Stereochemistry of the .alpha.-hydroxycarboxylic acids and related systems

Newton, Marshall D.

doi:10.1021/ja00450a003

Cited by 69 publications

(20 citation statements)

References 4 publications

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“…The dihedral angle cpo (CI-C2-C3=O4) for conformation I11 obtained from 4-3 1G geometry optimization is 129.84" which lies within the experimental range 131 k 6" suggested by Butcher It has been pointed out by earlier workers (22)(23)(24) that the calculated dipole moment at the 4-31G level overestimates the experimentalvalue by about 25%. A similar situation is found in the case of the s-cis conformer of propanal where the calculated value of the dipole moment in the 4-31G level is 3.27 D as against the experimental value of 2.58 D (25).…”

Section: Resultssupporting

confidence: 78%

Extended basis abinitio calculations on conformers of propanal

Gupta¹

1985

Can. J. Chem.

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V. P. GUITA. Can. J. Chem. 63, 984 (1985). Extended basis ab initio calculations on four conformations of propanal at the 4-31G and 6-3 1G** levels followed by many-body perturbative interaction calculations MP2 and MP3 have been conducted. Optimized geometries, heights of rotational barriers, dipole moments, ionisation potentials, and diagonal harmonic force constants have been reported. The s-cis conformer (dihedral angle CCCO = 0") is found to be more stable than the gauche conformer (dihedral angle CCCO = 129.84") by 5.07 kJ mol-'. Torisonal potential barriers s-cislgauche, gauchels-cis, and gauchelgauche have values 8.81, 3.74, and 1.84 kJ mol-', respectively. It appears that meaningful values of rotational barriers can be obtained only after a careful optimization of the geometries of the conformations involved.V. P. GUITA. Can. J. Chem. 63, 984 (1985). OpCrant aux niveaux 4-3 IG et 6-3 lG**, on a effectuC des calculs ab initio sur quatre conformations du propanal; on a ensuite effectut des calculs MP2 et MP3 impliquant une interaction perturbative de plusieurs corps. On rapporte les gComCtries optimistes, les hauteurs des barrikres h la rotation, les moments dipblaires, les potentiels d'ionisation et les constantes de force harmonique diagonale. On a trouvC que le conformkre s-cis (angle diedre CCCO = 0") est plus stable que le conformkre gauche (angle dikdre CCCO = 129,84") par 5,07 kJ/mol. Les valeurs des barrikres au potentiel de torsion sont respectivement 8,81, 3,74 et 1,84 kJ/mol pour s-cislgauche, gauchels-cis et gauchelgauche. 11 semble que l'on ne peut obtenir de valeurs significatives pour les barrikres a la rotation qu'aprks avoir effectut une optimisation adCquate des gComCtries des conformations impliqubes.[Traduit par le journal] Introduction Several studies using different experimental techniques such as microwave (1-3), vibrational (4-8) and nmr (9) spectroscopy, and the theoretical techniques such as molecular dynamics (10) and molecular orbital calculations (1 1 -14) have been reported in the literature for the determination of the conformation of propanal in gaseous and liquid phases. Some statistical mechanical calculations (15, 16) of the chemical and thermodynamic properties of propanal in the gaseous state have also been reported. All these studies indicate that propanal exists as a mixture of s-cis and gauche conformers with the methyl group eclipsing the carbonyl bond in the s-cis (I) conformation and skewed out of plane to a dihedral angle of ca. 130" in the gauche (111) conformer. In a separate communication (17), we have reported photorotamerisation studies on this molecule in low temperature argon and nitrogen matrices and have found that at 10 K the concentrations of the two conformers are 95% s-cis and 5% gauche which changes to 47% and 53% respectively, on irradiation with a broad band ir radiation. A considerable uncertainty exists in the literature about the conformations of the lowest energy conformer and also about the enthalpy difference between the two stable conforme...

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Section: Resultssupporting

confidence: 78%

Extended basis abinitio calculations on conformers of propanal

Gupta¹

1985

Can. J. Chem.

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“…H20 (Panagiotopoulos et al, 1974), in trisodium 6-phospho-D-gluconate dihydrate (Smith, Fitzgerald, Caughlan, Kerr & Ashmore, 1974) and in one of the gluconate ions of Mn(C6HI~O7)2.2H20 (Lis, 1979). The most interesting fact is that contrary to all other ~t-hydroxycarboxylic moieties (Newton & Jeffrey, 1977) the -C(OH)COO-group is not planar (Table 4). It may be assumed that the deviation of the 0(2) atom from the plane of the carboxylate group is brought about by the hydrogen bonds in this salt.…”

Section: Neutral-atom Scattering Factors Were Those Listed Inmentioning

confidence: 99%

Structure of ammonium D-gluconate

Lis¹

1981

Acta Crystallogr Sect B

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“…These figures are thus in good qualitative agreement with the relative abundances of the conformations in crystals. Inspection of Table 3 shows that the well known tendency of the a-hydroxyl group to be coplanar with the carboxyl group (Jeffrey & Parry, 1952;Kanters, Kroon, Peerdeman & Schoone, 1967;Newton & Jeffrey, 1977) exists in both types I and II. On the other hand, the torsion angle around the terminal C-C bond (Z) appears to be very sensitive to the carbon-chain conformation.…”

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confidence: 99%

“…"[" The symbol tp 2 for this torsion angle is chosen in accordance with the paper by Newton & Jeffrey (1977) dealing with model calculations on glycolic acid.…”

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confidence: 99%