March, 1SGl
Low TEMPERATURE THERMODYNAMIC PROPERTIES OF SIXHEPTANES
ment of CHrC(=NOH)-CsH6 yields products whose properties suggest the presence of the two isomers, whereas only one isomer mas found in the case of CzH5-C(=iYOH)-C6Hs. Since, as has been pointed out,22 the experimental conditions of the Beckmann rearrangement can be conducive to isomerization, and not all the rearrangement products are always accounted for in the literature, the conclusions drawn from reports on Beckmann rearrangement studies as to the isomeric composition of the original oxime may not always be valid. Appendix To check Phillips' assignment3 of the two -CH=NOH (24) For the preparation of CzHr-C(=NOH)-CsHs, see K. N* Campbell, B. K. Campbell and E. P. Chaput, J . Org. Chem., 8 , 99 (1943).
495
multiplets arising from syn-anti isomerism, the spectra of the two p-chlorobenzaldoxirnesz6 in dimethyl sulfoxide solution were examined. The significant portions of the spectra consisted of the following lines (c./eec.), with the center of the benzene ring multiplet taken as the origin. (With (CH&SO as reference, the origin of this multiplet in tlic antz oxime lies a t higher field by about 6 c/s than of the syn oxime.) Compound
-Ring 1
2
synoxime antioxime
-12
- 3 -13
-21
proton pealis-3
+
3 +I3
i
-12 +21
--Cg=NO!i peak
-27 +17
Thus, the -C_H=KOH resonance of the anti oxime indeed appears a t higher field, and Phillips' assignment3 seems to be correct. The syn-anti shift is, in the present case, of the order of 0.7 p.p.m., as compared to 0.6 p.p.m. for propionaldoximes. (25) H. Erdniann and E. Schwechten, Ann., 260, 53 (1890).
TEMPERATURE THERMODYNAMIC PROPERTIES OF SIX ISOMERIC HEPTAXES
~ 0 1 4 7
E:Y H. M. HUFFMAN,' M. E. GROSS,D. W. SCOTTAND J. 1.' MCCULLOUGH Contribution No. %$from the Thermodynamics Laboratory, Petroleum Research Center, Bureau of Mines, U. S. Department of the Interior, Bartlesville, Oklahoma Recewed September 21, 1960
I n a continuing program of studies of thermodynamic properties of aliphatic hydrocarbons, low-temperature thermal measurements were made on the nine isomeric heptanes, but definitive results could be obtained for the folloning six compounds only: n-heptane, 2-methylhexane, %ethylpentane, 2,2-dimethylpentane, 2,sdimethylpentane and 2,2,3-trimethylbutane. Values of heat capacity in the solid and liquid states and of the latent heats and temperatures of isothermal phase changes were determined for each of these six isomers. Also, the vapor pressure of 2-methylhexane was measured in the ranges, 0-45", 17-159 mm. From the observed data were calculated values of the free energy function, heat content function, heat conteni, entropy and heat capacity of the condensed phases at selected temperatures between 10 and 300'K. These results and literature values of heat of formation, heat of vaporization and vapor pressure mere used to compute values of the chemical thermodl namic properties for the liquid and ideal gas states a t 298.15"K.
The preparalcion of comprehensive tables of phase changes were determined for each of these thermodynamic property values for important six compounds. Also, the vapor pressure of 2homologous series of hydrocarbons requires knowl- methylhexane was measured in the ranges, 045", edge of the variation of such properties with both 17-159 mm. From the observed data were calmolecular size and structure. The Bureau of culated values of the free energy fuiiction, heat Mines has a continuing program to determine part content function, heat content, entropy and heat of the needed fundamental information by low capacity of the condensed phases at selected temtemperature calorimetric studies of selected groups peratures between 10 and 300°K. These results of hydrocarbons. For acyclic hydrocarbons, pre- and literature values of heat of formation, heat of vious publications have reported low temperature vaporization and vapor pressure were used to thermal data for nine five isomeric compute values of the chemical thermodynamic hexanes, seren 1-olefins, six isomeric ~ e n t e n e s , ~properties for the liquid and ideal gas states at and several olhers. This paper describes an 298.15"K. Detailed results of these studies are investigation of the isomeric heptanes. Studies in the Experimental section. of all nine isomers were attempted, but for reasons Discussion of Results discussed in a following section, definitive results could be obtained for only six isomers: %-Heptane, Chemical Thermodynamic Properties at 298.15' 2-methylhexane, 3-ethylpentane1 2,2-dimethyl- K.-Table I lists the chemical thermodynamic pentane, 2,4-dimethylpentane and 2,2.3-triniethyl- properties of the six heptanes a t 298.15"Ii. The butane. Talues of heat capacity in the solid and tabulated values are based only on experimental liquid states in the range 12-300°K. and of the data from this investigation and earlier studies of latent heats and temperatures of isothermal heats of formation and vaporization and vapor pressure cited in text and in the footnotes t u (1) Decease% (2) H. L. Finke, M. E. Gross, Guy Waddington and H. RI. IIuffman, Table I. Current tabulations of -4merican PeJ . Am. Chsm. Sac., 76 333 (1954). troleum Institute Research Project 14G also gii-c ( 3 ) I). R. Douslin and H. 31. Huffman, zbzd., 68, 1704 (1946). (4) J. P. McCullough, H. L. Finke. M. E. Gross. J. F. Messerly and Guy Waddington, J . I'hys. Chem., 61, 289 (1957). (5) S. 9. Todd, G. D. Oliver and H. M. Huffman, J . Am. Chem. S o c . , 69, 1519 (1947).
(6) American Petroleum Institute Research Project 44, "Selected Values of Physical and Thermodynamic Properties of Hydrocarbons and Related Compounds," Carnegie Press, Carnegie Institute of Technology, Pittsburgh, Pennsylvania, 1953.
H. M.
496
HUFFMSN,
M. E. GROSS,D. w.SCOTTAND J. P. h f C C U L L 0 U G H
Vol. 65
TABLE I MOLALTHERMODYNAMIC PROPERTIES AT 298.15”K. Compour1d
State
AHv’,a kcal.
ASva,a cai. deg.-l
SO,
b
cal. deg.-*
AHf”, b* kcal.
AFof8b* e kcal.
log Kfh c
n-Heptane
Liq. 8.749 23.74 78.53 -53.63d 0.24 -0.18 1.91 -1.40 Gas 102.27 -44.88 2-Riel hylhexane Liq. 8.343 23.10 77.28 -54. 93d -0.69 +0.51 Gas 100.38 -46.59 .77 - .56 3-Ethylpentme Liq. 8.436 23.17 75.18 -53.77d 1.10 - .81 2.63 Gas 9s. 35 -45.33 -1.93 -1.16 2,2-Dimethylpentanc Liq. 7.776 22.13 71.77 - 57. O j d +O. 85 - .01 Gas 93.90 -49.27 +O .02 - .40 -56. 17d 2 , 4 D imethylpentanc Liq. 7.885 22.36 72.46 .36 Gas 94.82 -48.28 .73 .54 2,2,3-’I’rimethylbutane Liq. 7.682 69.85 -56.63d - .I7 .12 21.76 Gas 91.61 -48.95 - .75 $1.02 The entropy, heat of formation, free energy of formation and logaThe Eitandard heat and entropy of vaporization. rithm of the equilibrium constant of formation in the standard liquid or gas state a t 298.15”K. For the reaction 7C(c, E. J. Prosen and F. D. Rossini, J. Research Natl. Bur. Standards, 34,263 (1945). 8H:!(g) = C7H16(1or g). graphite)
+
+
+ +
+
values of the properties in Table I. Some of the results in the API tabulations, which are based on preliminary data from this work, differ slightly from the values reported here. Although the differences are minor, the values in Table I are considered more accurate than the earlier results. Huffman, Parks and Thomas’ made low temperature thermal studies of these compounds over SO years ago. Their results for the entropy increment between 90 and 298°K. (the range of their measurements) agree with those of this work within 1%. However, because they had to compute the increment between 0 and 90°K. by an uncertain extrapolation, some of their values of 8 2 9 8 are in error by several per cent. Thermal Behavior of the Heptanes in the Solid State.-Normal heptane, 3-ethylpentane and 2,4dimethylpentane have regular heat capacity curves in the solid state; 2-niethylhexane and 2,2-dimethylpentane have peaks in the heat capacity curves, designated as Type H transitions in the empirical classification of McCullough.8 Much more compliaat8ed behavior is shown by 2,2,3trimethylbutane: two non-isothermal transitions (either Type 2N or Type H8) are followed by an isothermal transition (Type Is) as the crystals are heated from 80 to 125°K. Of the heptane isomers not studied completely, 3,3-dimethylpentane has at least three crystalline modifications, and 3methylhexane and 2,3-dimethj lpentane form glasses.9 The plots of heat capacity us. temperature in Fig. 1 depict the thermal behavior of the crystalline heptanes. For reference purposes in the discussion that follows, the heat capacity curve of n-heptane is superimposed on the curves of each of the other five isomers. Cryst 41 structure and other information needed for detailed understanding of the results shown in Fig. 1 are unavailable, but the results afford an unusual demonstration of the effect of isomeric differences on the thermal behavior of organic crystals. In addition to the occurrence of phase transformations, three points are to be noted: (7) H. hf. Huffman, G. S. Parka and S. B. Thomas, J. A m Chem. Soc., 62, 32’41 (1930). (8) J. P MeCullough, Proceedings of the Symposium on Chemical
Thermodynamics, Wattens, Bustria. August, 1959; to be published. (9) Further attempts to study these three compounds are planned.
First, the heat capacity of n-heptane is the lowest of all isomers in the region below 50”K., undoubtedly because the branched hydrocarbons form “softer” crystals. That is, the lattice contrihtion to the heat capacity becomes fully excited at lower temperatures for a branched heptane than it does for n-heptane. The fact that the heat capacity of 3-ethylpentane is only a little higher than that of n-heptane below 50°K. suggests that this symmetrically branched compound forms a more compact crystal than the less symmetrically branched isomers. Second, the heat capacity curve of n-heptane is higher than those of the other isomers in a t least part of the region from 50 to 120°K. This crossing of heat capacity curves is caused in part by the delayed excitation of the lattice contributicn of n-heptane. However, as unbranched conipounds usually have more low-lying intermi energy levels than branched compounds, the mo: e rapid increase in the heat capacity of n-heptanc. above 50°K. also is due in part to increased coiltributions from internal degrees of freedom. Third, the heat capacity of each branched isomer again becomes higher than that of n-heptane at some temperature above 100°K. For some of the branched isomers, the heat capacity curve has pronounced positive curvature in the region below the melting point. This effect undoubtedly is ducl to increased libration, or “prerotationJ’,loof molecules a t the lattice sites, as in the higher n-paraffins.2 The heat capacity of n-heptane also may be affected by “prerotation”, but at higher temperatures and probably to a lesser extent. The “softer” crystals of %methylhexme, 2,2-dimethylpentane and 2,4-dimethylpentane evidently allow appreciable libration of molecules about a crystal lattice site as the melting point is approached, perhaps including some degree of restricted rotation. The results for 3-ethylpentane do not provide evidence of significant “prerotation” effects, in keeping with the observation that this compound must form relatively compact crystals. With thermal evidence only, it is not practical to speculate about the details of the solid-phase transformations that occur in 2-1iicthylhexaiie~ (10) c. P. Smytb, Tranr. Faraday sot., 42A, 175 (1946).
March, 1961
Low TEMPERATURE THERMODYSAMIC PEOPEETIES OF SIXHEPTANES
r ---
497
2,2-dimethylpentane and 2,2,3-trimethylbutane. Because of slow thermal equilibration, the shapes of the heat capacity curves could not be defined precisely in the regions a few degrees above and below the temperatures a t which the peaks occur. However, the curves drawn are consistent with continuous enthalpy measurements made over the ranges of anomalous behavior and, therefore, are generally correct. Two of the isomeric hexanes-2,2-dimethylbutane and 2,3-dimethylbutane-also exhibit phase transformations in the solid state.3 Nuclear magnetic resonance” and X-ray diff ractionI2 studies have shown that the high-temperature phase of 2,2-dimethylbutane is highly disordered; that is, the molecules as a whole undergo restricted rotation a t crystal lattice sites. The three transformations in 2,2,3-trimethylbutane undoubtedly result in a high-temperature phase with a comparable degree ‘of orientational disorder. However, as the entropy of fusion of 2,2,3-trimethylbutane (2.17 cal. deg.-’ mole-’) is significantly larger than thoF,e of the two dim ethyl butane^,^ the high-temperature crystals of this heptane probably are not so completely disordered as those of the branched hexanes. On the basis of the thermal evidence, the crystals of the less symnietrically shaped molecules of 2methylhexane and 2,2-dimethylpentane do not obtain a high degree of orientational disorder in the solid phase Perhaps the transitions that occur in these two compounds result in slight changes in crystal structure that allow the increased librational freedom discussed before. Apparently, ?,4 - dimethylpentane is symmetrical enough that increased librational freedom occurs without a transition, but it is not symmetrical enough to form a highly disordered, or “rotating,”11 crystal at temperatures below its melting point. As D result, this last compound shows no anomaly other than the effects of “prerotation.” In general terms, the thermal behavior of the heptanes in the solid phase may be summarized as follows. The compact crystals of n-heptane and 3-ethylpentane undergo no phase transformation, although t’hey may show slight effects of “prerotatioii.” ( LLPrerotation”is used here as a term to describe the increased librational freedom, possibly including restricted over-all rotation about one axis, gained by molecules of some organic crystals a t temperatures below the melting point.) The less ciompact crystals of 2-methylhexane, 2,2-dimethylpentane and 2,4-&methylpentane show more pronounced effects of “prerotation.” The onset of “pi-erota tion” in 2-methylhexane and 2,2dimethylpentane is preceded by phase transformations that are evidenced by peaks in the heat capacity curves. The more symmetrical (cllipsoidal) molecule, 2,4-dimethylpentane, also exhibits “prerotation” effects, but without a preparatory phase change. The still more synimetrical (globular) molecule, 2,2,3-trimethylbutane undergoes thr1.e transformations in the solid phase,
Apparatus and Physical Constants.-The l o a temperature calorimetric1s and vapor pressure14measurements were
(11) J. G. Aston. B. Fbolger, R. Tranibarulo and H. Seeall. J . Chetn. PILUS.. 22, 460 (1954). (12) B. Post, R. S. Schwartz and I. Fankuchen. J . A m . Chem. Soc., 73,5113 (1961).
(13) H. M. Huffman, Chem. Reus., 40, 1 (1947); H. M. Huffman, S. S. Todd and G. D. Oliver, J. A m . Chem. Soc.. 71,584 (1949): D. w. Scott, D. R. Douslin, M. E. Gross, G. D. Oliver and H. M. Huffman, iaia., 74, 883 ~ 1 9 5 2 ) .
~ r -
I
A
2OC
401
(I
I
,
a0
,A
60
/
l
,
l
,
CRYSTALS ICR ,Y-
1
100 I20 TEMPERATURE, ‘ K .
80
l
L 140
16(
Fig. 1.-Heat capacity curves for six isomeric heptanes in the solid state: (1) n-heptane; (2) Zmethylhexane; (3) 3-ethylpentme; (4)2,Zdimethylpentane; (5) 2,4dimethylpentane; and (6) 2,2,3-trimethylbutme.
with the high temperature crystalline phase having a much higher degree of orientational disorder than usually implied by the term “prerotation.” Experimental
498
H. M. HUFFMAN, M. E. GROSS,D. W. SCOTTAND J. P. MCCULLOUGH
made m ith apparatus described by Huffman and co-workers. The 1951 International Atomic Weights'5 and values of the fundamental physical constants'p were used. Measurements of temperature were made with platinum-resistance thermometers calibrated in terms of the International Temperature Scale of 1948'' from 90 to 400°K.; and Celsius temper:ttures were converted to Kelvin temperatures by addition of 273.15'.'8 From 11 to SO'K., temperature measurements were made in terms of the provisional scale of the Xationzl Bureau of Standards.lQ Energy was measured in joules and converted to calories by the relation, 1 cal. = 4.184 (exactly) joules. Measurements of mass, electricid potential and resistance were made in terms of standard devices calibrated a t the Kational Bureau of Standards. The results in this paper originally were calculated with physical constants and temperatures related to the definition 0" = 273.16OK. Temperatures reported here are in terms of the newer definition,ls but only some of the experimental results were recalculated. Numerical inconsistencies less than the precision of the experimental data may have been introduced by this procedure. Materials.--The samples of the branched isomers were API Research hydrocarbons.20 As described in detail in another publichon,21 extensive measurements mere made on four different samples of n-heptane, two of which were ,4PI Research samples20 and two of which were Calorimetry Conference samples.22 Because the detailed results for n-heptane are l,o be published elsewhere,21only a summary of the data for this compound is given here for comparison with results for the other isomers. Heat Capacities in the Solid and Liquid States.-The heat capacity of each heptane was measured in the solid and liquid states in the approximate range 12 to 300°K. Observed values of heat capacity a t saturation pressure, Csat,j,are recorded for each isomer, exccpt n-heptane, in Table 11. T f e temperature increments used in the measuremeni s wert' small enough to obviate corrections for non-linear variation of Csatd with T , except as noted in Table 11. The prerision of the results was, in general, +O.lT, and above 30°K., the accuracy uncertainty should not exwed 0.2%, except in the regions of phase transformations. Kcar phase changes data for the solid state may be less precise and less accurate because of rapid changes of Csatdwith T,slow equilibration, or uncertainties caused hy the prewnce of impurities. The results in Table I1 have not been corrected for premelting caused by impurities. Empirical equations were obtained to represent the heat capacity of each compound in the liquid state. The constants of these equations are listed in Table 111. Solid-state Phase Transformations.-So far as could be determined, the phase tranformations in 2-methylhexane and 2,2-dimethylpentane and two of those in 2,2,3-trimethylbutane -sere non-isothermal. From the heat capacity data and enthalpy measurements including the entire temperature range of a transformation, the following peak values of heat c7apacitv were computed: 2-Methylhexane, 25.17 cal. deg.-l mole-' at 71.5'K.; 2,2-dimethylpentane, 25.17 ral. dee.-' mole-' at 83.2"K.: and 2.2.3-trimethvlbutanc, 39.00 &1. deg.-l mole-' at 86.8"K. and 50.13 c d . deg.? mole-'zit 108.CI°K. _____
(14) G. Waddington, J. W. Knowlton, D. 1 %'. Scott, G. D. Oliver, S. S.Todd, T. N. Hubbard, J. C. Smith and H. M. Huffman, J . Am. Chem. Soc., 71,797 (1949). (15) E. Wichera, ibid., 74, 2447 (19.52). (16) F.. D. Rossini, F. T. Gucker, Jr., H. L. Johnston, L. Pauling and G. W. Vinal, ibdd., 74, 2699 (1952). (17) H. F. Stimson. J . Research N a f l . Bur. Standards, 42, 209 (1949). (18) H. F. Stimson, A m . J. Phys., 23, 614 (1955). (19) H. J. Hoge and F. G. Brickwedde, J. Research Natt. B w . Standards, 22, ,351 (1939). (20) These samples of API Research hydrocarbons were made available through the American Petroleum Institute Research Project 44 on the "Collection, Analysis and Calculation of Data on Properties of Hydrozarbons" and were purified by the American Petroleum Institute Research F'roject 6 on the "Analysis, Purification and Properties of Hydrocarbons," both a t the Carnegie Institute of Technology. (21) J. P. McChllough and J. F. Messerly, U.8. Bur. Mines Bull.. to be published. ( 2 2 ) I).R. Stu.11, Chem. Eng. h'ews, 27, 2772 (1949).
Vol. 65
TABLE I1 THEMOLALHEATCAPACITIES OF FIVEISOMERIC HEPTANES IN THE SOLID AND LIQUIDSTATE,CAL.D E G . - ~ T,
ATb
Crystals 12.61 14.12 16.35 19.11 19.62 22.31 23.66 25.90 27.99 29.64 32.22 36.79 41.83 46.64 51.26 56.51 62.32 66.27 68.88 70.90 72.85 76.39 83.29 85.X 91.78
1.190 1.828 2.656 2.871 3.628 3.538 4.446 3.632 4.225 3.859 4.218 4.931 5.144 4.471 4.768 6.668 4.956 2.954 2.252 1.786 2.113 4.973 8.832 4.472 8.131
CsatdC
T , 'K.a
2-Alethylhexane 100.12 109.71 1.385 119.97 1.792 129.59 2.438 137.60 3.349 3.518 4.437 4.887 160.41 5.636 169.29 6.345 181.70 6.891 194.69 7.722 204.46 0.121 215.40 10.602 226.58 11.856 237.59 13.064 248.80 14.387 260.23 15.830 269.33 16.858 271.84 17.736 277.70 23.577 278.81 18.720 283.62 18.150 286.66 19.366 294.35 19.748 295.18 20.842 301.17
ATb
Csatdc
8.550 10.626 9.911 9.337 6.677
22.162 23.713 25.385 27.007 28.439
Liquid 6.594 11.150 13.686 8.954 10.590 11.283 11.095 10.904 11.532 11.319 9.549 11.899 8.636 9.396 11.669 9.279 6.103 11.442 7.540
43.134 43.543 44.176 44.879 45.474 46.183 46.054 47.816 48.678 49.665 50.467 50.693 51.258 51.356 51.781 52,122 52.880 52.913 53.564
1.112 2.088 1.209 2.240 2.248 2.659 5.847 3.123 8.266 7.025 7.751 7.463 7.057 6.697 3,932 7.065 6.578 G.494
24.492 22.625 21.802 20.371 20.042 20.209 20.550 21.848 21.895 22.985 23.383 24.387 25.886 27.399 28.058 29.065 29.765 32.192
2,2-Dimethylpentane Crystals 14.30 14.90 15.89 16.80 18.25 19.57 21.38 22.99 24.92 26.86 28.62 31.00 32.44 35.17 39.40 44.30 49.88 54.93 55.53 59.70 65.08 65.75 69.95 71.18 73.64 76.37 78.61 80.61 82.48 82.54
1.244 1.501 1.943 2.270 2.833 3.2@2 3.425 3.593 3.660 4.133 3.749 4.155 3.895 4.182 4.270 5.544 5.617 4.310 5.669 5.221 5.545 4.077 4.333 6.653 3.048 2.411 2.066 1.942 1.794 1.117
1.893 2.086 2.414 2.742 3.247 3.733 4.409 4.988 5.638 6.292 6.854 7.6Oid 8.045d 8.792 9.904 11.109 12.441 13.596 13.731 14.714 16.062 16.207 17.332 17.714 18.464 19.466 20.583 22.123 24.327 24.467
83.65 84.41 84.81 86.58 88.82 91.28 93.90 102.45 102.45 108.52 110.46 115.77 123.03 120.91 132.80 136.79 139.06 143.57
Liquid 154.68 159.28 159.81 166.52 168.89 175.02 178.77 184.75 194.74 204.98 215.45
4.475 39.554 '3.690 30.872
5.798 39.916 7.622 40.413 !).515 40.572 9.367 41.056 20.256 41.325 10.093 41,805 9.891 42.626 10.581 43.488 10.366 44.405
March, 1961
Low TEMPERATURE THERMODYNAMIC PROPERTIES OF SIXHEPTANES
225.71 10.162 45.341 235.78 9.964 ,46.304 242.38 9.869 46.941 252.15 9.672 47.932 261.73 9.490 48.917
12.82 14.03 15.91 16.46 18.37 19.96 21.37 24.28 25.33 29.05 29.87 34.06 39.50 45.10 50.81 56.10 56.61 61.01 66.61 72.61 78.59 84.53 90.43 90.84 96.71 97.47 102.90 104.54 109.23 112.54 116.12 119.89 120.92 123.46 126.28 129.55 131.19 133.90 138.41 141.11 146.65
9.317 9.151 8.994 8.841
2,4Dimethylpentane Liquid Crystals 160.81 5.780 0.921 1.769 162.71 7.759 1,488 2.182 167.98 8.556 2.291 2.807 171.33 9.492 3.230 2.971 176.93 9.340 2.628 3.632 186.18 9.167 3.777 4.164 195.46 8.984 3.357 4.653 195.71 9.896 4.871 5.592 205.32 10.746 4.572 5.895 205.52 9.706 4.670 7.034 215.13 9.529 4.498 7.263 215.89 10.378 5.340 8.402 224.99 10.192 5.530 9.756 '227.00 11.847 5.666 10.993 230.42 10.104 5.760 12.216 235.09 9.994 4.425 13.289 238.71 11.578 5.850 13.379 240.42 9.905 5.402 14.231 250.16 11.322 5.791 15.296 250.23 9.716 6.214 16.383 260.25 10.318 5.750 17.478 262.14 12.642 6.136 18.603 270.48 10.115 5.750 19.662 272.57 9.250 6.475 19,730 274.63 12,342 6.812 20.730 275.89 10.650 6.779 20.861 277.95 7.626 5.575 21.811 280.48 9.927 7.365 22.090 281.74 9.084 7.076 22.944 285.80 8.053 8.641 23.561 286.44 10.430 6.709 24.258 286.84 12.059 4.933 24.888 290.34 9.738 8.119 25.137 290.74 8.922 7.959 25 639 293.53 7.407 7.846 '26.221 296.77 10.228 9.142 26.964 299.59 8.769 7.513 ,27.343 300.00 9.563 7.403 27.982 301.15 7.819 8.570 29,009 307.09 7.180 7,013 29.776 7.925 ,31.993 Crystals
12.51 14.39 15.05 16.41 17.50 17.86 18.73 20.51 20.70 21.32 23.48 23.94 24.41 27.41
271.13 280.37 289.44 298.36
1.884 1.872 2.202 2.174 2.880 2.771 2.463 2.976 2.915 2.732 2.969 3.567 3.428 4.874
3-Ethylpentane 27.88 28.06 0.866 31.54 1.301 32.15 1.477 33.03 1.862 35.41 2.227 37.83 2.306 39.73 2.581 42.16 3.185 44.61 3.243 47.17 3.444 49.33 4.180 53.16 4.334 53.92 4.493 55.53 5.491 57.16
3.526 4.657 3.791 4.609 5.288 3.925 4.291 4.718 4.371 5.034 5.651 4.417 6.322 4.756 5.973 5.806
49.911 50.880 51.902 52.876
40.556 40.695 41.086 41.356 41.774 42.511 43.268 43.289 44.111 44,136 44.988 45.048 45.922 46.104 46.427 46.872 47.248 47.415 48.384 48.444 49.477 49.638 50.574 50.779 50.987 51.140 51.388 51.672 51.792 52.245 52.314 52.327 52.761 52.772 53.078 53.450 53.758 53.824 53.925 54.596
5.655 5.719 6.847 7.040 7.321 8.051 8.756 9.290 9.952 10.598 11,255 11.806 12.730 12.915 13.280 13.651
61.70 63.18 68.23 69.58 74.63 76.31 80.93 83.19 87.56 90.34 94.49 97.57 101.87 104.85 109.81 112.66 118.18 120.51 126.54 128.00 134.51 135.17 141.71 142.15 146.80
6.365 6.226 6.689 6.583 6.120 6.879 6.475 6.866 6.782 7.450 7.077 7.005 7.701 7.563 8.164 8.052 8.576 7.651 8.149 7.318 7.790 7.029 6.039 7.487 5.142
14.657 14.985 15.992 16.275 17.262 17.577 18.480 18.906 19.706 20.183 20.868 21.382 22.081 22.550 23.349 23.804 24.684 25.062 25.999 26.227 27.249 27.355 28 369 28.417 29.206
Liquid 145.19 153.25 161.20 163.92 165.92 170.00 174.52 176.42 180.11
8.123 8.004 7.890 9 I739 9.647 9.713 11.476 11.369 10.502
40.792' 41.228' 41.670 41,806 41,912 42.195 42.449 42.547 42.828
186.35 190.99 198.87 202.13 211.59 212.87 223.82 224.05 234.05 234.82 236.25 237.27 244.43 246.05 248.18 248.36 254.63 257.07 259.68 259.93 265.07 268.29 271.17 271.69 272.23 275.74 279.30 283.25 283.64 285.09 286.21 289.33 295.48 296.14 296.14 297.66 298.79
12.183 11.251 12.852 11.046 12.587 10.850 10.660 12.327 10.471 11.335 12.080 10.344 10.291 11.126 11.843 11.848 10.121 10.915 10.787 11.597 10.754 11.518 12.195 11.274 13.008 10.579 10.512 11.963 12.632 12.715 10.395 9.538 12.497 12.363 9.435 12.413 9.386
499 43 230 43 548 44 053 44 294 44 951 45 075 45 880 45 901 46 674 46 759 46 847 46 902 47 519 47 657 47 832 47 837 48 385 48 644 48.851 48 872 49 349 49 648 49 894 49 926 49 978 50 312 50 670 51 017 51 051 51 181 51 308 51 628 52 205 52 269 52 287 52 417 52 568
2,2,3-Tri me:thylbut,ane Cryst'als I1 83.57 2.537 19 181 85.79 1.898 27 854 13.08 0.975 1.731 87.43 1.367 41 373 14.34 1.514 2.225 88.25 2.977 27 490 16.32 2.282 2.930 89.28 2.336 20 900 16.89 3.178 3.136 91.58 2.272 21 509 18.75 2.575 3.847 91.86 4.244 21 579 19.99 3.035 4.314 94.04 2.038 22 285 22.16 4.237 5.110 96.63 2.542 23 223 23.99 4.955 5.740 96.82 5.695 23 320 25.93 3.300 6.389 99.12 2.443 24 296 29.22 5.519 7.479d 101.51 2.329 25 713 29.82 4.474 7 . 665d 102.24 5.142 26 278 34.90 5.843 9 . 044d 103.77 2.203 27 498 41.12 6.583 10.185 105.87 1.989 31 240 47.25 5.675 11.337 107.61 1.483 44 805 52.62 5.075 12.305 109.37 2.041 29 966 53.63 4.157 12.500 111.41 2.050 29 658 54.55 4.888 12.643 113.36 6.119 29 677 58.38 5.334 13.327 113.63 2.378 29 766 59.60 5.209 13.546 114.90 3.763 29 836 64.23 6.456 14.403 115.01 3.646 30 291 64.92 5.433 14.544 115.27 3.710 29 609 69.87 4,432 15.444 116.12 2.619 30 066 70.87 6.819 15.644 74.17 4.164 16.317 Crystals I 77.94 3.377 17.177 129.29 7.558 32.673 80.97 2.681 18.040
13. 31. HUFFMAN, 34. E. GROSS,D. W. SCOTTAXD J. P. MCCULLOUGH TABLEI1 (continued) T,
AT6
CsatdC
T,OK."
ATb
Css~o
137, 6D g . 176 33, 522
341. 74
5 ,407 44, 924
9.802 9.512 10.087 9.815 9.5137 9.323 7.968 9,116
34.422 35.403 36,388 37.418 38.434 39.446 40.211 40,457
241.89 242.93
5.396 44.967 6.302 45.088
253.03 255.09 258.69
5.250 46.319 6.110 46.557 6.066 46,916
21135 0.718 2 1 4 2 9 9.645 218, '19 9,577 221, ,j5 9,586
41.244 41.519 41.905 42,385
262.02 270.54 279.77 288.85
7.749 9.296 9.157 8.998
147. 156.30 166.60 176..55 186.24 196.69 203.10 204,,)1
Liquid
47.273 48.187 49,077 50.088
227.!15 0.342 43.161 298.17 9.654 51.015 230.00 7.367 43.439 306.95 7.917 51.913 235.83 6.410 44.139 313.26 4.696 52.610 236.45 5.486 44.175 a !Z'ie,the mean temperature of each heatcapacitv measureAT' is the temperature increment in each measurement. CJnt,fis the heat capacity of the condensed phase ment. under its own pressure. Curvature corrections applied. e Undercooled liquid.
Csatd(liq.) = a a
a
n-Heptaiie 2-Methylhesane 3-Etliylpentane 2,~-L)imc:thylpentane 2,4-l)imt:thylpentane 2,2,3-Triniethylbutane Thc, temperature range in nrhich
+
+
b X lo2
TABLE IV TRIPLEP O I X l ' TEMPEIL~TLRES, €$EATS O F FUSION AXD C R Y O S C o P I C CONSTANTS TT P . , "
n-Hei,tane 2-Methyl hexane 3-Ethylpentane 2,2-Dimethylpen'tanc 2,4-Dimethylpen;ane 2,2,3-Triniethylbutane
OK. 392.53 134.90 154.58 149.43 153.97 248.57
-In (1
- X 9 ) = AAT
(1 X BAT
+ . . .)
(1)
where N Z = A'~*/F. The cryoscopic constants, A = A H m / RT/T.P.( and B = ~/TT.P.- ilCm/2AHm, were calculated from the values of A H m and TT.P.in Table IV and values of ACm obtained from data in Table VI1 (discussed in the following section). Values of A and B are included in Table IV. The impurity values given in Table V were cal-
+
x 104 5 . 7813 c
a x 107 -4.1667 +0.10417 1,6667 - 1.3333 -4.0361
56.582 - 14.490 41.850 -2.6750 2.1531 34.578 $3,2850 0.41562 33.582 0.4340 2.4200 37.649 -4,2300 4.4188 21.854 +9 ,0867 0,23333 ..... ,. the equations represent the observcd heat capacity dat.a m-ithin ahout
The "isothcrmnl" transition in 2,2,3-trimethylbutane was studied b , ~ observing the temperature as a function of fraction transposed (fraction of sample in the form of crystals I) with t1.e results % Transposed 22 48 86 T , Or
