Naslov
Crystal Structure of 4-Ethoxycarbonyl-1, 1, 3-trimethyl-5-oxo-pyrazol-1-ylio-4-ide, C9H14N2O3

Autori
Poje, Mirko ; Bregant, Nada ; Paulus, F. Erich

Izvornik
Zeitschrift für Kristallographie (0044-2968) 212 (1997), 3; 243-244

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
aminimides; mesomeric 5-pyrazolone betaines; delocalization stabilization.

Sažetak
The title compound is a rare example of the 1-acyl-1, 2-aminimide functionality. The planar ring (within 0.006 Angstrom) is best described as mesomeric betaine. The negative charge, formally located at C4, is stabilized by delocalization over a triskelion type array of C=X bonds (X=O, N). An additional recourse is open to the specific stabilization of the positive charge on tetrahedral N1, which involves the non-bonding electron pair of the carbonyl O1 antiperiplanar to the polar C5-N1 bond. The operation of n-->sigma* delocalization should give a partial sp hybride character to the carbonyl group, thus accounting for the most interesting structural features: a large opening of the angle [O1-C5-C4 140.7(2)degrees] opposite the long N1-C5 bond and the O1-C5 distance typical for a double bond. The structural parameters are comparable to those of 1, 1-dimethyl-3-phenyl-pyrazolium-5-oxide, a sole precedent of this unusual system ; differences in bond lengths (ca. 0.02 Angstrom) within the C3-C4-C5-O1 fragment (lengthening of C-C bonds adjacent to C4 and shortening of the C-O bond) are in conformity with a further delocalization stabilization of the negative charge by electron-withdrawing substituent in the 4-position. Selected bond lengths: N1-C5 1.577(2), N1-N2 1.465(2), N2-C3 1.308(2), C3-C4 1.432(2), C4-C5 1.386(3), O1-C5 1.212(2), C4-C7 1.447(3), O2-C7 1.204(2) Angstrom.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA