Structures of ion-pairs derived from dihydroanthracenes I. Electronic spectra

1967 ◽  
Vol 301 (1466) ◽  
pp. 223-230 ◽  
Keyword(s):  
Wide Temperature Range ◽  
Electronic Spectra ◽  
Absorption Maximum ◽  
Ion Pairs ◽  
Alkyl Substituent ◽  
Ion Pair ◽  
The Other ◽  
Lithium Salts ◽  
Sodium Salts ◽  
The Stability

The optical spectra of the 9-lithium and sodium salts of 9, 10-dihydroanthracene and its 10-alkyl substituted derivatives have been investigated in tetrahydrofuran over a wide temperature range (25°C to about −70°C). The spectra of the lithium salts indicate the coexistence of two species having a different degree of solvation, one absorbing at λ max . = 400 nm, the other at λ max . = 450 nm. Lower temperatures favour the latter. It has been found that the presence of an alkyl substituent on carbon 10 greatly increases the stability of that species which absorbs at the longer wavelength. Only one absorption peak is seen in the spectrum of the respective sodium salts. The absorption maximum of the unsubstituted ion-pair shifts with temperature, namely λ max . = 455 nm at −70°C and 425 nm at +20°C. Similar behaviour was observed for the substituted salt. These observations suggest the need for a ‘dynamic’ model of ion-pairs in preference to the ‘static’ one in which the energy of the pair is uniquely determined by the interionic distance. Such models are discussed.

scholarly journals 5-Aryl-2-(3,5-dialkyl-4-hydroxyphenyl)-4,4-dimethyl-4H-imidazole 3-Oxides and Their Redox Species: How Antioxidant Activity of 1-Hydroxy-2,5-dihydro-1H-imidazoles Correlates with the Stability of Hybrid Phenoxyl–Nitroxides

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3118
Author(s):  
Svetlana A. Amitina ◽  
Elena V. Zaytseva ◽  
Natalya A. Dmitrieva ◽  
Alyona V. Lomanovich ◽  
Natalya V. Kandalintseva ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Alkyl Substituent ◽  
Nitroxyl Radicals ◽  
The Other ◽  
Redox Species ◽  
Phenol Group ◽  
Sterically Hindered Phenol ◽  
Hindered Phenol ◽  
The Stability ◽  
Opposite Tendency

Cyclic nitrones of the imidazole series, containing a sterically hindered phenol group, are promising objects for studying antioxidant activity; on the other hand, they can form persistent hybrid phenoxyl–nitroxyl radicals (HPNs) upon oxidation. Here, a series of 5-aryl-4,4-dimethyl-4H-imidazole 3-oxides was obtained by condensation of aromatic 2-hydroxylaminoketones with 4-formyl-2,6-dialkylphenols followed by oxidation of the initially formed N-hydroxy derivatives. It was shown that the antioxidant activity of both 1-hydroxy-2,5-dihydroimidazoles and 4H-imidazole 3-oxides increases with a decrease in steric volume of the alkyl substituent in the phenol group, while the stability of the corresponding HPNs generated from 4H-imidazole 3-oxides reveals the opposite tendency.

Ion-Pair Formation of Sodium Salts of Several Oxo Anions and Cadmium Halides in Water and the Distribution of Monovalent Sulfate Ion Pairs in Nitrobenzene

2010 ◽  
Vol 55 (7) ◽  
pp. 2463-2469 ◽  
Author(s):  
Yoshihiro Kudo ◽  
Daisuke Todoroki ◽  
Naoki Horiuchi ◽  
Shoichi Katsuta ◽  
Yasuyuki Takeda
Keyword(s):  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Sulfate Ion ◽  
Sodium Salts ◽  
Ion Pair Formation ◽  
Oxo Anions

Complexation of Cobalt(II), Nickel(II), and Copper(II) Ions with Pyridine, 2-Methylpyridine, 3-Methylpyridine, and 4-Methylpyridine in Acetonitrile

2000 ◽  
Vol 55 (3-4) ◽  
pp. 277-284 ◽  
Author(s):  
Makoto Kurihara ◽  
Takuji Kawashima ◽  
Kazuhiko Ozutsumi
Keyword(s):  
Electronic Spectra ◽  
Thermodynamic Data ◽  
The Other ◽  
Thermodynamic Quantities ◽  
Free Energies ◽  
Octahedral Structure ◽  
Spectrophotometric Data ◽  
The Difference ◽  
The Stability ◽  
The Individual

Abstract Thermodynamic data of the complexation of cobalt(II), nickel(II), and copper(II) ions with pyridine (py), 2-methylpyridine (2Me-py), 3-methylpyridine (3Me-py), and 4-methylpyridine (4Me-py) have been determined by calorimetry and spectrophotometry in acetonitrile (MeCN) containing 0.1 mol dm-3 (C2H5)4NClO4 as a constant ionic medium at 25 °C. The calorimetric and spectrophotometric data for py, 3Me-py, and 4Me-py revealed the formation of [ML]2+, [ML2]2+, [ML3]2+, and [ML4]2+ (M = Co2+, Ni2+, Cu2+; L = py, SMe-py, 4Me-py). For 2Me-py, on the other hand, the formation of only one complex, [M(2Me-py)]2+ (M = Co2+, Ni2+), was detected. The stepwise thermodynamic quantities and the individual electronic spectra of the complexes suggest that all of these have a six-coordinate octahedral structure. The stability of the [M(2Me-py)]2+ (M = Co2+, Ni2+) complexes is much lower than that of the corresponding py, 3Me-py, and 4Me-py complexes. The difference in the stability of the 2Me-py complexes is mainly due to their unfavorable entropy changes because the differences of enthalpies for all the complexes are not so significant. The free energies for the formation of the mono complexes follow the order Mn(II) > Co(II) > Ni(II) > Cu(II) < Zn(II) for the py, 3Me-py, and 4Me-py systems. The ΔH°1 values vary in the same order and the ΔS°1 values are similar. Hence, the stability difference of the mono complexes originates from the enthalpic term

REARRANGEMENT STUDIES WITH 14C: XIX. THE REACTION OF 2-PHENYL-1-14C-ETHANOL WITH THIONYL CHLORIDE

1964 ◽  
Vol 42 (5) ◽  
pp. 1130-1136 ◽  
Author(s):  
C. C. Lee ◽  
D. J. Kroeger ◽  
D. P. Thornhill
Keyword(s):  
Thionyl Chloride ◽  
Ion Pairs ◽  
Aqueous Sodium Hydroxide ◽  
Covalent Bonding ◽  
Ion Pair ◽  
Aqueous Sodium ◽  
Carbonium Ion ◽  
Partial Completion ◽  
The Stability ◽  
Excess Thionyl Chloride

The reaction of 2-phenyl-1-14C-ethanol with thionyl chloride in pyridine, dioxane, toluene, or excess thionyl chloride as solvent gave 2-phenylethyl chloride showing, respectively, about 0, 15, 44, and 48% rearrangement of the 14C-label from the C-1 to the C-2 positions. When reactions of 2-phenyl-1-14C-ethauol or 2-p-anisyl-1-14C-ethanol with thionyl chloride in dioxane or excess thionyl chloride were carried only to partial completion and the undecomposed chlorosulphites hydrolyzed by aqueous sodium hydroxide, the recovered alcohols showed only 0.1 to 0.5% isotope position rearrangement. This indicated a lack of return from ion-pairs to isotopically rearranged 2-arylethylchlorosulphite and suggested that the first stage of ionization may involve ion-pairs with structures that will not result in rearrangement on return to covalent bonding, or that the first ion-pair may decompose faster than it can return to reactant. The possibility that rearrangements via rigidly oriented ion-pairs and via the concerted SNi′ mechanism may represent the two extremes of a graded series is discussed. It is suggested that the relative contributions from the ion-pair and from the SNi′ mechanisms will depend on the stability of the carbonium ion as well as on the nature of the reaction solvent.

Rearrangement studies with 14C. XLIV. Ion-pairs and dissociated ions in the solvolysis of triphenyl[2-14C]vinyl and trianisyl[2-14C]vinyl bromides in 70% acetic acid – 30% water

1980 ◽  
Vol 58 (22) ◽  
pp. 2369-2376 ◽  
Author(s):  
Choi Chuck Lee ◽  
Eric C. F. Ko ◽  
Zvi Rappoport
Keyword(s):  
Acetic Acid ◽  
Ion Pairs ◽  
Ion Pair ◽  
The Other ◽  
Product Data ◽  
Vinyl Bromide ◽  
Ion Competition ◽  
Other Hand ◽  
The Mean

In the solvolysis of triphenyl[2-14C]vinyl bromide (1-Br-2-14C) in 70% HOAc – 30% H2O, the presence of up to 30 equiv. of added NaOAc or 25 equiv. of added Et4NBr did not significantly change the extent of scrambling of the label from C-2 to C-1 in the reaction product. The mean scrambling value observed for 1-Br-2-14C under a variety of conditions was 14.7 ± 0.7%. On the other hand, in the similar solvolysis of trianisyl[2-14C]vinyl bromide (2-Br-2-14C), the extent of scrambling in the product was found to decrease with increasing amounts of added NaOAc. The observed scramblings varied from a mean of 27.7% to 5.7%, respectively, for reactions without and with 10 M added NaOAc. With 1-Br-2-14C, the possibility is considered that ionization proceeds only to an ion-pair in which the scrambling via 1,2-phenyl shift is not affected by the presence of added OAc−. In the case of 2-Br-2-14C, further dissociation to the free trianisylvinyl cation took place and in the dissociated ion, competition between the scrambling process and capture reactions with all the nucleophiles present resulted in a decrease in the extent of scrambling with the presence of the more nucleophilic OAc−. Using the extents of scrambling as well as product data, various ratios including kSOH/kr, kOAc/kr, [Formula: see text], and kOAc/kHOAc, are evaluated.

Uniformity of Magnification from Different Electron Microscopes

1967 ◽  
Vol 25 ◽  
pp. 32-33
Author(s):  
Godfrey C. Hoskins ◽  
V. Williams ◽  
V. Allison
Keyword(s):  
Diffraction Grating ◽  
The Other ◽  
Carbon Replica ◽  
Electron Microscopes ◽  
The Stability

The method demonstrated is an adaptation of a proven procedure for accurately determining the magnification of light photomicrographs. Because of the stability of modern electrical lenses, the method is shown to be directly applicable for providing precise reproducibility of magnification in various models of electron microscopes.A readily recognizable area of a carbon replica of a crossed-line diffraction grating is used as a standard. The same area of the standard was photographed in Phillips EM 200, Hitachi HU-11B2, and RCA EMU 3F electron microscopes at taps representative of the range of magnification of each. Negatives from one microscope were selected as guides and printed at convenient magnifications; then negatives from each of the other microscopes were projected to register with these prints. By deferring measurement to the print rather than comparing negatives, correspondence of magnification of the specimen in the three microscopes could be brought to within 2%.

Stereospecific 1,3-H Transfer of Indenols Proceeds via Persistent Ion-Pairs Anchored By NH···Pi Interactions

2018 ◽  
Author(s):  
David Ascough ◽  
Fernanda Duarte ◽  
Robert Paton
Keyword(s):  
Computational Analysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Chirality Transfer ◽  
Activation Barriers ◽  
Sense And Avoid ◽  
Phase Dynamics ◽  
Pi Interactions

The base-catalyzed rearrangement of arylindenols is a rare example of a suprafacial [1,3]-hydrogen atom transfer. The mechanism has been proposed to proceed via sequential [1,5]-sigmatropic shifts, which occur in a selective sense and avoid an achiral intermediate. A computational analysis using quantum chemistry casts serious doubt on these suggestions: these pathways have enormous activation barriers and in constrast to what is observed experimentally, they overwhelmingly favor a racemic product. Instead we propose that a suprafacial [1,3]-prototopic shift occurs in a two-step deprotonation/reprotonation sequence. This mechanism is favored by 15 kcal mol<sup>-1</sup> over that previously proposed. Most importantly, this is also consistent with stereospecificity since reprotonation occurs rapidly on the same p-face. We have used explicitly-solvated molecular dynamics studies to study the persistence and condensed-phase dynamics of the intermediate ion-pair formed in this reaction. Chirality transfer is the result of a particularly resilient contact ion-pair, held together by electrostatic attraction and a critical NH···p interaction which ensures that this species has an appreciable lifetime even in polar solvents such as DMSO and MeOH.

scholarly journals Black Hole Algorithm for Sustainable Design of Counterfort Retaining Walls

2020 ◽  
Vol 12 (7) ◽  
pp. 2767 ◽  
Author(s):  
Víctor Yepes ◽  
José V. Martí ◽  
José García
Keyword(s):  
Black Hole ◽  
Sustainable Design ◽  
Retaining Walls ◽  
The Other ◽  
Trade Off ◽  
Construction Company ◽  
Geometric Variables ◽  
The Stability ◽  
The Cost ◽  
Black Hole Algorithm

The optimization of the cost and CO 2 emissions in earth-retaining walls is of relevance, since these structures are often used in civil engineering. The optimization of costs is essential for the competitiveness of the construction company, and the optimization of emissions is relevant in the environmental impact of construction. To address the optimization, black hole metaheuristics were used, along with a discretization mechanism based on min–max normalization. The stability of the algorithm was evaluated with respect to the solutions obtained; the steel and concrete values obtained in both optimizations were analyzed. Additionally, the geometric variables of the structure were compared. Finally, the results obtained were compared with another algorithm that solved the problem. The results show that there is a trade-off between the use of steel and concrete. The solutions that minimize CO 2 emissions prefer the use of concrete instead of those that optimize the cost. On the other hand, when comparing the geometric variables, it is seen that most remain similar in both optimizations except for the distance between buttresses. When comparing with another algorithm, the results show a good performance in optimization using the black hole algorithm.

scholarly journals Tripodal, Squaramide-Based Ion Pair Receptor for Effective Extraction of Sulfate Salt

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2751
Author(s):  
Damian Jagleniec ◽  
Marcin Wilczek ◽  
Jan Romański
Keyword(s):  
Ion Pairs ◽  
Binding Mode ◽  
Selective Extraction ◽  
Ion Pair ◽  
Hofmeister Series ◽  
Sulfate Salt ◽  
Lower Affinity ◽  
High Affinity ◽  
Binding Domains ◽  
Hydrated Sulfate

Combining three features—the high affinity of squaramides toward anions, cooperation in ion pair binding and preorganization of the binding domains in the tripodal platform—led to the effective receptor 2. The lack of at least one of these key elements in the structures of reference receptors 3 and 4 caused a lower affinity towards ion pairs. Receptor 2 was found to form an intramolecular network in wet chloroform, which changed into inorganic–organic associates after contact with ions and allowed salts to be extracted from an aqueous to an organic phase. The disparity in the binding mode of 2 with sulfates and with other monovalent anions led to the selective extraction of extremely hydrated sulfate anions in the presence of more lipophilic salts, thus overcoming the Hofmeister series.

scholarly journals A Fractional SAIDR Model in the Frame of Atangana–Baleanu Derivative

2021 ◽  
Vol 5 (2) ◽  
pp. 32
Author(s):  
Esmehan Uçar ◽  
Sümeyra Uçar ◽  
Fırat Evirgen ◽  
Necati Özdemir
Keyword(s):  
Existence And Uniqueness ◽  
Laplace Transformation ◽  
Cell Phones ◽  
Mobile Network ◽  
The Other ◽  
Banach Fixed Point Theorem ◽  
Propagation Models ◽  
Computer Worms ◽  
Computer Viruses ◽  
The Stability

It is possible to produce mobile phone worms, which are computer viruses with the ability to command the running of cell phones by taking advantage of their flaws, to be transmitted from one device to the other with increasing numbers. In our day, one of the services to gain currency for circulating these malignant worms is SMS. The distinctions of computers from mobile devices render the existing propagation models of computer worms unable to start operating instantaneously in the mobile network, and this is particularly valid for the SMS framework. The susceptible–affected–infectious–suspended–recovered model with a classical derivative (abbreviated as SAIDR) was coined by Xiao et al., (2017) in order to correctly estimate the spread of worms by means of SMS. This study is the first to implement an Atangana–Baleanu (AB) derivative in association with the fractional SAIDR model, depending upon the SAIDR model. The existence and uniqueness of the drinking model solutions together with the stability analysis are shown through the Banach fixed point theorem. The special solution of the model is investigated using the Laplace transformation and then we present a set of numeric graphics by varying the fractional-order θ with the intention of showing the effectiveness of the fractional derivative.

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