Emergence of magnetism in silicene by introducing carbon atom as foreign atom in all possible ways

2018 ◽  
Vol 194 (1) ◽  
pp. 53-59
Author(s):  
Jyoti Thakur ◽  
Monika Tomar ◽  
Vinay Gupta ◽  
Manish K. Kashyap
Keyword(s):  
Carbon Atom ◽  
Foreign Atom

An atomic resolution study of a carbide phase in platinum

1992 ◽  
Vol 50 (1) ◽  
pp. 20-21
Author(s):  
M.J. Witcomb ◽  
M.A. O'Keefe ◽  
CJ. Echer ◽  
C. Nelson ◽  
J.H. Turner ◽  
...  
Keyword(s):  
Solid Solution ◽  
Carbon Atom ◽  
Carbide Phase ◽  
Structural Changes ◽  
Critical Role ◽  
Alloy System ◽  
Atomic Resolution ◽  
Excess Carbon ◽  
Interstitial Carbon ◽  
Resolution Study

Under normal circumstances, Pt dissolves only a very small amount of interstitial carbon in solid solution. Even so, an appropriate quench/age treatment leads to the formation of stable Pt2C {100} plate precipitates. Excess (quenched-in) vacancies play a critical role in the process by accommodating the volume and structural changes that accompany the transformation. This alloy system exhibits other interesting properties. Due to a large vacancy/carbon atom binding energy, Pt can absorb excess carbon at high temperatures in a carburizing atmosphere. In regions rich in carbon and vacancies, another carbide phase, Pt7C which undergoes an order-disorder reaction was formed. The present study of Pt carburized at 1160°C and aged at 515°C shows that other carbides in the PtxC series can be produced.

Mass spectra of 4,4-dimethyl-A-homo-4a,6-cholestadien-3-ols, 4,4-dimethyl-A-homo-5-cholestene-3,4a-diols and their derivatives

1982 ◽  
Vol 47 (10) ◽  
pp. 2768-2778
Author(s):  
Antonín Trka ◽  
Helena Velgová
Keyword(s):  
Carbon Atom ◽  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions

Partial electron impact induced mass spectra are given of 3α-hydroxy-, 3β-hydroxy-, 3β-methoxy-, 3α-acetoxy- and 3β-acetoxy-4,4-dimethyl-A-homo-4a,6-cholestadienes, 3α,5α-epoxy-4,4-dimethyl-A-homo-5-cholestane, isomeric 4,4-dimethyl-A-homo-5-cholestene-3α(β),4aα(β)-diols, their 3-acetoxy derivatives and 3-methyl ethers. The fragmentation of the molecular ions of these substances involves the usual elimination of substituents (in the form of H2O, CH3OH, CH3COOH, CH2CO), but the most abundant and characteristic ions are products of the contraction of ring A (to a six- or five-membered one), accompanied by expulsion of a fragment containing the carbon atom C(4) with both methyls.

Intercalation of uranium hexafluoride into graphite

1985 ◽  
Vol 50 (4) ◽  
pp. 947-955 ◽  
Author(s):  
Karel Klouda ◽  
Václav Rak ◽  
Josef Vachuška
Keyword(s):  
Carbon Atom ◽  
Surface Area ◽  
Gaseous Phase ◽  
Uranium Hexafluoride ◽  
Graphite Particles ◽  
Fluorination Agent ◽  
Increasing Temperature ◽  
Elementary Fluorine

Intercalation of UF6 into graphite, both from the gaseous phase and from the Ledon 113 solution, was studied. The amount of intercalated UF6 from the gaseous phase was found to be inversely proportional to the size of graphite particles. Intercalation increases with the increasing temperature and surface area of graphite. The contact of gaseous UF6 with graphite led to the formation of β-UF5 that is not intercalated. In the Ledon solution, β-UF5 is not formed. "Passivation" of graphite by elementary fluorine also prevents the formation of β-UF5 but the amount of intercalated UF6 decreases. The intercalation of UF6 into graphite from the gaseous phase is accompanied by the increase of the distance between the parallel carbon atom layers up to the values of about 884 pm. Ternary intercalates graphite-UF6-Ledon 113 are formed during the intercalation of UF6 from the Ledon 113 solutions and the distance between the parallel carbon atom layers is 848-875 pm. Thermogravimetry in the presence of air revealed that the binary intercalates graphite-UF6 decompose in a 3-step reaction while the ternary intercalates decompose in a 4-step reaction. In both cases uranium hexafluoride is not released but acts as a fluorination agent on the graphite carbon.

scholarly journals Carbon Atom Insertion into Pyrroles and Indoles Promoted by Chlorodiazirines

2021 ◽  
Author(s):  
Balu D. Dherange ◽  
Patrick Q. Kelly ◽  
Jordan P. Liles ◽  
Matthew S. Sigman ◽  
Mark D. Levin
Keyword(s):  
Carbon Atom

scholarly journals Understanding the reaction mechanism of the regioselective piperidinolysis of aryl 1-(2,4-dinitronaphthyl) ethers in DMSO: Kinetic and DFT studies

2021 ◽  
Vol 46 ◽  
pp. 146867832110274
Author(s):  
Yasmen M Moghazy ◽  
Nagwa MM Hamada ◽  
Magda F Fathalla ◽  
Yasser R Elmarassi ◽  
Ezzat A Hamed ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Density Functional ◽  
Function Analysis ◽  
Density Functional Theory Method ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Nucleophilic Attack ◽  
Common Mechanism ◽  
Slow Step ◽  
Rate Determining Step

Reactions of aryl 1-(2,4-dinitronaphthyl) ethers with piperidine in dimethyl sulfoxide at 25oC resulted in substitution of the aryloxy group at the ipso carbon atom. The reaction was measured spectrophotochemically and the kinetic studies suggested that the titled reaction is accurately third order. The mechanism is began by fast nucleophilic attack of piperidine on C1 to form zwitterion intermediate (I) followed by deprotonation of zwitterion intermediate (I) to the Meisenheimer ion (II) in a slow step, that is, SB catalysis. The regular variation of activation parameters suggested that the reaction proceeded through a common mechanism. The Hammett equation using reaction constant σo values and Brønsted coefficient value showed that the reaction is poorly dependent on aryloxy substituent and the reaction was significantly associative and Meisenheimer intermediate-like. The mechanism of piperidinolysis has been theoretically investigated using density functional theory method using B3LYP/6-311G(d,p) computational level. The combination between experimental and computational studies predicts what mechanism is followed either through uncatalyzed or catalyzed reaction pathways, that is, SB and SB-GA. The global parameters of the reactants, the proposed activated complexes, and the local Fukui function analysis explained that C1 carbon atom is the most electrophilic center of ether. Also, kinetics and theoretical calculation of activation energies indicated that the mechanism of the piperidinolysis passed through a two-step mechanism and the proton transfer process was the rate determining step.

scholarly journals Zerumbone Inhibits Helicobacter pylori Urease Activity

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2663
Author(s):  
Hyun Jun Woo ◽  
Ji Yeong Yang ◽  
Pyeongjae Lee ◽  
Jong-Bae Kim ◽  
Sa-Hyun Kim
Keyword(s):  
Helicobacter Pylori ◽  
Carbon Atom ◽  
Natural Compound ◽  
Urease Activity ◽  
Negative Charge ◽  
Positive Charge ◽  
Gastric Epithelium ◽  
Functional Inhibition ◽  
Electrical Gradient ◽  
H Pylori

Helicobacter pylori (H. pylori) produces urease in order to improve its settlement and growth in the human gastric epithelium. Urease inhibitors likely represent potentially powerful therapeutics for treating H. pylori; however, their instability and toxicity have proven problematic in human clinical trials. In this study, we investigate the ability of a natural compound extracted from Zingiber zerumbet Smith, zerumbone, to inhibit the urease activity of H. pylori by formation of urease dimers, trimers, or tetramers. As an oxygen atom possesses stronger electronegativity than the first carbon atom bonded to it, in the zerumbone structure, the neighboring second carbon atom shows a relatively negative charge (δ−) and the next carbon atom shows a positive charge (δ+), sequentially. Due to this electrical gradient, it is possible that H. pylori urease with its negative charges (such as thiol radicals) might bind to the β-position carbon of zerumbone. Our results show that zerumbone dimerized, trimerized, or tetramerized with both H. pylori urease A and urease B molecules, and that this formation of complex inhibited H. pylori urease activity. Although zerumbone did not affect either gene transcription or the protein expression of urease A and urease B, our study demonstrated that zerumbone could effectively dimerize with both urease molecules and caused significant functional inhibition of urease activity. In short, our findings suggest that zerumbone may be an effective H. pylori urease inhibitor that may be suitable for therapeutic use in humans.

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