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

• Type: Article in International Scientific Journal
• Date: 1997

Authors

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

Journal

Title: Journal of Organic Chemistry

Vol. 62

Pages: 3722-3726

ISSN: 0022-3263

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 30 Citations

Scopus - 31 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 5