EHT study of reactivity of methylene group in 1-methyl-1,4-dihydronicotinamide

1980 ◽  
Vol 45 (9) ◽  
pp. 2425-2432
Author(s):  
Jiří Krechl ◽  
Josef Kuthan
Keyword(s):  
Heterocyclic Ring ◽  
Covalent Bonds ◽  
Electronic Mechanism ◽  
Methylene Group ◽  
Plane Form ◽  
Reaction Profile

It has been demonstrated that the EHT method predicts an almost plane form of the heterocyclic ring in 1-methyl-1,4-dihydronicotinamide I (R = CH3) and also reflects satisfactorily character of the covalent bonds in the 4-methylene group. An attempt has been made of calculation of the reaction profile of elimination of the centre 4', and electronic mechanism of its splitting off is discussed.

A CNDO/2 study of reactivity of methylene group in 1-methyl-1,4-dihydronicotinamide

1982 ◽  
Vol 47 (6) ◽  
pp. 1621-1631 ◽  
Author(s):  
Jiří Krechl ◽  
Josef Kuthan
Keyword(s):  
Hydrogen Atom ◽  
Electronic Mechanism ◽  
Methylene Group ◽  
Reaction Profile

An attempt has been made to use the CNDO/2 method for prediction of the reaction profile and electronic mechanism of elimination of 4-hydrogen atom of 1-methyl-1,4-dihydronicotinamide (I).

scholarly journals Crystal structure of (9S,10S)-10-ethoxy-9-hydroxy-6,6,9-trimethyl-3-pentyl-7,8,9,10-tetrahydro-6H-benzo[c]chromen-1-yl 4-methylbenzenesulfonate

2015 ◽  
Vol 71 (12) ◽  
pp. o1082-o1083 ◽  
Author(s):  
Waseem Gul ◽  
Ahmed Galal ◽  
Mahmoud A. ElSohly ◽  
Paulo Carvalho
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Hydrogen Bonds ◽  
Chair Conformation ◽  
Heterocyclic Ring ◽  
Helical Chain ◽  
Aromatic Rings ◽  
Compound C ◽  
Cyclohexene Ring ◽  
Methylene Group

In the structure of the title compound, C30H40O6S, the cyclohexene and heterocyclic rings are linked by a double bond. The cyclohexene ring has a half-chair conformation (the methylene group adjacent to the hydroxy substituent lies above the remaining atoms) and the hydroxy and ethoxy groups have equatorial and bisectional dispositions, respectively. The heterocyclic ring has an envelope conformation (with the CMe2C atom being the flap). The dihedral angle between the aromatic rings is 53.88 (10)°. A long intramolecular C—H...S interaction is noted. In the molecular packing, hydroxy-O—H...O(sulfonate) hydrogen bonds lead to a helical chain along [010]. Connections between chains are of the type methyl-C—H...O(sulfonate) and lead to supramolecular layers that lie parallel to (001). The studied crystal was an inversion twin.

Hemioxonol dyes

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Heinz Mustroph
Keyword(s):  
Silver Halide ◽  
Heterocyclic Ring ◽  
Transfer Printing ◽  
Open Chain ◽  
Thermal Transfer ◽  
Systematic Nomenclature ◽  
Dye Diffusion ◽  
Active Methylene ◽  
Methylene Group

Abstract Following the classification of hemicyanine dyes Leslie G. S. Brooker suggested the term hemioxonol dye be applied to the case of an oxonol colorant in which one of its terminal unsaturated heterocycles has been replaced by an open chain N(R1)R2 group or saturated heterocyclic ring. For historical reasons, dyes formed from the reaction of 4-N,N-dialkylaminobenzaldehydes or 4-N,N-dialkylaminocinnamaldehydes with a heterocycle containing an active methylene group adjacent to a carbonyl group are often called benzylidene dyes and cinnamylidene dyes, respectively. In terms of systematic nomenclature, their proper classification is as hemioxonol dyes. They are used as filter dyes and antihalation dyes in silver halide photography. Their current main usage is in dye diffusion thermal transfer printing (D2T2).

ATISINE: THE HETEROCYCLIC RING AND FUNCTIONAL GROUPS

1954 ◽  
Vol 32 (5) ◽  
pp. 465-473 ◽  
Author(s):  
O. E. Edwards ◽  
Tara Singh
Keyword(s):  
Functional Groups ◽  
Heterocyclic Ring ◽  
Double Bonds ◽  
Secondary Hydroxyl ◽  
Exocyclic Methylene ◽  
Methylene Group ◽  
Hydroxyethyl Group

Evidence is presented which confirms the presence in atisine and isoatisine of vinylamine double bonds, an N-(β-hydroxyethyl) group, an exocyclic methylene group, and a secondary hydroxyl in an allylic relation to the latter. The size and substitution of the heterocyclic ring is discussed. The pyrolysis of atisine and isoatisine hydrochlorides to give a C20H29ON base is described.

SOME STRUCTURAL FEATURES OF DELCOSINE

1958 ◽  
Vol 36 (5) ◽  
pp. 766-770 ◽  
Author(s):  
Ragini Anet ◽  
Léo Marion
Keyword(s):  
Heterocyclic Ring ◽  
Structural Features ◽  
Membered Ring ◽  
Hydroxyl Groups ◽  
Supporting Evidence ◽  
Methylene Group ◽  
Tertiary Hydroxyl

The alkaloid delcosine has previously been assigned tentatively the same carbon–nitrogen skeleton as lycoctonine to which it appears to be closely related in properties. Oxidation experiments now reported provide supporting evidence of the presence of two vicinal tertiary hydroxyl groups attached to a five- and a six-membered ring that are directly linked together at the two carbons carrying the hydroxyls. There is a methoxyl in a position β to the tertiary hydroxyl of the six-membered ring. Evidence is also provided as to the size of the heterocyclic ring and the presence of a methylene group next to the nitrogen.

Temperature Dependence of the Critical Electron Dose for Fatty Acid Monolayers

1982 ◽  
Vol 40 ◽  
pp. 78-79
Author(s):  
Kenneth H. Downing ◽  
Robert M. Glaeser
Keyword(s):  
Electron Beam ◽  
Fatty Acid ◽  
Inelastic Scattering ◽  
Temperature Dependence ◽  
Structural Damage ◽  
Direct Result ◽  
Second Step ◽  
Strong Temperature Dependence ◽  
Electron Dose ◽  
Covalent Bonds

The structural damage of molecules irradiated by electrons is generally considered to occur in two steps. The direct result of inelastic scattering events is the disruption of covalent bonds. Following changes in bond structure, movement of the constituent atoms produces permanent distortions of the molecules. Since at least the second step should show a strong temperature dependence, it was to be expected that cooling a specimen should extend its lifetime in the electron beam. This result has been found in a large number of experiments, but the degree to which cooling the specimen enhances its resistance to radiation damage has been found to vary widely with specimen types.

Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

1990 ◽  
Vol 48 (1) ◽  
pp. 52-53 ◽  
Author(s):  
Jean-Luc Rouvière ◽  
Alain Bourret
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Structural Transformation ◽  
Mirror Symmetry ◽  
High Resolution Electron Microscopy ◽  
Structural Transformations ◽  
Covalent Bonds ◽  
Resolution Electron ◽  
Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

Tele-Substitution Reactions in the Synthesis of a Promising Class of Antimalarials

2020 ◽  
Author(s):  
Marat Korsik ◽  
Edwin Tse ◽  
David Smith ◽  
William Lewis ◽  
Peter J. Rutledge ◽  
...  
Keyword(s):  
Heterocyclic Ring ◽  
Ring System ◽  
Substitution Reactions ◽  
Laboratory Notebook ◽  
Polar Solvents ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Core ◽  
Nmr Data

<p></p><p>We have discovered and studied a <i>tele</i>substitution reaction in a biologically important heterocyclic ring system. Conditions that favour the <i>tele</i>-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base, or the use of softer nucleophiles, less polar solvents and larger halogens on the electrophile. Using results from X-ray crystallography and isotope labelling experiments a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the <i>in vivo </i>active anti-plasmodium compounds of Series 4 of the Open Source Malaria consortium.</p> <p> </p> <p>Archive of the electronic laboratory notebook with the description of all conducted experiments and raw NMR data could be accessed via following link <a href="https://ses.library.usyd.edu.au/handle/2123/21890">https://ses.library.usyd.edu.au/handle/2123/21890</a> . For navigation between entries of laboratory notebook please use file "Strings for compounds in the article.pdf" that works as a reference between article codes and notebook codes, also this file contain SMILES for these compounds. </p><br><p></p>

Imine Based Self-Healing Hydrogel Triggered by Periodate

2020 ◽  
Author(s):  
Alexis Wolfel ◽  
Cecilia Inés Alvarez Igarzabal ◽  
Marcelo Ricardo Romero
Keyword(s):  
Functional Groups ◽  
Time Window ◽  
Crosslinking Reaction ◽  
Self Healing ◽  
Swelling Properties ◽  
Covalent Bonds ◽  
Smart Systems ◽  
Primary Amino ◽  
Vicinal Diols ◽  
Aldehyde Groups

<p>Design of materials with novel sensitivities and smart behaviour is important for the development of smart systems with automated responsiveness. We have recently reported the synthesis of hydrogels, cross-linked by <i>N,N'</i>-diallyltartardiamide (DAT). The covalent DAT-crosslinking points have vicinal diols which can be easily cleaved with periodate, generating valuable a-oxo-aldehyde functional groups, useful for further chemical modification. Based on those findings, we envisioned that a self-healable hydrogel could be obtained by incorporation of primary amino functional groups, from <a>2-aminoethyl methacrylate </a>hydrochloride (AEMA), coexisting with DAT into the same network. The a-oxo-aldehyde groups generated after the reaction with periodate would arise in the immediate environment of amine groups to form imine cross-links. For this purpose, DAT-crosslinked hydrogels were synthesized and carefully characterized. The cleavage of DAT-crosslinks with periodate promoted changes in the mechanical and swelling properties of the materials. As expected, a self-healing behavior was observed, based on the spontaneous formation of imine covalent bonds. In addition, we surprisingly found a combination of fast vicinal diols cleavage and a low speed self-crosslinking reaction by imine formation. Consequently, it was found a time-window in which a periodate-treated polymer was obtained in a transient liquid state, which can be exploited to choose the final shape of the material, before automated gelling. The singular properties attained on these hydrogels could be useful for developing sensors, actuators, among other smart systems.</p>

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