THE EPIMERIZATION OF DELCOSINE

1961 ◽  
Vol 39 (8) ◽  
pp. 1579-1587 ◽  
Author(s):  
Vinko Skarić ◽  
Léo Marion
Keyword(s):  
Infrared Spectra ◽  
Potassium Hydroxide ◽  
Methoxyl Group ◽  
Hydroxyl Group ◽  
Sodium Amalgam ◽  
Acid Catalyzed ◽  
Nitrogen Ring

Delcosine has been assigned tentatively the same C—N skeleton as lycoctonine. In lycoctonine, ring A carries at C-1 a methoxyl group which is directed away from the nitrogen ring. In delcosine, C-1 carries a hydroxyl group which has the opposite configuration and is directed towards the nitrogen. An attempt to correlate the two structures first involves epimerization at C-1 in delcosine. This has been carried out by oxidation of desethyldelcosine to an azomethine, the ethiodide of which, by the action of methanolic potassium hydroxide, is converted to oxo-1-epidelcosine in two steps. Oxo-1-epidelcosine in an acid-catalyzed rearrangement is transformed to a pinacone which, after methylation, gives O,O-dimethyl-anhydro-oxo-1-epidelcosine. This compound was compared with O-methylanhydro-oxolycoctonine, prepared from oxolycoctonine, but was not identical. Removal of a methoxyl, which in each compound is ortho to a carbonyl, by the action of sodium amalgam, produced O,O-dimethyl-6-desmethoxy-anhydro-oxo-1-epidelcosine and O-methyl-6-desmethoxy-anhydro-oxolycoctonine, which are not identical, but show in their infrared spectra much less dissimilarity than the spectra of the pair of compounds from which they were derived. These results are discussed in terms of the structure of delcosine.

scholarly journals Calculation of the Geometries and Infrared Spectra of the Stacked Cofactor Flavin Adenine Dinucleotide (FAD) as the Prerequisite for Studies of Light-Triggered Proton and Electron Transfer

Biomolecules ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 573
Author(s):  
Martina Kieninger ◽  
Oscar N. Ventura ◽  
Tilman Kottke
Keyword(s):  
Infrared Spectra ◽  
Density Functional ◽  
Flavin Adenine Dinucleotide ◽  
Hydroxyl Group ◽  
Flavin Mononucleotide ◽  
Experimental Investigations ◽  
Adenine Ring ◽  
Π Complex ◽  
Wide Range ◽  
Single Water Molecule

Flavin cofactors, like flavin adenine dinucleotide (FAD), are important electron shuttles in living systems. They catalyze a wide range of one- or two-electron redox reactions. Experimental investigations include UV-vis as well as infrared spectroscopy. FAD in aqueous solution exhibits a significantly shorter excited state lifetime than its analog, the flavin mononucleotide. This finding is explained by the presence of a “stacked” FAD conformation, in which isoalloxazine and adenine moieties form a π-complex. Stacking of the isoalloxazine and adenine rings should have an influence on the frequency of the vibrational modes. Density functional theory (DFT) studies of the closed form of FAD in microsolvation (explicit water) were used to reproduce the experimental infrared spectra, substantiating the prevalence of the stacked geometry of FAD in aqueous surroundings. It could be shown that the existence of the closed structure in FAD can be narrowed down to the presence of only a single water molecule between the third hydroxyl group (of the ribityl chain) and the N7 in the adenine ring of FAD.

The proton affinities and deprotonation enthalpies of β-D-fructopyranose and α-L-sorbopyranose

1991 ◽  
Vol 69 (12) ◽  
pp. 1917-1928 ◽  
Author(s):  
Robert J. Woods ◽  
Walter A. Szarek ◽  
Vedene H. Smith Jr.
Keyword(s):  
Hydrogen Bonding ◽  
Oxygen Atom ◽  
Intramolecular Hydrogen Bonding ◽  
Hydroxyl Group ◽  
Proton Affinities ◽  
Naturally Occurring ◽  
Acid Catalyzed ◽  
Acids And Bases ◽  
Intramolecular Hydrogen ◽  
Hydrolysis Of

The proton affinities (PAs) and deprotonation enthalpies (DPEs) were calculated for the pyranoid forms of two naturally occurring sugars, D-fructose and L-sorbose. In both molecules the PAs of the primary hydroxyl group (HO-1), the anomeric hydroxyl group (HO-2), and the ring-oxygen atom (O-6) were calculated, as were the DPEs of HO-1 and HO-2. The stabilities of the conjugate acids and bases of these sugars are enhanced by the presence of intramolecular hydrogen bonding, a feature that is significant in explaining the differences in sweetness and the rates of mutarotation of the title compounds, as well as the differences in the rates of acid-catalyzed hydrolysis of ketopyranosides. Key words: proton affinity, deprotonation enthalpy, ab initio calculations, AM1, hexuloses.

PREPARATION AND INFRARED SPECTRA OF DIVINYL SULPHIDE, 2-METHYL-1,3-THIOXOLANE, AND 1,4-THIOXANE

1959 ◽  
Vol 37 (6) ◽  
pp. 1104-1108 ◽  
Author(s):  
K. K. Georgieff ◽  
A. Dupré
Keyword(s):  
Physical Properties ◽  
Infrared Spectra ◽  
High Purity ◽  
Potassium Hydroxide ◽  
And Storage

Dehydration of thiodiglycol at 195°–230° with potassium hydroxide produced a 36% yield of divinyl sulphide, 9–10% of 2-methyl-1,3-thioxolane, 7–8% of 1,4-thioxane, and 3.5% of vinyl 2-hydroxyethyl sulphide. Physical properties and infrared spectra are reported. Divinyl sulphide of high purity for polymer work was obtained by distillation in a Podbielniak column. Precautions that must be observed in the preparation, distillation, and storage are given.

Synthesis of Double Alkyl EO/PO Random Copolyethers with KOH Catalyst

2012 ◽  
Vol 472-475 ◽  
pp. 2681-2685
Author(s):  
Jian Guo Guo ◽  
Su Qin He ◽  
Jian Ming Jiang
Keyword(s):  
Molecular Weight ◽  
Ethylene Oxide ◽  
Propylene Oxide ◽  
Potassium Hydroxide ◽  
Random Copolymer ◽  
Alkyl Halides ◽  
Ethyl Bromide ◽  
Hydroxyl Group ◽  
Molar Ratio ◽  
End Capping

Ethylene oxide (EO) and propylene oxide (PO) random copolymer was synthesized with 1,2-propanediol as initiator, then the end-capping process was carried out by adding various alkyl halides and potassium hydroxide (KOH) to produce the double alkyl EO/PO random copolyethers. The factors effecting alkyl-capping rate were discussed. The results showed that when the molar ratio of hydroxyl group/KOH/1-bromobutane was 1/1.9/1.9, reacting time 6.5 hr and reacting temperature 50°C, the alkyl-capping rate could reach over 80%. The end-capping rate would also increase with the increasing content of ethylene oxide in the random polyether, and the end-capping rate of the EO/PO/EO block-polyether was high than that of the random polyether with same molecular weight. Instead of 1-bromobutane, ethyl bromide promised a higher whereas chloralkane gave a lower end-capping rate respectively.

Infrared spectra of hydrogen bonded adducts of 2,6-dichlorophenols and oxygen bases

1985 ◽  
Vol 63 (12) ◽  
pp. 3568-3572 ◽  
Author(s):  
R. Wolny ◽  
A. Koll ◽  
L. Sobczyk
Keyword(s):  
Infrared Spectra ◽  
Infrared Region ◽  
Hydroxyl Group ◽  
Vibration Band ◽  
Inversion Point ◽  
Integrated Intensity ◽  
Stretching Vibration ◽  
Background Absorption ◽  
Hydrogen Bonded Systems ◽  
Hydrogen Bonded

Infrared spectra of hydrogen bonded complexes of 2,6-dichlorophenol derivatives and oxygen bases have been studied over a broad ΔpKa range (from −10.55 to +1.69). For the complexes of 1:1 stoichiometry typical evolution of spectra, similar to those for other hydrogen bonded systems, have been found. With an increase of ΔpKa the hydroxyl group stretching vibration band shifts to lower frequencies until the inversion region is reached, where hydrogen bonded (HB) and proton transfer (PT) forms occur in equilibrium, then abroad background absorption is observed. The centre of gravity of the broad protonic bands, veg, calculated from the integrated intensity over the whole infrared region have been correlated with ΔpKa and the contribution of the PT form. It has been shown that the minimum on the plot veg vs. ΔpKa is reached close to the inversion point, where KPT = 1. The observed correlations and the change in the shape of the broad protonic absorption are consistent with expectations of theories based on the concept of the double minimum potential function and the stochastic mechanisms of band broadening.

EXPLORING THE POTENTIAL ENERGY SURFACE OF THE CATALYZED ISOMERIZATION OF NITROSOMETHANE TO FORMALDOXIME

2007 ◽  
Vol 06 (01) ◽  
pp. 187-195 ◽  
Author(s):  
GUO-MING LIANG ◽  
YI REN ◽  
SAN-YAN CHU ◽  
NING-BEW WONG
Keyword(s):  
Activation Energy ◽  
Formic Acid ◽  
Energy Surface ◽  
Reaction Pathway ◽  
Hydroxyl Group ◽  
Rate Determining Step ◽  
Reaction Channels ◽  
Acid Catalyzed ◽  
Favorable Reaction ◽  
The One

The mechanism of the isomerization of nitrosomethane to formaldoxime catalyzed by neutral molecule ( H 2 O and HCOOH ) has been investigated at the level of B3LYP/6-311+G**. Calculated results indicate that the rearrangement from nitrosomethane to more stable trans-formaldoxime can proceed via two different reaction channels, but the favorable reaction pathway catalyzed by water and formic acid is different from the one in the catalyst-free reaction. It is more favorable that the tautomeric reaction involves the formation of cis-formaldoxime and a subsequent rotation about the N – O bond to form trans-formaldoxime in the catalyzed reaction. The activation energy of rate-determining step was reduced from 197.9 kJ/mol to 138.7 kJ/mol in the water-catalyzed reaction and 79.6 kJ/mol in the formic acid-catalyzed reaction, respectively, due to the catalysis of hydroxylic groups, but the catalysis of more acidic hydroxyl group in the latter system has been shown to be more efficient.

Mechanism and Stereochemistry of the Hydrolysis of 4-Arylamino-1,2,3,4- tetrahydroquinaldines

1974 ◽  
Vol 52 (6) ◽  
pp. 884-887 ◽  
Author(s):  
T. P. Forrest ◽  
G. A. Dauphinee ◽  
W. F. Miles
Keyword(s):  
Nitrogen Atom ◽  
Equilibrium Mixture ◽  
Hydroxyl Group ◽  
Amino Group ◽  
Heterocyclic Nitrogen ◽  
Carbonium Ion ◽  
Kinetically Controlled ◽  
Leaving Group ◽  
Acid Catalyzed ◽  
Hydrolysis Of

Rates of acid-catalyzed hydrolysis of the benzylic amino group in stereoisomers of 4-arylamino-1,2,3,4-tetrahydroquinaldines have been determined by n.m.r. spectroscopy. Those isomers which have a pseudo-axial leaving group react more rapidly than those with a pseudo-equatorial leaving group, forming in each case the isomer with a pseudo-axial hydroxyl group as the kinetically controlled product. This product is converted in time to an equilibrium mixture of the two stereoisomeric alcohols. The reaction is inhibited by excess acid and appears to proceed through an intermediate carbonium ion which is stabilized by the heterocyclic nitrogen atom.

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