The role of hydrogens in stabilizing organic ions

1996 ◽  
Vol 74 (6) ◽  
pp. 892-900 ◽  
Author(s):  
Kenneth B. Wiberg ◽  
Paul von Rague Schleyer ◽  
Andrew Streitwieser
Keyword(s):  
Free Radical ◽  
Electron Density ◽  
Negative Charge ◽  
Positive Charge ◽  
Radical Cations ◽  
Electrostatic Energy ◽  
Electron Density Difference ◽  
Organic Ions ◽  
Heavy Atoms

The changes in electron density that result from processes in which ions are formed were examined using both electron density difference maps and calculations of electron populations using Bader's theory of atoms in molecules. The processes include the loss of an electron from a neutral precursor forming a radical cation, the loss of an electron from a free radical forming a carbocation, the addition of a proton to ammonia, the addition of an electron to a free radical forming a carbanion, and the loss of a proton from a neutral precursor forming an anion. In the reactions forming cations, the new positive charge resides mainly at the hydrogens, and the heavy atoms generally gain electron density. The anion-forming reactions lead to negative charge being shared among atoms but, again, much of the charge appears at the hydrogens. σ–π polarization is an important feature of the charge distribution in all of the ions. There is an advantage to placing the charge at the periphery of an ion since this will minimize its electrostatic energy. Key words: electron density, anions, cations, radical cations, σ–π polarization.

The Role of Models in the Discovery of the Nucleus: Ernest Rutherford and his School

2021 ◽  
Vol 2 (2) ◽  
pp. 21
Author(s):  
Andrea Durlo
Keyword(s):  
20Th Century ◽  
Atomic Structure ◽  
Negative Charge ◽  
Positive Charge ◽  
Atomic Model ◽  
Early 20Th Century ◽  
Ernest Rutherford

Ernest Rutherford is remembered as the scientist who proposed a planetary atomic model that would overcome the atomic structure of the early 20th century, proposed by J.J. Thomson, and based on a volume of positive charge within which the negative charge was considered to be uniformly distributed. Reading Rutherford’s original paper published in 1911—allows us to compare the models of these two physicists and discuss the concept of the model itself.

scholarly journals Mass analysis of charged aerosol particles in NLC and PMSE during the ECOMA/MASS campaign

2009 ◽  
Vol 27 (3) ◽  
pp. 1213-1232 ◽  
Author(s):  
S. Robertson ◽  
M. Horányi ◽  
S. Knappmiller ◽  
Z. Sternovsky ◽  
R. Holzworth ◽  
...  
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Faraday Rotation ◽  
Negative Charge ◽  
Positive Charge ◽  
Aerosol Particles ◽  
Aerosol Sampling ◽  
Subsequent Growth ◽  
Charged Aerosol ◽  
First Time

Abstract. MASS (Mesospheric Aerosol Sampling Spectrometer) is a multichannel mass spectrometer for charged aerosol particles, which was flown from the Andøya Rocket Range, Norway, through NLC and PMSE on 3 August 2007 and through PMSE on 6 August 2007. The eight-channel analyzers provided for the first time simultaneous measurements of the charge density residing on aerosol particles in four mass ranges, corresponding to ice particles with radii <0.5 nm (including ions), 0.5–1 nm, 1–2 nm, and >3 nm (approximately). Positive and negative particles were recorded on separate channels. Faraday rotation measurements provided electron density and a means of checking charge density measurements made by the spectrometer. Additional complementary measurements were made by rocket-borne dust impact detectors, electric field booms, a photometer and ground-based radar and lidar. The MASS data from the first flight showed negative charge number densities of 1500–3000 cm−3 for particles with radii >3 nm from 83–88 km approximately coincident with PMSE observed by the ALWIN radar and NLC observed by the ALOMAR lidar. For particles in the 1–2 nm range, number densities of positive and negative charge were similar in magnitude (~2000 cm−3) and for smaller particles, 0.5–1 nm in radius, positive charge was dominant. The occurrence of positive charge on the aerosol particles of the smallest size and predominately negative charge on the particles of largest size suggests that nucleation occurs on positive condensation nuclei and is followed by collection of negative charge during subsequent growth to larger size. Faraday rotation measurements show a bite-out in electron density that increases the time for positive aerosol particles to be neutralized and charged negatively. The larger particles (>3 nm) are observed throughout the NLC region, 83–88 km, and the smaller particles are observed primarily at the high end of the range, 86–88 km. The second flight into PMSE alone at 84–88 km, found only small number densities (~500 cm−3) of particles >3 nm in a narrow altitude range, 86.5–87.5 km. Both positive (~2000 cm−3) and negative (~4500 cm−3) particles with radii 1–2 nm were detected from 85–87.5 km.

scholarly journals The Role of Models in the Discovery of the Nucleus: Ernest Rutherford and his School

2021 ◽  
Vol 2 (2) ◽  
pp. p21
Author(s):  
Andrea Durlo
Keyword(s):  
20Th Century ◽  
Atomic Structure ◽  
Negative Charge ◽  
Positive Charge ◽  
Atomic Model ◽  
Early 20Th Century ◽  
Ernest Rutherford

Ernest Rutherford is remembered as the scientist who proposed a planetary atomic model that would overcome the atomic structure of the early 20th century, proposed by J.J. Thomson, and based on a volume of positive charge within which the negative charge was considered to be uniformly distributed. Reading Rutherford’s original paper published in 1911—allows us to compare the models of these two physicists and discuss the concept of the model itself.

Study of antioxidant potential in leaves, stems, nuts of Juglans regia L.

2012 ◽  
Vol 1 (10) ◽  
pp. 79 ◽  
Author(s):  
G. Raja* ◽  
Ivvala Anand Shaker ◽  
Inampudi Sailaja ◽  
R. Swaminathan ◽  
S. Saleem Basha ◽  
...  
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Antioxidant Activities ◽  
Radical Scavenging Activity ◽  
Juglans Regia ◽  
Radical Scavenging ◽  
Antioxidant Compounds ◽  
Free Radical Damage ◽  
Radical Damage

Natural antioxidants can protect the human body from free radicals and retard the progress of many chronic diseases as well as lipid oxidative rancidity in foods. The role of antioxidants has protected effect against free radical damage that may cause many diseases including cancer. Primary sources of naturally occurring antioxidants are known as whole grains, fruits, and vegetables. Several studies suggest that regular consumption of nuts, mostly walnuts, may have beneficial effects against oxidative stress mediated diseases such as cardiovascular disease and cancer. The role of antioxidants has attracted much interest with respect to their protective effect against free radical damage that may cause many diseases including cancer. Juglans regia L. (walnut) contains antioxidant compounds, which are thought to contribute to their biological properties. Polyphenols, flavonoids and flavonols concentrations and antioxidant activity of Leaves, Stems and Nuts extract of Juglans regia L. as evaluated using DPPH, ABTS, Nitric acid, hydroxyl and superoxide radical scavenging activity, lipid peroxidation and total oxidation activity were determined. The antioxidant activities of Leaves, Stems and Nuts extract of Juglans regia L. were concentration dependent in different experimental models and it was observed that free radicals were scavenged by the test compounds in all the models.

Key Role of the Oxidized Citrate-Free Radical in the Nucleation Mechanism of the Metal Nanoparticle Turkevich Synthesis

2019 ◽  
Vol 123 (36) ◽  
pp. 22624-22633 ◽  
Author(s):  
Sarah Al Gharib ◽  
Jean-Louis Marignier ◽  
Abdel Karim El Omar ◽  
Adnan Naja ◽  
Sophie Le Caer ◽  
...  
Keyword(s):  
Free Radical ◽  
Nucleation Mechanism ◽  
Metal Nanoparticle

scholarly journals Role of the Anilinium Ion on the Selective Polymerization of Anilinium 2-Acrylamide-2-methyl-1-propanesulfonate

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2349
Author(s):  
Alain Salvador Conejo-Dávila ◽  
Marco Armando Moya-Quevedo ◽  
David Chávez-Flores ◽  
Alejandro Vega-Rios ◽  
Erasto Armando Zaragoza-Contreras
Keyword(s):  
Cyclic Voltammetry ◽  
Optical Properties ◽  
Thermal Properties ◽  
Free Radical ◽  
1H Nmr ◽  
Molecular Interactions ◽  
13C Nmr ◽  
Oxidative Polymerization ◽  
Cyclic Voltammetry Analysis

The development of anilinium 2-acrylamide-2-methyl-1-propanesulfonate (Ani-AMPS) monomer, confirmed by 1H NMR, 13C NMR, and FTIR, is systematically studied. Ani-AMPS contains two polymerizable functional groups, so it was submitted to selective polymerization either by free-radical or oxidative polymerization. Therefore, poly(anilinium 2-acrylamide-2-methyl-1-propanesulfonic) [Poly(Ani-AMPS)] and polyaniline doped with 2-acrylamide-2-methyl-1-propanesulfonic acid [PAni-AMPS] can be obtained. First, the acrylamide polymer, poly(Ani-AMPS), favored the π-stacking of the anilinium group produced by the inter- and intra-molecular interactions and was studied utilizing 1H NMR, 13C NMR, FTIR, and UV-Vis-NIR. Furthermore, poly(Ani-AMPS) fluorescence shows quenching in the presence of Fe2+ and Fe3+ in the emission spectrum at 347 nm. In contrast, the typical behavior of polyaniline is observed in the cyclic voltammetry analysis for PAni-AMPS. The optical properties also show a significant change at pH 4.4. The PAni-AMPS structure was corroborated through FTIR, while the thermal properties and morphology were analyzed utilizing TGA, DSC (except PAni-AMPS), and FESEM.

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.

Ferroptosis and cardiovascular disease: role of free radical-induced lipid peroxidation

2021 ◽  
pp. 1-11
Author(s):  
Xin Chen ◽  
Xuan Li ◽  
Xiaodong Xu ◽  
Luxiao Li ◽  
Ningning Liang ◽  
...  
Keyword(s):  
Cardiovascular Disease ◽  
Lipid Peroxidation ◽  
Free Radical

scholarly journals Possible Protective Role of Melatonin in Pediatric Infectious Diseases and Neurodevelopmental Pathologies

2020 ◽  
Vol 10 (01) ◽  
pp. e104-e109
Author(s):  
Antonio Molina-Carballo ◽  
Antonio Emilio Jerez-Calero ◽  
Antonio Muñoz-Hoyos
Keyword(s):  
Endothelial Cell ◽  
Free Radical ◽  
Chronic Administration ◽  
Protective Role ◽  
Free Radical Scavenger ◽  
Radical Scavenger ◽  
Energetic Metabolism ◽  
Beneficial Effects ◽  
Molecular Crosstalk

AbstractMelatonin, produced in every cell that possesses mitochondria, acts as an endogenous free radical scavenger, and improves energetic metabolism and immune function, by complex molecular crosstalk with other intracellular compounds. There is greatly increasing evidence regarding beneficial effects of acute and chronic administration of high melatonin doses, in infectious, developmental, and degenerative pathologies, as an endothelial cell and every cell protectant.

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