Thermochemical and theoretical study of some quinoxaline 1,4-dioxides and of pyrazine 1,4-dioxide

• Tipo: Artigo em Revista Científica Internacional
• Data: 1997

Autores

Acree, WE (Autor) Outra; Powell, JR (Autor) Outra; Tucker, SA (Autor) Outra; daSilva, MDMCR (Autor) FCUP; Matos, MAR (Autor) FCUP; Goncalves, JM (Autor) FCUP; Santos, LMNBF (Autor) FCUP; Morais, VMF (Autor) ICBAS; Pilcher, G (Autor) Outra

Revista

Título: Journal of Organic Chemistry

Vol. 62

Páginas: 3722-3726

ISSN: 0022-3263

Editora: American Chemical Society

Indexação

ISI Web of Knowledge - 28 Citações

Scopus - 29 Citações

Classificação Científica

FOS: Ciências exactas e naturais > Química

Outras Informações

ID Authenticus: P-001-BDX

DOI: 10.1021/jo962149s

Abstract (EN): The following standard molar enthalpies of formation in the gaseous state at 298.15 K were determined from the enthalpies of combustion of the crystalline solids, and their enthalpies of sublimation and the mean (N-O) bond dissociation enthalpies were derived. Delta(f)H(m)(0)(g); [D(N-O)] (kJ mol(-1)): quinoxaline 1,4-dioxide, 227.1 +/- 2.4; 255.8 +/- 2.0; 2-methylquinoxaline 1,4-dioxide, 169.9 +/- 7.2; 268.3 +/- 4.9; 2-methyl-3-acetylquinoxaline 1,4-dioxide, 33.1 +/- 5.0; 251.6 +/- 4.2; 2-phenyl-3-benzoylquinoxaline 1,4-dioxide, 355.2 +/- 7.1; 227.3 +/- 5.4; 2-methyl-3-carbomethoxyquinoxaline 1,4-dioxide, -148.7 +/- 3.2; 242.3 +/- 3.9; pyrazine 1,4-dioxide, 186.5 +/- 1.9; 254.0 +/- 2.3; 2-methyl-5-pyrazinecarboxylic acid, -213.6 +/- 1.7. Unconstrained geometry optimizations by ab initio calculations showed the effect of steric hindrance on changes in extended delocalizations and were in accord with the trends in the mean bond dissociation enthalpies.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 5