Enthalpies of formation of N-substituted pyrazoles and imidazoles

• Type: Article in International Scientific Journal
• Date: 1999

Authors

Mo, O (Author) Other; Yanez, M (Author) Other; Roux, MV (Author) Other; Jimenez, P (Author) Other; Davalos, JZ (Author) Other; da Silva, MAVR (Author) FCUP; da Silva, MDMCR (Author) FCUP; Matos, MAR (Author) FCUP; Amaral, LMPF (Author) Other; Sanchez Migallon, A (Author) Other; Cabildo, P (Author) Other; Claramunt, R (Author) Other; Elguero, J (Author) Other; Liebman, JF (Author) Other

Journal

Title: Journal of Physical Chemistry A

Vol. 103

Pages: 9336-9344

ISSN: 1089-5639

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 63 Citations

Scopus - 70 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-001-2TH

DOI: 10.1021/jp992244f

Abstract (EN): Accurate experimental enthalpies of formation measured using static bomb combustion calorimetry, the "vacuum sublimation" drop calorimetry method, and the Knudsen-effusion method are reported for the first time for four azoles: 1-methylimidazole (1MeIMI), 1-methylpyrazole (1MePYR), 1-benzylimidazole (1BnIMI), and 1-benzylpyrazole (1BnPYR). These values and those corresponding to imidazole (1HIMI), pyrazole (1HPYR), 1-ethylimidazole (1EtIMI), 1-ethylpyrazole (1EtPYR), 1-phenylimidazole (1PhIMI), and 1-phenylpyrazole (1PhPYR) are compared with theoretical values using the G2(MP2) and the B3LYP/ 6-311*G(3df,2p)//6-31G(d) approaches. In general, there is a very good agreement between calculated and experimental values for the series of N-substituted imidazoles, while the agreement is less good for the series of the N-substituted pyrazoles. Experimentally, the gap between the enthalpies of formation of imidazoles and pyrazoles decreases significantly upon N-substitution, while the theoretical estimates indicate that this decrease is smaller.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9