RESONANCE-ASSISTED HYDROGEN-BONDS BETWEEN OXIME AND CARBOXYL GROUP - COMPARISON OF TETRAMERIC STRUCTURES OF 4-METHYL-2-OXOPENTANOIC ACID OXIME AND LEVULINIC ACID OXIME
Jk. Maurin et al., RESONANCE-ASSISTED HYDROGEN-BONDS BETWEEN OXIME AND CARBOXYL GROUP - COMPARISON OF TETRAMERIC STRUCTURES OF 4-METHYL-2-OXOPENTANOIC ACID OXIME AND LEVULINIC ACID OXIME, Acta crystallographica. Section B, Structural science, 51, 1995, pp. 232-240
Crystal structures of oximes of two aliphatic keto-carboxylic acids, 4
-methyl-2-oxopentanoic acid oxime [(PEN) 4-methyl-2-(hydroxylimino)pen
tanoic acid] and levulinic acid oxime [(LEV) 4-(hydroxylimino)pentanoi
c acid], were determined by X-ray structural methods. The molecular st
ructures of monomers interacting via hydrogen-bond networks were analy
sed with the use of theoretical ab initio self-consistent field (SCF)
calculations on model systems. The results of present crystallographic
and theoretical studies show that a different structure of PEN and LE
V crystals originates mostly from electron charge distribution, depend
ing on the relative position of the oxime and carboxyl moieties. The o
bserved N-O and N=C bond lengths and O-H...N and O-H...O hydrogen-bond
contacts in PEN crystals are affected by the pi-electron resonance of
the oxime and carboxyl moieties in a way similar to that found in bet
a-diketones.