Experimental and computational thermochemistry of 1,3-benzodioxole derivatives

M. Agostinha R. Matos*, Clara C.S. Sousa, Victor M.F. Morais

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

The standard (p° = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, of four 1,3-benzodioxole derivatives (5-oxoethyl-1,3-benzodioxole, 5-cyano-1,3-benzodioxole, 5-nitro-1,3-benzodioxole, and 5-methyl-1,3- benzodioxole) were measured by static bomb calorimetry. The standard molar enthalpies of vaporization or of sublimation, at T = 298.15 K, were measured by Calvet microcalorimetry. Combining these results, the standard molar enthalpies of formation of the compounds in the gas phase, at T = 298.15 K, have been calculated: 5-oxoethyl-1,3-benzodioxole (-319.3 ±2.8) kJ·mo -1; 5-cyano-1,3-benzodioxole (-23.2 ±2.2) kJ·mol -1; 5-nitro-1,3-benzodioxole (-176.0 ±3.2) kJ·mol -1 and 5-methyl-1,3-benzodioxole (-184.7 ±3.5) kJ·mol-1. The most stable geometries of all the compounds were obtained using the density functional theory with the B3LYP functional and two basis sets: 6-31G** and 6-31 IG**. The nonplanarity of the molecules was analyzed in terms of the anomeric effect, which is believed to arise from the interaction between a nonbonded oxygen pπ orbital and the empty orbital σ*co involving the other oxygen atom. Calculations were performed to obtain estimates of the enthalpies of formation of all the substituted benzodioxoles using appropriate isodesmic reactions. There is good agreement between theoretical and experimental results. This agreement allows us to estimate the enthalpies of formation of some 1,3-benzodioxole derivatives whose experimental study was impossible.

Original languageEnglish
Pages (from-to)1089-1094
Number of pages6
JournalJournal of Chemical and Engineering Data
Volume52
Issue number3
DOIs
Publication statusPublished - May 2007

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