524
SHU-SING CHANGAND EDGAR F. WESTRUM,JR. TABLE
T,9C.
276 376
424 475
Vol. 66
IV
% D~UTERATIQN OF ETHANE AND BUTENE IN PRODUCTB OF PHOTOLYSlB OP eYCLVHEXANE-ACETQNE-da6 ---..., -Ethana---Y IButem--dr
@
46.5 62,2 66.1
1.3
2,s
27.4
2.7
1.6
di
da
do
dr
dg
da
dr
a6
0.2
100 22.5 4,R 1.6
0.3
35.9
1.3
6.3
65.0
1.1
0,6
---f
CH&H=CH2
___
dr
4.8
26.0
29-0
CH~CHCH~CH-CBCH, -_ _
dr
ds
-k CH&H=kH
(11)
CH~CHQCHICHCHCHQ ---t C H ~ C H ~ ~ ~(12) ~ ~
CH~CH~EE~EEZCH, -+ 6& + CRp=CHCH=CHCHz
(13)
CH3 and CzH6 radical found in the high temperature region. At low temperatures all the ethane results from the addition reaction of two OD3 radicals. The propylene formed in reaction 11 is only light. The further reactions of the CHs-
CH-CB radical generate C3Ba and CaHaD by abstraction, It also reacts in part with CD3 to give the preponderance of butene-d, found in the high temperature region. The only other butene ~of ~ significance, C H I butene-&, could form by the addition reaction of a CHB radical with a CHZCH-CH radical. Acknowledgments.--We wish to acknowledge the assistance of Mr. Joseph H. Johnson who helped with the mass spectrometer and gas chromatography analyses, and of Mrs. Helen R. Young who aided with the reduction of the analytical data.
HEAT CAPACITIES AND THERMODYNAMIC PROPERTIES OF GLOBULAR MOLECULES. 111. TWO METHYL-SUBSTITUTED POLYTHIAADAMANTANES1 BY SHU-SINGCHANG AND EDGAR F. WESTRUM,JR. Department of Chemistry, University of Michigan, Ann Arbor, Michigan Received October 23. I961
Heat ca acities of 1,5,5,7-tetramethyl-2 4 6,8,9,10-hexathiaadamantane and 1,3,5,7-tetramethyl-2,4,6~8-tetrathiaadarnantane have \,en determined from 5 to 350%. by adiabatic calorimetry. Derived thermodynamic functions were calculated from these data. No thermal anomaly has been found for either substance within the temperature range investigated. The molal values of heat capacity a t constant pressure; the entrogy; and the free energy function for the two oompounda are 67.74, 65.71; 70.63, 65.93; and -34.39, -31.84 cal. mole" K.-l, respectively, at 273.15'K.
htradactian I n continuation of the study of the thermal behavior of globular molecules with &n adamantmelike structure,2.s two methyl-substituted polythiaadamantanes have been studied. Both of them were known fang before the discovery of adamantane and were characteriaed as the dimers of dithioacetylacet~ne~ and of dithioacetic anhydride.6 More recently, the structures of these molecules have been reinterpreted by Fredga6J as that of cage molecules similar in structure to adamantane. Spectral dataa also favor the new structural formulas. Therefore, these two compounds could be designated, according to the nomenclature proposed by S t e t t ~ ,as~ 1,3,5,7tetramethyl - 2,4,6,8 - tetrathiaadamantane and (1) From the dissertation of 6. 9. Chang submitted in partial fulfillment of the requirements of the Doctor of Philosophy Degree a t the University of Michigan. This work was aupported in part by the Division of Research of the U. 9.Atomic Energy Commission. (2) 8 . 6.Chang and E. F. Westrum, Jr., J . Phys. Chem., 64, 1547 (1960). (3) 5. 5. Chang and E. F. Westrum, Jr., ibid., 64, 1551 (1960). (4) F. Leteur, Compt. rend., 133,48 (1901). (5) J. Bongarta, Ber., 19, 2182 (1886). ( 6 ) A. Fredga, Arkio Kemi, Mineral. G'eol., 26B, No. 8, I (1948). (7) A. Fredga and A. Brindatrcm. ibid., 26B, No. 4, 1 (1948). (8)R. Mecke and H. Spiesecke, Chem. Ber., 88, 1997 (1955). (9) H.Stetter and K.H. Steinscker, ibid., 8 6 , 451 (1952).
i,3,5,7- tetramethyl - 2,4,6,$,9,lO- hexathiaadamantarre, req~spectively. The former molecule posseeaea four co-planar methylene groups of an adamantane molecule and the latter all six replaced by corresponding numbers of sulfur atoms. In addition, one methyl group is attached to each of the four bridge-head carbon atoms in both molecules. Experimental Preparation of 1,3,3,'7-Tetramethyl-2,4,6,8-tetrathiaadamantme.-The calorimetric sample of this compound was prepared in accordance with a method described by Fredga and BrlndstrtimJ About 50 ml. of acetylacetone wm introduced into 200 ml. of absolute alcohol saturated with anhydrous hydrogen chloride gas a t 0'. The 801~tion was chilled in a Dry Ice-alcohol-bath. Into this a steady stream of hydrogen sulfide gas was passed until in excess beyond saturation. The mixture then was allowed to warm slowly to room temperature. The solid material was collected and washed with concentrated hydrochloric acid. The remaining yellowish tint which could not be removed by recrystallization was removed by refluxing the compound in an alcoholic solution with a quantity of active carbon (Norit). The substance was further recrystallized twice from absolute methanol. The final crystalline sample was compos;d of long prismatic needles with a melting point of 168 . Microanalysis indicated the following composition for this sam le: 45.560/, C, 6.05% H, and 48.21% S (calcd.: 45.41% 6.10% H, and 48.49% S for CloHlaS1). 1,3,5,7-Tetramethyl-2,4,6,8,9, IO-hexathiaadamantane.This compound was prepared by the method described for
8,
HEATCAPACITIES OF METHYL SUBSTITUTED POLYTHIAADAMANTANES
March, 1962
tetraethenyl hexasulfide.10 Thiolacetic acid was refluxed overni ht with one-third of its weight of c.rushed, fused zinc cboride. The crystalline product from the reaction mixture was washed with dilute hydrochloric acid and water to dissolve away zinc compouuds. It then was recrystallized twice from absolute methanol. The crvstals melted at'232' with slight decomposition. Microanalytical results indicated the composition: 31.94% C, 4.14% H, and 6 4 , ! 7 ' & S (calcd.: 31.94% C, 4.02% H,and 64.01% S for
-
1,3,5,7-Tetramethyl-2,4,6,8tetrathiaadamantane (C,HaS4: 1 mole 264.492g.) Series I 28.25 7.460 162.20 42.26 31,16 8.111 Series V 8.750 9.410 10.097 167.74 43.16 10.899 176.38 45.10 185.00 47.08 Series 111 193.81 49.01 1.003 202.71 50.84 1.325 1.664 46.48 11.06 211.60 62.74 .l,984 51.56 12.11 220.61 54.73 56.75 13.28 229.78 50.60 62.55 14.71 Series JI
4.85 6.38 6,13 7.09 7.97 8.87 9.86 10.82 11.75
0.136 .203 ,321 .503 .741
6.31 7.23 8.13. 9.07 10.13 11.26 12.48 13.74 15.04 16.47 18.06 19.82 21.85 24.14 25.47
0.337 ,545 .794 1.064 1.420 1.839 2.266 2.755 3.276 3.826 4.423 5.039 5.716 6.399 6.769
CsH12S01*
Cryogenic Technique.-The Mark I cryostat, a goldplated copper Calorimeter (laboratory designation W-Q), and a calibrated platinum resistance thermometer (laboratory designation A-3) were used iri measuring the heat capacities of both samples. These instruments and the general operating technique have been described in the previous papers of this series.*sa Samples weighing (in vacuo) 49.912 g. of tetramethyltetrathiaadamantane and 45.383 g . of tetramethylhexattiiaadamantane were used. After evacuation of the loaded calorimeter, helium gas at pressures of 6.0 and 10.5 cm., respectively, was sealed in at 300'K. in order to provide thermal contact between the sample and the calorimeter. The heat capacity of the heater-thcrrnometer-calorimeter assembly (without sample) was determined in a separate series of moasurements. This heat capacity represents a contribution increasing from 10% a t 10°K.to a maximum of 58% at 70°K. and gradually decreasing to less than 40% a t 350°K.
2,4,6,8,9,1~HEXAlHI~AMANTANE AND 1,3,5,7-T~TFlAMETHYLr2,4,6,8-TETRATH1AA.DAW4NTANE
Units: Cp
cal. mole-' OK.-' T,OK.
Cp
T,OK.
(10) E. Fronim and 0.Mangler, Ber.. 84, 204 (IQOI).
Series IV
64.89 70.92 77.78 85.34 93.59 101.97 110.07 118.33 126.80 135.42 144.25 153.29
15.36 16.93 18.87 21.18 23.56 25.93 28.27 30.32 32.89 35.18 37.46 39.88
235.14 57.63 244.41 59.61 253.66 61.60 262.70 63.44 271.53 65.33 280.34 67.14 289.28 69.09 298.33 70.80 307.47 72.44 316.86 74.22 326.43 76.12 336.00 78.09 345.56 80.00
TEMP E RAT UR E, " K . 100 200
Cp
1,3,5,7-Tetramethyl-2j4,6,8,9,l0-hexathiaadamantane ( C ~ H ~ Z1Smole ~ ; = 300.572g.) Series I 233.80 60.06 14.77 3.592 242.98 61.89 16.27 4.188 69.54 18.07 251.84 63.63 18.01 4.858 74.91 19.71 260.63 65.30 20.01 6.566 82.00 22.10 269.53 67.13 22.22 6.272 89.41 24.55 278.57 68.60 24.64 6.972 96.73 26.85 287.71 70.42 27.30 7.641 104.45 29.16 296.88 72.05 30.27 8.326 306.29 73.10 33.53 9.010 Series I1 315.81 74.91 324.55 76.06 Series VI1 114.68 32.21 332.03 77.38 123.31 34.76 339.62 78.58 32.86 8.875 131.88 37.15 346.93 79.98 36.52 9.622 140.47 39.50 40.49 10.423 149.14 41.88 Series V 44.62 11.297 49.14 12.345 Series I11 4.94 0.164 54.23 13.618 5.50 0.233 59.83 15.167 166.71 45.95 65.72 16.939 175.74 47.93 Series VI 72.00 18.798 184.82 50.05 194.01 52.02 5.14 0.185 Series VI11 203.45 54.07 6.29 .392 212.94 56.05 7.33 ,662 151.87 42.77 8.42 1.023 161.37 44.78 Series IV 9.54 1.423 10.71 1.890 Series IX 215.55 56.51 11.99 2.419 224.50 58.27 13.35 2.988 291.48 71.05
34.28 37.71 41.50 45.72
Series VI
Results The experimentally determined heat capacities of both compounds are presented in Table I in TABLE I HEATCAPACITIES OF 1,3,5,7-TETRAMETHYL-
T,OK.
525
0
300
80
960 0
2
w'
W
a
740 _I
Q U
u"
20
0 0
5 IO TEMPERATURE, "K,
15
Fig. 1.--Heat capacities of tetramethyltetrathiaadamantane 0 and tetramethylhexathiaadamantane 0.
chronological order to permit the estimation of the approximate temperature increments of the individual runs from the adjacent mean temperatures. The data are stated in terms of the defined thermochemical calorie equal to 4.1840 j., an ice point of 273.15'K., and the gram molecular weight of tetramethyltetrathiaadamantane and tetramethylhexathiaadamantane taken as 264.492 and 300.572
RHU-SINGCHAKGASD EDGAS F. WESTRUM,JR
526
g., respectively. An analytically determined curvature correction, amounting to less than 0.1%, has been applied to the observed m / B T values The molal values of heat capacities at constant pressure, %he entropy and enthalpy incremeiits, and the free energy functions are listed a t selected temperatures for both campounds in Tablo 11. These values were obtained by integration of a least-square-fit polynomial through the data points by means of a high-speed digital computer. Below 5'N. the data were extrapolated by means of the Debye limiting law. Nuclear spin and isotope nixing contributions have not been included in thc entropies and the free energy functions, The probable error of the reported heat capacity values is considered to be less than 0.1% at temperatures above 25'K., ly0at loOK., and about 5% TABLE I1 1,3,5,7-TETRARfETHYL2,4,6,8,9, 10-HEXATHIAADAMANTAKEAND
~ H E R Y O D Y N A I I I C PROPERTIES O F
1,3,5,7-TETRANETHYL-2,4,6,8-TETRATHIAADASSANTAWE
Units: cal., mole, T ,"K.
CP
so
"K.
HO - ROD
-(Fo -
H0o)T-l
1,3,5,7-Tetramethyl-2,4,6,8,9,10-hexathiaadamantane (C8H1&, 1 mole = 300.572 g.) 0 209 0.014 0.056 0.168 5 ,127 4 065 1.605 0.533 10 ,424 17 26 1.574 15 3.681 ,874 40 52 2.900 20 5.563 72 21 1 420 4.309 25 7.065 2 018 110 7 5.709 8.269 30 2 643 164.7 7.062 (4.300 35 3 277 203 7 8.369 10.31 40 3.914 257 9 9.645 11.39 45 4.550 317.7 12.56 10.905 50 5 819 456 3 13.424 15.22 60 7,088 623.3 18.22 15.992 70 8.365 821.4 21.41 18.632 80 9.656 1051.6 21.340 24.63 90 10.962 1313.9 27.82 24.101 100 12,283 1607.6 26.898 30.90 110 13.619 1931.5 29.715 33.87 120 14.965 2284 5 32.538 36.70 130 16.321 2665.2 35 358 39.41 140 17.684 3072.3 38.166 41.99 150 19.051 3504 6 40.955 44.45 160 20 421 3960.9 43.721 46.80 170 21.792 4440 3 46.460 49 05 180 23 162 4941 7 49.171 51.22 190 24 529 5464 3 51.851 53.31 200 25.894 6007.7 54.502 55.35 210 27.254 6571 3 57.123 57.36 220 7154.8 28.609 59.717 59.35 230 29.959 7758.2 62.284 61.32 240 31.303 838f .3 63.29 64.828 250 32.641 9023.9 65.24 67.348 260 33.9F2 9685.9 69.846 67.15 270 35.298 72.321 10366.6 68.99 '280 36.61f 11065.4 74.773 70. Y4 290 37.929 11781.1 77.200 72.39 300 15596.0 44.385 88.945 80.58 350 9898 34.39 67.74 70.63 273.15 37.69 11648 72.09 76.75 298,.15
Vol. 66
mantane 1,3,5,7--Tetramethyl-Z,4,6,8-tetrathiaadai
5 10 15
20 25 30 35 43 45 60 60
70 80 90
190 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 350 273.15 298.15
(CUHUSA, 1 mole 0 052 1 374 0 464 3.252 1.368 2 563 5.107 6 639 3 874 7.864 5 199 8 865 6 488 9.803 7.733 8 1943 io I76 11 79 10 129 14.10 12.418 16.72 14 845 19.53 17 259 19.927 22.43 22.241 25.34 28.22 24.792 31.02 27.368 33.75 29.959 32.558 36.40 35.157 38.95 41.41 37.750 43 77 40.332 46.04 42.898 45 446 48.22 50.35 47.974 52.43 50 481 52.968 54 50 -55 436 56 57 55 67 57.888 60 79 60.326 62.752 62 93 65.167 65 05 67.13 67.57@ 69.14 69.961 72.338 71.06 80.74 84.018 65 93 65.71 70.71 71.90
0,154
=
264.502 9 , ) 0 194 3 515
14.98 35 98 63.49 101.9 143 8 190Id 241 9 298 2
427 4 581 3 762 4 972 2 1211.1 1478.9 1775.2 2099.1 2480.0 2826 8 3228.7 3654 7 4103 8 4575.2 5068.1 5582.0 b116.6 6671.9 7248.1 7845 4 8464.1 9104.0 9765.0 M446.4 11147.4 14942.3 9310 11016 I
0 013 0>112 369 764 1.254 1 802 2 380
2.971 3 568 4.165 5 355 6 541 7.729 8 925 10.130 11 347 12 575 13 812 15 058 16 312 17 571 18 834 2Q 099 21 366 22 634 23 900 25 165 26 427 27 687 26 944 30.198 31 448 32 695 33.939 35 180 41.326 31.84 34 95 I
ab 5OK. The estimated probable error in the thermodynamic fuiictiQiis is less than 0.1% above 100°K. Pi$CUWhll
Xo thermal anomaly has been observed in the heat capacify measurements for either compound between 5 and 35OOK. Simple differential thermal alnalysis measurement8 establish t'he absence of such anonialies over the entire solid range. Failure to find tTansitioiis similar t o that of adamantane2 is not an ulilexpected result for these substances. The heat capacity us. temperature .curves for these two compounds are very similar in shape to each other, but they are distinctively different from that of adamantane and hexameLhyleiiete%ratminewhich form another pair. The sulfur atoms present in the skeletal strncture of the cage of Cheae two molecules may have increased the intermolecular force and hence bhe potential barrier for the reorientaition of the molecules into other equivalent positions. Moreover, it is likely that the four methyl groups extank in both molecules prevent the rotation of r;raoleculees through simple steric
March, 1862
ACID-BASEEQUILIBRIA OF METHYL RED
hindrances. These molecules deviate considerhbly from sphericity and appear to have molecular envelopes in the shape of a large tetrahedron. However, although tetrahedrally-shaped rnolecuies often show the onset of the plastically crystalline phase, this phnomenon does not appear to be present in either of the two methyl-substituted polythiaadamantanes studied. It is of‘ interest to note that the hexathia compound has been reported to exist in a crystal lattice of rather low symmetry. l1 The monoclinic
527
space group Cth-P21/c is said t o characterize the lattice and the molecules do not appear to possess any element of crystallographic symmetry. Acknowledgment,-The authors acknowledge with gratitude the assistance of Elfreda Chmg and H. Gary Carlson in the experimental measurements, and the financial support of the Division of Research of the United States Atomic Energy Commission in the performance of these studies. (11) G. Higg and B N ~ g a r d hreported by A Fredga, ref
0.
ACID-BASE EQUILIBRIA OF 3IETHYL RED BY RICHARD W . RAMETTE, EDWARD A. DRATZ, AND PRESTON W. KELLY Leighton Hull of Chemistry, Curleton College, North$eld, Minnesota Recoived
OCfObs3T
30, I961
-
The cation of methyl red, or o-(p-dimethylaminopheny1azo)-bennoicacid, has an acid dissociation constant IL 0.0040 according t o spectrophotometiic measurements as well as solubility studies in HCLKCI buffers in which S = 6.0 X 1.54 x 10“3[Ha0*]. Distribution studies using these bufferawith carbon tetrachloride show that the aqueous/CCL concentration ratio for methyl red follows the relationship E = 0.00295 0.585[H30+I, indicating the higher value far K1 of 0.0050, perhaps because of the dissolved CC14. Spectrophotometri? studies and solubility measurements in acetate buff ers, in which S = 6.0 x,X0-6+ 8.9 X I0;l1/[H30+], showthatthedissociatioii constant for the zwitterion Kz = 1.50 X 10-8, The intrinsic solubility of the zwitterion is %bus 6.0 X lo’* according to bath solubility studies. Thme values refer to a temperature of 2 6 O and ,are calculated for aero ionic strength, but the work was carried out a t ionic strength equal to 0.020.
+
+
Introduction Methyit red, or o-(p-dimethy1aminophenylazo)benzoic acid, has been the subject of ionization constant studies for half a The collected reaults refer to several temperatures, the effects of ionic strength often were not considered, and some of the experimen’cal approaches were inherently inaccurate. The purpose of the present work has been to use refined spectrophotometric techniques for the determination of accurate ionization conRtant values, and to examine the usefuIness of immiscible solvent extraction and solubility studies for the same purpose. In aquleous solution methyl red exists in three forms; a cation, HsMfl which is in%enselyred, a species H A 4 which is undoubtedly a zwitterion because of the similarity of its absorption spectrum to that of H2M+ (see Fig. I), and a yellow anion, M-. Thle famiIiar use of methyl red as an acidbase indicator is based on the equilibrium between IM-and IIM, In neutral solvents such as benzene and carbon tetrachloride HM in yellow, indicating that the switterion reverts to the non-ionic structure; (C~Es)2NCsH4;”\JZNCsH4COOR(o). The cation may be regarded as a diprotic acid, and two equilibrium quotients (in terms of rnolarities) may be defined iii the usual way &I = [H~O+l[HMl/[H&f+l Qz = [Ha.O+l[M-I/[HMl The corresponding equilibrium constants, Kl and
Kz may be calculated from the experimentally (1) H. T. Tizard, J . Chem. Sue.. 97, 2477 (1910). (2) A. Thiel, F. Wulfken, and A. Dassler, 2. anorg. u. allgem. Chem., 186, 393 (1924).
(3) I. M. Kolthoff, Ree. trav. chcm., 48, 144 (1924); 44, 75 (1925). (4) A. hlerstoja, Ann. Acad. Sei. Fennzeae Sec. A, I I , Chsmica, No. 12, 7 (1944). ( 5 ) F. A. F. Vermast, Indonesian J . Nut. Sci., 109, 57 (1953). (6) S. W. Tobey, J . Chem. Eduu., 86, 514 (1958). (7) C. N. Reilley and E. M. Smith, Anal. Chem., 82, 1233 (1960).
determined Q values if the values of the activity coefficients can be estimated reliably. Experimental Reagents.-lilethyl red (Eastman 431) was purified by slow recry&allization from redistilled toluene, resulting in large crystals. For the spectrophotometric work ethanolic stock solutions were prepared by weighing the cnlculated quantity and diluting to make the molarity eQual to 1.00 X 10-8. The carbon tetrachloride wa8 redistilled, solutions were standardized by conventional methods, and all reagents were of high quality. Apparatus -Photometric measurements were made with a Beckman Model B instrument using both 1-em. rectangular and 5-cm. cylindrical Pyrex cells. The 8-cm. cells were calibrated ‘
