Melting Point, Enthalpy of Fusion, and Heat Capacity Measurements of

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

pubs.acs.org/jced

Melting Point, Enthalpy of Fusion, and Heat Capacity Measurements of Several Polyfunctional, Industrially Important Compounds by Differential Scanning Calorimetry Joseph W. Hogge, Emily A. Long, Michael L. Christian, Andrew D. Fankhauser, Nicole L. Quist, Deborah M. Rice, Wade V. Wilding, and Thomas A. Knotts, IV* Department of Chemical Engineering, Brigham Young University, Provo, Utah 84602, United States S Supporting Information *

ABSTRACT: The present paper reports a differential scanning calorimetry (DSC) study of 19 industrially important compounds that lacked key experimental data in their respective two-phase vapor liquid regions. The compounds are o-tolualdehyde (CAS 529-20-4), m-tolualdehyde (CAS 620-23-5), p-tolualdehyde (CAS 104-87-0), 3-methylbenzyl alcohol (CAS 587-03-1), p-toluic acid (CAS 99-94-5), 1phenyl-1-propanol (CAS 93-54-9), 1-phenyl-2-propanol (CAS 698-87-3), 2-phenyl-1-propanol (CAS 1123-85-9), 2-isopropylphenol (CAS 88-69-7), 2,5-dimethylfuran (CAS 625-86-5), 5-methylfurfural (CAS 620-02-0), phenyl acetate (CAS 12279-2), ethyl 2-phenylacetate (CAS 101-97-3), n-hexylcyclohexane (CAS 4292-75-5), 6-undecanone (CAS 927-49-1), 1H-perfluorooctane (CAS 335-65-9), 2,6-dimethoxyphenol (CAS 91-101), trans-isoeugenol (CAS 5932-68-3), and 1-propoxy-2-propanol (CAS 1569-01-3). New experimental melting temperatures, enthalpies of fusion, glass transition temperatures, and heat capacities of the liquid compounds as a function of temperature are reported with a comparison to similar compounds.

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INTRODUCTION

6-undecanone, and trans-isoeugenol. The data for p-tolualdehyde range from 320.15 to 512.15 K, while the data for 6-undecanone only differ by several kelvins. The data for trans-isoeugenol span 8 K, including room temperature. Only one melting point was found in the literature for 2-phenyl-1-propanol, 2-isopropylphenol, and ethyl 2-phenylacetate. • Enthalpy of fusion: p-Toluic acid has experimental enthalpy of fusion data, which range from 165 to 208 J g−1, and 6-undecanone has one experimental enthalpy of fusion data at 169 J g−1. • Liquid heat capacity: Ethyl 2-phenylacetate, 2,5-dimethylfuran, and p-toluic acid each have one liquid heat capacity experimental data point. 1H-perfluorooctane has a set of liquid heat capacity data from 293.15 to 323.15 K, and 1-propoxy-2-propanol has a set of data from 275.15 to 339.15 K. These compounds were selected for measurement since liquid heat capacities were generally unknown. New melting point and heat of fusion measurements for these compounds

Many chemical processes operate at the saturation curve of the involved compounds including distillation, condensation, and boiling. Optimal design of such operations requires accurate, pure-component, thermodynamic data describing the physical phenomena. This work reports the results of DSC experiments performed on 19 industrially important compounds to determine melting temperature, enthalpy of fusion, and liquid heat capacity. The compounds studied are members of the DIPPR database,1 which selects compounds based on the needs of leading industrial companies (url: https://www.aiche.org/ dippr) in fields such as energy, pharmaceuticals, chemicals, semiconductors, oil and gas, and risk management. The 19 compounds studied in this work are listed in Table 1. Few experimental results exist in the literature for these compounds. For reference, these data are listed in the tables of the Supporting Information where each table is grouped by property. Table S1 contains the existing data for melting point and enthalpy of fusion, and Table S2 shows existing data for liquid heat capacity. A summary and analysis of the existing data appear below. • Melting point: Extensive melting point data exist for 2,6dimethoxyphenol and p-toluic acid. Two of these are 100 K apart for p-toluic acid, while the data for 2,6dimethoxyphenol differ by 4 K at most. Several melting point data exist for p-tolualdehyde, n-hexylcyclohexane, © XXXX American Chemical Society

Special Issue: Emerging Investigators Received: November 22, 2017 Accepted: April 20, 2018

A

DOI: 10.1021/acs.jced.7b01026 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. List of Compounds Studied and Their Purities Measured by Gas Chromatography compound

CASRN

MW

supplier

supplier purity

o-tolualdehyde m-tolualdehyde p-tolualdehyde 3-methylbenzyl alcohol p-toluic acid 1-phenyl-1-propanol 1-phenyl-2-propanol 2-phenyl-1-propanol 2-isopropylphenol 2,5-dimethylfuran 5-methylfurfural phenyl acetate ethyl 2-phenylacetate n-hexylcyclohexane 6-undecanone 1H-perfluorooctane 2,6-dimethoxyphenol trans-isoeugenol 1-propoxy-2-propanol

529-20-4 620-23-5 104-87-0 587-03-1 99-94-5 93-54-9 698-87-3 1123-85-9 88-69-7 625-86-5 620-02-0 122-79-2 101-97-3 4292-75-5 927-49-1 335-65-9 91-10-1 5932-68-3 1569-01-3

120.15 120.15 120.15 122.17 136.15 136.19 136.19 136.19 136.19 96.13 110.11 136.15 164.20 168.32 170.29 420.07 154.17 164.20 118.18

Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich TCI America TCI America TCI America TCI America Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich TCI America Sigma-Aldrich Aldrich Sigma-Aldrich Sigma-Aldrich Sigma-Aldrich

98.9% 98.9% 98.8% 98.9% 99.5% 99.4% 99.9% 99.8% 99% 99.8% 99.5% 99.8% 99.8% 98.6% 98.6% 99.9% 99.1% cis+trans: 99.3% 99.8%

main impurity

98.3%

m-, and p-tolualdehyde

99.7% 98.9% 99.8% 99.98% 99.7% 99.2%

benzylalcohol 2,2-dimethoxypropane propylbenzene 1,2-ethanediol-1,2-diphenyl 2-cyclohexyl-1-propanol m-, and p- isopropylphenol

99.5%

5-methyl-2(3H)furanone

97.9%

3-methylpentylcyclohexane

trans: >98.5% 98.6%

comparing melting points and enthalpies of fusion of six wellknown compounds to that in the literature.1 The melting temperatures and enthalpies of fusion were determined graphically in accordance with ASTM E793-06 and ASTM E794-06, respectively, using TA Instruments Universal Analysis software, and the melting points were given as the onset temperatures since none of the compounds acted like polymers. The MDSC heat capacity was calibrated using toluene and naphthalene with ASTM standard E2716-09. The modulation amplitude was decreased from 1 to 0.5 K and the modulation period increased from 100 to 180 s to accommodate the slow thermal reaction of the liquid samples. Additionally, the isothermal time was increased from 20 to 30 min to allow the heat capacity measurement to equilibrate. (These changes are in accordance with the ASTM standard.) Toluene was used to calibrate below 363 K, and naphthalene was used to calibrate 363 to 473 Kbelow the normal boiling points of each compound. The low temperature calibration was verified by measuring the heat capacity of n-heptane at 248.15, 298.15, and 348.15 K. This gave a bias of −0.05% with an average 95% confidence interval of 1.59%. The high temperature calibration was verified by measuring the heat capacity of sapphire at 373.15, 413.15, 453.15, and 473.15 K. This gave a bias of −0.34% with an average 95% confidence interval of 1.19%. The average 95% confidence intervals for both the low and high temperature verifications were within the 3.2% mean repeatability value given in ASTM 2716-09. A glass transition was observed for several of the compounds. In these cases, ASTM standard E1356-08 was followed using a 2 °C/min heating rate. Since these compounds have low molecular weights compared to polymers, and the measured glass transition temperatures were subambient, it is assumed that no other reactions occurred. Experimental Design and Uncertainties. On the basis of the stated purities (see Table 1), and the calibration/ verification tests described in the previous section, the process uncertainty in melting point and glass transition temperature measurements were determined to be ±1.0 K each, and the process uncertainty in the enthalpy of fusion measurements was determined to be ±5 J g−1. These uncertainties were found by

can also serve to resolve the differences discussed in the literature.

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measured purity

EXPERIMENTAL METHODS

Materials. Table 1 lists the compounds (with CAS number) examined in this study. Also found in the table are the molecular weight of the compounds, the supplier, the supplierstated purity, measured purities, and the main impurities (when known). All samples were used “as is” without further purification. The data found in the measured purities column were measured “in-house” to verify the supplier impurities. These experiments were done using an Agilent Technologies 7890A gas chromatograph system coupled with a 7683B series injector and 5975C inert XL EI MSD (GC−MS). Each compound ran through the GC−MS multiple times, with the results converted to mass fractions and compared to the supplier lot analyses (see Table 1). The solid samples were dissolved in acetone before running through the GC−MS. Besides n-hexylcyclohexane, all of the compounds were above 98.0% pure. Eleven of the 19 compounds were above 99.0% pure. Two well-known compounds were used for calibration toluene and naphthaleneand six compounds were used for verification of the DSC (1-octanol, n-eicosane, n-decane, nheptane, 1,6-hexanediol, and n-pentacosane). All eight of these compounds were above 99.0% pure. Calibrations/Methods. The melting points, enthalpies of fusion, heat capacities, and glass transition temperatures were measured using a TA Instruments Q2000 modulated differential scanning calorimeter (MDSC). TA Instruments’ Tzero aluminum pans were used with hermetic lids so that all samples were closed. The sample pans were weighed periodically using a Sartorius MSE125P microbalance with a reproducibility of 0.015 mg to ensure that no mass was lost. The baseline was calibrated using sapphire disks. The temperature was calibrated using indium, water, and adamantane in accordance with ASTM standard E967-08. The measured melting temperatures were compared to literature values, and a cubic spline was fit to the calibration curve over that range. The heat flow was calibrated daily using indium with ASTM standard E968-02. The temperature and heat flow calibrations were verified by B



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comparing the measured values and 95% confidence intervals to experimentally verified DIPPR values and uncertainties. For the compounds measured in this study, enough melting point and enthalpy of fusion replicates were performed so that the 95% confidence intervals were smaller than the process uncertainties from the verification results. 1-Phenyl-2-propanol, 2-phenyl-1-propanol, 2,5-dimethylfuran, and 1-propxyl-2-propanol were unable to freeze within the temperature range of the DSC, so their melting points were not measured. Compounds that were solid at room temperature were premelted before the melting point and heat of fusion measurements were taken. The impurities measured via GC−MS were estimated to affect the melting point and enthalpy of fusion to within the uncertainties found in the verification. The uncertainties in the heat capacity measurements were found from an analysis of the chemical purities since the bias in the verification study (described in the previous section) was small. It has been shown that purities around 95% gave an uncertainty of ±3% for liquid heat capacity measurements.2 In another study, purities near 99% gave an uncertainty around ±0.5% for liquid heat capacity measurements.3 Here, the purities were above 97%, and the main impurities were chemically similar to the compounds measured, so the uncertainty due to impurities was closer to ±1%. From this, the combined uncertainty Uc of the heat capacity measurements at the 95% confidence level is estimated to be Uc(cp) = 0.02cp with a coverage factor of k = 2. All liquid heat capacity measurements were carried out below the normal boiling point of each compound so that the vapor heat capacity could be ignored. In particular, no compound was measured within 10 K of its normal boiling point. The highest temperature measured for each compound was an average of 35 K below its normal boiling point.

Table 3. Summary of Experimental Enthalpy of Fusion Measurements Δfush at 0.085 MPaa

a

a

replicates

233.4 224.7 263.1 264.3 452.1 262.5 285.0 240.5 266.0 244.0 224.9 286.0 254.3 326.4 294.7

6 3 5 10 10 4 8 20 4 3 23 5 8 5 12

84.8 91.9 111 158 80.6 105 94.1 110 122 184 23.5 326 71.3

11 5 28 9 8 20 4 3 23 5 8 5 13

Standard uncertainties u are u(p) = 10 kPa and u(Δfush) = 5 J g−1.

DISCUSSION Toluene Derivatives. Several phenolic compounds were measured. These included toluenes with alcohol, aldehyde, or acid groups on the meta-, ortho-, or para- positions, as pictured in Figure 1. Figure 2 and Table 5 show the experimental melting points obtained in this work with the values from chemically similar compounds, such as the xylenes. The uncertainties are also depicted. The values for the similar compounds came from the DIPPR database. Notice that the meta- compounds all melt at lower temperatures for each family (xylene, alcohol, aldehyde, acid), though the difference between the meta- and orthocompounds for the aldehydes is quite small. Additionally, the meta- and ortho- toluic acid DIPPR uncertainties overlap. The paracompounds melt at significantly higher temperatures than the meta- and orthocompounds for each family. Also note that for each of the group positions (meta-, ortho-, para-), the melting point order is tolualdehyde, xylene, methylbenzyl alcohol, toluic acid. Of particular note is the melting point for p-toluic acid. This study places the value at 452.1 K, within several degrees of some studies5−9 but 100 K lower than others.10,11 The value measured was about 70 K above that for m-toluic acid, which is close to the same difference between the melting points of pand m-xylene. It therefore appears that the larger values are in error. Figure 3 and Table 6 show the experimental enthalpies of fusion obtained in this work with values from chemically similar compounds. Uncertainties are also depicted. The enthalpies of fusion for the xylenes and toluic acid follow the same trend seen for the melting points. That is, the meta- compounds generally give the smallest enthalpies of fusion, and the paracompounds give the largest enthalpies of fusion with the values for the orthocompounds somewhere between the meta- and

Table 2. Summary of Experimental Melting Point Measurements Tm at 0.085 MPaa Tm/K

replicates

o-tolualdehyde p-toluladehyde 2-methylbenzyl alcohol p-toluic acid 2-isopropylphenol 5-methylfurfural phenyl acetate ethyl 2-phenylacetate hexylcyclohexane 6-undecanone 1H-perfluorooctane 2,6-dimethoxyphenol trans-isoeugenol

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RESULTS Tables 2−4 contain the experimental results for the melting point, enthalpy of fusion, and liquid heat capacity, respectively. As explained above, the process uncertainty in the melting points is 1 K and that for the enthalpy of fusion is 5 J g−1, with combined expanded uncertainties for the heat capacities given

chemical name

Δfush /(J g−1)

as Uc(cp) = 0.02cp. Also found in the tables are the number of replicates needed to achieve the desired confidence. The melting point, enthalpy of fusion, and liquid heat capacity results of the selected compounds were compared to similar compounds not measured in this report. These comparative values and uncertainties were gathered from the DIPPR project 801 database. The data from the DIPPR database represent critically evaluated values with Type B uncertainties, as defined by the Guide to the expression of Uncertainty in Measurement.4

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o-tolualdehyde m-tolualdehyde p-toluladehyde 3-methylbenzyl alcohol p-toluic acid 1-phenyl-1-propanol 2-isopropylphenol 5-methylfurfural phenyl acetate ethyl 2-phenylacetate hexylcyclohexane 6-undecanone 1H-perfluorooctane 2,6-dimethoxyphenol trans-isoeugenol

chemical name

Standard uncertainties u are u(T) = 1.0 K and u(p) = 10 kPa. C



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Table 4. Summary of Temperatures T and Liquid Heat Capacity Measurements cp at p = 0.085 MPaa compound o-tolualdehyde

m-tolualdehyde

p-tolualdehyde

3-methylbenzyl alcohol

p-toluic acid

1-phenyl-1-propanol

1-phenyl-2-propanol

2-phenyl-1-propanol

2-isopropylphenol

5-methylfurfural

T/K

cp/(J g−1 K−1)

replicates

238.16 293.16 348.15 403.13 458.11 273.17 313.16 353.15 393.14 453.11 273.17 313.16 353.15 393.14 453.11 266.15 306.15 356.15 406.15 456.15 458.15 473.15 488.15 503.15 523.15 273.15 323.15 373.15 423.15 473.15 273.15 323.15 373.15 423.15 473.15 273.15 323.15 373.15 423.15 473.15 273.15 323.15 373.15 423.15 473.15 250.15 300.15 350.14 400.13

1.535 1.661 1.813 1.920 2.173 1.577 1.714 1.829 1.961 2.148 1.593 1.700 1.800 1.934 2.089 1.819 2.053 2.301 2.417 2.522 2.433 2.485 2.553 2.600 2.659 2.053 2.349 2.482 2.589 2.709 2.071 2.284 2.418 2.537 2.605 2.007 2.210 2.393 2.511 2.583 2.070 2.257 2.361 2.481 2.602 1.639 1.748 1.839 1.992

15 7 15 9 16 10 11 11 9 12 16 17 12 16 8 6 5 16 12 18 10 8 9 8 5 13 13 13 12 16 10 11 11 17 6 10 13 19 6 16 9 11 8 14 9 12 9 9 10

compound 2,5-dimethylfuran

phenyl acetate

ethyl 2-phenylacetate

n-hexylcyclohexane

6-undecanone

1H-perfluorooctane

2,6-dimethoxyphenol

trans-isoeugenol

1-propoxy-2-propanol

T/K

cp/(J g−1 K−1)

replicates

450.10 213.15 253.15 293.15 333.15 253.15 293.15 333.15 373.15 413.15 253.15 293.15 333.15 373.15 413.15 228.16 288.16 348.14 408.13 468.09 293.16 343.16 373.15 423.13 473.10 258.16 273.16 298.16 323.16 373.14 333.16 373.15 413.14 453.12 493.10 298.15 323.15 373.15 423.15 473.15 193.19 223.15 273.16 323.16 373.15

2.121 1.657 1.706 1.775 1.924 1.619 1.651 1.763 1.876 1.979 1.655 1.759 1.783 1.869 1.987 1.735 1.962 2.146 2.429 2.755 2.136 2.241 2.363 2.481 2.719 1.062 1.092 1.143 1.178 1.254 2.058 2.129 2.163 2.252 2.318 1.991 2.049 2.122 2.324 2.358 2.009 2.098 2.294 2.464 2.663

13 12 8 8 9 14 13 16 13 11 13 11 12 12 12 14 15 22 19 8 9 16 9 12 12 9 11 7 11 11 8 9 9 10 9 7 8 20 8 17 7 10 11 22 17

a Standard uncertainties u are u(T) = 1.0 K and u(p) = 10 kPa. Combined expanded uncertainty Uc for heat capacity is Uc(cp) = 0.02cp.

capacity shows a curve shape reminiscent of other alcohols,13,14 and the heat capacity for p-toluic acid fell within 5% of the literature value.12 Phenyl Propanols. The structures of four of the measured compounds, 1-phenyl-1-propanol, 1-phenyl-2-propanol, 2-phenyl-1-propanol, and 2-isopropylphenol, are found in Figure 5. 2-Isopropylphenol froze and melted like other compounds in this study, but the other phenyl propanols formed amorphous glasses, similar to glycerol.21 As in other studies, these glass transitions were identified by a step change

paracompounds. The uncertainties for the methylbenzyl alcohols and tolualdehydes were too large to be able to discern a trend. The measured value for p-toluic acid was about 5% lower than three literature values,7,10,12 but about 25% lower than one literature value.8 Figure 4 shows the newly measured experimental liquid heat capacity data for the toluenes. The position of the aldehyde group on the tolualdehydes do not clearly affect heat capacity, which is the same conclusion drawn from a review of m-, o-, and p- xylene heat capacities. The methylbenzyl alcohol heat D



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Figure 1. Toluene derivatives measured in this study.

Table 5. A Comparison of Experimental Melting Points Tm for the Toluene Derivatives Tm/K (reps)

uncertainty/K

type

source

o-xylene m-xylene p-xylene o-tolualdehyde

247.98 225.3 286.40 233.4(6)

0.5 0.45 0.57 1.0

experimental experimental experimental experimental

m-tolualdehyde

224.7(3)

1.0

experimental

p-toluladehyde

263.1(5)

1.0

experimental

2-methylbenzyl alcohol 3-methylbenzyl alcohol 4-methylbenzyl alcohol o-toluic acid

309.15

3

experimental

DIPPR DIPPR DIPPR this report this report this report DIPPR

264.3(10)

1.0

experimental

332.65

3.3

experimental

0.4 1.0

experimental experimental experimental experimental experimental experimental experimental experimental experimental

chemical name

Figure 2. Melting points from the literature for xylenes (blue ●), tolualdehydes (red ■), methylbenzyl alcohols (purple ◆), and toluic acids (green ▲) with uncertainties contained within the size of the markers, with new data from this study for tolualdehydes (red □), methylbenzyl alcohols (purple ◇), and toluic acids (green △). 22,23

in the baseline, or heat capacity. These glass transition temperatures were measured and are given in Table 7. The melting point of 1-phenyl-1-propanol was measured using methodology similar to glycerol which will be described here.24 The DSC was cooled at a rate of 0.1 K/min to just above the glass transition temperature at 203.15 K and held 180 min. Then, it was heated at a rate of 1 K/min to 218.15 K and held for 360 min. Finally, the cell was heated at a rate of 0.5 K/ min to 288.15 K to observe the exothermic freezing and endothermic melting peaks. Unfortunately, the data produced from these runs were not sufficiently consistent to repeat for the other phenyl propanols. Melting point results for 1-phenyl-1-propanol and 2isopropylphenol are given in Table 8. When the alcohol group is moved from the propane chain to the benzene as in 2isopropylphenol, no glass is observed, and the melting point can be easily determined. The measured heat capacities are plotted in Figure 6, showing that the placement of the phenyl and alcohol groups had little effect on the measured values. Furans. 2,5-Dimethylfuran and 5-methylfurfural (Figure 7) were measured to improve understanding of the furan family. These measurements were compared to existing data for furan and furfural whose structures are shown in Figure 8. Tables 9 and 10 summarize the experimental data (from both DIPPR and this study) for the four furans mentioned above. The measured melting point for 5-methylfurfural fell within the DIPPR assigned uncertainty of the melting point for furfural.

m-toluic acid

p-toluic acid

377.55 376.65 376.85 380.15 381.9 382.75 384.15 384.35 452.1(10)

this report DIPPR 15 16 12 17 12 15 17 18 this report

Unfortunately, the melting point for 2,5-dimethylfuran was too low for the DSC to measure, so the reported value in the table is the DIPPR value. Table 10 lists the enthalpy of fusion results for the four furans. The value for 2,5-dimethylfuran is listed as predicted because, as just explained, the melting point was too low for the DSC to measure. This predicted value came from the DIPPR database. The enthalpy of fusion for 5-methylfurfural was measured to be 105.22 ± 5 J g−1 which is much smaller than furfural. This would indicate that the methyl group makes it difficult for the compound to pack into a crystal lattice structure, so less energy would be needed to move to the liquid phase. Phenyl Acetates. The structures of the two phenyl acetates measured are shown in Figure 9. Figure 10 shows benzyl acetate and methyl benzoate, which are chemically similar to the phenyl acetates measured. E



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mentioned above. The measured melting point for ethyl 2phenylacetate is larger than the DIPPR value for benzyl acetate, which would be consistent with a molecular weight argument. The measured melting point for phenyl acetate is slightly larger than the DIPPR value for methyl benzoate, which means that the ester group packs better into a crystal lattice when the carbonyl group is moved away from the phenyl group. Table 12 shows the experimental enthalpy of fusion data for these esters. Both of the measurements by this study are larger than the DIPPR values for benzyl acetate and methyl benzoate. Figure 11 shows the liquid heat capacity data for these compounds, which compare well to the experimental point for benzyl acetate at 298.15 K. The new data are slightly above the experimental data for methyl benzoate, but follow the same trend with temperature. n-Hexylcyclohexane. Recently, DIPPR performed a family review of the n-alkyl cyclohexanes. To help bolster that review, n-hexylcyclohexane, pictured in Figure 12, was measured. The experimental melting point of this compound along with the accepted DIPPR values for ethyl-, butyl-, and octylcyclohexane are found in Table 13. Table 14 contains the values for the enthalpy of fusion for the same compounds. Notice that the experimental melting point and enthalpy of fusion for nhexylcyclohexane found in this work follows the family trends. Specifically, melting point appears to increase 20−30 K and enthalpy of fusion increases 20−30 J g−1 for every two carbons added to the alkyl chain. Figure 13 shows the experimental liquid heat capacity data as a function of temperature for ethyl-, butyl-, and hexylcyclohexane. (No experimental values exist for octylcyclohexane.) The family trends also hold for the newly measured data. The magnitudes of the values for n-hexylcyclohexane are comparable to those of the other to alkylcyclohexanes on a mass basis. 6-Undecanone. The di-n-alkyl ketone family needed more data to help bolster a DIPPR family review, so 6-undecanone (or dipentyl ketone, as shown in Figure 14) was measured. Table 15 shows that the measured melting point followed the family trends of about 15−20 K increments. Table 16 shows the enthalpy of fusion trend for the family, which is less clear. There is only 7 J g−1 difference between 3-pentanone and 4heptanone, but almost 34 J g−1 difference between 4-heptanone and 5-nonanone. The value for 6-undecanone from the literature31 is 6 J g−1 smaller than the value for 5-nonanone from a separate, trusted literature source.32 This does not follow the expected family trend. The new measurement for 6undecanone is 9 J g−1 above the value given for 5-nonanone, and 15 J g−1 above the value found previously in the literature, which fits better within the family. Figure 15 shows the heat capacities for the di-n-alkyl ketones. The measured values for 6undecanone compare well to those of 5-pentanone. 1H-Perfluorooctane. Few data exist for the 1H-perfluoro family in the DIPPR database, so 1H-perfluorooctane (as shown in Figure 16) was purchased and measured. It gave a slightly higher melting point than perfluorooctane (linear octane with fluorines substituted for all of the hydrogens), as shown in Table 17. The enthalpy of fusion measurement was the same as perfluorooctane within the experimental uncertainty, as shown in Table 18. Figure 17 shows the experimental liquid heat capacity data as a function of temperature for 1H-perfluorohexane, 1Hperfluorooctane, and perfluoro-n-heptane, including the data measured in this study. The data from this study for 1H-

Figure 3. Enthalpies of fusion Δfush for xylenes (blue ●), tolualdehydes (red ■), methylbenzyl alcohols (purple ◆), and toluic acids (green ▲) with uncertainties from DIPPR and new data from this study for tolualdehydes (red □), methylbenzyl alcohols (purple ◇), and toluic acids (green △) with experimental uncertainties.

Table 6. Summary of Enthalpy of Fusion Experimental Results Δfush for the Toluene Derivatives Δfush/(J g−1) (Reps)

uncertainty/ (J g−1)

type

source

o-xylene m-xylene p-xylene o-tolualdehyde

128.16 109.7 161.2 84.8(11)

0.26 1.1 1.6 5.0


m-tolualdehyde p-toluladehyde

90 91.9(5)

23 5.0

predicted19 experimental

2-methylbenzyl alcohol 3-methylbenzyl alcohol 4-methylbenzyl alcohol o-toluic acid m-toluic acid p-toluic acid

106

26

predicted20

DIPPR DIPPR DIPPR this report DIPPR this report DIPPR

111.0(28)

5.0

experimental

98

25

predicted19

148.1 115.3 158.3(9)

1.5 1.1 5.0

experimental experimental experimental

chemical name

this report DIPPR DIPPR DIPPR this report

Figure 4. Liquid heat capacity measurements cp as a function of temperature T for m-tolualdehyde (blue ●), o-tolualdehyde (red ▲), p-tolualdehyde (green ◆), 3-methylbenzyl alcohol (blue ○), and ptoluic acid (purple △) with experimental uncertainty from this study.

Table 11 summarizes the experimental melting point data (from both DIPPR and this study) for the four esters F



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Figure 5. Phenyl propanols measured in this study.

Table 7. A Comparison of Experimental Glass Transition Temperatures Tg for the Phenyl Propanols chemical name 1-phenyl-1propanol 1-phenyl-2propanol 2-phenyl-1propanol glycerol

Tg/K (reps)

uncertainty/K

type

198.8(5)

1.0

experimental

200.6(6)

1.0

experimental

197.6(8)

1.0

experimental

190

experimental

source this report this report this report 25

Figure 7. Furans measured in this study.

Table 8. A Comparison of Experimental Melting Points Tm for the Phenyl Propanols chemical name 1-phenyl-1propanol glycerol 2-isopropylphenol

Tm/K (reps)

uncertainty/K

type

262.5(4)

1.0

experimental

291.33 285.0(8)

2.9 1.0

experimental experimental

Figure 8. Comparison compounds for the furans.

Table 9. A Comparison of Experimental Melting Points Tm for the Furans

source this report DIPPR this report

chemical name 5-methylfurfural 2,5dimethylfuran furfural furan

Tm/K (reps)

uncertainty/K

type

source

240.5(20) 210.4

1.0 2.1


this report DIPPR

236.65 187.55

7.1 0.38


DIPPR DIPPR

Table 10. A Comparison of Enthalpy of Fusion Experimental Results Δfush for the Furans chemical name 5methylfurfural 2,5dimethylfuran furfural furan

Δfush /(J g−1) (reps)


type

source

105.22(20)

5.0

experimental

83

21

predicted19

this report DIPPR

149.9 55.87

4.5 0.56


DIPPR DIPPR

Figure 6. Liquid heat capacity measurements cp as a function of temperature T for 1-phenyl-1-propanol (blue ●), 1-phenyl-2-propanol (red ▲), 2-phenyl-1-propanol (green ◆), and 2-isopropylphenol (purple ■) with experimental uncertainty.

perfluorooctane (blue circles) cross through data from a reference book35 for the same compound (red crosses) at around 300 K. The reference book data for both 1Hperfluorooctane (red crosses) and 1H-perfluorohexane (purple x’s) have much steeper slopes than the data measured here.

Figure 9. Phenyl acetates measured in this study.

G



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data measured in this study compare well to data for perfluoron-heptane. 2,6-Dimethoxyphenol. 2,6-Dimethoxylphenol (Figure 18) was measured because no liquid heat capacity data exist in the literature for it nor chemically similar compounds such as guaiacol or ethyl vanillin (Figure 19). The measured melting point of 2,6-dimethoxylphenol was 326.4 K (see Table 19) and was within 1−2 K of other melting points for 2,6dimethoxyphenol in the literature.38−42 Moreover, its value was between that of guaiacol and ethyl vanillin, the relationship of which is reasonable considering the trends in molecular weight. Table 20 shows the measured enthalpy of fusion with that of the similar compounds. Unfortunately, the uncertainties in the predicted DIPPR enthalpy of fusion values for the comparison compounds were too high to make a worthwhile comparison, though they do lie in the vicinity of the new experimental point for 2,6-dimethoxyphenol. trans-Isoeugenol. trans-Isoeugenol (Figure 20) was selected for measurements due to the lack of experimental data which caused a thermodynamic consistency problem when the compound was being initially reviewed for addition to the DIPPR database. No experimental melting point existed for the compound prior to this work, and the initial strategy for obtaining a value was to use the prediction method of Constantinou and Gani.46 This gave a value of 324.25 K meaning the compound was a solid at the standard pressure and at the reference temperature of 298.15 K. The DIPPR researchers knew that this was unlikely based on the melting temperatures of comparison compoundsspecifically eugenol and anetholethe structures of which are found in Figure 21 and which were known to be liquids at room temperature. The experiments performed on trans-isoeugenol found a melting temperature more in line with expections. Table 21 contains the melting point measurements for all three compounds. Notice that the melting point of trans-isoeugenol is 294.7 K, which means it is a liquid at the standard pressure and at the reference temperature of 298.15 K. This was especially important when calculating the standard Gibb’s energy of formation for the compound. Without this experimental value, the incorrect prediction using the Constantinou and Gani method resulted in a thermodynamically inconsistent Gibb’s energy of formation. The new experimental value yielded Gibb’s energies that were consistent with other data. Table 22 shows that the measured enthalpy of fusion for trans-isoeugnol was much smaller than that of eugenol and anthole. This would indicate that the addition of the alcohol group from anethole to trans-isoeugenol makes it more difficult for the molecule to pack well in a lattice structure. 1-Propoxy-2-Propanol. The liquid heat capacity of 1propoxy-2-propanol (Figure 22) was measured and compared to that in the literature3 as shown in Figure 23. The combined expanded uncertainties for the measurements form this study at 273.16 and 323.15 K encapsulate the data from the literature.

Figure 10. Comparison compound for the phenyl acetates.

Table 11. A Comparison of Experimental Melting Points Tm for the Phenyl Acetates Tm/K (reps)

uncertainty/K

type

phenyl acetate

266.0(4)

1.0

experimental

ethyl 2phenylacetate benzyl acetate methyl benzoate

244.0(3)

1.0

experimental

221.65 260.65

2.2


chemical name

source this report this report DIPPR 26

Table 12. A Comparison of Enthalpy of Fusion Experimental Results Δfush for the Phenyl Acetates Δfush /(J g−1) (reps)


type

source

phenyl acetate

94.1(4)

5.0

experimental

ethyl 2phenylacetate benzyl acetate methyl benzoate

110(3)

5.0

experimental

79 108.73 108.93

19 0.10 0.09

predicted19 experimental experimental

this report this report DIPPR 27 28

chemical name

Figure 11. Liquid heat capacity data cp as a function of temperature T for phenyl acetate (blue ●) and ethyl 2-phenylacetate (red ▲) with experimental uncertainty, benzyl acetate (green ▲) with DIPPR uncertainty, and methyl benzoate (purple ■ ) with author uncertainty.27,29,30

■

CONCLUSIONS New melting point, enthalpy of fusion, and liquid heat capacity experimental data for 19 industrially important compounds were measured via DSC (see Table 1). The melting points and enthalpies of fusion were replicated enough times to yield 95% confidence intervals below 1 K and 5 J g−1, respectively, the values of which are below the process uncertainties determined

Figure 12. n-Hexylcyclohexane.

However, when these data are compared to experimental data for perfluoro-n-heptane from two independent sources36,37 (black diamonds), it is clear that the slopes of the data from the reference book are too steep for this family of compounds. The H



Article

Table 13. A Comparison of Experimental Melting Points Tm for the Alkylcyclohexanes chemical name

Tm/K (reps)

uncertainty/K

type

source

ethylcyclohexane butylcyclohexane hexylcyclohexane octylcyclohexane

161.5 198.42 224.9(23) 252.75

0.5 0.4 1.0 2.5


DIPPR DIPPR this report DIPPR

Table 14. Summary of enthalpy of fusion experimental resutls Δfush for the Alkylcyclohexanes chemical name

Δfush / (J g−1) (reps)


type

source

ethylcyclohexane butylcyclohexane hexylcyclohexane

74.3 101.0 122.1(23)

0.7 0.2 5.0


octylcyclohexane

153.4

7.7

experimental

DIPPR DIPPR this report DIPPR

Figure 15. Liquid heat capacity data cp as a function of temperature T for 3-pentanone (blue ●) and 5-nonanone (green ◆) with DIPPR uncertainty, and 6-undecanone (purple ■) with experimental uncertainty.

Figure 16. 1H-perfluorooctane. Figure 13. Liquid heat capacity data cp as a function of temperature T for n-ethyl- (blue ●) and n-butyl- (red ▲) with DIPPR uncertainty, and n-hexyl- (green ◆) cyclohexane and experimental uncertainty.

Table 17. A Comparison of Experimental Melting Points Tm for 1H-Perfluorooctane and Related Compounds chemical name 1Hperfluorooctane perfluorooctane 1Hperfluorohexane

Figure 14. 6-Undecanone.

Table 15. A Comparison of Experimental Melting Points Tm for the di-n-Alkyl Ketones chemical name

Tm/K (reps)

uncertainty/K

type

source

3-pentanone 4-heptanone 5-nonanone 6-undecanone

234.2 240.7 267.3 286.0(5)

2.3 2.4 2.7 1.0


DIPPR DIPPR DIPPR this report


3-pentanone 4-heptanone 5-nonanone 6undecanone

134.5 141.5 175.3 184(5) 169


type

source

5.0


DIPPR 33 DIPPR this report 31

experimental

uncertainty/K

254.3(8)

1.0

experimental

250 180.15

2.5 18

experimental DIPPR not specified34 DIPPR

type

source this report

Table 18. Summary of Enthalpy of Fusion Experimental Results Δfush for 1H-Perfluorooctane and Related Compounds chemical name 1Hperfluorooctane perfluorooctane 1Hperfluorohexane

Table 16. Summary of Enthalpy of Fusion Experimental Results Δfush for the di-n-Alkyl Ketones chemical name

Tm/K (reps)



type

source

23.5(8)

5.0

experimental

21.87 16

0.22 8

experimental predicted20

this report DIPPR DIPPR

by a verification study. Liquid heat capacity was measured at discrete temperatures and repeated as needed to reduce the standard uncertainty below 1% over all temperatures and compounds. This, combined with an analysis of the purities, gave a combined expanded uncertainty of 2% for the heat capacity measurements. All of the compounds’ properties were compared to similar compounds with favorable results. In particular, family plots for the toluene-like compounds, alkylcyclohexanes, and di-n-alkyl ketones increased confidence I



Article

Figure 20. trans-isoeugenol. Figure 17. Liquid heat capacity data cp as a function of temperature T for 1H-perfluorooctane measured in this report (blue ●) with combined expanded uncertainties, data for 1H-perfluorooctane (red +) and 1H-perfluorohexane (purple ×) from the same literature source,35 and data for perfluoro-n-heptane from the literature (⧫)36,37

Figure 21. Comparison compounds for trans-isoeugenol.

Figure 18. 2,6-Dimethoxyphenol.

Table 21. Summary of Experimental Melting Points Tm for trans-Isoeugenol and Related Compounds chemical name transisoeugenol eugenol anethole

Tm/K (Reps)

uncertainty/K

294.7(12)

1.0

experimental

this report

264 294.5

2.64 8.8

experimental not specified47

DIPPR DIPPR

type

source

Table 22. A Comparison of Experimental Enthalpies of Fusion Δfush for trans-Isoeugenol and Related Compounds Figure 19. Compounds compared to 2,6-dimethoxyphenol.

Table 19. Summary of Experimental Melting Points Tm for 2,6-dimethoxyphenol and related compounds chemical name 2,6dimethoxyphenol guaiacol ethyl vanillin

Tm/K (reps)

uncertainty/K

type

source

326.4(5)

1.0

experimental

301.2 302.05 349.8

0.5


this report 43 44 45

Table 20. Summary of Enthalpy of Fusion Experimental Results Δfush for 2,6-Dimethoxyphenol and Related Compounds chemical name 2,6dimethoxyphenol guaiacol ethyl vanillin

Δfush / (J g−1) (reps)


type

source

113.7(5)

5.0

experimental

100 152.5

50


this report DIPPR 45

chemical name



type

source

transisoeugenol eugenol anethole

71.3(13)

5.0

experimental

114 108.0

29 3.2


this report DIPPR DIPPR

Figure 22. 1-Propoxy-2-propanol.

in the experimental results. Additionally, a method for freezing and melting 1-phenyl-1-propanol was developed and used for DSC. These measurements represent a step forward in understanding these industrially important chemicals so they can be more effectively used in process design. J



Article

(9) Yalkowsky, S. H.; Valvani, S. C. Solubility and partitioning I: Solubility of nonelectrolytes in water. J. Pharm. Sci. 1980, 69, 912− 922. (10) Li, D.-Q.; Liu, J.-C.; Liu, D.-Z.; Wang, F.-A. Solubilities of terephthalaldehydic, p-toluic, benzoic, terephthalic and isophthalic acids in N,N-dimethylformamide from 294.75 to 370.45 K. Fluid Phase Equilib. 2002, 200, 69−74. (11) Li, D.-Q.; Lin, Y.-J.; Evans, D. G.; Duan, X. Solid−Liquid Equilibria for Benzoic Acid + p-Toluic Acid + Chloroform, Benzoic Acid + p-Toluic Acid + Acetic Acid, and Terephthalic Acid + Isophthalic Acid + N,N-Dimethylformamide. J. Chem. Eng. Data 2005, 50, 119−121. (12) Andrews, D. H.; Lynn, G.; Johnston, J. The Heat Capacities and Heat of Crystallization of Some Isomeric Aromatic Compounds. J. Am. Chem. Soc. 1926, 48, 1274−1287. (13) Fulem, M.; Ruzicka, K.; Ruzicka, V. Heat capacities of alkanols Part I. Selected 1-alkanols C-2 to C-10 at elevated temperatures and pressures. Thermochim. Acta 2002, 382, 119−128. (14) Zábranský, M.; Růzǐ čka, V.; Majer, V. Heat Capacities of Organic Compounds in the Liquid State I. C1 to C18 1-Alkanols. J. Phys. Chem. Ref. Data 1990, 19, 719−762. (15) Kendall, J. The Addition Compounds of Phenols with Organic Acids. J. Am. Chem. Soc. 1916, 38, 1309−1323. (16) von E Doering, W.; Bragole, R. A. The carbon analogue of the claisen rearrangement of phenyl allyl ether: Equilibration of Butenylbenzenes and ortho-propenyltoluenes. Tetrahedron 1966, 22, 385−391. (17) Sugunan, S.; Thomas, B. Salting coefficients of 2-, 3-, and 4methylbenzoic acids. J. Chem. Eng. Data 1993, 38, 520−521. (18) Noyce, D. S.; Nagle, R. J. Studies of Configuration. II. The Configurations of the 3-Methylcyclohexylamines. J. Am. Chem. Soc. 1953, 75, 127−129. (19) Chickos, J. S.; Braton, C. M.; Hesse, D. G.; Liebman, J. F. Estimating entropies and enthalpies of fusion of organic compounds. J. Org. Chem. 1991, 56, 927−938. (20) Bondi, A. A. Physical Properties of Molecular Crystals, Liquids, and Glasses; Wiley: New York, 1968. (21) Zondervan, R.; Xia, T.; van der Meer, H.; Storm, C.; Kulzer, F.; van Saarloos, W.; Orrit, M. Soft glassy rheology of supercooled molecular liquids. Proc. Natl. Acad. Sci. U. S. A. 2008, 105, 4993−4998. (22) Flynn, J. H. Thermodynamic properties from differential scanning calorimetry by calorimetric methods. Thermochim. Acta 1974, 8, 69−81. (23) Flynn, J. H. Analysis of DSC results by integration. Thermochim. Acta 1993, 217, 129−149. (24) Möbius, M. E.; Xia, T.; van Saarloos, W.; Orrit, M.; van Hecke, M. Aging and Solidification of Supercooled Glycerol. J. Phys. Chem. B 2010, 114, 7439−7444. (25) Zondervan, R.; Kulzer, F.; Berkhout, G. C. G.; Orrit, M. Local viscosity of supercooled glycerol near Tg probed by rotational diffusion of ensembles and single dye molecules. Proc. Natl. Acad. Sci. U. S. A. 2007, 104, 12628−12633. (26) Dozen, Y.; Fujishima, S.; Shingu, H. Structures and fusion parameters of methoxycarbonyl-benzenes and -naphthalenes. Thermochim. Acta 1978, 25, 209−216. (27) Blokhin, A. V.; Paulechka, Y. U.; Kabo, G. J.; Kozyro, A. A. Thermodynamic properties of methyl esters of benzoic and toluic acids in the condensed state. J. Chem. Thermodyn. 2002, 34, 29−55. (28) Maksimuk, Y. V.; Kabo, G. J.; Simirsky, V. V.; Kozyro, A. A.; Sevruk, V. M. Standard Enthalpies of Formation of Some Methyl Esters of Benzene Carboxylic Acids. J. Chem. Eng. Data 1998, 43, 293− 298. (29) Fuchs, R. Heat capacities of some liquid aliphatic, alicyclic, and aromatic esters at 298.15 K. J. Chem. Thermodyn. 1979, 11, 959−961. (30) Steele, W. V.; Chirico, R. D.; Cowell, A. B.; Knipmeyer, S. E.; Nguyen, A. Thermodynamic Properties and Ideal-Gas Enthalpies of Formation for Methyl Benzoate, Ethyl Benzoate, (R)-(+)-Limonene, tert-Amyl Methyl Ether, trans-Crotonaldehyde, and Diethylene Glycol. J. Chem. Eng. Data 2002, 47, 667−688.

Figure 23. Liquid heat capacity data cp as a function of temperature T for 1-propoxy-2-propanol measured in this report (blue ●) with combined expanded uncertainties, and the literature3 (red ◆) with standard uncertainties given as the size of the symbols.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.7b01026. Experimental melting point, enthalpy of fusion, and liquid heat capacity data found in the literature for the 19 compounds studied (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Joseph W. Hogge: 0000-0002-5009-9358 Thomas A. Knotts IV: 0000-0001-6248-4459 Funding

The authors thank DIPPR801 and AIChE for project funding. Notes

The authors declare no competing financial interest.

■

REFERENCES

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Melting Point, Enthalpy of Fusion, and Heat Capacity Measurements of

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