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Vapor Pressures and Gibbs Energies of Formation of the Three Hydroxybenzaldehydes Ana R. R. P. Almeida and Manuel J. S. Monte* Centro de Investigaçaõ em Química, Department of Chemistry and Biochemistry, Faculty of Science. University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal S Supporting Information *

ABSTRACT: This work reports experimental sublimation and vaporization vapor pressures at different temperatures of the three isomers of hydroxybenzaldehyde. A static method based on capacitance diaphragm manometers was used to measure the vapor pressures of both (crystalline and liquid) condensed phases of ortho, meta, and para hydroxybenzaldehydes, through the temperature ranges T = (264.6 to 341.7) K, T = (324.9 to 419.4) K, and T = (334.9 to 429.4) K, respectively. The Knudsen massloss effusion technique was also used to determine the vapor pressures of crystalline meta and para isomers in the temperature intervals T = (309.1 to 331.2) K and T = (319.1 to 341.2) K, respectively. The obtained results enabled the determination of the standard molar enthalpies and entropies of sublimation and of vaporization, at chosen reference temperatures, as well as the (p,T) values of the triple point of the compounds studied. The temperatures and enthalpies of fusion were determined from differential scanning calorimetry. The contributions of the formyl group to the sublimation properties of benzaldehydes were determined, and the standard Gibbs energies of formation in condensed and gaseous phases were calculated.

1. INTRODUCTION The phenolic benzaldehydes are widely used and have several applications as raw materials in several chemical industries (pharmaceuticals, agrochemical, fragrances, and dyes, etc.). ortho-Hydroxybenzaldehyde (o-HBAD), also known as salicylaldehyde, arises naturally in cassia oil and in the essential oils of some plants of the genus Spirea,1 and is also a characteristic component of buckwheat groats aroma.2 Because of its aromatic odor, it is used in perfumes and on a large scale as a starting material in the production of coumarin, which is an essential constituent used in flavors, soaps, fragrances, and electroplating.1,3 o-HBAD is also an intermediate reagent in the production of plastics, dyes, agricultural materials, electroplating elements, and drugs.1,3 The meta isomer of hydroxybenzaldehyde (m-HBAD) is an essential forerunner for the production of 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin that is used in the synthesis of chlorin4a photosensitizer used in the photodynamic therapy of tumors.4,5 m-HBAD is also employed in the preparation of monastrol, which is known to be a specific mitotic kinesin Eg5 inhibitor.6 Phytochemical studies of the orchid Gastrodia elata revealed the presence of phydroxybenzaldehyde (p-HBAD).7 This compound is a flavoring agent,8 and has been used as an intermediate for creating several kind of chemical products (pharmaceuticals, dyes, textile auxiliaries, agricultural chemicals, scents, cosmetics, and in electroplating).1 It has been derivatized with propargylamine to yield building blocks for the production of © 2017 American Chemical Society

dendrimers, which are a new group of strong antioxidant compounds.9 Like ortho and meta hydroxybenzaldehydes, this isomer is also involved in the synthesis of aldehyde methacrylates10,11 and chelating resins.11,12 In a previous study, a simple group method for estimating the standard Gibbs energy of sublimation (and then, the vapor pressures) and enthalpies of sublimation, at T = 298.15 K, of substituted benzenes was reported.13 The derived predictive equations estimate the contribution of each of 30 different substituents, and of the interactions of some of those substituents in ortho and para positions, in the volatility properties of crystalline benzene derivatives. This database contains the standard Gibbs energy and enthalpy of sublimation results, at T = 298.15 K, of meta and para hydroxybenzaldehydes, published in literature.14 Therefore, the contributions of the formyl group −CHO and the interaction −CHO/−OH between substituents in the para position were determined from experimental results of only those two benzaldehyde derivatives. The vapor pressure and the enthalpy of sublimation, at T = 298.15 K, of methyl p-formylbenzoate were recently determined15 showing some disagreement between the experimental and estimated results for this Special Issue: Memorial Issue in Honor of Ken Marsh Received: March 1, 2017 Accepted: April 28, 2017 Published: May 9, 2017 2982

DOI: 10.1021/acs.jced.7b00227 J. Chem. Eng. Data 2017, 62, 2982−2992

Journal of Chemical & Engineering Data

Article

Table 1. Origin and Purification Details of the Hydroxybenzaldehyde (HBAD) Isomers chemical name

CASRN

source

minimum initial puritya

purification methodb

final mass fraction purityc

analysis methodd

o-HBAD m-HBAD p-HBAD

90-02-8 100-83-4 123-08-0

Alfa Aesar Alfa Aesar Alfa Aesar

0.99 0.97 0.98

sublimation sublimation

0.9977 0.9981 0.9972

GC GC GC

a Minimum purity degree announced by the supplier. bUnder reduced pressure (p ≈ 1 Pa). cDry basis. dGas−liquid chromatography (flame ionization detector).

Table 2. Fusion Properties: Temperature (Tfus), Molar Enthalpy (Δ1crHom), and Molar Entropy (Δ1crSom) of the Hydroxybenzaldehyde (HBAD) Isomers Tfus/K

Δ1crHom(Tfus)/kJ mol−1

272.3 ± 0.2b 274.58 ± 0.04 271.3 ± 4.7c

13.3 ± 0.4b 13.3 ± 0.4

377.6 ± 0.2b 376 377.8 ± 3.2e

25.6 ± 0.4b 24.1

390.2 ± 0.2b 390.8 390.8 391.1 388.5 ± 2.2g

21.6 ± 0.4b 21.6 20.3 22.2

Δ1crSom(Tfus)a/J·K−1·mol−1

Δ1crHom(298.15 k)/kJ mol−1

o-HBAD 48.8 ± 1.5

refs this work 35 see Table S6

m-HBAD 67.8 ± 1.1

21.4 ± 1.6d

this work 53 see Table S6

p-HBAD 55.4 ± 1.0

16.5 ± 1.8f

this work 54 35 55 see Table S6

a

Standard uncertainties calculated through the RSS method. bStandard uncertainties calculated through the RSS method combining the standard uncertainties of the mean of five experimental runs with the standard uncertainties of the DSC calibration. cMean value of five results of Tfus reported in literature and presented in Table S6. dAdjusted to T = 298.15 K using Δ1crCop,m(298.15K)/J·K−1·mol−1 = (53.2 ± 19.8) that was calculated through the values of Δg1Cop,m(298.15 K) and ΔgcrCop,m(298.15 K) reported in Table 4. eMean value of 15 results of Tfus reported in the literature and presented in Table S6. fAdjusted to T = 298.15 K using Δ1crCop,m(298.15K)/J·K−1·mol−1 = (55.0 ± 19.8) that was calculated through the values of Δg1Cop,m(298.15 K) and ΔgcrCop,m(298.15 K) reported in Table 4. gMean value of 48 results of Tfus reported in literature and presented in Table S6.

solubilized in dimethylformamide and the carrier gas was nitrogen. 2.2. Differential Scanning Calorimetry. Using a power compensated PerkinElmer DSC calorimeter (model Diamond Pyris 1), the occurrence of eventual phase transitions in the crystalline phase was checked, and the onset temperatures and enthalpies of fusion of the compounds studied were determined. For each compound, five independent runs using fresh samples sealed in hermetic crucibles were performed. The samples were scanned at 3.3 × 10−2 K·s−1 from T/K = 173 to a temperature (15 to 25) K higher than the temperature of fusion. A controlled nitrogen flux was used to prevent contamination of the calorimeter in case of hermeticity failure of the crucibles. The calorimeter was calibrated using several reference materials: benzoic acid,16−18 naphthalene,16−18 triphenylene,16,17,19 diphenylacetic acid,16−18 perylene,16,17,19 o-terphenyl,17,19,20 and 4-methoxybenzoic acid.16,18 The respective purity degree and their values of the enthalpy and temperature of fusion are reported in Table S1 (Supporting Information). The standard uncertainties derived from the calibration results are u(T/K) = 0.2 and u(Δ1crHom/kJ mol−1) = 0.4. No crystalline phase transitions or signals of decomposition were observed under the experimental conditions used (sealed samples scanned at the following temperature intervals, oHBAD (173 to 293) K, m-HBAD (173 to 393) K, and p-HBAD (173 to 413) K), as can be observed in the thermograms presented in Figure S1a−c (Supporting Information). The onset temperature of fusion as well as the molar enthalpy and entropy of fusion of the compounds studied are reported in Table 2, together with the available literature results. The

compound. Therefore, it seemed necessary to confirm the reliability of the published results for meta and para HBAD.14 Thus, the sublimation vapor pressures of these two isomers were measured, in the present work, using a wider range of temperature and two different experimental methods, and the vaporization vapor pressures of the three isomers were also determined. To collect more sublimation results of a substituted benzaldehyde, we also aimed to estimate the standard Gibbs energy and enthalpy of sublimation of the ortho isomer from the measured liquid vapor pressures and its enthalpy of fusion. The thermodynamic stability of the three compounds in condensed and gaseous phases was evaluated by the determination of the Gibbs energies of formation. These results were calculated using literature values of the enthalpies of formation in the condensed phases and the thermodynamic properties of sublimation and of vaporization as well as the gaseous entropies determined in the present work.

2. EXPERIMENTAL SECTION 2.1. Materials. Table 1 presents information about the origin and the degree of purity of the three isomers of hydroxybenzaldehyde, and the method used for purification of the meta and para isomers. The ortho isomer was studied without further purification. The degree of purity of the original compounds and of the purified samples was evaluated by gas− liquid chromatography that was performed using an Agilent chromatograph model 4890D equipped with an HP-5 column and a flame ionization detector (FID). The samples were 2983



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Table 3. Vapor Pressure Resultsa T/K

p/Pa

100Δp/pb

264.55 266.52 268.49 270.45 266.54 268.50 270.45 272.44 274.40 276.37 278.29 280.27 282.24 284.23 286.21

0.84c 1.16c 1.51c 1.79c 5.05d 6.06d 7.27d 8.84 10.38 12.35 14.69 17.34 20.49 24.11 28.42

0.0 −0.3 −0.3 1.1 −0.5 −0.5 0.1 −0.2 −0.1 −0.2 0.1

324.86 326.85 328.83 330.84 332.78 334.76 336.76 338.72

0.61 0.76 0.94 1.16 1.42 1.76 2.19 2.69

2.1 1.6 0.7 −0.4 −1.4 −1.2 −0.7 −0.7

309.13 311.29 313.21 315.13

0.089 0.118 0.150 0.189

−0.9 0.0 0.4 0.3

368.31 370.35 372.25 374.24 376.14 378.15 380.15 382.09

58.07d 66.05d 74.35d 84.75d 94.34d 108.3d 121.7 136.7

0.2 −0.1 −0.4 0.2 −0.9 0.6 0.1 0.1

334.88 336.84 338.82 340.78 342.79 344.73 346.72 348.70

0.47 0.58 0.72 0.89 1.09 1.33 1.65 1.99

0.0 −0.3 0.1 0.5 −0.2 −0.4 0.8 −0.5

319.14 321.31 323.20 325.16

0.076 0.101 0.124 0.152

−0.1 2.5 1.1 −1.6

378.18 380.28 382.26 384.18

37.65d 43.31d 49.15d 55.75d

0.0 0.1 −0.2 0.1

T/K

p/Pa

100Δp/pb

T/K

o-Hydroxybenzaldehyde Liquid and Crystalline Phases, Static Method (Gauges Ic and II) 288.16 33.43 0.8 317.77 290.13 38.78 0.2 319.78 292.14 45.30 0.2 321.96 294.09 52.32 −0.3 323.95 296.00 61.45 1.5 325.91 298.06 70.20 −0.3 327.88 300.04 81.75 0.6 329.84 302.02 93.55 −0.1 331.84 304.24 107.5 −1.7 333.81 305.97 122.8 −0.3 335.78 307.92 140.9 0.2 337.76 309.88 160.3 0.0 339.74 311.90 183.2 0.2 341.67 313.81 207.1 −0.3 315.78 235.8 1.5 m-Hydroxybenzaldehyde Crystalline Phase, Static Method (Gauge I) 340.73 3.36 0.7 356.45 342.63 4.05 −0.2 358.45 344.71 4.95 −1.2 360.41 346.64 6.00 −1.3 362.40 348.61 7.33 −0.7 364.34 350.55 8.97 0.5 366.32 352.54 10.85 0.3 368.21 354.49 12.89 −1.2 Crystalline Phase, KMLEe 317.29 0.243 −0.7 325.23 319.20 0.308 0.5 327.14 321.13 0.390 1.6 329.29 323.29 0.490 −0.6 331.22 Liquid Phase, Static Method (Gauge II) 384.06 153.6 0.1 405.31 386.07 172.7 0.1 407.66 388.00 193.1 0.2 409.61 389.95 214.8 −0.3 411.60 391.96 241.5 0.1 413.56 395.88 300.2 0.3 415.52 399.75 368.7 0.0 417.46 403.71 454.0 0.0 419.41 p-Hydroxybenzaldehyde Crystalline Phase, Static Method (Gauge I) 350.66 2.41 −0.9 366.46 352.65 2.96 0.0 368.43 354.62 3.58 −0.2 370.43 356.58 4.33 −0.1 372.39 358.56 5.25 0.3 374.32 360.53 6.40 1.6 376.26 362.52 7.69 1.4 378.32 364.51 9.15 0.4 380.29 Crystalline Phase, KMLEe 327.35 0.196 −1.2 335.20 329.21 0.240 −2.0 337.14 331.15 0.305 0.3 339.28 333.36 0.383 −1.3 341.20 Liquid Phase, Static Method (Gauge II) 396.02 115.6 −0.1 413.71 398.08 132.0 1.0 415.68 399.97 146.6 0.4 417.65 402.15 165.9 0.2 419.62 2984

p/Pa

266.1 301.4 344.1 387.5 435.2 488.4 546.5 611.0 682.0 760.4 846.0 940.2 1042

15.75 18.98 22.75 27.27 32.26 38.84 46.37

0.616 0.763 0.957 1.188 490.0 553.9 618.0 675.4 751.0 814.0 902.0 994

10.71 12.74 15.45 18.42 22.06 26.06 30.67 36.25 0.476 0.583 0.737 0.910 315.0 347.7 383.1 426.4

100Δp/pb

0.0 −0.1 0.3 −0.1 −0.1 −0.1 −0.1 −0.1 0.0 0.0 −0.1 0.0 0.1

0.4 0.3 0.4 0.3 −0.4 0.5 1.5

0.4 0.3 −0.9 −0.4 −0.7 −0.4 0.7 −0.3 0.6 −0.9 0.1 0.5

−1.6 −2.0 −0.5 −0.2 1.0 1.0 −0.3 −0.2 0.4 −0.2 0.5 1.4 0.3 −0.3 −0.9 −0.4



Article

Table 3. continued T/K

p/Pa

100Δp/pb

385.95 388.15 390.14 392.11 393.98

62.55d 71.55d 80.85 91.45 101.3

0.3 −0.1 −0.2 0.0 −1.1

T/K

p/Pa

100Δp/pb

Liquid Phase, Static Method (Gauge II) 403.90 184.0 0.6 406.15 207.7 0.0 407.83 228.8 0.4 409.81 253.7 −0.2 411.77 281.0 −0.7

T/K

p/Pa

421.57 423.73 425.48 427.46 429.41

473.8 528.5 577.6 637.9 701.8

100Δp/pb 0.1 0.1 0.2 0.3 0.3

a

Estimated standard uncertainties: u(T/K) = 0.01; u(p/Pa) = 0.01 + 0.0025(p/Pa) for pressures measured using gauge I (static method); u(p/Pa) = 0.1 + 0.0025(p/Pa) for pressures measured using gauge II (static method), and u(p/Pa) = 0.01 for the pressures measured using the effusion method. bΔp = p − pcalc, where pcalc is calculated from the Clarke and Glew equation with parameters given in Table 4. cCrystalline phase. d Supercooled liquid. eKnudsen mass-loss effusion; the reported pressure are the mean of the values obtained using the small, medium, and large effusion orifices (Table S2).

A0 is the area of the effusion orifice, R is the gas constant (R = 8.3144598 J·K−1·mol−1),25 and M is the molar mass of the vapor of the sample assumed to be monomeric.

assigned standard uncertainties of the temperature and enthalpy of fusion reported in this table were calculated through the RSS method by combining the standard uncertainties of the mean of the five experimental runs with the referred to above standard uncertainties assigned to the calibration results. 2.3. Vapor Pressures Measurements. The vapor pressures of both condensed phases (crystalline and liquid) of the three isomers were measured at different temperatures using a static apparatus based on capacitance diaphragm gauges that was tested and fully described before.21 It can be equipped with two capacitance MKS diaphragm gauges that operate at self-controlled constant temperatures: (gauge I) Baratron 631A01TBEH (Tgauge = 423 K), suitable for measuring pressures in the range (0.5 to 1.3 × 102) Pa, and (gauge II) Baratron 631A11TBFP (Tgauge = 473 K), used for measuring pressures in the range (3 to 1.3 × 103) Pa.15,22 The standard uncertainty of the temperature measurements was estimated to be u(T/K) = 0.01 and the expressions u(p/Pa) = 0.01 + 0.0025(p/Pa) for gauge I and u(p/Pa) = 0.1 + 0.0025(p/Pa) for gauge II have been used to describe the standard uncertainties assigned to the pressure measurements. Before the vapor pressure measurements, the samples are thoroughly outgassed under reduced pressure. During this process eventual volatile impurities, including traces of water (which is considerably more volatile than the samples studied), are released. The Knudsen mass-loss effusion method (KMLE) was used for additional measurements of vapor pressures of the crystals of meta and para hydroxybenzaldehydes through a triple Knudsen-effusion apparatus that allows the simultaneous operation of nine effusion cells at three different temperatures. This apparatus is fully described in the literature23 and (shortly) in several subsequent articles.24 The effusion orifices, made out of platinum disks of (0.0125 ± 0.001) mm thickness, were purchased from Goodfellow Cambridge Ltd. The effusion orifices (A, B, C) used in this work have the following areas: A0(A1) = A0(A2) = A0(A3) = (0.636 ± 0.004) mm2, A0(B1) = A0(B2) = A0(B3) = (0.785 ± 0.004) mm2, A0(C1) = A0(C2) = A0(C3) = (0.985 ± 0.004) mm2. These areas were calculated from the diameters measured by the referred to above company with an uncertainty better than ±0.005 mm. The Clausing factor of the orifices of series A, B, and C were calculated as 0.986, 0.988, and 0.989, respectively, using the equation w0 = {1 + (l/2r)}−1, where l is the thickness of the platinum foil and r is the radius of the orifices. To calculate the vapor pressure p at the temperature T, eq 1 was used. The loss of mass of the sample contained in each cell, m, during the effusion time period t, is determined by weighing the cell to ±1 × 10−5 g before and after the effusion period. In this equation,

p = (m /Aowot )(2πRT /M )0.5

(1)

The standard uncertainties of the vapor pressure and temperatures measurements are estimated as u(p/Pa) = 0.01 and u(T/K) = 0.01.

3. RESULTS AND DISCUSSION 3.1. Vapor Pressures and Derived Thermodynamic Properties of Vaporization and Sublimation. Table 3 collects the sublimation and vaporization vapor pressures measured using the static method for the three compounds studied, as well as the mean sublimation vapor pressures of the meta and para isomers derived from the Knudsen effusion experiments. The detailed experimental vapor pressures determined at each temperature from the individual effusion cells, for these two isomers, are listed in Table S2 (Supporting Information). a. ortho-Hydroxybenzaldehyde. Frequently, literature boilling temperatures at only one pressure are not measured accurately. But the normal (p = 1 × 105 Pa) boiling temperature of this liquid has been determined by several authors. So, we used the mean of the values reported in the literature26−32 together with the (p,T) data measured in this work to fit all these values of vapor pressures by the Clarke and Glew equation,33 eq 2, over the wide range of temperatures T = (266.5 to 470) K. In this equation po is the standard pressure (po = 1 × 105 Pa), p is the vapor pressure at the temperature T, θ is a reference temperature, R is the molar gas constant, and the thermodynamic properties of sublimation or vaporization Δgcr,1Gom(θ), Δgcr,1Hom(θ), and Δgcr,1Cop,m(θ), are adjusted by the fitting. Because of the large temperature interval, it was possible to derive the variation of Δg1Cop,m(θ) with the temperature represented by the equation Δg1Cp,mo(θ)/J·K−1·mol−1 = [−(105 ± 6) + (0.081 ± 0.011).θ], assuming a linear variation of Δg1Cop,m(θ) with the temperature, accordingly to the fourth term of eq 2. g Gmo(θ ) Δcr,l p ⎛1 1⎞ g Hmo(θ )⎜ − ⎟ = − + Δcr,l o ⎝ p T⎠ θ θ ⎡⎛ θ ⎞ ⎛ T ⎞⎤ g C po,m(θ )⎢⎜ ⎟ − 1 + ln⎜ ⎟⎥ + Δcr,l ⎝ θ ⎠⎦ ⎣⎝ T ⎠

R ln

+

⎡⎛ T ⎞ ⎛ θ ⎞ ⎛θ⎞ ⎛ T ⎞⎤ g o ⎜ ⎟ ⎜ ⎟ ⎜ ⎟(∂Δ C ⎜ ⎟ cr,l p ,m / ∂T )θ ⎢⎝ ⎠ − ⎝ ⎠ − 2 ln⎝ ⎠⎥ + ··· ⎝2⎠ ⎣ θ T θ ⎦ (2)

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b. para-Hydroxybenzaldehyde. The sublimation vapor pressures of p-HBAD were determined using both the Knudsen effusion and the static methods. The close agreement between the vapor pressures determined using the two methods enabled a unique fit of these results by the Clarke and Glew equation, providing additional confidence to the experimental results. Furthermore, this close agreement supports our assumption of a monomeric vapor phase which also assures the absence of decomposition in the (p,T) experimental conditions usedthe Knudsen method depends on the molar mass of the vapor, as can be seen in eq 1, while the static method is independent of its molar mass. As it was not possible to get reliable values of the variation of Δgcr,1Cop,m with the temperature using eq 2, we used eq 3 that has been used in several previous works15,40−44 assuming as approximation that Δgcr,1Cop,m could be considered constant.

The thermodynamic properties of sublimation of o-HBAD could not be accurately derived due to the narrow temperature range and to the scarce number of the sublimation vapor pressures that were possible to measure for its crystalline phase. Even though it was possible to estimate the triple point coordinates (from the measured vaporization and the scarce sublimation vapor pressures) and also to estimate the enthalpy of sublimation of this compound at the temperature of fusion ΔgcrHom(272.3 K) = (69.9 ± 0.4) kJ·mol−1, calculated by adding the enthalpy of vaporization, Δg1Hom(272.3 K) = (56.6 ± 0.1) kJ· mol−1, to the enthalpy of fusion, Δ1crHom(272.3 K) = (13.3 ± 0.4) kJ·mol−1. For comparison reasons, the latter result was adjusted to the temperature 298.15 K, (using ΔgcrCop,m(θ) = − (29.1 ± 16.2) J·K−1·mol−1, assuming the same value as the one determined in this work for the para isomer using eq 3 as explained in the next subsection), yielding the result ΔgcrHom(298.15 K) = (69.2 ± 0.6) kJ·mol−1 for the hypothetical crystalline phase o-HBAD at that temperature. From this result and the vapor pressure at the triple point, the results ΔgcrGom(298.15 K) = 16.6 kJ·mol−1 and ΔgcrSom(298.15 K) = 176 J·K−1·mol−1 were estimated. For the vaporization of o-HBAD, two literature results derived from the Calvet drop microcalorimetry were reported as Δ 1g H mo (298.15 K) = (50.4 ± 1.3) kJ·mol −1 34 and Δg1Hom(298.15 K) = (53.3 ± 0.3) kJ·mol−1;35 these results are 3.5 kJ·mol−1 and 0.6 kJ·mol−1, respectively, smaller than the value derived in this work. The vapor presssures at different temperatures of the liquid and crystalline phases of o-HBAD are represented in Figure 1

g ⎛ p⎞ Gmo(θ ) Δcr,l ⎛1 1⎞ g R ln⎜ ο ⎟ = − Hmo(θ )⎜ − ⎟ + Δcr,l ⎝θ θ T⎠ ⎝p ⎠ ⎡⎛ θ ⎞ ⎛ T ⎞⎤ g + Δcr,l C po,m(θ )⎢⎜ ⎟ − 1 + ln⎜ ⎟⎥ ⎝ θ ⎠⎦ ⎝ ⎠ ⎣ T

(3)

When accurate experimental sublimation or vaporization vapor pressures are measured over a large temperature range (ca. 50 K), the fit of eq 3 frequently yields a consistent value of Δgcr,1Cop,m(θ).15,43 The fit of eq 3 to the experimental data of pHBAD yields the result ΔgcrCop,m = −(29.1 ± 16.2) J·K−1·mol−1, reported in Table 4 together with the other thermodynamic properties derived from this fit. As we explain in the Introduction, we wanted to confirm the results previously published14 that have been used for estimating the contribution of the formyl group in the predictive equations proposed before,13 considering that other different results have been published. The consistency of our previous results,14 however, was confirmed through the results obtained in this work. Figure S2 (Supporting Information) compares the results reported in the literature with the ones determined in this work. The published results14 were determined by the Knudsen effusion method over the temperature interval (324.2 to 341.3) K, yielding the value ΔgcrHom(298.15 K) = (102.5 ± 0.5) kJ·mol−1.14 This result is only 0.9 kJ·mol−1 smaller than the one determined in this work using a different Knudsen effusion apparatus23 and a static method21 over the global temperature interval (319.1 to 380.3) K. When extrapolated to the temperature 298.15 K, the vapor pressure of p-HBAD determined in this work, p = 4.9 × 10−3 Pa, is quite similar to the one previously reported, p = 5.6 × 10−3 Pa.14 Other results for the sublimation of this compound have been reported in the literature. Sublimation vapor pressures were determined between T = (320.6 and 350.6) K by using a Knudsen effusion apparatus and three cells with different effusion orifices.35 The result ΔgcrHom(298.15 K) = (99.7 ± 0.9) kJ·mol−1 was calculated in this work as the weighted mean of the values reported by the authors for each of the three effusion cells used. This value is 3.7 kJ·mol−1 smaller than our result. The value of ΔgcrGom(298.15 K), presented in Table 4, was calculated in this study from the vapor pressures results for the three effusion cells used by the authors,35 yielding the result p = 6.9 × 10−3 Pa at the temperature 298.15 K, that is only 2.0 × 10−3 Pa larger than our result. There are other two literature results for the sublimation of this compound, also derived using the Knudsen effusion

Figure 1. Phase diagram of o-hydroxybenzaldehyde: ○, vaporization; ◇, vaporization (supercooled liquid); □, sublimation; ▲, mean value of normal (p = 1 × 105 Pa) boiling temperature reported in literature;26−32 ●, boiling temperature, T = 366 K at p = 3.3 × 103 Pa;36 ×, boiling temperature, T = 368 K at p = 4.7 × 103 Pa;37 ★, boiling temperature, T = 360 K at p = 1.7 × 103 Pa;38 ■, boiling temperature, T = 309 K at p = 5.3 × 102 Pa.39 Triple point data determined in this work: T = 272.8 K; p = 9.1 Pa.

together with the mean value, T = (470 ± 1) K, of the normal (p = 1 × 105 Pa) boiling temperatures reported in the literature.26−32 Other literature boiling temperatures, T = 366 K at p = 3.3 × 103 Pa,36 T = 368 K at p = 4.7 × 103 Pa,37 T = 360 K at p = 1.7 × 103 Pa,38 and T = 309 K at p = 5.3 × 102 Pa39 are also presented in this figure. As may be observed, the literature value at T = 366 K is well within the fitting curve, but the other three literature results are clearly out. 2986



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Table 4. Standard (po = 105 Pa) Molar Thermodynamic Properties of Sublimation and of Vaporization at the Reference Temperature θ: Gibbs Energies (Δgcr,1Gom), Enthalpies (Δgcr,1Hmo), and Entropies (Δgcr,1Smo) ΔT/K

θ/K

Δgcr,1Gom(θ)a / kJ mol−1

Δgcr,1Hom(θ)a/kJ·mol−1 Δgcr,1Som(θ)b/J·K−1·mol−1 o-Hydroxybenzaldehyde Liquid Phasee

266.5 to 341.7

304.11f

17.26 ± 0.01

53.4 ± 0.1

298.15 298.15 298.15

17.98 ± 0.01

53.9 ± 0.1 50.4 ± 1.3 53.3 ± 0.3

R2

Δgcr,1Cop,m(θ)a/J·K−1·mol−1

sc

method/ref

d

1.0000

−(105 ± 6) + (0.081 ± 0.011)θg

0.0049

static/this work

120.5 ± 0.3 calorimetric/34 calorimetric/35 m-Hydroxybenzaldehyde Crystalline Phase

309.1 to 368.2

312.2 to 330.2 303 to 328

338.67f

29.63 ± 0.01

99.8 ± 0.1

298.15 378.54i 298.15

38.11 ± 0.04 21.43 ± 0.04 37.98 ± 0.05

101.0 ± 0.7 98.7 ± 0.7 100.1 ± 0.6

315.5

37.8

93.6 ± 0.6

1.0000

−29.1 ± 16.2h

0.0106

static + KMLE/ this work

210.9 ± 2.4 204.1 ± 1.9 KMLE/14 KMLE/46 Liquid Phasee

368.3 to 419.4

319.1 to 380.3

324.2 to 341.3 303 to 328 303.4 to 336.0 320.6 to 350.6 312.0 to 335.9

393.86f

19.39 ± 0.01

71.2 ± 0.1

1.0000

−82.3 ± 11.4j

0.0045

static/this work

298.15 378.54i

33.03 ± 0.14 21.43 ± 0.01

79.1 ± 1.1 72.5 ± 0.2

349.72f

31.18 ± 0.01

101.9 ± 0.1

0.9999

−29.1 ± 16.2j

0.0134

static + KMLE/ this work

298.15 389.81i 298.15

41.73 ± 0.05 23.14 ± 0.03 41.41 ± 0.05

103.4 ± 0.8 100.8 ± 0.7 102.5 ± 0.5

315.5 298.15

41.0 41.4

94.4 ± 0.6 98.2 ± 1.3

KMLE/46 KMLE/45

298.15

40.87 ± 0.16k

99.7 ± 0.9l

KMLE/35

298.15m

40.30 ± 0.06

92.1 ± 0.8

VG/47

154.5 ± 3.7 134.9 ± 0.5 p-Hydroxybenzaldehyde Crystalline Phase

206.8 ± 2.7 199.2 ± 1.8 KMLE/14

99.8 ± 0.5

298.15

calorimetric/35 Liquid Phasee

378.2 to 429.4

403.80f

21.18 ± 0.01

76.9 ± 0.1

298.15 389.81i

37.05 ± 0.17 23.14 ± 0.01

85.8 ± 1.2 78.1 ± 0.2

1.0000

−84.1 ± 11.3j

0.0045

static/this work

163.5 ± 4.1 141.0 ± 0.5

Uncertainties are standard deviations of the least-squares regressions and includes the uncertainty of Δgcr,1Cop,m. bCalculated as {[Δgcr,1 Hom(θ) − Δgcr,1 Gom(θ)]/θ}; uncertainties calculated through the RSS method. cs is the standard deviation of the fit defined as a

n

s = [∑ (ln p − ln pcalc )2i /(n − m)]1/2 i−1

where n is the number of experimental points used in the fit and m is the number of adjustable parameters of the Clarke and Glew equation. dThe thermodynamic properties of sublimation could not be accurately determined due to the narrow temperature range and the scarce number of the measured sublimation vapor pressures. eIncluding supercooled liquid. fMean temperature. gDetermined from the fitting of eq 2 to the present work and the literature (p,T) data covering the temperature range (266.5−470) K. hEstimated as the same value derived from the fittings of eq 3 to the sublimation data of the p-HBAD. iTemperature of triple point. jAdjustable parameter derived from the fittings of eq 3 to the (pressure−temperature) data. kMean value, calculated from the literature vapor pressures results for each of the three effusion cells used by the authors.35 lCalculated as the weighted mean of the results reported by the authors.35 mCalculated from the literature vapor pressures,47 using ΔgcrCop,m= −(29.1 ± 16.2) J·K−1· mol−1.

kJ·mol−146 and ΔgcrGom(315.5 K) = 41.0 kJ·mol−146 (values of vapor pressure were not reported). This reported enthalpy of sublimation was adjusted in this work to the temperature 298.15 K (using ΔgcrCoP,m = −(29.1 ± 16.2) J·K−1·mol−1) yielding ΔgcrHom(298.15 K) = (94.9 ± 0.7) kJ·mol−1, 8.5 kJ·

method. 45,46 One of these works reports the value ΔgcrHom(298.15 K) = (98.2 ± 1.3) kJ·mol−1,45 which is 5.2 kJ· mol−1 smaller than the result determined by us, and the value ΔgcrGom(298.15 K) = 41.4 kJ·mol−1,45 that is similar to ours. The other study reported the values ΔgcrHom(315.5 K) = (94.4 ± 0.6) 2987



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mol−1 smaller than our result. A viscosity gauge was used to measured the sublimation vapor pressures between (312.0 to 335.9) K.47 Fitting the reported data by eq 3 (using the value ΔgcrCop,m = (−29.1 ± 16.2) J·K−1·mol−1) the derived results are ΔgcrHom(298.15 K) = (92.1 ± 0.8) kJ·mol−1 (11.3 kJ·mol−1 smaller than ours) and ΔgcrGom(298.15 K) = (40.30 ± 0.06) kJ· mol−1, that corresponds to a vapor pressure p = 8.7 × 10−3 Pa (that is 3.8 × 10−3 Pa larger than ours). The vaporization vapor pressures of p-HBAD were determined over a large temperature interval (378.2 to 429.4) K, using the static method. The fitting of eq 3 to the experimental (p,T) data yields the value Δg1Cop,m = −(84.1 ± 11.3) J·K−1·mol−1, which is reported in Table 4. The other thermodynamic properties of vaporization derived from this fitting are also presented in this Table. The triple point temperature was estimated by the intersection of the related (p,T) curves. Figure 2 shows the phase diagram of p-HBAD in

could be considered constant, but the fit of eq 3 to the (p,T) sublimation results of meta-HBAD did not yield a trustful value of ΔgcrCop,m(θ). Therefore, the result ΔgcrCop,m(θ) = −(29.1 ± 16.2) J·K−1·mol−1, derived from the fittings of eq 3 to the sublimation vapor pressures of the p-HBAD, was assumed to hold for the meta isomer and inserted in eq 3. The literature result ΔcrgHmo(298.15 K) = (100.1 ± 0.6) kJ·mol−1 was determined by the Knudsen effusion method over the temperature interval (312.2 to 330.2) K.14 This result is only 0.9 kJ·mol−1 smaller than our result. When extrapolated to the temperature 298.15 K, the vapor pressure of m-HBAD determined in this work (p = 2.1 × 10−2 Pa) is equal to the one previously reported,14 confirming again the consistency of the results published therein. The other available literature results46 are ΔgcrHom(315.5 K) = (93.6 ± 0.6) kJ·mol−1 and ΔgcrGom(315.5 K) = 37.8 kJ·mol−1 (values of vapor pressure are not reported) and were also derived using the Knudsen effusion method. The reported result of the enthalpy of sublimation was adjusted in this work to the temperature 298.15 K (using ΔgcrCop,m = −(29.1 ± 16.2) J·K−1·mol−1) yielding ΔgcrHom(298.15 K) = (94.1 ± 0.7) kJ·mol−1, which is 6.9 kJ·mol−1 smaller than our value. The vapor pressures of the liquid m-HBAD were measured using the static method, over the large temperature interval (368.3 to 419.4) K that enabled to get the value Δg1Cop,m = −(82.3 ± 11.4) J·K−1·mol−1 from the fit of eq 3 to the experimental (p,T) data. This result, as well as the other properties of vaporization derived from this fit, are also collected in Table 4. Figure 3 shows the phase diagram of m-

Figure 2. Phase diagram of p-hydroxybenzaldehyde: ○, vaporization; ◇, vaporization (supercooled liquid); □, sublimation (static); ×, sublimation (effusion); ★, normal (p = 1 × 105 Pa) boiling temperature extrapolated from the Clarke and Glew equation, eq 3; △, normal (p = 1 × 105 Pa) boiling temperature reported in literature.48 Triple point data determined in this work: T = 389.8 K; p = 79.3 Pa.

the neighborhood of the triple point, Ttp = 389.8 K and ptp = 79.3 Pa. This figure also shows the normal (p = 1 × 105 Pa) boiling temperature, T = 577.8 K, extrapolated in this work from eq 3, assuming that the constant value Δg1Cop,m= −(84.1 ± 11.3) would remain valid for temperatures far out the experimental interval. As this is probably not the case, our estimation of the normal boiling temperature may be wrong. But we have no means to evaluate the consistency of the unique normal boiling temperature reported in the literature for this isomer, T = 583.2 K48 that differs ca. 5 K from our extrapolated value. c. meta-Hydroxybenzaldehyde. The vapor pressures of crystalline m-HBAD were measured using both the mass-loss Knudsen effusion and the static methods. The concordance between the vapor pressures determined using the two methods over the global temperature interval (309.1 to 368.2) K, also allowed a single fit of the results through eq 3, and gives additional confidence to the determined results as referred to above for the para isomer. Similarly to the procedure used for p-HBAD, it was assumed that ΔgcrCop,m

Figure 3. Phase diagram of m-hydroxybenzaldehyde: ○, vaporization; ◇, vaporization (supercooled liquid); □, sublimation (static); ×, sublimation (effusion); ★, normal (p = 1 × 105 Pa) boiling temperature extrapolated from the Clarke and Glew equation, eq 3. Triple point data determined in this work: T = 378.5 K; p = 110.3 Pa.

HBAD in the neighborhood of the triple point, Ttp = 378.5 K and ptp = 110.3 Pa (determined as explained before). This figure also presents a rough estimation of the normal (p = 1 × 105 Pa) boiling temperature (T = 561.5 K) extrapolated in this work from eq 3, assuming that the value Δg1Cop,m = −(82.3 ± 11.4) J·K−1·mol−1 would be valid for temperatures far out the experimental interval. 3.2. The Contributions of the Formyl Group for the Sublimation Properties of Benzene Derivatives. Equations 4 and 5 were proposed to estimate, respectively, standard 2988



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Table 5. Experimental (exp) and Estimated (est) Values of Standard Molar Enthalpies and Gibbs Energies of Sublimation, at T = 298.15 K, of Substituted Benzaldehydes ΔgcrGom/kJ·mol−1 exp

est

exp

esta

ref

(16.6) 38.11 ± 0.04 41.73 ± 0.05 30.96 ± 0.01

(19.2 ± 1.3) 35.2 ± 1.5 40.0 ± 1.6 33.4 ± 1.4

(69.2 ± 0.6) 101.0 ± 0.7 103.4 ± 0.8 91.3 ± 0.1

(74.1 ± 2.6) 94.9 ± 2.8 101.5 ± 2.9 95.6 ± 2.6

this work this work this work 15

Tfus/K

compound b

o-HBAD m-HBAD p-HBAD methyl p-formylbenzoate

272.3 377.6 390.2 335.2

± ± ± ±

0.3 0.2 0.3 0.1

ΔgcrHom/kJ·mol−1 a

a Values estimated through eq 4 and eq 5. bValues estimated for an hypothetical crystalline phase, through the values of Δg1Hom(T = 298.15 K), Δ1crHom(T = 298.15 K), and of p(Tfus).

Table 6. Standard (po = 0.1 MPa) Molar Enthalpies and Gibbs Energies of Formation, at T = 298.15 K −ΔfHoma

−ΔfGoma

compound

crystal

liquid

gas

crystal

liquid

gas

o-HBAD

309.8 ± 1.6

240.6 ± 1.5

170.8 ± 1.5

172.2 ± 1.5c

154.2 ± 1.5

m-HBAD p-HBAD

313.8 ± 1.6c14 320.3 ± 1.314 320.0 ± 2.035 320.1 ± 1.7d

296.0 ± 1.834 291.6 ± 2.535 294.5 ± 1.5b,c 291.9 ± 2.0 302.5 ± 2.2

212.8 ± 1.7 216.7 ± 1.9

168.0 ± 1.7c 175.2 ± 1.9c

162.9 ± 1.7 170.6 ± 1.9

129.9 ± 1.7 133.5 ± 1.9

a

Standard uncertainties calculated through the RSS method. bSelected value; calculated as the weighted mean of the two results reported in the literature.34,35 cStable phase at 298.15 K. dSelected value; mean of the two values reported in the literature.14,35

benzene derivatives. Later, results for the sublimation of methyl p-formylbenzoate were determined.15 Despite the discrepancy observed between the experimental and estimated values of the latter compound, the reliability of the literature results14 was confirmed through the results of this work. Thus, the results of the standard molar enthalpy and Gibbs of sublimation of methyl p-formylbenzoate15 and the results estimated in this work for o-HBAD were included in a multivariable linear regression analysis on the extended database. This regression yielded gi = (12.4 ± 0.6) kJ·mol−1 and hi = (20.2 ± 1.3) kJ· mol−1 for the contributions of the −CHO substituent to the volatility and enthalpy of sublimation of their benzene derivatives. The interactions between the −CHO and −OH G = (4.1 ± groups in the para position were estimated as y(R j/Rk) −1 −1 H 0.3) kJ·mol and y(Rj/Rk) = (6.2 ± 0.7) kJ·mol . The structures of o-HBAD in crystalline49 and gaseous phases35 show the presence of an intramolecular H-bond involving the phenolic OH group and the CO group of the formyl substituent. So, a very significant ortho effect (designated as ortho-113) exists between the CHO and OH groups, corresponding to xG(Rj/Rk) = −(10.1 ± 0.4) kJ·mol−1 and xH(Rj/Rk) = −(17.5 ± 0.8) kJ·mol−1. Tables S3 and S4 (Supporting Information) compares the original and the referred to the above revised contributions. Table 5 reports experimental and estimated values of the standard molar enthalpies and Gibbs energies of sublimation, at T = 298.15 K, of substituted benzenes containing the formyl group. Some discrepancies between the experimental and estimated values seem larger than expected, which may be a consequence of the scarce number of benzaldehyde results. Therefore, the thermodynamic study of the sublimation of other benzaldehydes derivatives would be useful to validate the consistency of the contributions of the formyl group to the referred to above estimation method. 3.3. Standard Molar Thermodynamic Properties of Formation. The standard molar Gibbs energy of formation

Gibbs energies and enthalpies of sublimation, at the temperature 298.15 K, of substituted benzenes. These equations take into account the influence of 30 different substituents and the eventual interactions of those substituents in ortho and para positions.13 No relevant interactions of substituents in meta position were observed.13 The contribution of each substituent i to [Δ crg G mo (298.15 K) − 0.056(T fus /K)], and to [ΔgcrHom(298.15 K) − 0.031(Tfus/K)], are denoted by gi and hi, respectively, and ni stands for their number. xG(Rj/Rk) and xH(Rj/Rk) refer to the contributions of the eventual interactions between the substituents Rj and Rk in ortho positions, and nx represents the number of these interactions; yG(Rj/Rk) yH(Rj/Rk), and ny have analogous meanings as above for substituents in para positions to each other. Δcrg Gmo(298.15 K)/kJ ·mol−1 = −(11.5 ± 0.7) + (0.056 ± 0.003)(Tfus/K) +

∑ ni . gi + ∑ nx . x(RG /R ) + ∑ ny . y(RG /R ) j

k

j

k

(4)

Δcrg Hmo(298.15 K)/kJ ·mol−1 = (40.0 ± 1.5) + (0.031 ± 0.005)(Tfus/K) + +

∑ nx . x(RH /R ) + ∑ ny . y(RH /R ) j

k

j

k

∑ ni . hi (5)

The database that supports the predictive method includes the standard Gibbs energy and enthalpy of sublimation results, at T = 298.15 K, of meta and para isomers of hydroxybenzaldehyde, reported in the literature.14 Therefore, the contributions assigned before to the formyl group, gi = (14.7 ± 0.9) kJ· mol−1 and hi = (23.8 ± 1.8) kJ·mol−1,13 and to the interaction between −CHO and −OH groups in the para position, yG(Rj/Rk) = (3.9 ± 0.3) kJ·mol−1 and yH(Rj/Rk) = (6.0 ± 0.7) kJ·mol−113 were determined from experimental results of only those two 2989



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Table 7. Standard (po = 0.1 MPa) Molar Entropies in Crystalline, Liquid, and Gaseous Phases at T = 298.15 K compound o-HBAD m-HBAD p-HBAD a

Som(g)a/J·K−1·mol−1

Som(1)/J·K−1·mol−1

347.7 359.5 358.5

227.2 ± 0.3 205.0 ± 3.7 195.0 ± 4.1

b

Som(cr)/J·K−1·mol−1 171.7 148.6 ± 2.4b 151.7 ± 2.7b

−ΔfSom(g)/J·K−1·mol−1

−ΔfSom(1)/J·K−1·mol−1

−ΔfSom(cr)/J·K−1·mol−1

289.7 277.9 278.9

410.2 ± 0.3 432.4 ± 3.7 442.4 ± 4.1

465.7 488.8 ± 2.4b 485.7 ± 2.7b

b

Calculated at the B3LYP/6-31G(d) level. bStable phase at T = 298.15 K.

Figure 4. Relation between standard thermodynamic properties of formation in the crystalline, liquid, and gaseous phases, ΔfHom (g, 1, cr) and ΔfGom (g, 1, cr), of the three isomers of hydroxybenzaldehyde.

[C(graphite)] = 5.740 J·K−1·mol−1; (H2, g) = 130.680 J·K−1· mol−1 and (O2, g) = 205.147 J·K−1·mol−1. The results of the standard Gibbs energy of formation in the gaseous phase were calculated as [ΔfGom(298.15 K) = ΔfHom(298.15 K,g) − 298.15 ΔfSom(298.15 K, g)] and the results in condensed phases (including the hypothetical ones for comparison reasons), ΔfGom(298.15 K, cr or l), were calculated by subtracting from ΔfGom(298.15 K, g) the values of Δgcr,1Gom(298.15 K). Figure 4 compares the results of ΔfHom and ΔfGom in the gaseous, liquid, and crystalline phases for the three compounds studied. Taking into account the experimental uncertainty, the order of ΔfGom in the gaseous phase is ortho < meta ≈ para. The values of ΔfHom also follow this sequence. The higher stability (lower value of ΔfGom) of the ortho isomer in this phase is due to the intramolecular hydrogen bond OH···O that exists between the hydroxyl and formyl groups.35 The sequences of the values of ΔfGom and of ΔfHom in the condensed phases differ only slightly. In the liquid phase, the sequence of ΔfGomis ortho ≈ para < meta, while for ΔfHom the sequence is para < ortho ≈ meta. In the crystalline phase the sequences for the values of ΔfGom and of ΔfHom are, respectively, para < ortho ≈ meta and para < meta < ortho.

(ΔfGom) may be used to evaluate the thermodynamic stability of a compound at standard conditions. Furthermore, the values of ΔfGom of pure compounds are very important to calculate equilibrium constants of reactions where they act as reagents or products. Therefore, we calculated for the three isomers of hydroxybenzaldehyde in crystalline, liquid, and gaseous phases, the values of (ΔfGom, cr), (ΔfGom, l), and (ΔfGom, g), at T = 298.15 K, reported in Table 6. This table also presents the literature values of ΔfHom(298.15 K) for liquid o-HBAD,34,35 and for crystalline m-HBAD14 and p-HBAD.14,35 Combining these literature results with the values of Δg1Hom(298.15 K) or ΔgcrHom(298.15 K) determined in this work, the results of ΔfHom(298.15 K), in the gaseous phase, were determined and are also reported in that table. To calculate ΔfSom(298.15 K, g) the values of Som(T, g), and also the values of Cop,m(T, g), of the three isomers, were calculated over the temperature interval (150−500) K, from statistical thermodynamics, by means of the Gaussian 03 software package, 50 using the vibrational frequencies from DFT calculations, B3LYP/6-31G(d) approach (scaled by 0.960 ± 0.02251). These values are reported in Table S5 (Supporting Information). The values of ΔfSom(298.15 K, g) were then calculated from the values of Som(298.15 K, g) and from the following reference standard molar entropies:52 2990



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(3) Pouramini, Z.; Moradi, A. Structural and orthoselectivity study of 2-hydroxybenzaldehyde using spectroscopic analysis. Arabian J. Chem. 2012, 5, 99−102. (4) Bonnett, R. Photosensitizers of the porphyrin and phthalocyanine series for photodynamic therapy. Chem. Soc. Rev. 1995, 24, 19−33. (5) Paixão, J. A.; Beja, A. M.; Silva, M. R.; Veiga, L. A.; Serra, A. C. 3Hydroxybenzaldehyde. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2000, C56, 1348−1350. (6) Dallinger, D.; Kappe, C. O. Rapid preparation of the mitotic kinesin Eg5 inhibitor monastrol using controlled microwave-assisted synthesis. Nat. Protoc. 2007, 2, 317−321. (7) Ahn, E.-K.; Jeon, H.-J.; Lim, E.-J.; Jung, H.-J.; Park, E.-H. Antiinflammatory and anti-angiogenic activities of Gastrodia elata Blume. J. Ethnopharmacol. 2007, 110, 476−482. (8) Evaluation of certain food additives and contaminants. Fifty-seventh report of the joint FAO/WHO expert committee on Food Additives; Technical Report Series 909; WHO, 2002, pp 1−171. ISBN 92-4120909-7. (9) Lee, C. Y.; Nanah, C. N.; Held, R. A.; Clark, A. R.; Huynh, U. G. T.; Maraskine, M. C.; Uzarski, R. L.; McCracken, J.; Sharma, A. Effect of electron donating groups on polyphenol-based antioxidant dendrimers. Biochimie 2015, 111, 125−134. (10) Antonucci, J. M. Aldehyde methacrylates derived from hydroxybenzaldehydes. J. Dent. Res. 1978, 57, 500−505. (11) Jasinski, J. P.; Butcher, R. J.; Narayana, B.; Swamyd, M. T.; Yathirajan, H. S. Redetermination of 4-hydroxybenzaldehyde. Acta Crystallogr., Sect. E: Struct. Rep. Online 2008, E64, o187. (12) Samal, S.; Das, R. R.; Sahoo, D.; Acharya, S. Chelating resins V: synthesis and characterization of chelating resins of formaldehydecondensed phenolic schiff bases derived from 4,4′-diaminodiphenylsulphone with hydroxybenzaldehydes. Polym. Int. 1997, 44, 41−48. (13) Monte, M. J. S.; Almeida, A. R. R. P. A new approach for the estimation of sublimation enthalpies and vapor pressures of crystalline benzene derivatives. Struct. Chem. 2013, 24, 2001−2016. (14) Ribeiro da Silva, M. D. M. C.; Gonçalves, M. V.; Monte, M. J. S. Thermodynamic study on hydroxybenzaldehyde derivatives: 3- and 4hydroxybenzaldehyde isomers and 3,5-di-tert-butyl-2-hydroxybenzaldehyde. J. Chem. Thermodyn. 2010, 42, 472−477. (15) Almeida, A. R. R. P.; Monte, M. J. S. Vapor pressures of four methyl esters of substituted benzoic acids. The intermolecular hydrogen bond OH···O. J. Chem. Eng. Data 2016, 61, 1012−1020. (16) Sabbah, R.; El Watik, L. New reference materials for the calibration (temperature and energy) of differential thermal analysers and scanning calorimeters. J. Therm. Anal. 1992, 38, 855−863. (17) Sabbah, R.; Xu-wu, A.; Chickos, J. S.; Planas Leitão, M. L.; Roux, M. V.; Torres, L. A. Reference materials for calorimetry and differential thermal analysis. Thermochim. Acta 1999, 331, 93−204. (18) Della Gatta, G.; Richarson, M. J.; Sarge, S. M.; Stølen, S. Standards, calibration, and guidelines in microcalorimetry part 2. Calibration standards for differential scanning calorimetry. Pure Appl. Chem. 2006, 78, 1455−1476. (19) Roux, M. V.; Temprado, M.; Chickos, J. S.; Nagano, Y. Critically evaluated thermos chemical properties of polycyclic aromatic hydrocarbons. J. Phys. Chem. Ref. Data 2008, 37, 1855−1996. (20) Chang, S. S.; Bestul, A. B. Heat capacity and thermodynamic properties of o-terphenyl crystal, glass, and liquid. J. Chem. Phys. 1972, 56, 503−516. (21) Monte, M. J. S.; Santos, L. M. N. B. F.; Fulem, M.; Fonseca, J. M. S.; Sousa, C. A. D. New static apparatus and vapor pressure of reference materials: naphthalene, benzoic acid, benzophenone and ferrocene. J. Chem. Eng. Data 2006, 51, 757−766. (22) Freitas, V. L. S.; Monte, M. J. S.; Gomes, J. R. B.; Santos, L. M. N. B. F.; Ribeiro da Silva, M. D. M. C. Energetic studies and phase diagram of thioxanthene. J. Phys. Chem. A 2009, 113, 12988−12994. (23) Ribeiro da Silva, M. A. V.; Monte, M. J. S.; Santos, L. M. N. B. F. The design, construction and testing of a new Knudsen effusion apparatus. J. Chem. Thermodyn. 2006, 38, 778−787. (24) Almeida, A. R. R. P.; Oliveira, J. A. S. A.; Monte, M. J. S. Thermodynamic study of nicotinamide, N-methylnicotinamide and

The differences of the stability of a condensed phase relatively to the gaseous phase are a consequence of the intensity of the intermolecular interactions that are reflected in the values of the thermodynamic properties of the transition between the condensed and the gaseous phases. According to the crystalline structures,5,11,49 the molecules of the three isomers present intermolecular hydrogen bonds OH···O in the crystalline phase (and most probably also in the liquid phase). From the determined bond distances, it is possible to conclude that the hydrogen-bonding interactions are stronger in the para isomer than in the meta one.5 In the ortho isomer the crystalline structure shows both intra- and intermolecular hydrogen bonds.49 This combination weakens the strength of the intermolecular hydrogen bonds compared to the ones formed in the other two isomers.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.7b00227. Reference materials used in the calibration of the DSC calorimeter; effusion vapor pressures of crystalline meta and para hydroxybenzaldehydes determined using each of the nine effusion orifices; contributions gi and hi of −CHO, −OH and −COOCH3 groups for estimating thermodynamic properties of sublimation of benzene derivatives; contributions of interactions between substituent groups −CHO/−OH in ortho and para positions for estimating standard molar Gibbs energies and enthalpies of sublimation of substituted benzenes; absolute entropies and heat capacities in the gaseous phase of the three isomers of hydroxybenzaldehyde; values of temperature of fusion reported in the literature for the three hydoxybenzaldehydes; examples of the DSC thermograms for the three isomers studied; comparison of sublimation vapor pressures of p-HBAD, published in the literature with the fitting curve of the ones determined in this work (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Manuel J. S. Monte: 0000-0002-2210-3559 Funding

Thanks are due to Fundaçaõ para a Ciência e Tecnologia (FCT), Lisbon, Portugal, for the financial support to Project UID/QUI/0081/2013 and to FEDER (COMPETE 2020) for the financial support to Project POCI-01-0145-FEDER006980. A.R.R.P.A also thanks FCT, Operational Program and European Union for the award of the postdoctoral fellowship (SFRH/BPD/97046/2013). Notes

The authors declare no competing financial interest.

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REFERENCES

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