthalate .00001414 -3.54846 n-Methylpiperidine-acid-phthalate Dipropyl amine-acid-phthalate .00001 -3.69897
109.3 1 112.6 1 120.0 1 133.8 10 140.5 1 152.2 1
.02
108.8 151.5 152.6
1 0.27 1 1.20 1 1.40
2.60 1.34 1.40
155.6
1
1.09
1.11
118.8 1 0.19 135.0 1 0.35
0.191 0.356
178.7
1 1.16
1.14
123.6
1 0.09
I . 0918
220.1
1 0.12
0.132
243.6
1 0.15
0.161
264.4 264.9
1 0.15 1 0.1:
0.153 0.156
289.4 305.5
1 0.18 1 0.3:
0.188 0.349
. Homer W . Smith
726
TABLEI (Continued)
B calc. Trimethyl amine-acid-phthalate *
308.2
1 0.270
0.274
Benzylethyl amine-acid-phthalate 328.6 Di-isobutyl amine-acid-phthalate 346.7
1 0,313 1 0.60
0.299 0.600
378.1
1 1.18
1.21
388.1
1 0.816
0.831
000005
-4.00000
,000003
-4.22185
.000001414
-4.54846
Tripropyl amine-acid-phthalate
Di-isoamyl amine-acid-phthalate
p Chloroacetic acid Piperidine n-Methylpiperidine Glutaric acid o-Phthalic acid Gallic acid
142.2 135.0
obs.
4.45 0.45 0.57 0.88 1.28 0.352
+1.34836 -0.16012 -0.47413 -0.42750 -0.48612 -0.74757
1.115 .03458 .01678 .01877 .01633 .008942
5 3. The Series Behavior It was shown in the previous communication that a series must be recognized between Series 1 and Series 2 ; a value of 1.414 was arbitrarily assigned to this series, and it has been included in the above table. Compounds not falling in the recognized series are given at the end of the table. Note that n-methylpiperidine, glutaric acid and phthalic acid give an average value of .01729 which approximates a series corresponding to the 43, or 1.732. Reference to the following experimental section will show that in many cases the ratio C,/Cc is constant. For the rest, this ratio increases in about as many cases as it decreases. It is not known whether association in one solvent or dissociation in the other is the predominant factor; but whatever the cause of the inconstant ratio, the interpolation method of obtaining the partition coefficient yields results which are in excellent agreement with those compounds which show a constant distribution ratio, so far as the series behavior is concerned.
T h e N a t u r e of Secondary Valence
727
The number of compounds occurring in the various series is as follows: Series
1.414, .1414, etc. 1.0 .1 etc. .8 .08 etc. .7 .07 etc. .06 etc. .6 -05 etc. .5 .4 .04 etc. .3 .03 etc. .2 .02 etc.
Ca=l m / L
6 6 3 1 3 6 2 10 4
CZ= 10 m / L 2
0 3 2 2 1 0 2 0
Another important point is that some compounds pass completely into the acetone layer. On the supposition that the fundamental forces involved in this behavior are discontinuous in nature, both as regards the solute and the solvents, it is not surprising that limiting conditions could exist whereby a solute would pass completely in just this way, into one or the other solvent. That is, in a mechanism working by abrupt changes, there must both be a maximum and a minimum activity, and in any system in which one of these limits was reached, the all (unit) or none principal would necessitate complete concentration of the solute in one solvent or the other. Evidence in this direction was seen in the system water: xylene, where it was found that xylene did not extract perceptible amounts of the dibasic acids and other compounds It was thought at that time that this was largely a matter of experimental error, for the predicted partition coefficients were so low that they were difficultly determined. But when the reverse situation is found in this system, i. e., when the solute passes entirely into the organic solvent, it seemed probable that this failure to get a perceptible distribution is a real and not an apparent failure of the distribution law. In general we know that with increasing length in the carbon chain, there comes a time when the solubility in water falls off abruptly; this fact is rendered more intelligible by the recognition of the existence of abrupt, linzitiwg coflditions in intermolecular relations.
Homer W . Smith
728
As an example consider the simple aliphatic acids; acetic, propionic, and sec-butyric occurring in Series 8, n-butyric in Series 1.0 and iso-valeric in Series 1.414. One is led to look for n-valeric in Series 2, where it would have a partition coefficient of about 59.0, a determinable value. Contrarily, in this and other similar instances the concentration of the solute in the acetone layer is increased (per unit volume) by the diminution in volume of this layer. This increased Concentration makes the failure of the distribution law even more apparent.
I4. The Acid-Phthalate Salts The original intention in including some salts of this nature in this study was to determine whether the series .constants for the salts would be in agreement with the acids or the amines, or different from both of these. It has been found, however, that the acids and the amines have identical series constants so that this question remains unsettled. It cannot be satisfactorily settled by studying any of the systems previously used containing water, because the partition coefficients in these systems are too small to be determinable with any accuracy. Though little significance can be attached to the fact that the salts do have the same series constants as the amines and acids, it is a very satisfactory way to have the thing work out.
Summary 1. The partition coefficients of fifty acids, amines, and acid-phthalate salts have been determined in the system glycerine : acetone. The results yielded by these data are in excellent agreement with the results obtained in the systems previously studied. 2. A fact not brought out by previous studies is that under certain conditions concerning the nature of the solvents and solute, a solute is not distributed, but is concentrated entirely in one or the other of the solvents. 1
Jour. Phys. Chem., 25, 160, 204, 605 (1921).
The Nature of Secondary Valence
729
3. It is a noteworthy point that the series constants for the acids and the amines (and the amine salts of phthalic acid) have the same absolute value in this system, as contrasted with the different values found in systems containing water as one solvent.
Experimental. Section IV The Partition Coefficients of the Amines, Acids and AcidPhthalate Salts between Glycerine and Acetone, 25
The following compounds pass completely into the acetone layer : Benzilic acid Benzoic acid a-p-Dibromopropionicacid 2.4-Dinitrobenzoic acid Di-isobutyl amine Salicylic acid 2.4.6-Trinitrobenzoic acid n-Valeric acid CG
Acetic acid
17.30 10.00 4.85 4.60 3.875 2.775 2.77 1.6 1.oo
Anthranilic acid
Benzylethyl amine-acidphthalate
0.9425 4.60 3.20 1.55 1.05 10.35 7.80 5.45
CA
CAKG
29.30 17.60 8.60 8.20 7.00 4.775 4.70 3.025 1.825 1.725 14.70 8.95 3 .SO 2.20 3.65 2.55 1.80
1.69 1.76 1.77 1.78 1.81 1.72 1.70 1.80 1.82 1.83 3.20 2.80 2.45 2.09 0.302 0.327 0.330
Q
I
1.85 IO
2.92 I
1.80
730
Homer W . Smith TABLE(Continued) CG
Bromoacetic acid
a-Bromopropionic acid
Bromosuccinic acid
n-Butyric acid
sec-Butyric acid
Chloroacetic acid
Dichloroacetic acid
Diethyl amine
3.975 2.525 4.35 2.25 1.60 0.645 0.90 0.70 0.4875 0.40 0.30 0.21 7.675 3.925 I.775 1.28125 2.10 1.15 0.50 0.275 2.20 1.30 0.65 0.625 0.375 0.350 6.15 3.125 2.00 0.975 0.325 2.40 1.90 1.375 0.925 0.61 0.43 18.10 6.55 6.775 3.375 1.75
9
CA
1.30 0.70 14.20 7.25 4.70 2.00 20.65 11.20 6.7625 4.50 2.62 1.42 11.575 5.575 2.375 1.625 26.65 14.60 6.4375 3.45 20.20 11.85 6.80 6.825 3.375 3.40 29.25 15.925 8.60 3.90 1.30 37.9 17.8 9.725 4.625 2.20 0.83 15.80 4.50 4.70 1.75 0.625
0.327 0.277 3.26 3.22 2.94 3.10 23.0 16.0 13.9 11.2 8.73 6.75 1.51 1.42 1.34 1.27 12.7 12.7 12.8 12.5 9.2 9.14 10.45 9.90 9.00 9.72 4.76 4.60 4.30 4.00 4.00 15.8 19.38 7.07 5.02 3.61 1.93 0.873 0.687 0.693 0.518 0.357
Mean 0.313 Mean 3.13 IO
16.2 I
5.80 I
1.25 Mean 12.7
Mean 9.68 IO
4.45 I
3.90 IO
7.0 I
2.5 IO
0.81 I
0.42
The N a t u r e of Secondary Valence
731
CG
Diethyl amine-acidphthalate
Di-iso-amyl amine-acidphthalate
Di-iso-butyl amineacid-phthalate
Dimethyl amine (anhydrous)
Dimethyl amine-acidphthalate
Dipropyl amine
Dipropyl amine-acidphthalate
Ethyl amine
12.80 '9.975 6.65 4.15 2.0375 7.85 6.30 4.875 3.075 1.9375 9.65 7.60 5.85 3.95 1.90 27.8 15.8 7.525 4.325 2.25 14.75 10.875 7.80 5.4875 3.725 2.75 2.275 2.025 1.60 1.50 1.325 0.925 10.90 7.625 4.525 2.50 1.45 8.20 4.72 4.55 2.70 1.76 1.625 1.20
1.65 _.1:325
1.05 0.775 0.450 6.15 4.80 3.625 2.725 1.750 4.45 3.80 3.10 2.10 1.10 20.1 10.6 4.775 2.425 1.125 1.70 1.30 1.00 0.8125 0.6250 10.1 8.775 5.425 3.85 2.90 1.925 1.30 2.45 1.825 1.35 0.8875 0.600 9.76 4.76 4.65 2.25 1.26 1.25 0.67
0.129 0.133. 0.158 0.187 0.221 0.783 0.762 0.744 0.886 0.905 0.462 0.500 0.530 0.530 0.580 0.723 0.672 0.635 0.561 0.510 0.115 0.119 0.128 0.148 0.168 3.67 3.64 2.69 2.40 1.93 1.45 1.40 0.224 0.239 0.298 0.335 0.413 1.19 1.01 1.02 0.835 0.715 0.77 0 . 558
1
0.158
Mean 0.816
1
0.60, IO
0.67 1
0.50,
1
0.128 IO
3.75
1
1.2
1
0.335 IO
1.20
I
*
0.71
732
Homer W . Smith TABLE(Contiwed)
Formic acid
Fumaric acid
Galic acid
Glutaric acid
Hippuric acid
Maleic acid
Malic acid
Malonic acid
Mandelic acid
n-Methylpiperidine
CG
CA
16.0 5.65 3.70 2.0625 1.525 5.275 2.225 1.3375 0.730 29.85 12.85 6.625 2.45 9.65 3.025 2.950 1.55 0.875 19.85 8.20 4.10 12.40 3.05 7.40 32.85 1.50 1.925 11.0625 5.50 3.75 2.60 14.0 6.05 3 * 775 2.4875 1.20 11.6 8.25 4.25 2.075 20.8 11.05
20.8 7.8 5.65 2.8875 2.075 5.175 2.125 1.1875 0.6350 9.55 4.45 2.325 0.8625 8.15 2.60 2.575 1.350 0.775 22.80 9.70 4.80 2.75 6.85 3.50 1.75 0.95 0.4375 2.2875 1.10 0.675 0.475 6.05 2.80 1.8875 1.05 0.475 23.0 16.45 8.65 4.225 22.2 11.15
CAI’CG
1.30 1.38 1.39 1.40 1.36 0.981 0.954 0.888 0.870 0.320 0.346 0.351 0.352 0.845 0.860 0.874 0.870 0.885 1.15 1.18 1.17 1.15 0.525 0.473 0.454 0.380 0.454 0.207 0.200 0.180 0.182 0.433 0.462 0.500 0.423 0.396 1.98 1.99 2.04 2.04 1.068 1.010
$9
Mean 1.36 IO
1.02 1
0.89 IO
0.318 1
0.352
1
0.880
Mean 1.16
Mean 0.457 1
0.192
Mean 0.443 1
2.05 IO
0.99
733,
T h e N a t u r e of Secondary Valence CG
n-hlethylpiperidineacid-phthalate o-Phthalic acid
6.40 3.50 2.68 2.00 1.73 1.30 1.03 12.75 4,55 2.460 1.280 6.375 3.200 1.5875 0 8750 33.3 23.4 17.35 12 00 gb95 6.775 5.45 3.25 2.85 1.3125 10.31 3.86 1.85 0.79 0.356 9.60 5.80 3'. 50 2.15 1.48 0.78 0.43 5.70 4.725 2.675 1.9625 1.35 16.25 16.25 I
Piperidine
L
Piperidine-acid-phthalate
Propionic acid
Succinic acid
Tartaric acid
v
CA
6.10 3.10 2.06 1.375 0.95 0.65 0.29 1.76 0.90 0.680 0.480 8.025 3.800 1.775 0.9375 16.0 10.6 7.8 4.925 4.0 2.375 1.875 0.85 0.725 0.225 1.475 0.700 0.482 0.369 0.250 31 .OO 19.40 10.85 7.45 5.76 3.06 1.74 3.275 2.925 1.550 1.325 0.7625 1.30 1.25
0.954 0.886 0.767 0.687 0.550 0.500 0.282 0.138 0.198 0.276 0.375 1.26 1.19 1.12 1.07 0.48 , 0.453 0.45 0.41 0.402 0.350 0.344 0.262 0.254 0.144 0.143 0.181 0.261 0.467 0.702 3.23 3.34 3.10 3.46 3.89 3.93 4.05 0.575 0.619 0.580 0.675 0.565 0.080 0.077
1
0.57
'
1
0.180 IO
1.28 1
1.09 IO
0.45
1
0.275
1
0.155 IO
3.55
1
4.20
Mean 0.603?
Hcmer W . Smith
734
TABLE (Continued)CG
Thiacetic acid
Trichloroacetic acid
Triethyl amine
Triethyl amine-acidphthalate
Trimethyl amine-acidphthalate Tripropyl amine-acidphthalate iso-Valeric acid
6.00 5.77 3.075 2.75 9.40 4.60 3.60 2.36 1.56 1.70 1.25 1.075 0.7625 0.600 3.20 2.25 1.65 1.175 0.865 12.775 9.35 5.60 4.075 2.35 13.55 10.35 5.65 4.20 6.80 4.45 2.55 1.375 0.500 0.300 0.1375 0.1125
School of Hygiene and Public Health Defit. of Physiology, Baltimore, Md.
CA
0.60 0.625 0.425 0.4125 30.10 14.30 9.40 5.36 3.04 20.90 7.70 5 -40 2.8375 1.50 25.80 13.20 6.35 2.875 1.470 2.70 2.00 1.45 1* 10 0.70 1.95 1.50 0.90 0.70 4.25 3.125 2.125 1.400 23.00 10.30 5.15 4.75
0 * 100 0.105 0.136 0.150 3.20 3.10 2.62 2.27 1.95 12.30 6.17 5.02 3.72 2.50 8.06 5.87 3.85 2.44 1.70 0.2115 0.214 0.259 0.270 0.398 0.144 0.145 0.159 0.167 0.625 0.702 0.843 1.020 46.0 34.4 37.4 42.3
1
0.090 IO
2.65 1
1.45 IO
7.55 1
1.96 IO
4.9 1
1.40 1
0,270
r 0.157 1
1.18
Mean 40.0
