Heat capacities of pent-1-ene (10 K to 320 K), cis-hex-2-ene (10 K to 330 K), non-1-ene (10 K to 400 K), and hexadec-1-ene (10 K to 400 K)

O-386 J. Chem.

Thermo&namics

1990, 22, 1107-l 128

Heat capacities of pent-l -ene (10 K to 320 K), cis-hex-2-ene (10 K to 330 K), non-l -ene (10 K to 400 K), and hexadec-I -ene (10 K to 400 K) anb J. F. MESSERLY,” S. S. TODD,d H. L. FINKE.’ S. H. LEE-BECHTOLD,’ G. B. GUTHRIE,’ W. V. STEELE, R. D. CHIRICO’

and

IIT Research Institute, National Institute jbr Petroleum and Energ? Research, P.O. Box 2128. Bartlesville, OK 74005-2128, U.S.A. i Received

23 May

1990;

in ,final

jbrm

25 June

1990)

Heat capacities and phase-transition enthalpies measured by adiabatic calorimetry are reported for pent-l-ene (10 K to 320 K), cis-hex-2-ene (10 K to 330 K). non-1-ene (10 K to 400 K), and hexadec-l-ene (10 K to 400 K). Entropies and enthalpies relative to the crystals at T -+ 0 are derived. Results are compared with published heat-capacity results for less pure samples of pent-1-ene and hexadec-l-ene.

1. Introduction As part of research projects conducted in this Laboratory and sponsored by the American Petroleum Institute (API project 62) and by the U.S. Bureau of Mines, thermodynamic-property measurements were made on a series of alkenes to provide the experimental foundation for development of estimation methods to predict “Contribution number 318 from the Thermodynamics Research Laboratory at the National Institute for Petroleum and Energy Research. * By acceptance of this article for publication, the publisher recognizes the Government’s (license) rights in any copyright and the Government and its authorized representatives have unrestricted right to reproduce in whole or in part said article under any copyright secured by the publisher. This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency, thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy. completeness. or usefulness of any information, apparatus, product or process disclosed. or represents that its use would not infringe privately owned rights, References herein to any specific commercial product. process, or service by trade name trademark, manufacturer. or otherwise, does not necessarily constitute or imply its endorsement, recommendation. or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the L!nited States Government or any agency thereof. ‘Retired. d Deceased. e Present address: National Archives and Records Administration. Conservation Branch. Washington. DC 20408. U.S.A. ‘To whom correspondence should be addressed.

1108

J. F. MESSERLY

ET .4L.

accurately properties of the myriad alkenes not studied experimentally. Though the heat-capacity experiments reported here were completed in the early 1960s (pent-1-ene and non- 1-ene) and 1970s (cis-hex-2-ene and hexadec- 1-ene). the supporting projects were terminated prior to publication of the results. The results are published now as part of a review of the thermodynamic properties of the alkenes (carbon number 25) sponsored by the National Institute of Standards and Technology.” ’ Heat-capacity studies were published previously for pent-l -ene”’ and hexadec- l-ene.‘3’ The measurements on pent-l -ene were considered unreliable because of the low purity of the sample used and unexplained phase behavior near the triple-point temperature. (*) The published measurements on hexadec- 1-ene were also made on a sample of low purity, and the results implied that the crystal phases were disordered. When high-purity ( > 99.9 moles per cent) samples of pent- 1-ene and hexadec-1-ene became available, the studies reported here were initiated. The derivation of ideal-gas thermodynamic properties for the compounds studied here will be published separately as part of the general review of the thermodynamics of the alkenes.“’

2. Experimental The samples of pent-1-ene, non-1-ene, and cis-hex-2-ene were “API Research Samples” purified as part of API Project 6. (4) The sample of hexadec- l-ene was obtained from API Research Project 58B at the Carnegie-Mellon University, A. J. Streiff, Director. The pent-1-ene, cis-hex-2-ene, and hexadec- 1-ene were designated as “B” samples. The mole percentage impurities estimated by API were (0.18 fO.12). (0.034 f 0.006), (0.24 + 0.18), and (0.26 + 0.12) for pent-l -ene, cis-hex-2-ene, non- 1-ene, and hexadec-1-ene, respectively. The value for cis-hex-2-ene agreed well with that obtained in this research from fractional-melting studies described later. The results of the fractional-melting studies for pent-l -ene, non- 1-ene, and hexadec-1 -ene indicated mole-fraction impurities less than 0.1 per cent. Molar values are reported in terms of the relative atomic masses of 1981”’ and the gas constant R = 8.31451 J. K ~‘. mol ‘, adopted by CODATA.r6’ The platinum resistance thermometers used in these measurements were calibrated by comparison with a standard thermometer whose constants were determined at the National Institute of Standards and Technology (NET), formerly the National Bureau of Standards. All temperatures reported are in terms of the IPTS-68.‘7’ Measurements of mass, time, electric resistance, and potential difference were made in terms of standards traceable to calibrations at NIST. Adiabatic heat-capacity and enthalpy measurements were made with a calorimetric system similar to that described by Huffman and his colleagues.‘8 lo) The four gold-plated copper adiabatic shields were controlled to within 1 mK by electronic controllers with proportional, derivative, and integral actions responding to imbalance signals from (copper-to-constantan) difference thermocouples. The copper calorimetric vessel@ r I’ and the loading and sealing procedures@, ’ ” have been described. All samples were received in sealed ampoules, and were

HEAT

CAPACITIES

OF

FOUR

1109

ALKENES

TABLE 1. Calorimeter and sample characteristics: m is the sample mass; V, is the internal volume of the calorimeter; T,,, is the temperature of the calorimeter when sealed; pEnlis the pressure of the helium and sample when sealed, r is the ratio of the heat capacity of the full calorimeter to that of the empty; T,,, is the highest temperature of the measurements; SC/C is the vaporization correction; and xpre is the mole-fraction impurity used for pre-melting corrections Pent-1-ene

cis-Hex-2-ene

35.58 59.55 273.0 31.2 4.9 3.7 0.073 0.00080

36.58 59.86 273.0 9.3 4.1 3.1 0.061 0.00013

Non-I-ene 37.54 59.55 273.2 4.0 5.4 3.4 0.033 0.00030

Hexadec-

I -ene

35.71 59.86 293.0 8.0 4.3 2.7 0.002 0.00049

transferred to the calorimeters without exposure to air. The sample of pent-1-ene was distilled directly into the calorimeter and sealed under its own vapor pressure. The non-1-ene and cis-hex-Zene samples were vapor-transferred to a volume-measuring bulb and forced into the calorimeters with a small pressure of helium gas. The hexadec-l-ene sample was poured into the volume-measuring bulb in a dry box, sealed on to a vacuum line, outgassed, and forced into the calorimeter with helium gas. The calorimeter characteristics and sealing conditions are given in table 1. The temperature- and energy-measurement systems employed direct-current methods described prevously. (8-1o) Energies were measured to a precision of 0.01 per cent, and temperatures were measured to a precision of 0.0001 K. The energy increments to the filled calorimeter were corrected for enthalpy changes in the empty calorimeter, for the helium exchange gas, and for vaporization of the sample. The correction to the measured energy for the helium exchange gas was negligible at all temperatures for all samples. The sizes of the other two corrections are indicated in table 1. 3. Results Crystallization of the pent-1-ene was initiated by slowly cooling (roughly 0.01 K. s- ‘). The sample invariably supercooled to some extent. A glass was formed on cooling faster than 0.02 K*s-‘. Crystallization began upon reheating to 15 K above the glass-transition temperature (Tg z 70 K). The crystals formed initially were metastable ( TP = 107.8 K). Conversion to the stable crystalline form (7;, = 108.0 K) did not occur until 25 per cent of the sample was melted. This allowed heat-capacity measurements to be made from 11 K to the triple-point temperature for both forms. Complete conversion to the stable crystalline form was accomplished by melting more than 25 per cent of the metastable crystals to initiate the conversion, followed by slow cooling at an effective rate of 0.1 mK . s ‘. The thermal behavior of the non-1-ene sample was closely analogous to that observed for pent-1-ene. A metastable form (I&, = 19 1.6 K) invariably formed

1110

J. F. MESSERLY

ET AL.

0.01 5 rz c g

cr(1) cr(II)

-.-FIGURE crystalline

stable

0.00 stable

170

1. The difference forms of non-1-ene.

175 between

the functions

-180 T/K @~*~‘A$~-A&‘H~T

185

190

for the stable and metastable

initially on cooling. Conversion to the stable form (?;, = 191.9 K) commenced when more than 50 per cent of the metastable crystals were melted. Transformation to the stable form occurred slowly over a 9 d period, while adiabatic conditions were maintained. Measurements from 11 K to the triple-point temperature were made on each form without evidence of transformation. Standard Gibbs energy calculations described later showed that the form stable near the triple-point temperature was metastable below 182 K. The difference between the functions @G for the two crystalline phases are shown in figure 1. Analogous phase behavior was observed previously for hept- l-ene.‘3’ The cis-hex-2-ene and hexadec-1-ene samples showed a single crystalline form in the vicinity of the triple-point temperatures. Complete crystallization for each sample was achieved by slowly cooling the liquid samples at an effective rate of approximately 2 mK . s- I until the sample had crystallized and cooled a minimum of 10 K below the triple-point temperature, followed by heating to partially remelt (20 to 50) per cent of the sample, and immediately cooling again at an effective rate of 2mK.s-‘. The good reproducibility obtained for the enthalpy-of-fusion determinations for these samples shows that for these compounds this approach to obtaining complete crystallization was successful. In subsequent work in this laboratory, far more extensive annealing procedures have been found to be necessary for some materials.‘12. ’ 3’ The hexadec-1-ene showed three crystalline phases as evidenced by a lambda-type transition near 217.7 K and a first-order transition near 249.2 K. Phase conversions

HEAT CAPACITIES

OF FOUR ALKENES

1111

loo -

80 -

300 D T/K FIGURE 2. Heat capacity against temperature for hexadec-l-ene. The vertical lines indicate phasetransition temperatures. The upward-pointing arrows indicate first-order phase transitions.

were accomplished by slow cooling across the phase transitions. Cooling rates ranged from approximately 0.08 mK. s ’ to 2 mK . s ‘. Incomplete conversion was observed for cooling rates greater than 0.3 mK . ssl as evidenced by spontaneous warming within 20 K of the phase-transition temperature. The smooth curve of heat capacity against temperature is shown in figure 2. The triple-point temperatures &, and sample purities were determined from the measurement of the equilibrium melting temperature T(F) as a function of fraction F of the sample in the liquid state. (i4) The results for hexadec-1-ene indicated the presence of a solid-soluble impurity. Published procedures” ‘) were used to derive the mole fraction of impurity, the triple-point temperature, and the effective distribution coefficient for that material. The results for all compounds and crystalline phases studied are summarized in table 2. Experimental molar enthalpies are given in table 3. Corrections for pre-melting caused by impurities were made in these evaluations. Results with the same series number in tables 3 and 4 were taken without interruption of adiabatic conditions. One enthalpy-of-fusion determination for cis-hex-2-ene (series 4) and one for non-1-ene (series 2) were not included in the calculation of the average values. These measurements served as fractional-melting studies and extended over a period of several days with a large associated uncertainty in the heat leak. The series 2 and 3 results for the cr(TII)-to-cr(I1) transition for hexadec-1 -ene were not averaged because the crystals were not converted completely to phase cr(II1) prior to commencement

1112

J. F. MESSERLY

TABLE 2. Melting-study triple-point temperature:

summaries: F is the fraction melted at observed temperature T(F); T& IS the x is the mole-fraction impurity; and K, is the distribution coefficient for the impurity as defined in reference 15

F

F

W)IK Pent-l-ene cr

0.103 0.299 0.496 0.693 0.880

T&K x Kd

107.889 107.969 107.987 107.996 108.ooo

0.055 0.094 0.151 0.245 0.390

TdK

191.912 0.0002 1 0.0

Kd

TABLE

N”

3. Experimental

107.579 107.681 107.702 107.749 107.766

Non-1-ene cr(II) 0.156 0.306 0.511 0.771

191.883 191.899 191.904 191.906 191.908

T(FW

191.501 191.534 191.557 191.576

measurements

0.099 0.245 0.498 0.698 0.899

131.968 132.004 132.018 132.021 132.024

132.030 0.00037 0.0

191.604 0.00014 0.0

enthalpy

F

cis-Hex-2-ene cr

107.797 0.00073 0.0

Non-1-ene WI)

X

W)IK

Pent-I-ene cr(metastable)

108.016 0.00087 0.0

0.119 0.253 0.458 0.622 0.786

ET AL.

Hexadec-1-ene u(I) 0.093 277.338 0.245 277.361 0.498 277.375 0.701 277.381 0.904 277.384 277.396 0.0010 0.13

(R = 8.31451 J. K- ’ mol

r)

Af,sHmd

h*

R,K Pent-l-ene cr to liquid

3 16

9 1

88.292 89.318

6

4

78.618

110.125 115.922 cr(metastable)

1 4 8

2 14

3 6 2

8 3

108.016

911.97 994.18 Average:

713.9 714.2 714.1

707.4 707.4

to liquid

111.316

107.797

1003.01 Average:

118.321 124.499 117.076

cis-Hex-2-ene cr to liquid 138.619 139.637 137.674

132.030

1349.24 1294.57 1345.66 Average:

1067.8 1064.5 e 1067.8 1067.8

163.279 164.982

Non-1-ene cr(I) to liquid 193.662 196.658

191.912

2949.60 2998.30 Average:

2336.3’ 2328.3 2328.3

HEAT

CAPACITIES

OF

TABLE

N‘

6 5 I

Ii

178.568 187.187 173.324

Ill3

T ,r. K

7;

h”

ALKENES

3-continued

cr(I1) 4 5 6

FOUR

to liquid

195.796 198.944 197.556

‘404. I 2402.4 ‘398.9 2401.x

191.604

2784.95 7706.40 2931.12 Average:

217.7

407.24 189.96 1028.99 1102.73 1178.11 Average:

~ 0.9 *’ -7.0’ -0.6 0.3 0.4 0.0

249.2

925.68 2085.04 1580.32 2224.96 2317.17 Average:

459.0 “ 468. I 465.2 464.1 464. I 465.4

217.396

4910.52 5183.84 4903.36 5785.12 5777.04 5508.89 Average:

Hexadec- 1-ene cr(III) to cr(II) 2 3 14 I5 22

1 I 1 I I

217.536 213.436 197.360 194.804 194.657

227.194 217.x75 223.232 222.791 224.441

3 9 II 15 2’

4 I I I 1

246.161 223.688 235.408 222.771 224.402

253.362 254.640 254.X96 256.210 258.605

I 4 5 11 15 22

4 6 I I I I

264.187 264.273 266.273 254.902 256.203 258.573

cr(1) to liquid 279.947 284.860 282.445 283.990 285.472 283.61 I

u(H)

to u(I)

‘I Adiabatic series number. h Number of heating increments. ‘ A,,,,H, is the molar energy input from the initial temperature h A,,,H, is the net molar enthalpy of transition at the transition “This value was not included in the calculation of the average:

7; to the final temperature temperature 7;,,. see text.

3621.7 3618.5 3626.9 3622.5 3616.0 3614.X 3620. I

q.

of measurements (see above). The series 3 enthalpy results were rejected for the cr(lI)to-cr(I) transition in hexadec-1-ene because the measurements extended over a period of several days in an unsuccessful attempt to reach equilibrium in the transition region. The uncertainty in associated heat leaks was large. The experimental molar heat capacities under vapor-saturation pressure C,,,~ m are listed in table 4. The differences between C,., and C,,,, m are insignificant at the highest measured temperatures. Values in table 4 were corrected for effects of sample vaporization into the gas space of the calorimeter. The temperature increments were small enough to obviate the need for corrections for non-linear variation of C,,,., with temperature. The precision of the heat-capacity measurements ranged from

1114

J. F. MESSERLY

TABLE

4. Experimental

N”



14 15 15 15 12 12 15 15 12 15 12 15 12 15 12 15 12 15 12 13 15 12 13

11.301 11.497 12.488 13.683 13.806 14.766 14.929 16.298 16.462 17.999 18.319 19.903 20.192 21.875 22.295 23.995 24.386 26.45 1 26.643 27.303 29.121 29.488 30.638

K

molar

heat capacities

AT K

ET ,4L.

at vapor-saturation

c *a,,mh R

pressure

(R = X.31451 J. K

N ”

CT> K

AT K

13 13 13 13 13 I1 I1 11 16 11 16 11 16 10 11 16 10 3 10 3 10 3

34.362 38.194 42.104 46.28 1 50.844 51.820 57.265 62.839 66.376 68.795 72.997 75.236 79.531 80.552 81.627 85.997 86.878 91.033 93.671 96.393 100.418 101.493

3.7835 3.8720 3.9395 4.4069 4.7109 5.3755 5.5085 5.6358 6.4601 6.2668 6.7799 6.6170 6.2891 6.0192 6.1662 6.6444 6.6269 5.4823 6.9554 5.2375 6.5372 4.9620

21 21 21 21 22 22 22 22 22 22 22 22 22 23 23 23

167.236 176.900 187.403 198.719 202.330 213.429 224.360 235.127 245.725 256.155 266.420 276.520 286.456 289.802 299.428 308.437

‘. mol

cw,mh R

Pent-1-ene 0.942 1 0.9092 1.0394 1.3306 0.5160 1.3035 1.1873 1.5774 1.8501 1.8476 1.7841 1.9483 1.8901 1.9795 2.2834 2.2477 1.8655 2.6548 2.6206 3.0044 2.6766 3.0530 3.6588

0.276 0.286 0.379 0.495 0.510 0.608 0.622 0.779 0.798 0.991 1.029 1.243 1.281 1.516 1.576 1.815 1.871 2.164 2.190 2.282 2.533 2.586 2.740

3.239 3.720 4.179 4.630 5.091 5.188 5.685 6.141 6.415 6.590 6.886 7.040 7.336 7.386 7.480 7.736 7.785 8.018 8.179 8.355 8.695 8.834

liquid 25 25 25 19 19 19 19 17 17 6 6 6 21 21 21 21 21

68.918 70.504 73.109 73.264 76.225 79.683 83.818 104.675 111.021 114.300 120.246 126.154 132.301 140.310 149.239 157.467 159.071

1.1393 2.0888 3.1668 2.7218 3.2003 3.7163 4.5546 6.3675 6.3285 5.9672 5.9291 5.8909 8.0449 7.9819 9.8847 9.8135 9.7837

16.442 16.346 16.249 16.268 16.178 16.070 15.970 15.609 15.547 15.518 15.490 15.473 15.463 15.468 15.499 15.556 15.564

8 9 8 9 8 9 8 9

11.329 12.182 12.345 13.296 13.569 14.564 14.871 15.934

0.9486 1.1177 1.0763 1.1594 1.3566 1.3585 1.2012 1.3529

0.278 0.357 0.371 0.462 0.494 0.590 0.625 0.738

9.7176 9.6166 11.3984 11.2431 Il.1890 11.0219 10.8519 10.6844 10.5157 10.3466 10.1813 10.0176 9.8534 9.703 1 9.5441 8.4671

15.620 15.713 15.848 16.018 16.080 16.279 16.515 16.763 17.027 17.315 17.609 17.911 18.23 1 18.342 18.670 19.037

4.7711 4.2514 5.0053 5.5913 5.1636 5.2059 5.3150 5.5938

5.079 5.369 5.548 5.649 5.796 5.996 6.237 6.440

crcmetastable) 7 5 7 7 5 7 5 7

50.97 1 53.903 55.862 56.991 58.613 60.973 63.857 66.379

’

HEAT

CAPACITIES TABLE

N”


AT K

8

16.281 17.88 1 18.013 19.931 20.33 1 21.932 22.640 23.936 24.987 26.309 27.47 1 29.220 30.050 33.014 36.771 40.979 45.389 49.415 50.120

1.5920 2.5201 1.8610 1.9658 2.3502 2.0028 2.2527 1.9788 2.4198 2.7411 2.5324 3.0573 2.5968 3.3112 4.1887 4.2171 4.5909 4.7165 4.8614

9 8 8 9 8 9 x 9 8 9 X 9 9 9 9 9 5 9

OF FOUR

1115

ALKENES

4-continued

c sat, m h

R 0.785 0.983 0.999 1.250 1.304 1.520 1.615 1.794 1.942 2.121 2.283 2.511 2.628 3.025 3.501 4.012 4.Xil 4.922 4.994

N”

<_T? K

AT K

c ra,. mh

5 7 5 7 5 4 1 5 I 4 7 7 5 1 4 7 7 I 4

69.082 72.192 74.438 78.406 80.2 12 84.894 X4.969 X6.697 87.936 90.452 90.956 9 I.847 93.053 94.08 1 95.142 97.146 98.668 100.201 loo.777

5.1287 6.029 1 5.5827 6.3998 5.9700 5.6989 6.7269 6.9939 6.3088 5.4111 5.6603 7.0229 5.7149 5.9784 5.1683 6.7141 6.6235 6.2660 4.9043

6.646 6.876 1.045 7.328 7.457 7.161 1.769 7.886 7.939 X.126 8.140 x.207 8.291 8.317 x.474 x.533 8.666 8.843 8.040

7 7 7 7 7 5 5 5 5 5 5 I 1 1 1 I 1

38.922 43.087 47.850 53.446 59.496 61.450 66.622 72.123 77.580 X2.986 88.673 91.808 97.620 103.428 109.231 1 15.285 121.041

4.0047 4.3261 5.1989 5.9834 6.1179 4.9855 5.3592 5.6439 5.2707 5.5455 5.8323 5.6792 5.9451 5.6749 5.9348 6.1820 5.440 1

3.918 4.46 1 5.042 5.709 6.352 6.562 7.079 7.595 8.069 x.530 8.972 9.221 9.648 10.073 10.494 10.911 11.387

2 2 2 2 2 2 2 3 2 3 2

23 1.943 242.141 252.638 263.156 213.740 284.157 294.4 19 300.630 304.506 309.787 314.455

R

(is-Hex-2-ene CT 6 7 6 7 6 7 6 7 6 7 6 6 7 7 I I 7 7

I 1.378 11.940 13.757 13.207 14.205 14.648 15.674 16.310 17.267 18.660 18.973 20.700 21.212 23.460 25.953 28.808 31.935 35.231

2 2 2 2 2 2 2 2 2 2 2

129.062 137.174 145.239 153.259 162.026 171.521 180.930 190.336 200.557 211.158 121.615

1.3640 1.2007 I .4863 1.3330 1.4834 1.5488 1.5285 1.7750 1.6996 2.9255 1.7461 1.7194 2.1762 2.3185 2.6712 3.0379 3.2137 3.3778

0.273 0.313 0.38 1 0.426 0.509 0.549 0.664 0.733 0.847 1.023 1.064 1.293 1.357 1.678 2.048 2.466 2.925 3.397 liquid

8.1397 8.0879 8.0487 8.0022 9.5448 9.4646 9.3450 9.762 1 10.6806 10.5372 10.4098

18.531 18.475 18.427 18.403 18.390 18.432 18.517 18.622 18.724 18.904 19.102

10.2876 10.1368 10.9108 10.6848 10.5077 10.3611 10.2142 8.3940 10.0608 9.9186 9.8839

19.334 19.591 19.887 20.214 20.563 20.936 21.31 I 21.515 21.697 21.885 22.090

1116

N”

.I. F. MESSERLY

(T> K

ET AL

AT K

AT K Non-l-em cr(II)

18 19 18 19 18 19 18 19 18 19 18 19 18 19 18 19 18 19 18 19 19 19 19 19 19 16 19

11.527 11.650 12.667 12.768 13.916 14.154 15.286 15.734 16.876 17.425 18.852 19.522 21.117 21.922 23.212 24.393 25.333 27.022 28.079 29.776 32.987 36.728 40.815 45.153 49.704 51.875 54.577

1.1252 I .0807 I .2732 1.2366 1.3180 1.5651 I .4672 1.5901 1.7358 1.7824 2.2257 2.3994 2.3015 2.3861 1.8817 2.5430 2.3565 2.7055 3.1376 2.7965 3.6242 3.8579 4.3165 4.3606 4.7361 5.0468 5.007 1

0.372 0.389 0.499 0.514 0.645 0.678 0.809 0.870 1.023 1.103 1.312 1.413 1.669 1.801 2.017 2.221 2.385 2.678 2.866 3.177 3.760 4.436 5.173 5.9 12 6.674 7.019 7.449

11 11 II 11 12 11 12 11 12 11 12 11 12 12 11 12 11 12 12 12 12 I2

11.378 12.640 13.946 15.325 15.416 16.900 16.958 18.810 18.868 21.001 21.047 23.242 23.274 25.483 25.627 28.081 28.366 3 1.240 34.720 38.470 42.531 46.945

1.1927 1.2728 1.2862 1.4172 1.3887 1.6720 1.6545 2.1416 2.1234 2.2212 2.2059 2.2342 2.224 I 2.1743 2.5122 2.9956 2.9394 3.3003 3.6470 3.8425 4.2659 4.5490

0.354 0.503 0.666 0.847 0.864 1.074 1.084 1.382 1.394 1.756 1.766 2.157 2.163 2.571 2.595 3.051 3.102 3.644 4.296 4.984 5.707 6.453

17 17 17 17 17 5 17 5 15 5 15 5 15 5 15 5 15 5 5 5 5 5 6 5 6 5 5

57.369 62.829 68.505 74.294 80.184 83.833 86.321 91.889 94.049 99.373 101.237 106.763 108.361 114.125 115.474 121.326 122.587 128.831 136.485 144.268 152.186 160.090 161.411 168.152 169.415 175.937 183.479

5.3037 5.6084 5.7285 5.8456 5.9337 8.3760 6.3387 7.7258 7.4046 7.2425 6.9670 7.5401 7.2766 7.1869 6.9504 7.2157 7.2741 7.7976 7.5112 8.059 I 7.7828 8.2112 8.1830 7.9291 7.8471 7.6830 7.4297

7.869 X.653 9.416 IO. 149 IO.836 11.220 11.514 12.068 12.275 12.798 12.969 13.49 1 13.623 14.117 14.228 14.720 14.832 15.328 15.922 16.510 17.113 17.720 17.843 1 x.422 18.509 19.074 19.879

IO 10 10 I 9 I 9 I 9 1 9 I 1 2 2 2 2 2 8 2 8 8

67.202 73.349 79.985 83.461 87.920 90.884 95.175 98.192 102.010 105.427 108.987 112.797 120.001 120.496 128.237 136.08 1 144.045 151.572 152.133 159.314 159.633 166.904

5.8086 6.4873 6.7873 7.3008 7.4899 7.5344 7.02 12 7.0842 6.6516 7.3919 7.3022 7.3543 7.0596 7.9144 7.5795 8.1237 7.8230 7.5506 7.6384 7.9496 7.3914 7.1748

9.42 I 10.190 10.951 11.320 11.779 12.082 12.490 12.778 13.128 13.436 13.744 14.070 14.667 14.702 15.336 15.961 16.597 17.188 17.255 17.865 17.908 18.513

WI)

HEAT

CAPACITIES TABLE

N”

(T) ic

AT Ii

OF

R

50.596 51.723 55.871 6 I ,436

5.1329 4.9949 5.4070 5.7168

7.047 7.228 7.865 8.659

4 6 s 6 5 6 6 6 6

199.413 201.206 202.506 209.013 209.613 217.915 227.990 238.395 248.674 253.968 258.821 263.813 268.834

7.2380 7.4884 7.1266 8.1399 7.0935 9.6812 10.4782 10.3441 10.2155 9.9196 10.0831 9.7791 9.9495

29.258 29.251 29.253 29.257 29.274 29.367 29.590 29.892 30.257 30.463 30.663 30.870 3 1.088

1117

ALKENES

4-continued

cs.r. Fh

10 12 10 10

FOUR

N”

CT)

AT K

c \a,. m h

K

2 13 2 I4

167.122 172.530 174.653 177.11 1

7.6875 6.9319 7.3936 24.2534

18.559 19.050 19.390 19.709

21 21 21 21 22 22 22 22 22 22 22 22

274.320 285.464 296.429 307.2 16 307.825 316.845 327.229 337.452 347.524 358.142 369.295 380.271

11.2354 11.0543 10.8749 10.6976 7.5761 10.4649 10.3017 10.1437 9.9886 11.2385 I I .0559 10.8846

31.340 31.877 32.429 32.992 33.033 33.519 34.095 34.680 35.246 35.85 1 36.479 37.097

89.455 89.695 96.735 101.691 103.690 107.771 111.037 114.735 118.505 121.892 128.869 135.941 143.420 152.524 157.879 163.130 168.249 173.282 175.105 178.230 180.014 183.066 185.297 187.823 188.290 188.697 190.214 190.476 192.497 194.352 194.774

7.6054 7.0194 7.0845 5.6662 7.2816 6.4978 7.4438 7.4387 7.6079 7.1168 6.8644 7.2939 7.6762 5.3956 5.3199 5.1906 5.0802 4.9896 4.9616 4.8924 4.8551 4.7964 5.7153 4.7194 6.1456 7.2163 4.6888 4.6493 4.6319 5.9781 6.1844

19.544 19.598 20.771 21.556 21.883 22.521 23.052 23.586 24.157 24.659 25.645 26.636 27.674 28.801 29.604 30.295 3 1.053 31.853 32.010 32.602 32.848 33.349 33.716 34.246 34.166 34.419 34.502 34.600 35.109 35.381 35.576

R

liquid

21

6 21 6

19 21 I9 21 20 19 21 20 19 21 20 19 20 21 20 19 21 20 19 21 20 21 20 21 20 20 20 20 20 20 20

11.522 I 1.635 12.574 12.961 13.019 13.925 14.267 14.583 15.442 15.827 16.029 17.159 17.403 17.603 19.111 19.178 19.495 21.201 21.346 21.430 23.485 23.581 25.851 25.875 28.315 30.938 34.049 37.733 41.506 45.407 49.901

1.1603 1.0670 1.4145 1.227 I 1.3906 1.6911 1.4337 1.3664 1.5727 1.6734 1.3428 2.0010 1.5869 1.9297 1.9262 2.1060 1.8342 2.2939 2.2296 1.9787 2.2715 2.2247 2.4263 2.3201 2.4786 2.7705 3.4492 3.9203 3.6212 4.1760 4.8078

Hexadec- 1-ene cr(III) 18 0.676 17 0.664 17 0.852 0.869 5 17 0.860 1.055 5 1.117 I7 1.172 5 1.346 17 1.422 5 1.462 5 1.714 5 1.761 5 1.815 15 2.159 15 2.181 15 2.254 15 2.669 15 2.710 14 2.730 15 3.269 14 3.294 15 3.920 14 3.926 15 4.613 13 2 5.373 6.294 12 7.387 14 8.504 I5 9.586 13 10.845 3

1118

J. F. MESSERLY TABLE


N”

K

17 20 17 17 16 16 17 17 16

51.995 55.08 1 57.981 64.133 65.739 71.888 76.154 82.821 84.783

ET AL.

4--continued

c rat. mh k

N”

CT?

5.8582 5.5421 6.0742 6.2438 6.0732 6.2588 6.6034 6.749 1 6.6394

11.396 12.249 13.014 14.500 14.882 16.225 17.062 18.410 18.740

12 14 2 3 2 3 3 2 3

194.856 195.095 196.501 200.877 204.727 206.33 1 211.118 213.151 215.656

4.5895 4.591 I 8.3807 6.0223 8.0715 4.8888 4.6804 8.7806 4.4394

35.486 35.572 35.893 36.848 37.683 38.160 40.233 41.414 42.791

41.601 42.164 42.708 42.825 44.109 45.024

3 3 2 3 3 3

234.262 239.236 240.619 243.920 247.373’ 248.929’

5.0801 4.8725 8.4525 4.4828 2.4244 0.6879

46.062 48.623 50.253 53.736 70.8 258.7

2 5 2 1 2

261.742 263.583 266.934 267.322 271.677

5.3998 5.3354 4.9796 6.2683 4.4102

70.506 72.798 77.935 78.725 88.928

323.049 323.684 325.431 325.744 328.339 330.717 333.604 336.084 338.839 344.29 1 349.527 354.361 359.461 364.808 371.066 380.856

5.2936 9.0825 5.2747 5.0898 5.2682 5.1790 5.2468 5.0555 5.1973 5.1407 5.1245 5.1015 5.0688 5.0366 5.0055 5.6242

60.407 60.468 60.760 60.639 60.922 61.177 61.345 61.608 61.804 62.403 62.885 63.422 63.891 64.441 65.094 66.187

AT K

K

AT K

(‘w. rnh R

u(H)

3 2 3 14 3 2

220.156 222.365 224.682 225.227 229.322 231.791

4.5732 9.6586 4.4806 3.9787 4.8067 9.1995

3 3 1 2 5 1

249.333’ 251.378’ 254.479 256.222 258.068 260.738

0.1208 3.9686 5.6222 5.6382 5.6512 6.903 1

1 4 1 4 25 25 6 4 6 25 6 25 4 22 25 22

283.930 288.840 291.864 296.715 296.820 301.527 301.918 305.288 306.813 306.964 311.683 312.347 314.541 315.569 317.755 320.533

7.9586 7.9067 7.9037 7.8414 3.9323 5.4715 4.9003 9.3016 4.8816 5.3972 4.8518 5.3604 9.1952 4.5969 5.2820 5.3299

cd) 1791.0 91.3 67.016 67.075 67.745 69.705

liquid 57.668 57.873 58.055 58.336 58.343 58.687 58.664 58.951 59.08 1 59.059 59.470 59.509 59.694 59.773 59.912 60.266

25 4 24 22 25 24 25 23 25 25 25 25 25 25 25 25

‘Adiabatic series number. b Average heat capacity for a temperature increment of AT with a mean temperature (T). ‘Thermal equilibrium was not reached for the average heat-capacity value listed at this temperature. These results were used to estimate 7;,, only.

HEAT

1%

CAPACITIES

OF

205

FOUR

ALKENES

215

225

T/K FIGURE hexadec-I-ene.

3. Experimental average heat capacities in the cr(III)-to-cr(I1) 0, Series 2; 0. series 3; A, series 14; 0, series 15: A. series 22.

transition

region

for

approximately 3 per cent at 11 K to 0.2 per cent near 20 K and improved gradually to less than 0.1 per cent above 100 K, except near phase transitions where equilibration times were long. The heat capacities in table 4 were not corrected for pre-melting, but from the provided temperature increments an independent calculation can be made. Details of the heat-capacity measurements in the solid-state transition regions for hexadec-1-ene are shown in figures 3 and 4. The temperature of the cr(II)-to-cr(1) transition: (249.2kO.l) K, was estimated from the results of series 3. The series 3 results are not shown in the figure, but are included in table 4. Equilibrium was reached too slowly to allow accurate calculation of heat capacities from the results of series 3. The curves were drawn to be consistent with the measured heat capacities of table 4 and the enthalpies listed in table 3. Heat-capacity values sufficient to define the curves are included in table 5. Results of least-squares fits of the Debye heat-capacity equation to values between 13 K and 19 K were used to calculate heat capacities below 13 K. Values of the derived Debye characteristic temperatures 0 and number N of degrees of freedom were as follows: pent-1-ene (stable crystals), 0 = 125.8 K with N = 5.16; pent-1-ene (metastable crystals), 0 = 127.6 K with N = 5.38; cis-hex-2-ene, 0 = 133.2 K with N = 5.60; non-1-ene (cr(II)}, 0 = 125.1 K with N = 6.45; non-1-ene {(cr(l)j, 0 = 13 1.4 K with N = 7.22; hexadec-1-ene, 0 = 110.9 K with N = 7.51.

J. F. MESSERLY

ET AL.

T/K FIGURE 4. Experimental average heat capacities in the cr(II)-to-cr(I) transition region for hexadec-1-ene. 0. Series 1; 0. series 2; 0, series 3; A, series 5; n . series 11; A, series 14: 0. series 15: x , series 22. The series 9 result is omitted for clarity. It is nearly identical with that of series 15.

Condensed-phase entropies and enthalpies relative to those of the crystals at T -+ 0 for the solid and liquid phases under vapor-saturation pressure are listed in table 5. These were derived by integration of the smoothed heat capacities corrected for pre-melting, together with the entropies and enthalpies of transition and fusion. The heat capacities were smoothed with cubic-spline functions by least-squares fits to six points at a time and by requiring continuity in value, slope, and curvature at the junction of successive cubic functions. Due to limitations in the spline-function procedure, some acceptable values from table 4 were not included in the fit, while in other regions graphical values were introduced to ensure that the second derivative of the heat capacity with respect to temperature was a smooth function of temperature. Pre-melting corrections were made according to standard methods for a solid-insoluble impurity and the mole-fraction impurity values shown in table 1.

4. Discussion Heat capacities for pent-l-ene (12 K to 295 K),‘2’ and hexadec-1-ene (11 K to 304 K),‘3’ were reported previously on materials of lower purity than those used in the present studies. The heat-capacity measurements reported here for non- 1-ene and cis-hex-2-ene are the first reported in the literature for these compounds.

HEAT TABLE

5. Molar

thermodynamic

CAPACITIES functions

OF

FOUR

at vapor-saturation

1121

ALKENES pressure

(R = 8.31451 J. Km ’ mol

C sat. m R

T K

g, R

Wf, RT

Pent- I -ene cr 10.000 12.000 14.000 16.000 18.000 20.000 25.ooo 3o.OcG 35.000

0.201 0.343 0.526 0.745 0.991 1.255 1.959 2.654 3.321

0.067 0.116 0.182 0.266 0.368 0.486 0.841 1.260 1.720

0.050 0.087 0.136 0.198 0.272 0.357 0.607 0.890 1.190

70.ooo” X0.000 90.000 100.000 107.797 108.016 110.000 120.000 130.000 140.000 15o.ooo 16O.ooO 170.000 180.000 I90.000

16.379 16.062 15.827 15.662 15.576 15.574 15.556 15.491 15.465 15.467 15.505 15.571 15.644 15.750 15.884

8.243 10.408 12.286 13.944 15.117 15.148 15.432 16.782 18.02 1 19.167 20.235 21.238 22.184 23.081 23.936

9.013 9.913 10.582 11.098 I 1.425 11.433 Il.508 11.842 12.122 12.360 12.569 12.754 12.922 13.076 13.220

IO.000 12.ooo 14.000 16.000 18.000 20.000 25.oca 30.000 35.000

0.201 0.344 0.528 0.751 0.998 1.258 1.941 2.618 3.280

0.073 0.122 0.188 0.273 0.375 0.494 0.848 1.262 1.716

0.165 0.182 0.218 0.270 0.337 0.416 0.653 0.924 1.214

40.000 45.000 50.000 60.000 70.000 80.000 90.000 1oo.coo 108.016”

3.936 4.496 5.010 5.912 6.669 7.360 7.933 8.480 8.895

2.204 2.700 3.201 4.197 5.167 6.103 7.003 7.868 8.538

I.496 1.799 2.094 2.658 3.178 3.658 4.102 4.513 4.823

16.040 16.215 16.417 16.643 16.88’ 17.143 17.423 17.714 18.021 18.348 18.627 18.696 19.097 19.505

24.754 25.541 26.300 27.035 27.748 28.442 29.120 29.783 30.433 31.071 31.583 31.698 32.318 32.93 I

13.357 13.4x9 13.617 13.744 13.870 13.995 14.122 14.249 14.378 14.510 14.618 14.643 14.780 14.992

3.895 4.459 4.982 5.914 6.709 7.428 8.050 8.673 9.170

2.194 2.686 3.183 4.176 5.149 6.093 7.005 7.884 8.554

I.51 I I .X08 2.099 2.660 3.183 3.669 4. I22 4.546 4.862

5.303 6.407 7.400 8.277 9.077 9.821 10.541 I 1.248 12.022 12.182

3.207 4.274 5.338 6.385 7.406 8.402 9.372 10.319 11.250 11.437

2.127 2.750 3.345 3.908 4.438 4.940 5.417 5.x73 6.316 6.405

liquid 2oo.ooo 210.000 22o.tMX.l 230.000 240.000 250.000 360.000 270.000 280.000 ‘90.000 298.150 300.c00 31O.OflO” 320.000 ’

cr(metastable1 40.000 45.000 50.000 60.000 7o.OOCl 80.000 90.000 100.000 107.797”

cis-Hex-2-ene cr 10.000 12.000 14.000 16.000 18.OtXI 20.000 25.ooo 30.000 35.000 40.004l 45.000

0.184 0.316 0.489 0.699 0.938 I.202 1.906 2.642 3.365 4.062 4.698

0.062 0.106 0.167 0.246 0.342 0.454 0.795 1.208 1.670 2.165 2.681

0.046 0.080 0.125 0.184 0.254 0.335 0.577 0.860 1.166 1.485 1.807

50.000 60.000 70.000 80.000 9o.OQo lOO.ooO 110.000 I20000 130.000 y 132.030”

’1

1122

J. F. MESSERLY TABLE T K

C wt. m R

A&S; R

A%,

17.751 19.238 19.525 20.608 21.880 23.067 24.182 25.238 26.241 27.199 28.116 28.998

14.085 14.429 14.492 14.719 14.967 15.181 15.371 15.542 15.701 15.850 15.990 16.125

ET Al.

S~~mttinued

RT

T K

c cat,m R

230.000 240.000 250.000 260.000 270.000 280.000 290.000 298.150 300.000 310.000 320.000” 330.000”

19.288 19.535 19.810 20.113 20.437 20.785 21.148 21.452 21.523 21.912 22.315 22.748

29.851 30.677 31.480 32.262 33.028 33.777 34.513 35.103 35.236 35.948 36.650 37.343

16.258 16.389 16.521 16.653 16.787 16.923 17.063 17.179 17.205 17.351 17.500 17.652

80.000 90.000 100.000 110.000 120.000 13o.Oco 140.000 150.000 160.000 170.000 180.000 182.000 190.000 o 191.604“

10.817 11.884 12.858 13.769 14.608 15.417 16.184 16.938 17.720 18.533 19.364 19.532 20.2 12 20.350

8.099 9.437 10.740 12.009 13.243 14.444 15.615 16.757 17.875 18.974 20.057 20.27 I 21.126 11.297

4.986 5.694 6.362 6.995 7.595 8.166 8.711 9.234 9.740 10.233 10.717 10.813 11.195 I I.271

80.000 90.000 100.000 110.000 12o.ooo 130.000 140.000 150.000 160.000 170.000 180.000” 182.000 a 190.000 ‘l 191.912”

10.952 11.992 12.945 13.829 14.665 15.474 16.269 17.073 17.913 18.827 19.853 20.068 20.968 ‘1.192

8.382 9.732 11.046 12.32 1 13.561 14.767 15.943 17.092 18.221 19.334 20.438 20.659 21.541 21.752

5.684 6.328 6.942 7.529 8.089 8.626 9.144 9.645 10.136 10.619 Il.104 II.201 1 I.593 I 1.687

298.150 300.000 310.000 320.000 330.000

32.517 32.613 33.143 33.692 34.253

47.212 47.414 48.492 49.553 50.598

26.155 26.195 26.410 26.629 ‘6.852

ArS 0 m R

RT

liquid 120.000” 130.000 132.030 140.000 150.000 160.000 170.000 180.000 19o.ooo 200.000 210.000 220.000

18.617 18.524 18.509 18.456 18.410 18.391 18.422 18.507 18.616 18.721 18.881 19.070

Non- I -ene h cr(II) lO.ooo 12.ooo 14.000 16.000 18.000 20.000 25.000 30.000 35.OaI 40.000 45.000 50.000 60.000 70.000

0.253 0.427 0.649 0.903 1.184 1.490 2.326 3.217 4.124 5.027 5.888 6.722 8.254 9.610

0.085 0.145 0.227 0.330 0.453 0.593 1.014 1.516 2.080 2.690 3.332 3.996 5.360 6.736

0.064 0.109 0.170 0.245 0.334 0.434 0.727 1.067 1.439 1.831 2.235 2.642 3.452 4.237

10.000 12.000 14.Oca 16.000 18.000 2o.ooo 25.ooO 30.000 35.000 40.000 45.000 50.000 60.000 70.000

0.256 0.436 0.667 0.944 1.253 1.583 2.482 3.411 4.347 5.260 6.128 6.953 8.460 9.778

0.080 0.142 0.226 0.333 0.461 0.610 1.059 I .593 2.189 2.830 3.500 4.189 5.593 6.998

4.450 3.765 3.306 2.993 2.782 2.646 2.522 2.592 2.776 3.030 3.326 3.648 4.328 5.014

191.604” 191.912” 200.000 210.000 220.000

29.328 29.325 29.259 29.276 29.406

33.837 33.885 35.093 36.521 37.885

WI)

liquid 23.811 23.820 24.04 1 24.289 24.518

HEAT

CAPACITIES TABLE

T K 230.000 240.000 250.000 260.000 270.000 280.000 290.000

C Sal.m R 29.642 29.945 30.308 30.711 31.141 31.609 32.103

A&S;;, R 39.197 40.465 41.695 42.891 44.058 45.199 46.317

OF

FOUR

1123

ALKENES

5-continued c Eat.m R

Lips,

34.823 35.387 35.955 36.519 37.082 37.643 38.203

5 1.629 52.647 53.65 1 54.644 55.626 56.596 57.556

27.078 27.307 27.540 27.775 28.0 12 28.252 28.494

140.000 150.000 16O.ooO 170.000 180.000 185.000 190.000 195.000 2oo.ooo 202.ooo 204.000 206.000 208.ooO 210.000 212mO 214.000 215.000 216.000” 2 17.000 ” 2 17.700 o

27.204 28.48 1 29.883 31.330 32.866 33.706 34.647 35.576 36.555 37.013 37.536 38.144 38.857 39.702 40.646 41.693 42.419 43.477 45.102 46.749

25.622 27.543 29.426 3 1.279 33.114 34.025 34.937 35.849 36.761 37.127 37.495 37.864 38.236 38.61 1 38.992 39.378 39.574 39.774 39.978 40. I26

14.391 15.288 16.156 17.005 17.x44 18.261 18.680 19.101 19.525 19.696 19.868 20.042 20.220 20.401 20.588 20.780 20.879 20.98 I ‘1.088 21.167

236.000 238.000 240.000 242.ooO 744.ooa 246.000” 248.000” 249.000 o 249.200 o

46.827 47.999 49.484 51.399 53.877 57.070 61.149 63.580 64.100

43.636 44.036 44.444 44.862 45.295 45.747 46.225 46.476 46.527

‘2.902 23.107 23.32 I 23.545 ‘3.783 ‘4.040 24.322 24.475 24.506

264.000 266.000 268.000 270.000 272.000” 274.000 ‘l 276.000” 277.396”

73.063 76.033 79.573 83.680 88.350 93.579 99.362 103.725

52.343 52.905 53.488 54.094 54.729 55.395 56.096 56.608

28.733 29.077 29.440 29.826 30.239 30.682 31.158 31.512

A;H; RT

T K

24.736 24.946 25.153 25.359 25.565 25.773 25.982

340.000 350.000 360.000 370.000 380.000 390.000” 400.000 lJ

R

A,‘H; RT

Hexadec-1-ene cr(III) 10.000 12.000 14.000 16.000 18.000 20.000 25mo 30.000 35.000 40.000 45.000 50.000 60.000 7omO X0.040 90.000 lomoo 110.000 120.000 13o.ooo

0.424 0.709 1.064 1.465 1.x97 2.374 3.683 5.099 6.576 8.062 9.477 10.871 13.522 15.828 17.826 19.639 21.298 22.865 24.379 25.804

0.137 0.239 0.314 0.542 0.739 0.963 1.630 2.426 3.322 4.298 5.330 6.401 8.621 10.883 13.128 15.335 17.49 1 19.595 21.650 23.658

0.103 0.179 0.280 0.402 0.544 0.703 1.165 1.702 2.292 2.921 3.572 4.232 5.563 6.868 8.115 9.297 10.415 I 1.476 12.489 13.459

217.700” 218.0GOY 220.000 222.000 224.000 226.000 228mO 230.000 232.000 234.000

41.081 41.145 41.581 42.038 42.532 43.08 1 43.690 44.350 45.064 45.873

40.126 40.182 40.560 40.938 41.318 4 1.698 42.080 42.465 42.852 43.242

21.168 21.195 21.378 21.562 21.741 21.934 22.122 22.312 22.505 22.701

249.200’ 250.000 * 252.000” 254.000 256.000 258SXKI 260.000 262.000

69.225 68.600 67.46 I 66.920 66.975 67.621 68.853 70.669

48.395 48.616 49.157 49.688 50.2 13 50.736 51.263 51.797

26.374 26.510 26.839 27.156 27.467 27.775 28.086 28.404

U(H)

u(1)

1124

J. F. MESSERLY TABLE T K

h R

A$;;, R

A;H;n RT

69.658 70.195 72.219 73.832 74.194 76.126 78.022 79.886

44.563 44.682 45.131 45.488 45.568 45.999 46.428 46.857

E7’ .41,

5-continurd T K

C iat. m R

ASS 0 m R

61.976 62.940 63.946 64.996 66.089 67.224 68.402

81.723 83.533 85.320 87.086 X8.834 90.565 92.282

liquid 277.396” 280.000” 290.000 298.150 3Oo.ooo 310.000 320.000 330.000

57.400 57.486 57.939 58.432 58.557 59.307 60.151 61.052

“Values at this temperature were calculated b For non-1-ene, cr(II) is the stable crystalline from 182 K to ‘&,.

34o.OOil 350.000 360.000 370.000 380.000 390.000 a 400.000”

47.288 47.721 48.158 48.599 49.045 49.496 49.954

with graphically extrapolated heat capacities. form below 182 K, and cr(I) is the stable crystalline

form

In the earlier work on pent-1-ene by Todd et al., (‘) the existence of two crystalline forms was not recognized. This was most probably due to the lower purity of the sample (roughly 99.5 moles per cent) relative to that used in the present study (99.91 moles per cent). Todd et ~1.‘~’ were unable to reconcile their melting-study results with independent checks of the melting temperature and purity. By hindsight, it

l/F FIGURE 5. Fractional 0, metastable crystalline

melting-study results for pent-1-ene. 0, Stable form (this research); x , Todd et a/.‘*’

crystalline

form

(this research);

HEAT

CAPACITIES

OF

FOUR

1125

ALKENES

0 l

0 l

8”

l o 000 80 00

O 0

0 0

0

l

tooa

0

0, 0 0

0

08

0

@ B

0 0”

0 o” 0

1.5 0

O

0

20

0

40

60

80

I00

T/K FIGURE 6. Percentage deviations lO*WJC, of the heat-capacities pent-1-ene of 0. this research; and 0, those measured by Todd et al..” stable phase measured in this research.

of the metastable phase of from the heat capacity of the

appears that their sample was transforming from the metastable to the stable crystalline form during their melting studies. Figure 5 shows the melting-study results for pent-1-ene obtained by Todd and colleagues together with the results of the present study. It is seen that the values obtained in the early work at low fractions melted can be reasonably extrapolated to the 7& for the metastable form. At higher fractions melted, the earlier results approach those found in the present study for the stable crystalline form. The original values used in the earlier study ‘16) show evidence for phase conversion (i.e. spontaneous warming) in the melting studies for low fractions melted. This implies that the measurements made on the crystalline phase by Todd and co11eagues’2’ were probably for the metastable phase. Figure 6 shows the deviations of the heat-capacity of the metastable phase and those measured by Todd et al., from the heat capacity of the stable phase measured in this research. Though similarities exist between the results of Todd et al. and those for the metastable form, the comparison is obscured by the high impurity level in the pent-1-ene used in the earlier study. Figure 7 shows the deviations of the liquid-phase heat capacities measured by Todd et al. (converted to IPTS-68) from those of this research. The differences are easily within the combined uncertainties of the two studies. Liquid heat-capacity

1126

J. F. MESSERLY

ET AL.

FIGURE 7. Percentage deviations 1026C~C, of literature this research. 0, pent-l-ene;‘2’ 0, hexadec-1-enc.@)

liquid-phase

heat-capacities

from

those of

measurements are far less sensitive to impurities generally than corresponding crystalline-phase studies. Heat-capacity studies of hexadec-1-ene by McCullough et &‘3’ were made on a sample of relatively low purity (98.7 moles per cent) compared with that of the present study (99.9 moles per cent). The first-order transition near 249.2 K was broadened considerably in the earlier study, while the lambda-type transition near 217.7 K was obscured almost entirely. There is a slight excess heat capacity near 215 K in the earlier results, but nothing to suggest a lambda transition. Figure 8 shows the deviations of the smoothed heat capacities for the crystalline phases reported by McCullough et al. (3) from the results reported here. Differences are typically about 1 per cent. The enthalpies across the first-order cr(II)-to-cr(1) and cr(I)-to-liquid transitions were approximately (0.6 to 0.7) per cent lower, respectively, than the corresponding values obtained in this research. Liquid-phase heat-capacity differences are shown in figure 7. The differences are much smaller than those found for the crystalline phases, as was observed for the pent-l-ene results. For both pent-1-ene and hexadec-1-ene, higher crystal-phase heat capacities were counter-balanced by lower phase-transition enthalpies, resulting in small differences in the calculated liquid-phase entropies for the two studies. This was in spite of the lower purity of the earlier samples. The liquid-phase entropies at 300 K are (0.02 and 0.14) per cent higher in the present study for pent-1-ene and hexadec-1-ene, respectively.

HEAT

CAPACITIES

OF FOUR

1127

ALKENES 0

cr(III)

,-

cr(II)

cr(I)

0 00 0000

03 0

00

l-

0 0 00

o-

0

000

0 0

” 0

u

0 ,

0

i-

C

IO

n. 50

100

150

200

1

T/K FIGURE 8. Percentage deviations hexadec-l-em measured by McCullough solid-state phase-transition temperatures,

lO%C,/C, of the heat-capacities of the crystalline phases of et al. 13) from those of this research. The vertical lines indicate

The experimental portion of this research was funded by the U.S. Bureau of Mines and the American Petroleum Institute under Project 62. Preparation of this manuscript and part of the analysis of results were funded by the National Institute of Standards and Technology under Grant No. 60NANB9D0988. The authors acknowledge the assistance of L. A. Tharp with the heat-capacity measurements on non- 1-enc. REFERENCES I. Steele. W. V.; Chirico, R. D. J. Phys. Chem. ReJ Datu to be submitted. ’ Todd. S. S.: Oliver, G. D.; Huffman, H. M. J. Am. Chem. Sot. 1947, 69, I5 19. ? McCullough. J. P.; Finke. H. L.; Gross, M. E.: Messerly. J. F.: Waddington, G. J. Phys. Chem. 1957, 61. 289. 4. Rossini, F. D.; Mair. B. J.; Streiff. A. J. Hydrocarbonsfrom Perroleum (An Account ofrhe Work of the American Petroleum Institute Project 6). American Chemical Society Monograph Series. Reinhold: New York. 1953. 5. Pure Appl. Chem. 1983, 55. 1101. 6. Cohen, E. R.; Taylor, B. N. J. Phys. Chem. Ref. Duta 1988, 17. 1795. I. Metrologiu 1969, 5, 35. X. Huffman. H. M. Chem. Rev. 1947, 40, 1. 0. Ruehwein. R. A.; Huffman, H. M. J. Am. Chem. Sot. 1943, 65. 1920. IO. Scott, D. W.: Douslin. D. R.; Gross, M. E.; Oliver, G. D.: Huffman. H. M. J. Am. Chem. .%K. 1952, 14. 883. I I. Messerly. J. F.: Finke. H. L.: Good, W. D.: Gammon, B. E. J. Cham. Them~odynan~ics 1988, 30. 485.

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12. Chirico, R. D.: Hossenlopp, I. A.: Nguyen. A.; Stcelc. W. V.: Gammon. B. F. ./. (‘/I~~,I. Thermodynumics 1989. 2 I, 179. 13. Steele, W. V.: Chirico. R. D.: Hossenlopp. I. A.; Nguyen. A.; Smith. N. K.: Gammon. B. E. .I. (‘/~cvrt. Thrrmo+m7~ics 1989, 2 I. 8 I. 14. McCullough, J. P.: Waddington, G. A~ILI/. Chmr. ,-lc,rrr 1957. 17. X0. 15. Mastrangelo. S. V. R.; Dornte. R. W. J. Anl. C/tent. Sot. 1955, 77. 6200. 16. Unpublished. Notebooks listing all the “raw” results of experimental measurements on all compounds studied in the Thermodynamics Research Laboratory since 1945 arc available for consultation at NIPER.