Kinds Of Reactions Research Articles

Classical and quantum control of electrons using the carrier‐envelope phase of strong laser fields

AbstractElectrons are among the lightest quantum particles in nature, yet they are of paramount importance in any kind of chemical reaction as they are the essence of molecular bonds. For several years, laser fields have been used towards the final goal of controlling chemical reaction dynamics. While early experiments focused mainly on the control of the internuclear wavefunction of rather heavy molecules, advances in short‐pulse laser technology now allow the control of lighter molecules all the way down to hydrogen and even the direct control of electrons and their quantum wavefunctions. In this context, the stabilization and control of the carrier‐envelope phase (CEP) of laser pulses has been one of the crucial technological advances that set off a revolution in ultrafast laser science. The authors review and summarize some of the past and current experimental achievements and theoretical ideas on CEP laser control of electrons. It will become clear that in some cases, depending on the control scenario, electrons can be considered to behave as classical particles and the control of their trajectories follow the laws of classical Newtonian mechanics while in other cases, the quantum nature of electrons is directly exploited to steer electron dynamics by means of quantum interference.

Highly Enantioselective Synthesis of α‐Amino Acid Derivatives by an NHC‐Catalyzed Intermolecular Stetter Reaction

PROTONtype: An NHC-catalyzed (NHC=N-heterocyclic carbene), highly asymmetric intermolecular Stetter reaction allows the atom-economic and efficient formation of valuable α-amino acid derivatives (see scheme); the key step is an intramolecular stereoselective protonation. For the first time, a β-unsubstituted Michael acceptor was employed successfully in this kind of reaction, most importantly, with a broad range of different aldehydes.

Theoretical investigations of the reactivities of saturated five-membered ring N-heterocyclic carbenes with heavier Group 14 elements

The potential energy surfaces for the chemical reactions of group 14 carbenes have been studied using density functional theory (B3LYP/LANL2DZ). Five saturated five-membered-ring N-heterocyclic carbene Dipp[upper bond 1 start]N(CH(2))(2)N(Dipp)E[upper bond 1 end]: (five-ring-E:) species, where E = C, Si, Ge, Sn and Pb, have been chosen as model reactants in this work. Also, four kinds of chemical reactions; addition of water, methane insertion, alkene cycloaddition and dimerization, have been used to study the chemical reactivities of these group 14 carbenes. The present theoretical investigations suggest that the relative carbenic reactivity decreases in the order: C > Si > Ge > Sn > Pb. That is, the heavier the group 14 atom (E), the more stable is the carbene towards chemical reactions. This may be the reason that there have been many instances reported of the synthesis and characterization of stable group 14 five-membered-ring N-heterocyclic carbene species with various alkyl protecting substituents at room temperature. Furthermore, the singlet-triplet energy splitting of the five-ring-E:, as described in the configuration mixing model attributed to the work of Pross and Shaik, can be used as a diagnostic tool to predict their reactivities. The results obtained allow a number of predictions to be made.

Incorporating Chemical Reactions in Dissipative Particle Dynamics Simulations

We introduce a reaction model combining with dissipative particle dynamics to study the chemical reactions in polymer systems at mesoscopic level. In this model, we employ an idea of reaction probability to control the whole process of chemical reactions. We apply this model on the study of surface initiated polymerization and the network structure of typical epoxy resin systems. This method can be further modified to study different kinds of chemical reactions at mesoscopic scale.

The Ring-Opening Reaction of 7,7’-Dimethyl-2, 5-bis(trimethylsilyl)-dithieno[2,3-b:3’,2’-d]silole in the Presence of NXS (X = Cl, Br, I)

In this paper, the synthetic method for making 7,7’-dimethyl-2,5-bis(trimethylsilyl)-dithieno[2,3-b:3’,2’-d] silole (1) was developed by using 2,2’-dibromo-5,5’-bis-trimethyl-silanyl[3,3’]bithiophenyl as starting material in one pot reaction. In the presence of NXS (X = Cl, Br, I), a novel ring-opening reation was occurred on the silole ring of 1 in DMF or THF. By using such kind of reaction, two types of ring opened products, (2’-halo-5,5’-bis(trimethylsilanyl)[3,3’]bithiophenyl-2-yl)-dimethylsilanols and 2,2’-dihalo-5,5’-bis(trimethylsi- lanyl)[3,3’]bithiophenyls were obtained efficiently.

Food allergy and atopic dermatitis in children: relationship and diagnosis

About one third of children with moderate to severe atopic dermatitis have a food allergy,but whether foods are responsible for triggering or worsening their atopic dermatitis still remains controversial.Foods can lead to two kinds of reactions in children with atopic dermatitis: non-eczematous reaction, which is IgE-mediated and can be diagnosed through medical history, skin prick or specific IgE testing in most cases,and eczematous reaction, which is cell-mediated and can only be confirmed by oral food challenge. In case that oral food challenge is unavailable, diagnostic elimination diet is a way to identify suspected food allergens. Key words: Dermatitis, atopic; Child; Food hypersensitivity

Pressure- and temperature-dependent combustion reactions

In combustion systems, many reactions are simple thermal unimolecular isomerizations or dissociations, or the reverse thereof. It is well understood that these reactions typically depend on temperature, pressure and the nature of the bath gas. These kinds of reactions are a subset of the more general behavior that can be described as free radical association reactions that produce highly energized intermediates, which can isomerize or dissociate via multiple chemical pathways. Each reaction rate depends on excitation energy and all of the competing reactions occur in competition with collisional activation and deactivation. These complicated multi-well, multi-channel reaction systems can only be simulated accurately by using master equation techniques. In this paper, master equation calculations are discussed for several examples of reactions important in combustion (and atmospheric chemistry). Current master equation codes are based on statistical RRKM reaction rate constants (including quantum mechanical tunneling) and simplified models for collisional energy transfer. A pragmatic semi-empirical approach is adopted in order to compensate for limited knowledge. The reaction energies needed for RRKM calculations are usually obtained from quantum chemistry calculations, which are often of limited accuracy and may be adjusted empirically. Energy transfer cannot be predicted accurately and must be parameterized by fitting experimental data. For combustion modeling, the master equation results are usually expressed as chemical reactions with rate constants fitted to empirical algebraic equations. However, the results may be expressed more accurately by interpolating from look-up tables. Several current research issues are also mentioned, including the effects of angular momentum conservation, vibrational anharmonicity, slow intramolecular vibrational energy redistribution, and assumptions surrounding the details of collisional energy transfer.

Design of low-temperature Pt-carbon combustion catalysts for VOC's treatments

Two series of Pt/C-catalysts were prepared using pure carbon aerogels as supports. The influence of porosity, surface chemistry and Pt dispersion on the activity of Pt/C combustion catalysts was analyzed. The synthesis of the supports was fitted to have a monomodal pore size distribution in the meso and macropore range respectively. Both supports were functionalized by oxidation treatment with H 2O 2 or (NH 4) 2S 2O 8. These treatments did not modify the porosity significantly, but the surface chemistry changed from basic to acid as oxygen content increased. In this way, Pt-dispersion decreased as a result of the low thermal stability of surface carboxylic acid groups. Benzene was selected as target VOCs and the catalytic combustion performance depended mainly on the porous texture and Pt-dispersion, while the variations in the surface chemistry of carbon supports due to oxidation treatments seemed to have a weak influence on this kind of reaction.

QUANTUM CHEMITRY STUDY ON STRUCTURES, ACTIVITIES AND REACTIONS OF ONIUM-BORONIUM DICATIONS

This paper provides information about theoretical investigations of structures of onium-boronium dications X+BH3+, X+BH5+; (X= NH3, PH3, H2O, H2S) and some reactions of them in thermodynamic control and kinetic control. Two kinds of reactions studied are complexation of onium-boronium dications X+BH3+ with H2 leading to X+BH5+ and deprotonation of X+BH5+ to give X+BH4. The similar studies with boronium ion analog BH4+ and BH6+ is carried out and results obtained pointed out that the eletrophility of onium-boronium dications is more stronger than that of boronium ion: onium-boronium dications X+BH3+, X+BH5+ are superelectrophiles. The structures of onium-boronium dications and boronium ions are optimized by using ab initio methods at the MP2/6-311+G** level of Gaussian 03W, revision B.04 and represented with Gaussview 3.0. Frequency calculation is performed to assure the obtained structures corresponding to minimun energies and have no any imaginary frequency. The transition structures are calculated and verified due to Intrinsic Reaction Coordinate Calculations. The properties of structures, as MP2 energy, Gibbs free energy, activation energy are also examined.

Tribocatalytic oxidation of ethylene in the rubbing of palladium against aluminum oxide

Friction experiments of palladium rubbed against aluminum oxide in ethylene/oxygen mixed atmosphere have been carried out. The complete oxidation of ethylene to carbon dioxide and water at room temperature was demonstrated. The evolution of carbon dioxide was initiated just after the start of friction; momentarily the pressure reached its equilibrium whereas water was produced gradually. On the other hand, by heating the palladium wire in the same partial pressure of both gases, carbon monoxide and hydrogen were generated at 600 K and above. By increasing oxygen partial pressure, carbon dioxide and water were produced. These results indicate that the ethylene oxidation activity on palladium catalyst is enhanced by the friction of catalyst. Two kinds of reactions, fast and slow, are attributed to near-contact and out-of-contact activities of friction surfaces. The near-contact reaction is governed by tribo-electron emission, whereas the out-of-contact activity is due to the generated nascent surface.

Recalculation and Reevaluation of the Complete Sets of Neutron Data for 63Cu and 65Cu below 20 MeV

Complete sets of neutron nuclear data, including all kinds of cross sections, angular distributions of elastic scattering, energy spectra and/or double-differential cross sections of all emitted particles, and gamma production data (production cross sections and multiplicity, angular distributions, and energy spectra) in all kinds of reactions for n + 63Cu and n + 65Cu below 20 MeV are calculated and evaluated. The calculated or evaluated cross sections are in good accordance with the experimental values for those reactions with experimental data. Particularly for the neutron leakage current in the benchmark Oktavian and the effective multiplication factors in six benchmark assemblies, our calculated values are in much better agreement with experimental data than those of several existing evaluation files.

A French Approach to Minority Islam? A Study in Normative Confusion

In this paper, the author argues (1) that the normative model of the “Republican school” the school agents adhere to is not opposed to the expression of social or religious memberships: rather, it ignores them. (2) That this model of school is currently being deeply undermined by the visibility of the “second generation” of postcolonial immigrants. (3) That this generates various kinds of reactions in the school space: first, reactions from Muslim students themselves and secondly, erratic reactions from teachers and other school personal who try to manage issues they feel important, without having been trained at all to do so.

Theoretical investigations of the reactivities of lattice-framework carbene analogues of the group 14 elements

The potential energy surfaces for the chemical reactions of lattice-framework group 14 heavy carbene species have been studied using density functional theory (B3LYP/LANL2DZ) and the Gibbs free energy method. Five lattice-framework group 14 heavy carbene species, L-F-X: , where X = C, Si, Ge, Sn, and Pb, have been chosen as model reactants in this study. Also, four kinds of chemical reactions, O-H bond insertion, C-H bond insertion, alkene cycloaddition, and dimerization, have been used to study the chemical reactivities of these species. Basically, our present theoretical work predicts that the larger the ∠C(1)XC(2) bond angle of the lattice-framework group 14 heavy carbene species, the smaller the singlet-triplet splitting, the lower the activation barrier, and, therefore, the greater the rates of its chemical reactions with various other species. Moreover, the theoretical investigations suggest that the relative lattice-framework reactivity decreases in the order: C > Si > Ge > Sn ≫ Pb. That is, the heavier the group 14 atom (X), the more stable is its lattice-framework carbene towards chemical reactions. As a result, we predict that the L-F-Pb should be stable, and can be synthesized and isolated at room temperature. Furthermore, the singlet-triplet energy splitting of the lattice-framework group 14 carbene species, as described in the configuration mixing model attributed to the work of Pross and Shaik, can be used as a diagnostic tool to predict their reactivities. The results obtained allow a number of predictions to be made.

Theoretical study on the mechanism of extraction reaction between silylene carbene and its derivatives and thiirane

The mechanism of the sulfur extraction reaction between singlet silylene carbine and its derivatives and thiirane has been investigated with density functional theory (DFT), including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated by B3LYP/6-311G(d, p) method. From the potential energy profile, it can be predicted that the reaction pathway of this kind consists in two steps: (1) the two reactants firstly form an intermediate through a barrier-free exothermic reaction; (2) the intermediate then isomerizes to a product via a transition state. This kind of reactions has similar mechanism: when the silylene carbene and its derivatives [X2Si=C: (X = H, F, Cl, CH3)] and thiirane approach each other, the shift of 3p lone electron pair of S in thiirane to the 2p unoccupied orbital of C in X2Si=C: gives a p → p donor-acceptor bond, thereby leading to the formation of intermediate (INT). As the p → p donor-acceptor bond continues to strengthen (that is the C-S bond continues to shorten), the intermediate (INT) generates product (P + C2H4) via transition state (TS). It is the substituent electronegativity that mainly affect the extraction reactions. When the substituent electronegativity is greater, the energy barrier is lower, and the reaction rate is greater.

Oxidative addition reaction of diarylplatinum(ii) complexes with MeI in ionic liquid media: a kinetic study

A kinetic study of the oxidative addition reaction of diarylplatinum(II) complexes [Pt(p-MeC(6)H(4))(2)(NN)] (1a: NN = 1,10-phenanthroline (phen) and 1b: NN = 4,4'-di-tert-butyl-2,2'-bipyridine ((t)Bu(2)bpy)) with MeI in ionic liquids 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][bta]) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]) is described. The reactions were investigated as a function of MeI concentration and temperature under pseudo-first-order conditions using UV-vis spectroscopy techniques. In general, the oxidative addition reactions in ionic liquids followed an S(N)2 mechanism, similar to that reported for the related reactions in conventional solvents, e.g. benzene or acetone. The reaction rates in different solvents followed the order acetone > ionic liquids > benzene. The trend in the values of k(2) clearly indicated that ionic liquids behave like conventional solvents and that no particular 'ionic liquid effect' was detected in this kind of reaction. The effect of solvent on the reactions was examined using a linear solvation energy relationship (LSER) based on the Kamlet-Taft solvent scale. The activation parameters, DeltaH(++) and DeltaS(++), were obtained for the reactions in each solvent and the investigation of enthalpy-entropy compensation confirmed that the mechanism operated in all solvents is similar.

Analysis of cross sections and Vector Analysing Powers of (d,p) reactions within the CDCC+DWBA approach.

Transfer reactions like A X(d,p) A+1 X are a powerful tool to investigate nuclear structure properties (see e.g. [1–3]) and the emergence of radioactive beams with high intensity will allow the use of this kind of reactions to study the properties of exotic nuclei. Nevertheless the analysis of reactions involving deuteron remains a difficult task because of its weakly bound and composite features. To overcome these issues, R.C. Johnson et al [4] and G.H. Ratwitcher [5] proposed in the seventies the Continuum Discretized Coupled Channels (CDCC) formalism which explicitly takes into account the composite property of the deuteron and includes the effects on cross sections of the coupling between the breakup and the deuteron ground state channels. Since then the CDCC approach has been widely studied [6–8] and it has been quite successfully applied to analyse elastic [7–9] , inelastic [8,10] and transfer cross sections [11–13]. In this contribution, I will propose to re-analyse transfer reactions by the means of CDCC+adiabatic approach for a set of targets with N = 20 or N ≈ 28. I will show that with this approach, using both the differential cross sections and the vector analysing powers one can determine the orbital angular momentum and the spin of the captured nucleon without any adjustment.

Cinema in the City: Tangible Forms, Transformations and the Punctuation of Everyday Life

In India, cinema does not exist merely on the screen; it permeates everyday life. Just as formula films are punctuated with song and dance, fantastic interludes which at times break from the narrative to express the dreams, wishes and desires—in short the “inner-world” [Kakar 1980] of characters—everyday life in India may be seen to be punctuated with the fantasy world of cinema. If popular Indian cinema is indeed a “collective fantasy” or “group daydream…containing the unconscious material and hidden wishes of a vast number of people” [Kakar 1980: 12], what is to be made of the images from this fantasy world which populate the urban landscape? What does cinema's spectacular presence in the Indian city mean for cinema? For urban life? Scholars of film in India have commented on cinema's ubiquity and presence outside the theater, noting the pervasiveness of film music, film fashions and film magazines and of the posters and other visible icons of films, such as “decals, painted signboards, giant movie hoardings [billboards] and towering cut-outs” that clutter urban space [Dickey 2005: 69; see also Dickey 1993]. The colorful posters, “cut-outs” and hoardings which announce a film and which make cinema's presence in the city tangible have been studied as art [Dwyer and Patel 2002] and as advertisements, “circulations and reproductions” of cinema which form a mediascape and which provide urban spectacle [Jacob 1998]. Taking a phenomenological perspective, this essay provides a descriptive analysis of the incorporation of cinema into everyday settings, addressing the significance of this presence in the context of the flow of urban life and for the “extra-cinematic experience” [Spitulnik 2002]. While study of posters and billboards as advertisement acknowledges their intentional role, this essay comments on the unintentional aspects of cinema's visual and tangible presence outside the theater, and the kinds of reaction and interaction it attracts.

Guidance for nuclear medicine staff on radiopharmaceuticals drug interaction

Numerous drug interactions related to radiopharmaceuticals take place every day in hospitals many of which are not reported or detected. Information concerning this kind of reaction is not abundant, and nuclear medicine staff are usually overwhelmed by this information. To better understand this type of reaction, and to help nuclear medicine staff deal with it, a review of the literature was conducted. The results show that almost all of radiopharmaceuticals marketed around the world present drug interactions with a large variety of compounds. This suggests that a logical framework to make decisions based on reviews incorporating adverse reactions must be created. The review also showed that researchers undertaking a review of literature, or even a systematic review that incorporates drug interactions, must understand the rationale for the suggested methods and be able to implement them in their review. Additionally, a global effort should be made to report as many cases of drug interaction with radiopharmaceuticals as possible. With this, a complete picture of drug interactions with radiopharmaceuticals can be drawn.

Visualization of the infectious pancreatic necrosis virus replication cycle by labeling viral intermediates with a TUNEL assay

Investigating the capacity of the infectious pancreatic necrosis virus (IPNV) to promote apoptosis with a TUNEL kit, designed to visualize fragmented DNA, a striking labeling pattern was found. In addition to the fluorescence observed in the nucleus of cells with fragmented DNA, the infected cells showed an intense particulate fluorescence in their cytoplasm. The cytoplasmic labeling seems to be concomitant with the timing of virus life cycle because labeled viral proteins coexist with TUNEL cytoplasmic fluorescence at different times during infection. In principle the terminal deoxynucleotidyl transferase (TdT) used in TUNEL assays should not be able to label substrates other than DNA, however, our results are consistent with the idea that viral structures are being labeled. We propose that the TdT enzyme label the 3′-hydroxyl ends of viral RNAs during its polymerization. This kind of reaction could be possible because it has been reported that TdT is an enzyme that can use rNTPs as substrates and the 3′-hydroxyl priming end can be provided by a ribonucleotide as well. Thus, allowing the visualization of virus RNA-containing intermediates during IPNV replication.

Role of the food additives in the development of food allergy and pseudoallergic reactions tofood (Part two)

This is the 2 part of review, devoted to the role of food additives in food allergy and other kind of reactions to food.