oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Eco-friendly and fast bromination of industrially-important aromatic compounds in water using recyclable AlBr3-Br2 system  [PDF]
Sushil Kumar Sharma
Chemistry Internatioanl , 2015,
Abstract: A fast, efficient, simple, eco-friendly, regioselective, controllable and economical method for the bromination of aromatic compounds using AlBr3-Br2 system was invetigated. The direct bromination of anilines and phenols with molecular bromine in solution frequently results in polybromination, and when brominated in the existence of oxidants, they also get oxidized rather than experiencing substitutions and in some cases, require fortification of the amino (-NH2) group.
A direct and simplistic bromination of commercially important organic compounds in aqueous media by eco-friendly AlBr3-Br2 reagent system  [PDF]
Sushil Kumar Sharma, D. D Agarwal
Chemistry Internatioanl , 2015,
Abstract: A facile, simplistic, highly efficient, environmentally safe, regioselective, controllable and economical method for the bromination of organic compounds using aqueous AlBr3-Br2 reagent system was investigated.
Competition of Aromatic Bromination and Nitration in Concentrated Sulfuric Acid  [PDF]
Alexander M. Andrievsky, Mikhail V. Gorelik
Open Journal of Synthesis Theory and Applications (OJSTA) , 2013, DOI: 10.4236/ojsta.2013.21005
Abstract:

Composition of bromine and nitric acid in concentrated sulfuric acid is effective for bromination of strongly deactivated aromatic compounds and for nitration and bromination of moderately deactivated compounds in one stage. The question why brominating agent is more reactive than nitrating agent in relation to strongly deactivated aromatic compounds and is less reactive in relation to moderate deactivated ones is discussed.

Pd-W and Pd-Mo catalysts for NO decomposition and NO/CO reduction reactions
Dallago, Rogério M.;Baibich, Ione M.;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009000500011
Abstract: pd/γ-al2o3 catalysts with two different metal particle sizes were prepared from [pd(acac)2]. subsequently, the photochemical reaction of [m(co)6] (m = mo or w) in the presence of pd/γ-al2o3 was used to prepare bimetallic pd-m/γ-al2o3 catalysts. drifts ftir spectra of the catalyst surfaces prior to thermal decomposition showed unstable subcarbonyl [m(co)n] species. chemisorption and co/no adsorption results indicated a blockage of the pd active sites when the second metal was incorporated. the catalytic activity and the selectivity for the no/co reaction were higher for pd with higher particle size, but they were both inhibited when mo or w were incorporated. on the other hand, when the catalysts were tested for no decomposition, the presence of mo or w led to an increase in the catalytic activity, with optimal results observed in the presence of mo.
Synthesis of cetylpyridiniumtribromide (CetPyTB) reagent by noble synthetic route and bromination of organic compounds using CetPyTB  [PDF]
Sushil Kumar Sharma, D. D Agarwal
Chemistry Internatioanl , 2015,
Abstract: Cetylpyridiniumtribromide (CetPyTB) has been produced by a noble synthetic path protocol and its reactivity studied. Result indicates that the reagent shows good capability as a brominating agent for carbon/electron-rich heterocyclic aromatic compounds in addition to an efficient catalyst for acetylation of the alcohols, therefore proving it to be a note-worthy addition to the current organic tribromide reagents.
On the bromination of the dihydroazulene/vinylheptafulvene photo-/thermoswitch
Virginia Mazzanti,Martina Cacciarini,S?ren L. Broman,Christian R. Parker
Beilstein Journal of Organic Chemistry , 2012, DOI: 10.3762/bjoc.8.108
Abstract: Background: The dihydroazulene (DHA)/vinylheptafulvene (VHF) system (with two cyano groups at C1) functions as a photo-/thermoswitch. Direct ionic bromination of DHA has previously furnished a regioselective route to a 7,8-dibromide, which by elimination was converted to a 7-bromo-substituted DHA. This compound has served as a central building block for functionalization of the DHA by palladium-catalyzed cross-coupling reactions. The current work explores another bromination protocol for achieving the isomeric 3-bromo-DHA and also explores the outcome of additional bromination of this compound as well as of the known 7-bromo-DHA.Results: Radical bromination on two different VHFs by using N-bromosuccinimide/benzoyl peroxide and light, followed by a ring-closure reaction generated the corresponding 3-bromo-DHAs, as confirmed in one case by X-ray crystallography. According to a 1H NMR spectroscopic study, the ring closure of the brominated VHF seemed to occur readily under the reaction conditions. A subsequent bromination–elimination protocol provided a 3,7-dibromo-DHA. In contrast, treating the known 7-bromo-DHA with bromine generated a very labile species that was converted to a new 3,7-dibromoazulene, i.e., the fully unsaturated species. Azulenes were also found to form from brominated compounds when left standing for a long time in the solid state. Kinetics measurements reveal that the 3-bromo substituent enhances the rate of the thermal conversion of the VHF to DHA, which is opposite to the effect exerted by a bromo substituent in the seven-membered ring.Conclusion: Two general procedures for functionalizing the DHA core with a bromo substituent (at positions 3 and 7, respectively) are now available with the DHA as starting material.
Bromination of Graphene and Graphite  [PDF]
A. Yaya,C. P. Ewels,I. Suarez-Martinez,Ph. Wagner,S. Lefrant,A. Okotrub,L. Bulusheva,P. R. Briddon
Physics , 2011, DOI: 10.1103/PhysRevB.83.045411
Abstract: We present a density functional theory study of low density bromination of graphene and graphite, finding significantly different behaviour in these two materials. On graphene we find a new Br2 form where the molecule sits perpendicular to the graphene sheet with an extremely strong molecular dipole. The resultant Br+-Br- has an empty pz-orbital located in the graphene electronic pi-cloud. Bromination opens a small (86meV) band gap and strongly dopes the graphene. In contrast, in graphite we find Br2 is most stable parallel to the carbon layers with a slightly weaker associated charge transfer and no molecular dipole. We identify a minimum stable Br2 concentration in graphite, finding low density bromination to be endothermic. Graphene may be a useful substrate for stabilising normally unstable transient molecular states.
Substrate Directed Regioselective Monobromination of Aralkyl Ketones Using N-Bromosuccinimide Catalysed by Active Aluminium Oxide: α-Bromination versus Ring Bromination  [PDF]
Reddy Bodireddy Mohan,G. Trivikram Reddy,N. C. Gangi Reddy
ISRN Organic Chemistry , 2014, DOI: 10.1155/2014/751298
Abstract: Bromination of aralkyl ketones using N-bromosuccinimide in presence of active Al2O3 provided either α-monobrominated products in methanol at reflux or mononuclear brominated products in acetonitrile at reflux temperature with excellent isolated yields depending on the nature of substrate employed. The α-bromination was an exclusive process when aralkyl ketones containing moderate activating/deactivating groups were subjected to bromination under acidic Al2O3 conditions in methanol at reflux while nuclear functionalization was predominant when aralkyl ketones containing high activating groups were utilized for bromination in presence of neutral Al2O3 conditions in acetonitrile at reflux temperature. In addition, easy isolation of products, use of inexpensive catalyst, short reaction time (10–20?min), and safe operational practice are the major benefits in the present protocol. 1. Introduction Nowadays, researchers are focusing on the development of more acceptable bromination protocols to accomplish increasing demands for “organohalogen” chemistry and to achieve higher efficiency and selectivity of the bromination reactions which include α-bromination and nuclear bromination. The resulting α-brominated or nuclear brominated products acquired wide range of utility in organic synthesis [1–3]. Nuclear brominated ketones are found to be useful intermediates in C–C coupling reactions, as precursors to organometallic species and in nucleophilic substitutions. It is well known that use of molecular bromine [4] as a basic electrophilic brominating reagent has several drawbacks. Alternative reagents were reported in the literature, for example, cupric bromide [5], dioxane dibromide [6], tetrabutyl ammonium tribromide [7], H2O2-HBr [8], bromodimethyl sulfoniumbromide [9], ethylene bis(N-methyl imidazolium) ditribromide [10], trihaloisocyanuric acids [11], pyridinium bromochromate [12], and NH4Br-oxone [13]. In addition, a popular and superior brominating agent such as N-bromosuccinimide [14] was utilized for α-bromination of carbonyl compounds using a radical initiator such as azobisisobutyronitrile (AIBN) or dibenzoyl peroxide (BPO) [15] and, later, it has been demonstrated that the reactivity of NBS could be modulated with ionic liquids [16], photochemical energy [17]; sonochemical energy [18], solvent free reaction conditions (SFRC) [19] and various catalysts such as Mg(ClO4)2 [20], NH4OAc [21], amberlyst-15 [22], silica supported NaHCO3 [23], sulfonic acid functionalized silica [24], FeCl3 [25], montmorillonite-K10 [26], and Silica gel [27]. NBS also is
Spin-polarization-induced structural selectivity in Pd$_3X$ and Pt$_3X$ ($X=3d$) compounds  [PDF]
Z. W. Lu,B. M. Klein,A. Zunger
Physics , 1995, DOI: 10.1103/PhysRevLett.75.1320
Abstract: Spin-polarization is known to lead to important {\it magnetic} and {\it optical} effects in open-shell atoms and elemental solids, but has rarely been implicated in controlling {\it structural} selectivity in compounds and alloys. Here we show that spin-polarized electronic structure calculations are crucial for predicting the correct $T=0$ crystal structures for Pd$_3X$ and Pt$_3X$ compounds. Spin-polarization leads to (i) stabilization of the $L1_2$ structure over the $DO_{22}$ structure in Pt$_3$Cr, Pd$_3$Cr, and Pd$_3$Mn, (ii) to the stabilization of the $DO_{22}$ structure over the $L1_2$ structure in Pd$_3$Co and to (iii) ordering (rather than phase-separation) in Pt$_3$Co and Pd$_3$Cr. The results are analyzed in terms of first-principles local spin density calculations.
Thermal decomposition of solid state compounds of lanthanide and yttrium benzoates in CO2 atmosphere
Locatelli, J. R.;Siqueira, A. B.;Carvalho, C. T.;Ionashiro, M.;
Eclética Química , 2008, DOI: 10.1590/S0100-46702008000100006
Abstract: solid-state ln-bz compounds, where ln stands for trivalent lanthanides and bz is benzoate have been synthesized. simultaneous thermogravimetric and differential thermal analysis in a co2 atmosphere were used to study the thermal decomposition of these compounds.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.