title: Vapor pressures, thermodynamic stability, and fluorescence properties of three 2,6-alkyl naphthalenes.
abstract: This work reports the experimental determination of relevant thermodynamic properties and the characterization of luminescence properties of the following polycyclic aromatic hydrocarbons (PAHs): 2,6-diethylnaphthalene, 2,6-diisopropylnaphthalene and 2,6-di-tert-butylnaphthalene. The standard (p(o) = 0.1 MPa) molar enthalpies of combustion, ΔcHm(o), of the three compounds were determined using static bomb combustion calorimetry. The vapor pressures of the crystalline phase of 2,6-diisopropylnaphthalene and 2,6-di-tert-butylnaphthalene were measured at different temperatures using the Knudsen effusion method and the vapor pressures of both liquid and crystalline phases of 2,6-diethylnaphthalene were measured by means of a static method. The temperatures and the molar enthalpies of fusion of the three compounds were determined using differential scanning calorimetry. The gas-phase molar heat capacities and absolute entropies of the three 2,6-dialkylnaphthalenes studied were determined computationally. The thermodynamic stability of the compounds in both the crystalline and gaseous phases was evaluated by the determination of the Gibbs energies of formation and compared with the ones reported in the literature for 2,6-dimethylnaphthalene. From fluorescence spectroscopy measurements, the optical properties of the compounds studied and of naphthalene were evaluated in solution and in the solid state.
authors.affiliation: Centro de Investigação em Química (CIQ-UP), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal.
authors.forename: Ana Filipa L O M
authors.initials: AF
authors.lastname: Santos
authors.affiliation: Centro de Investigação em Química (CIQ-UP), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal.
authors.forename: Juliana A S A
authors.initials: JA
authors.lastname: Oliveira
authors.affiliation: Centro de Investigação em Química (CIQ-UP), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal.
authors.forename: Maria D M C
authors.initials: MD
authors.lastname: Ribeiro da Silva
authors.affiliation: Centro de Investigação em Química (CIQ-UP), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 687, P-4169-007 Porto, Portugal. Electronic address: mjmonte@fc.up.pt.
authors.forename: Manuel J S
authors.initials: MJ
authors.lastname: Monte
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D005453:Fluorescence; D009281:Naphthalenes / Q000032:analysis*; D013816:Thermodynamics; D055548:Vapor Pressure; D014835:Volatilization
chemical_list: D000393:Air Pollutants; D009281:Naphthalenes; C018520:2,6-diisopropylnaphthalene
keywords: Enthalpy of formation; Fluorescence; Gibbs energy of formation; Naphthalene derivatives; Vapor pressure