Experimental and theoretical NMR study of selected oxocarboxylic acid oximes

Abstract

1H and 13C NMR spectra of the oxocarboxylic acid oximes 2-hydroxyiminopropanoic acid (1), 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (2) and 2-cyano-2-(hydroxyimino)acetic acid (3) were measured in DMSO-d6, D2O and acetone-d6 solutions. The data indicate the presence of hydrogen bonding in 1 and 2 and a strong electron-withdrawing effect due to the cyano group in 3. The effect of intra- and intermolecular hydrogen bonding on the hydrogen and carbon chemical shifts in these molecules was studied theoretically. Total energy calculations of the stability of various hydrogen-bonded species, in addition to equilibrium parameters and chemical shifts, were calculated using ab initio methods (RHF, MP2) and density functional theory (B3LYP), implemented in the Gaussian 98 software package. The gauge-including atomic orbital (GIAO) method was used to predict magnetic shielding constants. Chemical shift calculations for the most stable species agree fairly well with the observed data, especially for the hydroxyl protons. Substituents adjacent to the alpha-carbon show some influence of the oximic and carboxyl groups on the 13C chemical shifts, as expected for groups with different polar and anisotropic character.

New Route to Polynuclear Ni(II) and Cu(II) Complexes with Bridging Oxime Groups That Are Inaccessible by Conventional Preparations

“…63,64 The majority of the metal complexes formed after these hydrolysis reactions are mononuclear. Malek et al (2004) did some experimental and theoretical calculations on the H 2 AACO oxime, in order to understand their coordination to metal ions, 65 and Sliva et al (1998) studied the Cu(II) and the Ni(II) complexes of prepared pure H 2 AACO, with successes in obtaining the monomeric Cu(II) and Ni(II), as well as only one dimeric Cu(II) (pH > 5) complex of the AACO 2− dianion 41−43 reported thus far. In our case, the Ni(II) complexes, made in situ with metal ion catalyzed hydrolysis of the 2-cyano-hydroxyimino acetic acid ethyl ester (HECO) and 2-cyano-2-hydroxyimino-acetic acid methyl ester (HMeCO), are dinuclear and trinuclear crystallohydrate metal complexes.…”

“…The catalysis of nucleophilic organic reactions by metal ions has been a subject of interest, due to their possible correlations with biological systems, where they have a role in the mechanism of hydrolytic metalloenzymes, e.g., carboxypeptidase A with a Zn 2+ at the active site, , where metal ion may be coordinated to the carbonyl of the ester and the amide substrate where the Zn 2+ coordination polarizes the carbonyl group of the substrate, thereby increasing its susceptibility to nucleophilic attack. , The majority of the metal complexes formed after these hydrolysis reactions are mononuclear. Malek et al (2004) did some experimental and theoretical calculations on the H 2 AACO oxime, in order to understand their coordination to metal ions, and Sliva et al (1998) studied the Cu­(II) and the Ni­(II) complexes of prepared pure H 2 AACO, with successes in obtaining the monomeric Cu­(II) and Ni­(II), as well as only one dimeric Cu­(II) (pH > 5) complex of the AACO 2– dianion − reported thus far. In our case, the Ni­(II) complexes, made in situ with metal ion catalyzed hydrolysis of the 2-cyano-hydroxyimino acetic acid ethyl ester (HECO) and 2-cyano-2-hydroxyimino-acetic acid methyl ester (HMeCO), are dinuclear and trinuclear crystallohydrate metal complexes.…”

E/Z configurational determination of oximes and related derivatives through quantum mechanics NMR calculations: scope and limitations of the leading probabilistic methods

“…[19][20][21][22][23] These tools have been consolidated over time to the extent that nowadays they are routinely used in structural elucidation, complementing synergistically experimental NMR spectroscopy. It is therefore surprising that despite a few isolated reports, 24,25 there is no systematic study of the use of NMR calculations for the configuration determination of oximes and analogous systems. Here, we wish to evaluate the performance of three popular methodologies (DP4+, 26 DP4, 27 and ML-J-DP4 28 ) with a large set of oximes and related molecules, exploring their scopes and limitations, along with a comprehensive evaluation of prediction quality and computational cost.…”

Density Functional Study of the Reaction Mechanism of Two Oxiimine Alcohol Formations and Their Novel Rearrangements

“…The reactivity of the oxime group and its metal coordination capability have been studied experimentally and well documented in the literature . Isomerization reaction mechanisms and spectroscopic studies of some oximes were also performed theoretically . Schiff bases are well‐known compounds and are commonly used in industrial and biological area as a reaction intermediate.…”