3210
A. JOHNSTON EVELYN LAINGMCBAIN,WALTERB. DYEAND STEWART
Vol. 61
Summary The vapor-liquid equilibrium pressure and compositions of carbon tetrachloride-cyclohexane E,"I = --(\',G - daG)~v:zlz2 (22) For an equimolal mixture this yields E% = mixtures have been measured at 40 and 70" over 3.8 cal. per mole instead of the measured 20.7. the whole composition range, and a t 30, 50, and However, if we calculate -UIZ from the relation 60" for approximately equimolal mixtures. The densities have been determined at 25'. E Z = (2a12 - all - (1.22) i'O2,ZZ (23) These measurements have been expressed and the measured 20.7 for equimolal mixtures, we analytically, and corresponding equations derived obtain -as = 69.34, which is only 0.5% less than for the thermodynamic functions, including the 4 7 2 . 9 6 X 66.54 = 69.67. So, quadratic combi- energy and entropy of mixing a t constant total nation gives a very good approximation for uf2, and volume. the small error is in the direction predicted by the The dependence upon composition agrees with quantum theory. The treatment of solutions the predictions of the simple theory. The deviamakes too drastic demands for a simple theory tion from regularity is relatively large but most of in requiring a small difference between large it is explained by the volume change on mixing. numbers. On the other hand, measurements on The unexplained entropy increase on mixing solutions afford a correspondingly accurate meas- is only one-thirteenth as large as for benzeneure of one of these quantities if the others are cyclohexane mixtures. known. CAMBRIDGE, MASSACHUSETTS RECEIVED AUGUST29,1939 that the mutual energy per unit volumes, equal to -2 leads t o the result
[CONTRIBUTION FROM THE
a12,
is
DEPARTMENT O F CHEMISTRY, STANFORD UNIVERSITY]
Solutions of the Paraftin-Chain Sulfonic Acids as Colloidal Electrolytes BY EVELYN LAINGMCBAIN,WALTERB. DYEAND STEWART A. JOHNSTON Colloidal electrolytes since their first recognition by McBain in 1913 have received steadily increasing attention, because of their interesting departures from the behavior of ordinary electrolytes and because they embrace such large groups of substances. The soaps originally studied do not lend themselves to precise examination in very dilute solution on account of the prominent effects of hydrolysis. It remained therefore for Lottermoser and Piischell to show that in great dilution many non-hydrolyzable salts of alkyl sulfuric acids conform to the behavior of the Debye-Huckel theory, rather suddenly departing from it a t a very low concentration designated, by Bury and collaborators, the critical concentration for micelles. This has been confirmed by many subsequent investigators, and necessitated a modification of the original formulation to conform more dosely to later conceptions of interionic attraction. Different authors, however, differ in their sirable to have exact different properties of a non-hydrolyzable pure (1) Lottermoser and Puschel, Kolloid 2 , 68, 175 11933)
material of simple chemical composition sufficiently soluble that it may be studied over a wide range of concentrations. The present communication comprises measurements of lowering of freezing point, conductivity, viscosity and density of straight chain sulfonic acids with special emphasis upon dodecyl sulfonic acid. The results for diffusion have been published2 and a provisional discussion is being given elsewhere,aalthough it is not until our measurements of transport number are completed that a sufficient number of equations will be available for a deiinitive solution of the problem, except in its principal outlines which are already generally known, Experimental An especially pure preparation of laurylsulfonic acid was made by M. E. Synerholm by the method of Noller and Gordon4; its equivalent weight by titration was 100.05% of the theoretical, the excess probably being water. The other sulfonic (2) Evelyn Laing McBaio, Proc. Roy. SOC.(London). A178,415 (1939). (3) Van Rysselberghe, Colloid Symposium, 1939. '4) Noller and Gordon, THIY JOURNAL, 55, 1090 (1933).
PARAFFIN-CHAIN SULFONIC ACIDSAS COLLODAL ELECTROLYTES
Nov., 1939
acids from CZ to C14 were prepared by F. M. McMillan. The potassium methyl, ethyl and propyl sulfonates were purchased from Kahlbaum, their solutions being filtered before use. The acids were made up by weight on the basis of their titrated value with conductivity water, from a Barnstead still, of specific conductance 0.3 to 0.4 X 10-6mho. The conductivity measurements were made with complete Leeds and Northrup Jones-Dike equipment, with an oil thermostat a t 25'. Potassium chloride solutions were made up by the Jones and Bradshaw method. The cells were Hshaped with electrode leads from opposite ends, one5 for use with stronger solutions and 1.060 another shortened one for the most dilute solutions.
SPECIFIC
AND
TABLEI1 EQUIVALENT CONDUCTIVITY SULFONIC ACIDAT 25"
m k P 0.0007187 0.0002627 366.7 .001486 ,0005405 365.0 .001597 ,0005820 365.5 .002348 .0008533 364.7 .002515 .0009123 364.0 .003102 .0011237 363.6 ,003818 .001382 363.3 ,004059 ,0014655 362.5 .004552 .001645 362.8 .005175 .001871 363.0
3211
OF
UNDECYL
m k P 0.006113 0.002199 361.3 .006432 .002319 362.2 .006704 ,002410 361.1 .007233 ,002598 360.8 .008332 .002982 359.6 ,009027 ,003236 360.3 .009303 .003523 359.0 .009860 ,003518 358.6 .01732 .006021 350.0
publication,G except those for nonylsulfonic acid where very little material was available and where the density is so nearly that of water (dZs40.9994
1
The Conductivity Data To save space the density and conductivity results obtained by one of us (W. B. D.) for the lower members of the homologous series are given graphically in Figs. 1 and 2, which also include for comparison the "I. C. T." values for hydrochloric acid. Figure 2 also includes the data for the higher I " " ' " " ' ~ ' ' homologs and for the potassium salts. 0 0.2 0.4 0.6 0.8 1.0 1.2 It will be noted that the first clear Nw. indication of departure from the be- Fig. 1.-The density (at 25/4") of the sulfonic acids Cz to C,: of the 8 , C3H7S03K; havior of ordinary strong electrolytes potassium sulfonates C1 to Ca: (3, CH3S03K;0 , C2H6SO3K; A, C!d&S03H; occurs with Cy and that in concentra- 0 , CH$OaH; A, CsH7SOsH; 0 , CdHSOsH;e, C~HIISO~H; M, C7HisSOsH. tion above about 0.4 N . There is a slight effect in solutions of Ca approaching 1 N , for 0.098 m) that other concentrations are based and it is possible that in still greater concentra- upon a linear graph. tions the lower homologs of the free acids would TABLE 111 give similar indications. SPECIFIC AND EQUIVALENT CONDUCTIVITY OF DODECYL The conductivity data for the higher homologs SULFONIC ACIDAT 25' are given in Tables I to IV for the sulfonic acids 0I , 00002466 0.000009135 371.5 O.OO4630 0.001628 360.8 .00004183 .00001550 371.5 ,004677 .001684 361.2 C9, Cll, CU, and C14. The necessary density data ,00004816 371.2 ,005325 .001924 359.7 .0001303 by one of us (E. L. M.) were included in a previous .0001462 ,00005424 370.8 ,005546 .001987 358.6 .0001903
TABLEI .0003937 EQUIVALENT CONDUCTIVITY OF AQUEOUS SOLUTIONS OF ,0004098 N o m STJLFONICACIDAT 25O, AT VAFUOUSMOLALITIES .0004130 m . 0 .0008505
.001993 .002917 .003226 .003801 .004756 .005604
P
369.3 367.8 366.6 366.9 365.7 364.7 363.9
m
0.006366 .007159 .01270 .01984 .03032 .03610
P
m
c
362.5 365.0 359.8 354.4 347.5 342.9
0.04908 .05560 .06556 .07450 .08232 .08804
329.7 320.1 305.8 293.1 283.9 277.1
.0004183 .000547 .0006454 .0008925 .001398 .001693 .001828 .002149 .002377 ,003473 .003760
,00007060 ,0001462 .0001519 .0001532 .0001550 .0002024 ,0002395 .0003298 .0005185 .0006250 .0006842 .0007861 .0008746 .001255 .001352
372.0
371.1 371.2 371.2 371.5 371.1 371.0 370.5 370.9 369.6 369.1 367.6 367.1 362.8 362.0
.005867 ,006592 ,007037 .007920 .007941 .008067 .009581 .01077 .02059 .03018 .0510 .OS16 ,0705 ,0958
.002107 ,002347 ,002513 .002806 ,002821 ,002874 .003188 .003211 .004345 .005411 .007991 .008098 ,01054 ,01505
(5) McBain, Laing and Titley, Trans. Chcm. Soc., 116, 1279 (1919).
(6) McBain and Betz. THIS JOURNAL, 67, 1906 (1935).
359.8 356.1 358.0 355.2 356.1 356.6 333.6 299.1 211.4 180.6 159.8 156.5 146.8 147.6
VOl. 61
EVELYNLAINGMCBAIN,WALTER R. DYEAND STEWART ,4.JOHNSTON
3212 -l40
400
360
320
280
& 240
'CP CP
200
160
120
80
02 Fig. 2 -The
0.4
malar conductance at 25" nf
OR
10
08
V,Nu.. HCI, the sulfonic acids and same of their
dts,
A
b
1.2
\'allies hy
Miss Betz. TABLE I\ EQUIVALEN~ AND
limiting equivalent conductances are, for the
SPECIFIC CONDUCTIVITY OF TETRADECYL, acids, 385 for Cz, 374 for Cg, 372 for CB acd 361 SULFONIC ACIDAT 25"
m
0 0001089 0001384 0001802 0002221 0004878 0007667 0010570 001852
k 0 00003914 00004968 00006464 00008002 ,0001754 0002758 0003806 0006739
P
360 8 359 9 359.7 361 3 360 6
m
b
P
0 002556 0 0008045 315 9 ,003419 0008941 262 5 0009953 224 2 004458 001089 200 1 005459
.006265
a60.8
.007iio
361.2 359 3
,008317 010065
001163 001247 001365 001537
186 5 176 2 165.0 153 6
The most interesting portions of the data for the present purpose are those for extreme diluin Fig. 3 ;the measurements lutions of C11 and CM (by ly be d e c t e d by some systematic error. Indeed, it was found to be the case in the corresponding measurements of Cn (by W. B. D.). However, i t does not show in the measurements with CZin the same dilutions. Figure 3 also includes the straight lime representing the Onsager slope pe = 1.1,- I0.2274 p, 39 781 fi for complete dissociation. The
+
for C14;and for the potassium salts 109, leaving 35.5 for the Czanion. From this the limiting mobilities of the anions are, for Ca 35, for Cg 24, and for CI222. For sodium dodecyl sulfate, Ward7 obtained p , = 65.46 a t 20') from which we deduce for the anion 22 to 23 depending upon whether one uses the data for Na+ from "I. C. T.," Ward or MacInnes, Shedlovsky and Longsworth.8 Howell and Robinson for the same sulfate had p, = 85.1 a t 2 5 O , but with a systematic error still to be corrected, meanwhile leaving 35.1 mhos for the C s ion. Reed and Tartar had pco = 86 for the sodium dodecyl sulfonate or 36 mhos for the anion, but their more recent paperg contains eonductivities for this particular substance that differ by as mueh as 6 to 20y0from their previous paper. (7)W d ,2. C h .Soc., 522 (1939). (8) MacIooes. ShedIovskp and Longsworth, TRISJOURNAL, 54, 2762 (1932). (9) Wright, ilQ310
Abbot.
Sirvrrts
and
Tutu,
rbrd,
61,
550
Nov., 1939
3213
PARAFFIN-CHAIN SULFONIC ACIDSAS COLLOIDAL ELECTROLYTES
390
370
$350
330
310 0.02
0.04
0.06 d NW. Fig.3.
Their value for C I ~at 40’ was 2 mhos less. Lottermoser and Piischel obtained 1.1, = 75 for sodium dodecyl sulfate at 25’ (but extrapolating linearly against giving 24.5 mhos for this anion, and a value for CU 4 mhos less than CU a t 40’. We shall take our own value of 22 mhos as being the most likely for C12 anion with 35 mhos for the C2 anion, which may be compared with the “I. C. T.” value of 36.7 mhos for acetate and the MacInnes, Shedlovsky and Longsworth value of 40.87 mhos for the acetate ion. The slope of the conductivity curve a t extreme dilution in Fig. 3 is exactly the Onsager value for C2 but with the higher members the conductivity of the colloidal electrolyte in this range decreases less than expected with concentration. Tartar’s collaborators likewise noted the same effect. For example, for sodium dodecyl sulfonate at 40, 60 and 80°, they obtained slopes of 80, 109 and 140; whereas Onsager’s equation would demand 106, 115 and 203, respectively. A noticeable increase of conductivity above that derived by the Onsager equation a t infinite dilution could in these great dilutions only be accounted for on the basis of small amounts of highly conducting ionic micelle. Indeed, the fact that in dilutions such as 0.0004 N the conductivity of methylene blue is very greatly above the value for infinite dilution (of the order of 25-30% excess) was explained similarly by Noillet, Collie, Robinson and
iYr)
Hartley. They noted that even when with m-benzopurpurin the conductivity slope appeared normal, transport measurements conclusively proved the presence of micelles conducting better than the ions from which they were formed. The mass law requires that for small micelles or complexes their formation must be gradual and extend over the whole range of concentration. A sharp break in the slope, a t the “critical concentration to form micelles,” is incompatible with the mass law even for the largest mi0.08 0.10 celles. Writers since Lottermoser and Piischel have tended to overstress the sharpness of this break. Our critical concentrations are Cs 0.04, CI10.015, CI20.08 and CI40.0026 N , as read from the graph of equivalent conductivity, Fig. 3, with slightly different and likewise arbitrary values if read from the graph of specific conductivity, Fig. 4. The value for Cl2 is less than would be expected from those of the sodium salts,g whereas that for C14 is slightly greater. 0.012
0.010
A
x
.,” 0.008 Y
4
9v 0.006
9
8
a
rn
0.004
0.002
0.01
0.02
Nw. Pig. 4.
0.03
0.04
0.06
EVELYN LAKNGMCBAIN,WALTERB. DYE AND STEWART A. JOHNSTON
3214
VOl. 61
Those for the acids of uneven carbon atoms lie likewise a t lower concentrations than those predicted for the sodium saIts, being more nearly equal to the next highest homolog of even carbon number. The curve is very smoothly rounded for C g with increasing abruptness for the higher homologs. Refractive Index Refractive index, being essentially a measurement of atomic volumes, is but little d e c t e d by change from crystalloid to colloid. Lifshitz and BrandtlO found that the molar refraction for the soaps as observed in soap solutions agreed with that calculated for ordinary organic chemicals. For this reason refractive index is frequently a valuable method of analysis of soap solutions since with the dipping refractometer and auxiliary prism only 0.03 cc. is required for measurement and the readings a t 25' are linear when plotted against % or against equivalent weights in 1000 g. of total solution, as shown in Fig. 5. The slopes for the first four homologs are as shown in the figure 0.0293, 0.0247, 0.0210, and 0.0186, respectively.
0.2
0.4 0.6 Concentration, Fig. 6
0.8
1.0
Nw.
corresponds to structural viscosity. Thus the equivalent conductivity throughout the most concentrated range is rising in spite of an increase in viscosity amounting to many fold. Were it not for this, the increase of conductivity with increase of concentration evidently would be still greater. In the most concentrated solutions diffusion and conductivity show definite signs of reduction.
Freezing Point Data (by S.A. J.) The freezingequipment was modelled after that of Scatchard.ll The e. m. f. across the twentyfour junction thermocouple is measured by a relatively inexpensive null method designed by Dr. Stuart W. Grinnell, Fig. 8, and sensitive to 5X degree or 5 X lobs volt. The voltage divider AB (ratio 1:1627.3) ,like the galvanometer circuit, is of copper; P is a simple potentiometer to give a fine adjustment. 01 . . . . . . , The thermocouple is calibrated directly by measuring the thermal e. m. f. produced by the 0 0.2 0.4 0.6 0.8 1.0 1.2 freezing point lowering of approximately 0.15 N Normal factor. potassium chloride solutions, and calculating the Fig. 5.-The refractometer reading at 25" of the sulfonic acids Ca to CI plotted against the normal factor freezing point depression using g values obtained (equiv./1000 g. of solution) : 0,C2HbSOaH; A, C~H~SOIH;by Scatchard. i,CaHsSOsH; 8 , CaHriSOIH. The freezing point results for dodecylsulfonic acid are assembled in Table V and are shown Viscosity Data ,
,
,
The following results were obtained {by E. L. M.) for the viscosity of dodecyl sulfonic acid solutions a t 25', taking the value for water as unity, and employing an Ostwald viscometer. N\v 7
Nw I
0 020 0.035 0.050 0.060 0.090 0.105 0.302 0.36 1 14 1 19 121 1 2 2 1.26 1.30 1.82 2.01
0.455 0.565 0.77 2.28 3 01 4.64
0.805 0.95 5.04 7.64
1.026 1.052 10.93 13.4
The viscosity results are graphed in Fig. 6. The rapid rise in the more concentrated solutions 110) Lifshite and Brandt, Kdloid Z., Ps, 142 (1918).
TABLEV Concn. 0.08713
.07778 .05674 .05612 ,05373 ,03466 .03978 .02208 .02045 .01804 ,01778
6
g
0.05297 0.1636 .05101 .1765 .2130 ,04492 ,04589 .2200 .04635 ,2321 .OM38 .3135 ,04111 .3714 .03915 .4772 .03866 .5074 .5799 .03W .5822 .03847
Concn. 0 01211
,01148 ,01029 ,009233 ,006843 .005985 .005797 .004470
.003469 .002716 .002174
0
g
0.03704 0.8231 .03686 ,8638 .03581 .9367 .03254 .9483 .02427 ,9543 .02135 .9599 .02079 .9649 ,01592 .9584 .01238 .9604 .009817 ,9726 .007905 ,9785
(11) Scatchard, Jones and Prentiss, THISJOURNAL, 64, 2676 (1932).
Nov., 1939
PARAFFIN-CHAIN SULFONIC ACIDSAS COLLOIDAL ELECTROLYTES
graphically in Fig. 7. The concentrations are in moles per 1000 g. of water, 8 is the number of degrees lowering of freezing point, and g is the Bjerrum osmotic coefficient, g = 8/2 X m, where X = 1.858’ and g = van’t Hoffs i/2 and Lewis and Randall’s 1 - j . 1.0
I
A MERMXrUFCE
SS90n hEPS
c? lad) 3
E
c
P
VOLTS
VOLTS
tmn
2mn
B
0.8
0.6
dc 0.4
0.2
0
0.10
0.20
0.30
d N T Fig. 7.
Attention may be called to the extremely steep drop in the values of g in the neighborhood of 0.020.03 N where the actual freezing point, -eo1 is only just progressively lowered by increase in concentration. In other words, these dilute solutions are almost on the verge of separating into a heterogeneous mixture of two solutions both dilute and within this range. The requirement that 0 should increase continuously with concentration to prevent such separation is paralleled by the requirement that g/N dg/dN must be positive where N is the mole fraction of the solute.
+
Discussion The salient features of the data are, jirst, the regularity within the homologous series showing a gradual transition from typical fully dissociated electrolytes in the lowest members to well characterized colloidal electrolytes in the higher mem-
3215
K-2
m o m o m
I,. F. FIESER,W. P. CAMPBELL, E. M. PRYAND M. D. GATES,JR.
3216
dissociation in extreme dilution, then rather suddenly lose much of their conductivity through association of ion-pairs and ions to form colloidal particles of low conductivity, but after a welldefined minimum in moderately dilute solution, regain some of their conductivity through increas-
[CONTRIBUTION FROM
THE
1701. til
ing formation of better conducting or ionic micelles. 2 , This interpretation is in agreement with exact freezing point and diffusion data for dodecylsulfonic acid. STANFORD UNIVERSITY,
CALIF. RECEIVED JULY 10, 1939
CHEMICAL LABORATORY OF HARVARD UNIVERSITY I
Naphthoquinones of the Vitamin K,Type of Structure’ BY LOUISF. F ~ S E R WILLIAM , P. CAMPBELL, EDWARD M. FRY^ AND MARSHALL D. GATES,JR. The synthesis of various allyl derivatives of cr-naphthoq~inone~~~ by utilization of the Claisen rearrangement reaction was undertaken to provide model substances of the structural types postulated for vitamins K1 and Kz. It was recognized that methods involving use of this reaction probabiy would not be applicable to the synthesis of the vitamins themselves, and the present paper reports attempts to develop methods suitable for accomplishing this second objective. One scheme tried without success consisted in the attempted addition of a Grignard reagent to a naphthoquinone oxide. The reaction between allylmagnesium bromide and 2,6-dimethyl-l,4naphthoquinone oxide (I) was studied because addition in the desired direction would lead to 2,6-dimethyl-3-allyl-1,4-naphthoq~inone,~ which was already characterized. The chief product isolated, however, proved to be the bromohydrin 11, the structure following from the analysis of the colorless product and from its conversion to 0
0
I/ H
I1
I
/I
0 111 of P part of this work see Fieser, Si, 2659 (1989).
J~URNAL,
, Jonea,
RIrgel,
a yellow bromodimethylnaphthoquinone of the composition of 111. That cleavage of the oxide ring is due, as in comparable cases,5 to interaction of the oxide with magnesium bromide present in the Grignard solution was established by the observation that the bromohydrin can be obtained in 7 3 % yield from the oxide and magnesium bromide in ether. On attempted coupling of the MgBr derivative of I1 with allylmagnesium bromide there was isolated a small amount of the oxide, indicating that the cleavage reaction is reversible. When 2-methyl-l,4-naphthoquinone oxide was treated with methylmagnesium chloride and the oily product refluxed with alcoholic hydrochloric acid, a colorless substance resulted which appears to be formed by the addition of the elements of methane and of hydrogen chloride. The investigation was not pursued beyond these unpromising observations. A useful outcome of the brief study is the development of a method of preparing 1,4-naphthoquinone oxides which is much more convenient than Zincke’s6 hypochlorite procedure. A few trials were made of the method of introducing a &unsaturated group by direct C-alkylation of a phenolic salt, and it was observed that a small amount of 2-methyl-3-benzyl-l,4-naphthoquinone can be isolated from the very dark mixture produced by refluxing of 2-methyl-1,4naphthohydroquinone with benzyl bromide and potassium carbonate in acetone. When the reaction was conducted a t room temperature with two equivalents of benzyl bromide the mixture remained light in color and the sole crystalline product was methylnaphthohydrquinone dibenzyl ether (73% yield). With one equivalent ( 5 ) Gilmrn, “Organic Chemistry,” Vol. I , John Wdey and Sons, Ine., New York, N. Y., pp. 428429. 1988. (6) Zincke, Bar., S i , 8602 (1892).
