Anisatin: a Crystallographic, N.M.R. and Theoretical Conformation Study

1988 ◽  
Vol 41 (7) ◽  
pp. 1071 ◽  
Author(s):  
MG Wong ◽  
JM Gulbis ◽  
MF Mackay ◽  
DJ Craik ◽  
PR Andrews
Keyword(s):  
Molecular Geometry ◽  
Intramolecular Hydrogen Bonding ◽  
Coupling Constants ◽  
Solution Conformation ◽  
Proton Proton ◽  
X Ray Crystallography ◽  
Yield Information ◽  
Intramolecular Hydrogen ◽  
Experimental Geometry ◽  
Hydroxy Groups

The convulsant compound anisatin has been studied by 1H n.m.r ., and X- ray crystallography, to establish its molecular geometry. The n.m.r . measurements included an analysis of proton-proton vicinal coupling constants and saturation transfer experiments which monitored exchange of the hydroxy groups of anisatin. The former analysis was used to obtain a solution conformation via the Karplus equation while the latter experiments yield information on intramolecular hydrogen bonding. The experimental geometry is compared to that obtained by several theoretical methods, including MINDO/3, MNDO, AM1 and MM2. The AM1 optimized geometry was closest to that of the crystal structure.

Theoretical study of intramolecular hydrogen bonding and molecular geometry of 2-trifluoromethylphenol

10.1002/jcc.2 ◽  
1996 ◽  
Vol 17 (16) ◽  
pp. 1804-1819 ◽  
Author(s):  
Attila Kov�cs ◽  
Istv�n Kolossv�ry ◽  
G�bor I. Csonka ◽  
Istv�n Hargittai
Keyword(s):  
Hydrogen Bonding ◽  
Theoretical Study ◽  
Molecular Geometry ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen

Crystal structure, spectroscopic studies and theoretical studies of thiobarbituric acid derivatives: understanding the hydrogen-bonding patterns

2018 ◽  
Vol 74 (12) ◽  
pp. 1703-1714 ◽  
Author(s):  
Anamika Sharma ◽  
Sizwe J. Zamisa ◽  
Sikabwe Noki ◽  
Zainab Almarhoon ◽  
Ayman El-Faham ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Materials Science ◽  
Thiobarbituric Acid ◽  
Intramolecular Hydrogen Bonding ◽  
Spectroscopic Studies ◽  
Enol Form ◽  
Keto Form ◽  
X Ray Crystallography ◽  
Schiff Base Formation ◽  
Intramolecular Hydrogen

In addition to their wide-ranging applications in the pharmaceutical industry, thiobarbituric acid (TBA) derivatives are also known to possess applications in engineering and materials science. 20 TBA derivatives, with diversity at the N and C-5 positions through acylation, Schiff base formation, Knoevenagel condensation, thioamide and enamine formation, were studied. The absolute configurations for six derivatives, namely 5-acetyl-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, C10H14N2O3S, A01, 1,3-diethyl-5-propionyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, C11H16N2O3S, A02, tert-butyl [1-(1,3-diethyl-4,6-dioxo-2-thioxohexahydropyrimidin-5-yl)-3-methyl-1-oxobutan-2-yl]carbamate, C18H29N3O5S, A06, 1,3-diethyl-4,6-dioxo-2-thioxo-N-(p-tolyl)hexahydropyrimidine-5-carbothioamide, C16H19N3O2S2, A13, 5-(1-aminoethylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, C10H15N3O2S, A17, and 5-(1-aminopropylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, C11H17N3O2S, A18, were confirmed by single-crystal X-ray crystallography, which indicates the formation of intramolecular hydrogen bonding in all six cases and intermolecular hydrogen bonding for A17. In A13, the presence of two intramolecular hydrogen bonds was observed. The stabilization of the enol form over the keto form was confirmed by computation. In order to convert the keto form to the enol form, an energy barrier of 55.05 kcal mol−1 needs to be overcome, as confirmed by transition-state calculations.

1,1-Diphenylbutane-1,3-diol: the First Structurally Characterized Example of an Intramolecularly Hydrogen-Bonded Open-Chain 1,3-diol

1996 ◽  
Vol 49 (11) ◽  
pp. 1251
Author(s):  
CF Carvalho ◽  
DP Arnold ◽  
RC Bott ◽  
G Smith
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Orthorhombic Space Group ◽  
Open Chain ◽  
Space Group ◽  
A Cell ◽  
Intramolecular Hydrogen ◽  
Hydroxy Groups ◽  
Hydrogen Bonded

The crystal structure of the asymmetric 1,3-diol 1,1-diphenylbutane-1,3-diol has been determined and refined to a residual R of 0.039 for 795 observed reflections. Crystals are orthorhombic, space group P212121, with four molecules in a cell of dimensions a 9.625(4), b 16.002(3), c 8.834(3) Ǻ. The compound is unique among the known crystallographically characterized open-chain 1,3-diols in having only intramolecular hydrogen bonding involving the hydroxy groups [O-- -O 2.602(5) Ǻ].

Aromatic amides. V. Intramolecular hydrogen bonding in ortho-substituted anilides

1970 ◽  
Vol 23 (8) ◽  
pp. 1667 ◽  
Author(s):  
JM Appleton ◽  
BD Andrews ◽  
ID Rae ◽  
BE Reichert
Keyword(s):  
Hydrogen Bonding ◽  
Molecular Geometry ◽  
Intramolecular Hydrogen Bonding ◽  
Amide Group ◽  
Amide Proton ◽  
Substituted Anilines ◽  
Real Value ◽  
Intramolecular Hydrogen ◽  
Acyl Derivatives ◽  
Ortho Substituent

The proton magnetic resonance spectra of deuterochloroform solutions of a number of ortho-substituted anilines and their S-acyl derivatives have been measured. Variations in the acylation shifts of the ring protons are explained in terms of intramolecular hydrogen bonding between the amide proton and the ortho-substituent. Calculations of the contribution made to the acylation shifts by the anisotropy of the amide group were found to be too sensitive to the molecular geometry to be of any real value. Acylation shifts for a series of 4'-substituted 2'-nitroacetanilides correlate well with the σp values of the 4'-substituents.

scholarly journals Conformational study of L-methionine and L-cysteine derivatives through quantum chemical calculations and 3 J HH coupling constant analyses

2017 ◽  
Vol 13 ◽  
pp. 925-937 ◽  
Author(s):  
Weslley G D P Silva ◽  
Carolyne B Braga ◽  
Roberto Rittner
Keyword(s):  
Solvent Effects ◽  
Noncovalent Interactions ◽  
Conformational Stability ◽  
Intramolecular Hydrogen Bonding ◽  
Polarizable Continuum Model ◽  
Coupling Constants ◽  
Implicit Solvent ◽  
Conformational Preferences ◽  
Joint Contribution ◽  
Intramolecular Hydrogen

The understanding of the conformational behavior of amino acids and their derivatives is a challenging task. Here, the conformational analysis of esterified and N-acetylated derivatives of L-methionine and L-cysteine using a combination of 1H NMR and electronic structure calculations is reported. The geometries and energies of the most stable conformers in isolated phase and taking into account the implicit solvent effects, according to the integral equation formalism polarizable continuum model (IEF−PCM), were obtained at the ωB97X-D/aug-cc-pVTZ level. The conformational preferences of the compounds in solution were also determined from experimental and theoretical 3 J HH coupling constants analysis in different aprotic solvents. The results showed that the conformational stability of the esterified derivatives is not very sensitive to solvent effects, whereas the conformational equilibrium of the N-acetylated derivatives changes in the presence of solvent. According to the natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) and noncovalent interactions (NCI) methodologies, the conformational preferences for the compounds are not dictated by intramolecular hydrogen bonding, but by a joint contribution of hyperconjugative and steric effects.

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