The crystal and molecular structure of 3-methyl-3-pyrazolin-5-one

Abstract

The crystal structure of 3-methyl-3-pyrazolin-5-one (C4H6N20) has been determined by X-ray diffraction as a model for the pyrazolin-5-one compounds. The space group is P2a/a. Cell dimensions are a= 10.520 (3), b=6.499 (2), c= 8.052 (1)/~, fl= 114.45 (1) °, Z=4, D~= 1.299 (1) g.cm-3. Three-dimensional X-ray data were collected using Mo Ka radiation. The structure was solved using statistical methods of phase determination, and refined by the full-matrix least-squares method to R= 0.071 (unit weights). Hydrogen-bonded layers are found parallel to the ab plane. The predominant tautomer is established as 3-methyl-3-pyrazolin-5-one. A comparison of structures based on data gathered by moving-crystal moving-counter and stationary-crystal stationary-counter methods shows no significant differences in bond lengths and angles calculated from atomic parameters refined on either set of data.

The crystal structure of potassium picrate: a comparison between stationary-crystal stationary-counter, densitometer, and visual data

“…Two independent studies of histamine acid phosphate monohydrate (Veidis, Palenik, Schaffrin & Trotter, 1969) and /t-oxo-bis(nitrosyltriphenylphosphine)-diiridium(l) (Dellaca, Mathew, Palenik & Robinson, 1971) indicated that stationary-crystal stationary-counter and moving-crystal data yield identical results. A similar conclusion was reached recently by DeCamp & Stewart (1971). Therefore, one can conclude that stationary-crystal stationary-counter measurements are indeed a valid measurement of the integrated intensity and compare favorably with other methods of intensity measurements.…”

AMHB: (Anti)aromaticity-Modulated Hydrogen Bonding

“…A survey of the online Cambridge Structural Database (WebCSD), in which H-bond-donor/-acceptor distances were compared, found that the average distance for 2a in five crystals of its derivatives − is 0.147 Å shorter (2.703(2) vs 2.850(4) Å, see Figure a) than for 2a ′ in 12 crystal structures. − Conversely, the average N···N distance in 3a derivatives in three crystal structures − is 0.110 Å longer (3.013(3) vs 2.903(3), see Figure b) than 3a ′ derivatives in five crystal structures. − These observations offer strong experimental support for the notion of aromaticity assisted H-bonding and aromaticity disrupted H-bonding in the cases of 2a and 3a , respectively.…”

3-(2-methylthiopyridin-3-yl)-3-oxopropionic esters

“…The 1 H NMR spectra are characterized by the presence of the signal for the NH group as a singlet with the intensity of one proton at δ 11.4-11.8 It is known that pyrazol 5 ones can exist as different tautomeric forms, 12 however, compounds unsubstituted at the nitrogen atom exist as 1,2 dihydropyrazol 5 ones, which was confirmed by X ray diffraction analysis. 13 The spectral characteristics of ob tained by us pyrazoles 4a,d,e are analogous to those pub lished earlier, 14 that allows us to assign to them the struc ture of 1,2 dihydropyrazol 5 ones. The IR spectra of pyr azoles 4a,d,e exhibit an absorption band of the conjugated carbonyl group at 1616-1620 cm -1 .…”