Experimental and computational study of the energetics of methoxycoumarins

• Type: Article in International Scientific Journal
• Date: 2010

Authors

Victor M F Morais (Author) ICBAS; Clara C S Sousa (Author) FCUP; Agostinha A R Matos (Author) FCUP

Journal

Title: Journal of Molecular Structure: THEOCHEM

Vol. 946

Pages: 13-19

ISSN: 0166-1280

Publisher: Elsevier B.V.

Indexing

ISI Web of Knowledge - 5 Citations

Scopus - 5 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-003-7CM

DOI: 10.1016/j.theochem.2009.11.036

Abstract (EN): The structure and energetics of the methoxy-derivatives of coumarin with the substituent either on the benzenic ring (5-, 6-, 7- and 8-methoxy coumarin) or on the pyrone ring (3- and 4-methoxycoumarin) is addressed on the basis of some well documented computational methods. Estimates of the enthalpies of formation are obtained using appropriate homodesmotic reactions and also atomization reactions. The condensed phase standard (p(o) = 0.1 MPa) molar enthalpy of formation for 7-methoxycoumarin was derived from the standard molar enthalpy of combustion, in oxygen, at T = 298.15 K. measured by static bomb combustion calorimetry. The standard molar enthalpy of sublimation, at T = 298.15 K, was measured by Calvet microcalorimetry. Combining these values, the enthalpy of formation in gas-phase, at T = 298.15 K. was derived: -(321.6 +/- 2.8) kJ mol(-1). The temperature of fusion, T(fusion), and fusion enthalpies, at T = T(fusion), are also reported. Good agreement between experimental and computational data is achieved. The aromaticity of these systems has been assessed through the evaluation and analysis of the Nucleus Independent Chemical Shifts (NICS) and their most significant components. NICS scan analyses have also been conducted to help clarifying the aromatic nature of the pyrone rings of these systems. (C) 2010 Published by Elsevier B.V.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7