Effects of methoxy and formyl substituents on the energetics and reactivity of α-naphthalenes: A calorimetric and computational study

Chemosphere xxx (2014) xxx–xxx

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Effects of methoxy and formyl substituents on the energetics and reactivity of a-naphthalenes: A calorimetric and computational study Ana L.R. Silva, Vera L.S. Freitas, Maria D.M.C. Ribeiro da Silva ⇑ Centro de Investigação em Química, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, P-4169-007 Porto, Portugal

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 Experimental and computational

molecular energetics of a-naphthalenes.  Intramolecular hydrogen interaction on a-formylnaphthalene.  Influence of different substituents on the energetics and reactivity of a-naphthalene.  Molecular energetics of a-naphthalene derivatives.

a r t i c l e

i n f o

Article history: Received 18 October 2013 Received in revised form 12 December 2013 Accepted 13 December 2013 Available online xxxx Keywords: 1-Naphthaledehyde 1-Methoxynaphthalene Intramolecular hydrogen bonds Enthalpy of formation Electrostatic potential energy maps Frontier orbitals

a b s t r a c t A combined experimental and computational study was developed to evaluate and understand the energetics and reactivity of formyl and methoxy a-naphthalene derivatives. Static bomb combustion calorimetry and the Calvet microcalorimetry were the experimental techniques used to determine the standard (po = 0.1 MPa) molar enthalpies of formation, in the liquid phase, Df Hom ðlÞ, and of vaporization, Dgl Hom , at T = 298.15 K, respectively, of the two liquid naphthalene derivatives. Those experimental values were used to derive the values of the experimental standard molar enthalpies of formation, in the gaseous phase, Df Hom ðgÞ, of 1-methoxynaphthalene, (3.0 ± 3.1) kJ mol1, and of 1-formylnaphthalene, (36.3 ± 4.1) kJ mol1. High-level quantum chemical calculations at the composite G3(MP2)//B3LYP level were performed to estimate the values of the Df Hom ðgÞ of the two compounds studied resulting in values in very good agreement with experimental ones. Natural bond orbital (NBO) calculations were also performed to determine more about the structure and reactivity of this class of compounds. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction The naphthalene (C10H8) framework contains two coplanar ortho-fused benzene rings, sharing an edge, and can be classified as the simplest polycyclic aromatic hydrocarbon (PAH). This and

⇑ Corresponding author. Tel.: +351 220 402 538; fax: +351 220 402 659. E-mail address: [email protected] (M.D.M.C. Ribeiro da Silva).

related compounds are well known potent atmospheric pollutants. They are widespread in the environment found primarily in soil (Vanschooten et al., 1995; Cousins et al., 1999), sea-bottom sediments (Kirso et al., 1990), waters associated with urbanized estuaries and coastal areas (Law et al., 1997; Viguri et al., 2002), and as components in particular matter suspended in air, persisting for extended periods of time (Callén et al., 2008). Due to the volatility of these compounds, they are present both in vapor form (You and Bidleman, 1984) and/or associated to particles,

0045-6535/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2013.12.044

Please cite this article in press as: Silva, A.L.R., et al. Effects of methoxy and formyl substituents on the energetics and reactivity of a-naphthalenes: A calorimetric and computational study. Chemosphere (2014), http://dx.doi.org/10.1016/j.chemosphere.2013.12.044

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A.L.R. Silva et al. / Chemosphere xxx (2014) xxx–xxx

facilitating their long-range transport. The human activity, including fossil fuel combustion and industrial processing, is the primary source of PAHs contamination in the environment, but they can be also generated by natural phenomena, such as forest fires. Recent studies have shown that high level of PAHs are found in meat cooked at high temperatures (Sinha et al., 2005) and in smoked fish (Stolyhwo and Sikorski, 2005). These ubiquitous environmental contaminants have raised considerable misgivings, because many PAHs, besides the negative impacts on the surrounding ecosystem, have been shown to have potential mutagenic, carcinogenic and teratogenic activities after being metabolized (Bofetta et al., 1997; Ismert et al., 2002), causing adverse health effects; their hydrophilic character allows them to enter cells easily, inducing the metabolic system that will transform these molecules (Ismert et al., 2002). Different physicochemical methods have been used in the attempt to remove these compounds from the environment. The knowledge of the energetic parameters of these kinds of compounds provides important information regarding their relative thermochemical stabilities and is intimately related to their structures, these parameters are also useful in these understanding corresponding structural, electronic, and reactivity trends. Therefore, parameters can play a relevant role as key instruments in understanding the formation mechanism of the species, predicting their behavior, and finding possible solutions to remove them from the environment. Despite their relevance, knowledge of the thermochemical data for some basic structures is incomplete. Oja and Suuberg (1998) determined vapor pressures of some PAHs and derived the enthalpies of sublimation using the Knudsen effusion technique. More recently, experimental thermodynamic properties of benzene, toluene, and 63 other PAHs were critically evaluated by Roux et al. (2008). Confirming our interest on the thermochemistry of naphthalene derivatives (Ribeiro da Silva et al., 1988, 1989, 1993, 2006), this paper presents a joint experimental and computational study of two liquid a-naphthalene derivatives, 1-formylnaphthalene and 1-methoxynaphthalene, in an attempt to enlarge the thermochemical data of these type of compounds. The experimental study was based in calorimetric measurements using combustion calorimetry and Calvet microcalorimetry techniques, from which were determined, at T = 298.15 K, the values of the standard (po = 0.1 MPa) molar enthalpies of combustion, Dc Hom ðlÞ, and of vaporization, Dgl Hom ; in turn, these values were used to calculate the standard molar enthalpies of formation, in the gas-phase, Df Hom ðgÞ, at the same temperature. This last parameter was also estimated by computational studies, performed with the composite G3(MP2)//B3LYP approach (Baboul et al., 1999), which provided the optimized structures and energies of 1-formylnaphthalene and 1methoxynaphthalene, and also of some other pertinent molecules that we used in the calculation of the Df Hom ðgÞ values of the a-naphthalene compounds, at T = 298.15 K, considering several working chemical reactions. For the title compounds, computations were also extended to gas-phase molar heat capacities at different temperatures, dipole moment, electrostatic potential energy maps mapped onto electron density isosurface, and frontier orbitals.

2. Materials and methods

equipped with an HP-5 column, cross-linked, 5% diphenyl and 95% dimethylpolysiloxane (15 m  0.530 mm i.d.  1.5 lm film thickness), resulting in final molar fractions of over 0.999. The purity of a-naphthalene derivatives were also confirmed by the average ratio between the mass of carbon dioxide recovered in the combustion experiments and the calculated mass of carbon dioxide for a complete combustion reaction. For the calibration of the static bomb was used benzoic acid, NIST Standard Reference MaterialÒ 39j (SRM 39j), while undecane, supplied by Aldrich Chemical Co. with molar fraction purity of 0.99+, was used in the calibration of Calvet microcalorimeter. The literature values of the specific densities used were q = 1.148 g cm3 and q = 1.094 g cm3 for 1-formylnaphthalene and for 1-methoxynaphthalene, respectively (Alfa Aesar Catalogue, 2011–2013); the relative atomic masses used for the elements were the ones recommended by the IUPAC commission in 2011 (Wieser et al., 2013). 2.2. Static-bomb calorimetry The standard (po = 0.1 MPa) massic energies of combustion for the two compounds were measured using a static-bomb combustion calorimeter, originally constructed at the National Physical Laboratory (Teddington, Middlesex, UK) (Gundry et al., 1969). This is an isoperibol calorimeter equipped with a twin valve bomb (internal volume 0.290 dm3) whose detailed description and procedure have been already described in the literature (Ribeiro da Silva et al., 2003). The energy equivalent of the calorimeter (ecal) was determined from the combustion of benzoic acid (NBS 39j) having a massic energy of combustion, under standard bomb conditions, of (26434 ± 3) J g1. From six calibration experiments, ecal = (15551.7 ± 1.2) J K1, for an average mass of water added to the calorimeter of 2900.0 g. Liquid samples of the two compounds, enclosed in MelinexÒ bags, were ignited in an oxygen atmosphere (p = 3.04 MPa), at T = 298.15 K, with 1.00 cm3 of deionized water added to the bomb. The Melinex bags were made according to the technique described by Skinner and Snelson (1960), in which the massic energy of combustion of dry Melinex was Dcuo = (22902 ± 5) J g1. For the cotton thread fuse (empirical formula CH1.686O0.843), Dcuo = 16240 J g1 (Coops et al., 1956); this value was previously confirmed by combustion in our laboratory. The electric energy for ignition was determined from the change in potential difference on discharge of a 1400 lF condenser across a platinum wire. The corrections for nitric acid formation were based on 59.7 kJ mol1 (Wagman et al., 1982), for the molar energy of formation of 0.1 mol dm3 HNO3 (aq) solution from N2 (g), O2 (g) and H2O (l). The value for the pressure coefficient of specific energy (ou/op)T= 0.2 J g1 MPa1 at T = 298.15 K, a typical value for organic compounds, was assumed (Washburn, 1933). Corrections for carbon formation were based on massic energy of combustion of carbon, Dcuo = 33 J g1 (Coops et al., 1956). The amount of the compound burned in each experiment was determined from the total mass of carbon dioxide produced, taking into account that formed from the combustion of the cotton thread fuse and from Melinex. For these compounds, the standard massic energy of combustion, Dcuo, was calculated by a similar procedure to that developed by Hubbard et al. (1956).

2.1. Compounds studied and reference materials 2.3. Calvet microcalorimetry 1-Formylnaphthalene [66-77-3] and 1-methoxynaphthalene [2216-69-5] were obtained commercially from Alfa Aesar with molar fraction purities of 0.989 and 0.983, respectively. Both compounds were purified by successive fraction distillation under reduced pressure. The purity of each compound was checked by gas–liquid chromatography, using an Agilent 4890 apparatus

The enthalpies of vaporization of the two compounds were measured with a high-temperature Calvet microcalorimeter (Setaram HT 1000), using the ‘‘vacuum sublimation’’ drop microcalorimetric method described by Adedeji et al. (1975), adapted to the study of liquid samples by Ribeiro da Silva et al. (1995). The details

Please cite this article in press as: Silva, A.L.R., et al. Effects of methoxy and formyl substituents on the energetics and reactivity of a-naphthalenes: A calorimetric and computational study. Chemosphere (2014), http://dx.doi.org/10.1016/j.chemosphere.2013.12.044

A.L.R. Silva et al. / Chemosphere xxx (2014) xxx–xxx

of the apparatus and the technique were previously described (Santos et al., 2004). Samples, about 5–8 mg of the compounds, contained in thin glass capillary tubes, were dropped from room temperature into the hot reaction vessel, in the calorimeter held at T = 370 K (1-formylnaphthalene) and T = 391 K (1-methoxynaphthalene), and then removed from the hot zone by vacuum vaporization. The calibration constants of the calorimeter, k, were obtained as the average of six independent experiments, k = (1.0115 ± 0.0051) and k = (1.0008 ± 0.0030) for the vaporization experiments of the undecane, for the pre-defined temperatures, T = 370 K and T = 391 K, respectively. 3. Theoretical calculations The computational strategy used to determine the enthalpies of formation, in the gas-phase, of 1-formylnaphthalene and 1-methoxynaphthalene, consisted on the design of appropriate gas-phase work reactions (George et al., 1976a, b; Hehre et al., 1995; Wheeler et al., 2009), using auxiliary molecules with similar structures, so that the types of bonds are conserved on both sides of the reaction, canceling systematic errors in the computational methods. For each work reaction, the value of the enthalpy of formation in the gas-phase of the title compound was calculated from the variation of the enthalpy of the work reaction Dr Hom , (equal to the difference of the values of the enthalpies, at T = 298.15 K, Ho298:15 K , obtained computationally, for the products and reagents) and the experimental standard molar gas-phase enthalpies of formation of the auxiliary species used, available in the literature. G3(MP2)//B3LYP method (Baboul et al., 1999), a variation of Gaussian-3 (G3) theory (Curtiss et al., 1998), was the chosen method to calculate the energy of 1-formylnaphthalene, 1methoxynaphthalene, and all auxiliary species used, considering the good results obtained for similar compounds (Freitas et al., 2013). All calculations were done with the Gaussian-03 computer program (Gaussian 03, Revision D.01, 2004). The natural bond orbitals (NBO) calculations were performed using NBO 3.1 program (NBO Version 3.1, 1998) as implemented in the Gaussian-03 package, at the B3LYP/6-31G(d) level of theory. 4. Results and discussion 4.1. Computational results 4.1.1. Geometry, electrostatic potential energy maps and frontier orbitals (HOMO and LUMO) In Fig. 1 are presented some useful graphical representations of naphthalene, 1-formylnaphthalene and 1-methoxynaphthalene to evaluate the influence of the two functional groups on the naphthalene ring. The molecular structures (optimized at the B3LYP/6-31G(d) level of theory) of 1-formylnaphthalene and 1methoxynaphthalene, that correspond to the global minimum on the potential energy surface, show the orientation of the formyl and methoxy functional groups in the a position of the naphthalene ring (full structural details are given in Figs. S1 and S2 in the Supplementary Data). Graphical representations of the electrostatic potential energy mapped onto an electron density isosurface (isodensity surface value of 0:015 e  a3 0 , where a0 is the Bohr radius) are also depicted in Fig. 1. These maps provide information about overall charge distribution in the molecules using for that a color scale, where red and dark blue regions correspond to the extreme values of the electrostatic potential, 6.00  102 J and 6.00  102 J, respectively, and the intermediate potentials are then assigned to the remaining colors of the color spectrum; it is possible

3

to identify the electron-rich regions (basic), subject to attack by electrophiles, and the electron-poor regions (acidic), subject to attack by nucleophiles. The electrostatic potential map of naphthalene clearly shows that electron density is concentrated near the p-faces (green color) and the periphery is electron poor (blue color). Comparing the three maps it is clear that the introduction of functional groups in the a position, have effects on the electron density of the rings. In the alkoxy group, its oxygen is an electron-withdrawing group by induction (orange color near the oxygen) but also exerts the function of being an electron-donating group by resonance, which is evident by the electron environment in the rings, which are almost unchanged when compared with naphthalene. In the carbonyl group of a-formylnaphthalene, the difference in electronegativity between the carbon and oxygen, leads to both r and p electron transference from carbon to oxygen and to a positively charged carbon (making carbon–oxygen double bond very highly polar). This group is an electron-withdrawing group both by induction and resonance, clearly observable by the decrease of charge in the central rings and high concentration of charge near the oxygen atom. As a result, the presence of the functional groups enables different polarities for the two molecules; 1-methoxynaphthalene is slightly polar, with dipole moment of 1.46 Debye, and the 1-formylnaphtahlene is highly polar, with dipole moment of 3.22 Debye. From the electron density surface of 1-formylnaphthalene is possible to observe that the conformational arrangement allows the occurrence of an intramolecular hydrogen bond involving the oxygen of the carbonyl group and the hydrogen of the carbon in the peri position, C–H  O. The possible intramolecular hydrogen bond by second-order perturbative theory analysis of the Fock Matrix, in NBO basis, is conventionally interpreted by the interaction between the ‘‘filled’’ Lewis-type NBO (donor NBO, i) and ‘‘empty’’ non-Lewis NBO (acceptor NBO, j), and by the estimation of the stabilization energy associated with delocatization, DE2ij . The result of NBO analysis on the molecular system shows that the stabilization energy associated with the interaction between the oxygen lone pair (LP2) and the carbon–hydrogen antibonding orbital, nO ! rCH , is 9.87 kJ mol1. In Fig. S3 of the Supplementary Data the overlap between the oxygen lone pair orbital and the antibonding carbon–hydrogen orbital is shown. The presence of a finite, nonzero overlap between the orbitals obviously manifests the presence of a finite, nonzero stabilization interaction due to the charge transfer interaction from the oxygen lone pair orbital to the antibonding carbon–hydrogen orbital, resulting in the formation of the intramolecular hydrogen bonding interaction. For this kind of hydrogen bond, C–H  O, where the hydrogen is attached to carbon, the degree of hydrogen bonding is much smaller than with conventional hydrogen bonds (X–H  X, where X are electronegative atoms). In this case, the hydrogen interaction affords a low stabilization energy of about 7.2 kJ mol1, calculated from the enthalpic difference at the G3(MP2)//B3LYP level, between the most stable conformation and the alternative equilibrium conformation which results from rotating the carbonyl substituent in such a way that no hydrogen bond type interaction is allowed. An additional theoretical analysis of electron density topology (christened as Atoms in Molecules theory, AIM theory, by Bader, 1990) was made, with the program AIMAll (Version 13.05.06), aiming at the location of critical points in the electronic charge density distribution in the region between de C–H  O; this analysis revealed a bond critical point between the interaction mentioned, with an electron density of q = 0.017 and a Laplacian of the electron density, r2q = 0.068, and also a ring critical point formed due to this interaction. Views of the highest-occupied molecular orbitals (HOMO) and of the lowest-unoccupied molecular orbitals (LUMO) for these compounds obtained from natural bond orbital analyses

Please cite this article in press as: Silva, A.L.R., et al. Effects of methoxy and formyl substituents on the energetics and reactivity of a-naphthalenes: A calorimetric and computational study. Chemosphere (2014), http://dx.doi.org/10.1016/j.chemosphere.2013.12.044

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A.L.R. Silva et al. / Chemosphere xxx (2014) xxx–xxx

Electrostatic potential map (Dipole moment)

HOMO

LUMO

(0 D)

1-formylnaphthalene

−6.00 × 10-2 J

naphthalene

Molecular Structure

1-methoxynaphthalene

+6.00 × 10-2 J

(3.22 D)

(1.46 D)

Fig. 1. Molecular structures, dipole moment values, electrostatic potential energy maps mapped onto an electron density isosurface (isodensity value of 0:015 e  a3 0 , where a0 is the Bohr radius), HOMO and LUMO mapped onto an electrostatic potential energy isosurface (isodensity value of 0:015 e  a3 0 ). Table 1 Highest-occupied and lowest-unoccupied molecular orbitals energy values, E(HOMO) and E(LUMO), respectively, and HOMO–LUMO energy gap, EGAP, for naphthalene, 1-formylnaphthalene and 1-methoxynaphthalene. Compounds

E(HOMO)/eV

E(LUMO)/eV

EGAP/eV

Naphthalene 1-Formylnaphthalene 1-Methoxynaphthalene

6.12 6.46 6.08

1.17 0.30 1.16

7.29 6.75 7.24

performed with Gaussian NBO Version 3.1 are also shown in Fig. 1. With the values of the HOMO and LUMO energies, listed in Table 1, is possible to calculate de energy gap, EGAP, calculated from the difference between the LUMO and HOMO energies. The HOMO orbitals of the three molecules are located at a p (C8–C9) bond shared by the two benzene ring; while the LUMO orbitals have different positions: in naphthalene is at p (C8–C9), in 1-formylnaphthalene the LUMO is at the empty antibonding carbonyl bond, p* (C–O), one of the characteristics of these type of compounds, and in 1-methoxynaphthalene it is at p* (C1–C2). All the electronic transitions from HOMO and LUMO are of the type p ? p*. The HOMO is the orbital that primarily acts as an electron donor (nucleophile) while the LUMO largely acts as the electron acceptor (electrophile). These frontier orbitals, HOMO and LUMO, determine the way a molecule interacts with other species and helps to characterize its chemical reactivity and kinetic stability. Molecules with low frontier orbital gaps are more polarizable and are generally associated with a high chemical reactivity and low kinetic stability (Fleming, 2010). The comparison of HOMO– LUMO gap energies between the three compounds (Table 1) shows that 1-formylnaphthalene has the lowest energy gap (6.75 eV) suggesting higher chemical reactivity relatively to the others two compounds.

4.1.2. Estimation of the gas-phase enthalpies of formation The numerical values calculated for the enthalpies of reaction, Dr Hom ðgÞ, and of formation, Df Hom ðgÞ, at T = 298.15 K, of the isolated 1-formylnaphthalene and 1-methoxynaphthalene, considering different gas-phase working reactions appear in Table 2. The G3(MP2)//B3LYP absolute enthalpies and the experimental gasphase enthalpies of formation, at the T = 298.15 K, for all the species considered in this work (title compound and auxiliary species appearing in the equations in Table 2) are given as Supplementary Data (Table S1). In the calculation of the gas-phase enthalpy of formation of 1-formylnaphthalene, eight working reactions (Eqs. (1)–(8)) were considered, with values ranging from 32.3– 39.7 kJ mol1, yielding a mean value of (35.4 ± 1.6) kJ mol1 (the uncertainty assigned equal to twice the standard deviation of the mean). In the case of 1-methoxynaphthalene, the mean value obtained was of (2.8 ± 2.8) kJ mol1 (the uncertainty assigned equal to twice the standard deviation of the mean), considering the working reactions, Eqs. (9)–(14), with values ranging from 5.3 to 1.1 kJ mol1. 4.2. Experimental results 4.2.1. Crystalline-phase enthalpies of formation Detailed results of each combustion experiment, for 1-formylnaphthalene and 1-methoxynaphthalene, are presented in Tables S2 and S3, respectively, of the Supplementary Data. DU(IBP) is the internal energy for the isothermal bomb process calculated according to Eq. (15). Dm(H2O) is the deviation of the mass of water added to the calorimeter from 2900.0 g. The remaining terms have been previously described (Hubbard et al., 1956).

DUðIBPÞ ¼ fecal þ C p ðH2 O; lÞ  DmðH2 OÞ þ ef gDT ad þ DUðignÞ

ð15Þ

Please cite this article in press as: Silva, A.L.R., et al. Effects of methoxy and formyl substituents on the energetics and reactivity of a-naphthalenes: A calorimetric and computational study. Chemosphere (2014), http://dx.doi.org/10.1016/j.chemosphere.2013.12.044

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A.L.R. Silva et al. / Chemosphere xxx (2014) xxx–xxx

Table 2 Working reactions for 1-formylnaphthalene, 1-methoxynaphthalene and correspondent calculated values for the enthalpies of reaction, DrH(g), and formation, Df Hom ðgÞ, in the gaseous-phase, at T = 298.15 K. Working reactions

Dr HðgÞ=kJ mol1

Df Hom ðgÞ=kJ mol1

(1)

4.95

35.9

(2)

5.66

35.0

(3) (4)

X = 2, 5.66 X = 3, 3.07

X = 2, 39.7 X = 3, 36.3

(5) (6)

X = 2, 6.47 X = 3, 4.41

X = 2, 34.7 X = 3, 32.3

(7) (8)

X = 2, 23.69 X = 3, 11.21

X = 2, 34.3 X = 3, 34.7

Mean value

h35.4 ± 1.6i

1-Formylnaphthalene

1-Methoxynaphthalene (9)

2.24

2.4

(10)

1.53

3.8

(11)

5.67

2.6

(12)

0.27

1.5

(13)

2.27

5.3

(14)

1.69

1.1

Mean value

The standard massic energies of combustion, Dcuo, for 1-formylnaphthalene and 1-methoxynaphthalene, refer to the combustion reactions (16) and (17), respectively.

C11 H8 OðlÞ þ 12:5O2 ðgÞ ! 11CO2 ðgÞ þ 4H2 OðlÞ

ð16Þ

C11 H10 OðlÞ þ 13O2 ðgÞ ! 11CO2 ðgÞ þ 5H2 O

ð17Þ

o

The standard massic energies, Dcu , the derived standard molar energies, Dc U om ðlÞ, and enthalpies of combustion, Dc Hom ðlÞ, and the standard molar enthalpies of formation, in the liquid phase,

h2.8 ± 2.8i

Df Hom ðlÞ for each compound, at T = 298.15 K, are given in Table 3. The uncertainties associated to the standard molar energy and enthalpy of combustion are twice the overall standard deviation of the mean and include the uncertainties in calibration with benzoic acid and in the energy of combustion of Melinex, used as combustion auxiliary (Rossini, 1956 and Olofson, 1979). To derive Df Hom ðlÞ from Dc Hom ðlÞ, the standard molar enthalpies of formation, at T = 298.15 K, for H2O(l), (285.830 ± 0.040) kJ mol1 and CO2(g), (393.51 ± 0.13) kJ mol1 (values from Cox et al. (1989)) were used.

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Table 3 Standard (po = 01 MPa) massic energies of combustion, Dcuo, standard molar energies of combustion, Dc U om , standard molar enthalpies of combustion, Dc Hom , and standard molar enthalpies of formation, Df Hom , for the compounds studied at T = 298.15 K. Compound

Dcuo/(J g1)

Dc U om ðlÞ=ðkJ  mol1 Þ

Dc Hom ðlÞ=ðkJ  mol1 Þ

Df Hom ðlÞ=ðkJ  mol1 Þ

1-Formylnaphthalene 1-Methoxynaphthalene

34789.88 ± 9.91 35916.11 ± 4.26

5433.5 ± 3.5 5681.8 ± 2.3

5437.3 ± 3.5 5686.8 ± 2.3

34.7 ± 3.7 71.0 ± 2.7

4.2.2. Enthalpies of vaporization Measurements of the standard molar enthalpy of vaporization for 1-formylnaphthalene and 1-methoxynaphthalene obtained by Calvet microcalorimetry are given in Table 4, with uncertainties of twice the standard deviation of the mean. The observed enthalpies of vaporization, at the experimental temperature g o o T, Dg;T l;298:15 K H m , were corrected to T = 298.15 K, Dl Hm , according to Eq. (18), using the term DT298:15 K Hom ðgÞ

DT298:15 K Hom ðgÞ ¼

Z

T

298:15 K

C op;m ðgÞdT;

Table 5 Standard (p° = 0.1 MPa) molar enthalpies of formation, in the gas-phase, obtained by experimental and computational methods, respectively, Df Hom ðg; expÞ and Df Hom ðg; compÞ, at T = 298.15 K for the compounds studied, and the absolute difference between these values, D (Values in kJ mol1). Compound

Df Hom ðg; expÞ

Df Hom ðg; compÞ

D

1-Formylnaphthalene 1-Methoxynaphthalene

36.3 ± 4.1 3.0 ± 3.1

35.4 ± 0.8 2.8 ± 1.4

0.9 0.2

ð18Þ

where C op;m ðgÞ is the molar heat capacity in the gaseous phase of the compounds, derived from statistical thermodynamics using the vibrational frequencies calculated at the B3LYP/6-31G(d) level (Irikura, 2002). The C op;m ðgÞ ¼ f ðTÞ obtained for the studied compounds (values in Table S4 of the Supplementary Information) are represented by Eqs. (19) and (20), respectively.

of benzene and naphthalene (framework), the enthalpic increments (marked next to the arrows) for the introduction of the R groups (presented in Fig. 2) were calculated from Eq. (21). In this equation, values of Df Hom ðR  framework; gÞ and Df Hom ðframework; gÞ are the experimental values of the gas-phase standard molar enthalpies of formation, written above the molecular structures of the substituted compounds and of benzene or naphthalene, respectively.

1

C op;m ðgÞ=ðJ  K1  mol Þ ¼ 9:015  107 ðT=KÞ3

R  increment ¼ Df Hom ðR  framework; gÞ  Df Hom ðframework; gÞ

þ 7:055  104 ðT=KÞ2

ð21Þ

þ 3:461  101 ðT=KÞ þ 2:140  101 ð19Þ 1

C op;m ðgÞ=ðJ  K1  mol Þ ¼ 5:533  107 ðT=KÞ3 þ 3:165  104 ðT=KÞ2 þ 5:240  101 ðT=KÞ þ 4:050

ð20Þ

Comparing the results obtained for the two sets of compounds, there is good agreement between the enthalpic increments. The presence of the different functional groups mentioned in the benzene and the naphthalene frameworks causes a decrease on the enthalpy value, resulting in an enthalpic stabilization in the following order: formyl < methoxy < hydroxyl < carboxyl.

Dgl Hom ð298:15

The uncertainties associated to the values of KÞ are twice the overall standard deviation of the mean and include the uncertainties in calibration. 4.2.3. Experimental gas-phase enthalpies of formation The experimental standard (po = 0.1 MPa) molar enthalpies of formation in the gaseous phase, at T = 298.15 K, Df Hom ðgÞ, of 1-formylnaphthalene and 1-methoxynaphthalene were derived from the experimental values of the enthalpies of vaporization, Dgl Hom ; (presented in Table 4, Section 4.2.2) and of formation in the liquid phase, Df Hom ðlÞ, at the same temperature, (presented in Table 3, Section 4.2.1), yielding the respective values, (36.3 ± 4.1) kJ mol1 and (3.0 ± 3.1) kJ mol1. These values are compiled in Table 5 together with the estimated gas-phase enthalpies of formation calculated for the two compounds; the good agreement between these two values obtained by this computational methodology confirms again the applicability of the method for these type of compounds (Freitas et al., 2013). For the assessment of the energetic effect of different functional groups (hydroxyl, R = OH, methoxy, R = OCH3, formyl, R = CHO, and carboxylic acid, R = COOH) on the gas-phase enthalpy of formation

ð22Þ In order to evaluate the stabilization or destabilization due to a substituent change from benzene to naphthalene, the computed values for the enthalpy of reaction (22) at the G3(MP2)//B3LYP level (the computed enthalpy values are available in the Supplementary Data in Table S1) lead to the following results: for R = OH, 0.71 kJ mol1; for R = OCH3, 2.24 kJ mol1; for R = CHO, 4.95 kJ mol1; and for R = COOH, 11.45 kJ mol1. These data confirm that the substitution on the naphthalene ring is energetically preferred to the equivalent on the benzene ring for hydroxyl and methoxy groups, unlike that for formyl and carboxyl groups. One of the possible explanations may due to the fact that hydroxyl and methoxy affect the p-cloud of the naphthalene ring as a mesomeric electron donor (p-donor), more so than as an inductive electron-withdrawing group, despite the electronegativity of the oxygen. The energetic effect due to the presence of the intramolecular C–H  O hydrogen bonding in 1-formylnaphthalene (mentioned in Section 4.1.1) is not reproduced when compared to the same

Table 4 Standard (po = 0.1 MPa) molar enthalpies of phase transition, Dgl Hom , at T = 298.15 K for the compounds studied determined by Calvet microcalorimetry. Compound

No. exp.

Texp/(K)

1 Dg;T Ho =ðkJ  mol Þ l;298:15 K m

DT298:15 K Hom =ðkJ  mol1 Þ

Dgl Hom ð298:15 KÞ=ðkJ  mol1 Þ

1-Formylnaphthalene 1-Methoxynaphthalene

6 6

370 391

84.2 ± 0.3 86.6 ± 0.3

13.2 18.6

71.0 ± 1.7 68.0 ± 1.5

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References

Fig. 2. Enthalpic increments for the insertion of hydroxyl, methoxy, formyl and carboxylic acid fragments in benzene and naphthalene frameworks. All values in kJmol1. aValues from Pedley (1994); bValues from Ribeiro da Silva et al. (1988); c This work.

benzene derivative, possibly due to the weakness of this type of interaction (Fleming, 2010). 5. Conclusions The gas-phase standard molar enthalpies of formation, at T = 298.15 K, of 1-formylnaphthalene and 1-methoxynaphthalene have been derived through experimental and computational methods. The structural, the charge polarization and the HOMO and LUMO maps of 1-formylnaphthalene and 1-methoxynaphthalene were studied at the B3LYP/6-31G(d) level of theory, providing an enhanced knowledge about the reactivity of these compounds. Finally, it is found that the calculated data reported in this work are in excellent agreement with those determined experimentally, providing confidence to the values calculated in this work for the properties without prior experimental data available in the literature. Acknowledgments Thanks are due to Fundação para a Ciência e Tecnologia (FCT), Lisbon, Portugal, and to Programa Ciência 2008 (PEst-C/QUI/ 491UI0081/2011), for garanting the financial support to Centro de Investigação em Química – UP and for financing the research project PTDC/QUI-QUI/102814/2008. We thank A.R.G. Leite, T.J.C. Teixeira and R.C.G. Ferreira, B. Sc. students, for their help on performing part of the calorimetric experiments. VLSF thanks FCT for the post-doctoral grant SFRH/BPD/78552/2011. ALRS thanks FCT for the award of a Ph.D. Grant (SFRH/BD/69606/2010). Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.chemosphere. 2013.12.044.

Adedeji, F.A., Brown, D.L.S., Connor, J.A., Leung, W.L., Paz-Andrade, I.M., Skinner, H.A., 1975. Thermochemistry of arene chromium tricarbonyls and the strengths of arene-chromium bonds. J. Organomet. Chem. 9, 221–228. AIMAll (Version 13.05.06), Keith, T.A., TK Gristmill Software, Overland Park KS, USA, 2013 (aim.tkgristmill.com). Alfa Aesar Catalogue, Germany, 2011–2013. Baboul, A.G., Curtiss, L.A., Redfern, P.C., Raghavachari, K., 1999. Gaussian-3 theory using density functional geometries and zero-point energies. J. Chem. Phys. 110, 7650–7657. Bader, R.F.W., 1990. Atoms in Molecules: A Quantum Theory. Oxford University Press, Oxford. Bofetta, P., Jourenkova, N., Gustavsson, P., 1997. Cancer risk from occupational and environmental exposure to polycyclic aromatic hydrocarbons. Cancer Causes Control 8, 444–472. Callén, M.S., de la Cruz, M.T., López, J.M., Murillo, R., Navarro, M.V., Mastral, A.M., 2008. Some inferences on the mechanism of atmospheric gas/particle partitioning of polycyclic aromatic hydrocarbons (PAH) at Zaragoza (Spain). Chemosphere 73, 1357–1365. Coops, J., Jessup, R.S., van Nes, K., 1956. Calibration of calorimeters for reactions in a bomb at constant volume. In: Rossini, F.D. (Ed.), Experimental Thermochemistry, vol. 1. Interscience, New York (Chapter 3). Cousins, I.T., Gevao, B., Jones, K.C., 1999. Measuring and modelling the vertical distribution of semi-volatile organic compounds in soils. I: PCB and PAH soil core data. Chemosphere 39, 2507–2518. Cox, J.D., Wagman, D.D., Medvedev, V.A., 1989. CODATA Key Values for Thermodynamics. Hemisphere, New York. Curtiss, L.A., Raghavachari, K., Redfern, P.C., Rassolov, V., Pople, J.A., 1998. Gaussian3 (G3) theory for molecules containing first and second-row atoms. J. Chem. Phys. 109, 7764–7776. Fleming, I., 2010. Molecular Orbitals and Organic Chemical Reactions, Reference ed. John Wiley & Sons, Ltd: Department of Chemistry, University of Cambridge, UK. Freitas, V.L.S., Gomes, J.R.B., Ribeiro da Silva, M.D.M.C., 2013. A computational study on the energetics and reactivity of some xanthene and thioxanthene derivatives. Struct. Chem. 24, 661–670. Gaussian 03, Revision D.01, Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Montgomery, Jr., J.A., Vreven, T., Kudin, K.N., Burant, J.C., Millam, J.M., Iyengar, S.S., Tomasi, J., Barone, V., Mennucci, B., Cossi, M., Scalmani, G., Rega, N., Petersson, G.A., Nakatsuji, H., Hada, M., Ehara, M., Toyota, K., Fukuda, R., Hasegawa, J., Ishida, M., Nakajima, T., Honda, Y., Kitao, O., Nakai, H., Klene, M., Li, X., Knox, J.E., Hratchian, H.P., Cross, J.B., Bakken, V., Adamo, C., Jaramillo, J., Gomperts, R., Stratmann, R.E., Yazyev, O., Austin, A.J., Cammi, R., Pomelli, C., Ochterski, J.W., Ayala, P.Y., Morokuma, K., Voth, G.A., Salvador, P., Dannenberg, J.J., Zakrzewski, V.G., Dapprich, S., Daniels, A.D., Strain, M.C., Farkas, O., Malick, D.K., Rabuck, A.D., Raghavachari, K., Foresman, J.B., Ortiz, J.V., Cui, Q., Baboul, A.G., Clifford, S., Cioslowski, J., Stefanov, B.B., Liu, G., Liashenko, A., Piskorz, P., Komaromi, I., Martin, R.L., Fox, D.J., Keith, T., Al-Laham, M.A., Peng, C.Y., Nanayakkara, A., Challacombe, M., Gill, P.M.W., Johnson, B., Chen, W., Wong, M.W., Gonzalez, C., Pople, J.A. Gaussian Inc, Wallingford CT, 2004. George, P., Trachtman, M., Bock, C.W., Brett, A.M., 1976a. An alternative approach to the problem of assessing destabilization energies (strain energies) in cyclic hydrocarbons. Tetrahedron 32, 317–323. George, P., Trachtman, M., Bock, C.W., Brett, A.M., 1976b. Homodesmotic reactions for the assessment of stabilization energies in benzenoid and other conjugated cyclic hydrocarbons. J. Chem. Soc. Perkin Trans. 2, 1222–1227. NBO Version 3.1, 1998. Glendening, E.D., Reed, A.E., Carpenter, J.E., Weinhold F., Theoretical Chemistry Institute, University of Wisconsin, Madison. Gundry, H.A., Harrop, D., Head, A.J., Lewis, G.B., 1969. Thermodynamic properties of organic oxygen compounds 21. Enthalpies of combustion of benzoic acid, pentan-1-ol, octan-1-ol, and hexadecan-1-ol. J. Chem. Thermodyn. 1, 321–332. Hehre, W.J., Radom, L., Schleyer, P.v.R., Pople, J.A., 1995. Ab initio Molecular Orbital Theory. John Wiley & Sons. Hubbard, W.N., Scott, D.W., Waddington, G., 1956. Standard states and corrections for combustions in a bomb at constant volume. In: Rossini, F.D. (Ed.), Experimental Thermochemistry, vol. 1. Interscience, New York (Chapter 5). Irikura, K.K., 2002. THERMO. PL, National Institute of Standards and Technology (http://www.cstl.nist.gov/div838/group_06/irikura/prog/thermo.html). Ismert, M., Oster, T., Bagrel, D., 2002. Effects of atmospheric exposure to naphthalene on xenobiotic-metabolising enzymes in the snail Helix aspersa. Chemosphere 46, 273–280. Kirso, U., Paalme, L., Voll, M., Urbas, E., Irha, N., 1990. Accumulation of carcinogenic hydrocarbons at the sediment-water interface. Mar. Chem. 30, 337–341. Law, R.J., Dawes, V.J., Woodhead, R.J., Matthiessen, P., 1997. Polycyclic aromatic hydrocarbons (PAH) in seawater around England and Wales. Mar. Pollut. Bull. 34, 306–322. Oja, V., Suuberg, E.M., 1998. Vapor pressures and enthalpies of sublimation of polycyclic aromatic hydrocarbons and their derivatives. J. Chem. Eng. Data. 43, 486–492. Olofson, G., 1979. Assignment of uncertainties. In: Sunner, S., Månsson, M. (Eds.), Combustion Calorimetry, vol. 1. Pergamon Press, Oxford (Chapter 6). Pedley, J.B., 1994. Thermochemical Data and Structures of Organic Compounds. Thermodynamics Research Center, College Station, TX. Ribeiro da Silva, M.A.V., Ribeiro da Silva, M.D.M.C., Pilcher, G., 1988. Enthalpies of combustion of 1-hydroxynaphthalene, 2-hydroxynaphthalene, and 1,2-, 1,3-, 1,4-, and 2,3-dihydroxynaphthalenes. J. Chem. Thermodyn. 20, 969–974.

Please cite this article in press as: Silva, A.L.R., et al. Effects of methoxy and formyl substituents on the energetics and reactivity of a-naphthalenes: A calorimetric and computational study. Chemosphere (2014), http://dx.doi.org/10.1016/j.chemosphere.2013.12.044

8

A.L.R. Silva et al. / Chemosphere xxx (2014) xxx–xxx

Ribeiro da Silva, M.A.V., Ribeiro da Silva, M.D.M.C., Teixeira, J.A.S., Bruce, J.M., Guyan, P.M., Pilcher, G., 1989. Enthalpies of combustion of 1,4-naphthoquinone, 9,10anthraquinone, 9,10-phenanthraquinone, 1,4,9,10-anthradiquinone, 5,8dihydroxy-1,4-naphthoquinone, and 1,4-dihydroxy-9,10-anthraquinone. J. Chem. Thermodyn. 21, 265–274. Ribeiro da Silva, M.A.V., Ferrão, M.L.C.C.H., Lopes, A.J.M., 1993. Enthalpies of combustion of each of the two bromonaphthalenes. J. Chem. Thermodyn. 25, 229–235. Ribeiro da Silva, M.A.V., Agostinha, M.A.R., Amaral, L.M.P.F., 1995. Thermochemical study of 2-, 4-, 6-, and 8-methylquinoline. J. Chem. Thermodyn. 27, 565–574. Ribeiro da Silva, M.D.M.C., Santos, L.M.N.B.F., Silva, A.L.R., Fernandes, O., Acree Jr., W.E., 2003. Energetics of 6-methoxyquinoline and 6-methoxyquinoline Noxide: the dissociation enthalpy of the (N–O) bond. J. Chem. Thermodyn. 35, 1093–1100. Ribeiro da Silva, M.A.V., Amaral, L.M.P.F., Santos, A.F.L.O.M., Gomes, J.R.B., 2006. Thermochemistry of nitronaphthalenes and nitroanthracenes. J. Chem. Thermodyn. 38, 748–755. Rossini, F.D., 1956. Assignment of uncertainties to thermochemical data. In: Rossini, F.D. (Ed.), Experimental Thermochemistry, vol. 1. Interscience, New York (Chapter 14). Roux, M.V., Temprado, M., Chickos, J.S., Nagano, Y., 2008. Critically evaluated thermochemical properties of polycyclic aromatic hydrocarbons. J. Phys. Chem. Ref. Data 37, 1855–1996. Santos, L.M.N.B.F., Schröder, B., Fernandes, O.O.P., Ribeiro da Silva, M.A.V., 2004. Measurement of enthalpies of sublimation by drop method in a Calvet type calorimeter: design and test of a new system. Thermochim. Acta 415, 15–20. Sinha, R., Peters, U., Cross, A.J., Kulldorff, M., Weissfeld, J.L., Pinsky, P.F., Rothman, N., Hayes, R.B., 2005. Meat, meat cooking methods and preservation, and risk for colorectal adenoma. Cancer Res. 65, 8034–8041.

Stolyhwo, A., Sikorski, Z.E., 2005. Polycyclic aromatic hydrocarbons in smoked fish – a critical review. Food Chem. 91, 303–311. Skinner, H.A., Snelson, A., 1960. The heats of combustion of the four isomeric butyl alcohols. Trans. Faraday Soc. 56, 1776–1783. Vanschooten, F.J., Maas, L.M., Moonen, E.J.C., Kleinjans, J.C.S., Vanderoost, R., 1995. DNA dosimetry in biological indicator species living on PAH-contaminated soils and sediments. Ecotoxicol. Environ. Saf. 30, 171–179. Viguri, J., Verde, J., Irabien, A., 2002. Environmental assessment of polycyclic aromatic hydrocarbons (PAHs) in surface sediments of the Santander Bay, Northern Spain. Chemosphere 48, 157–165. Wagman, D.A., Evans, W.H., Parker, V.B., Schumm, R.H., Halow, I., Bailey, S.M., Churney, K.L., Nuttall, R.L., 1982. The NBS Tables of Chemical Thermodynamics Properties. J. Phys. Chem. Ref. Data II (Suppl. 2). Washburn, E.W., 1933. Standard States for Bomb Calorimetry. J. Res. Natl. Bur. Stand. (US) 10, 525–558. Wheeler, S.E., Houk, K.N., Schleyer, P.V.R., Allen, W.D., 2009. A Hierarchy of homodesmotic reactions for thermochemistry. J. Am. Chem. Soc. 131, 2547– 2560. Wieser, M.E., Holden, N., Coplen, T.B., Böhlke, J.K., Berglund, M., Brand, W.A., De Bièvre, P., Gröning, M., Loss, R.D., Meija, J., Hirata, T., Prohaska, T., Schoenberg, R., O’Connor, G., Walczyk, T., Yoneda, S., Zhu, X.-K., 2013. Atomic weights of the elements 2011 (IUPAC Technical Report). Pure Appl. Chem. 85, 1047–1078. You, F., Bidleman, T.F., 1984. Influence of volatility on the collection of polycyclic aromatic hydrocarbon PAH vapors with polyurethane foam. Environ. Sci. Technol. 18, 330–333.

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