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Nucleophilic Substitution Reaction (nucleophilic + substitution_reaction)
Kinds of Nucleophilic Substitution Reaction Selected AbstractsChemInform Abstract: Nucleophilic Substitution Reaction at an sp2 Carbon of Vinyl Halides with an Intramolecular Thiol Moiety: Synthesis of Thio-heterocycles.CHEMINFORM, Issue 51 2009Mao-Yi Lei Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Novel Mannich-Type Nucleophilic Substitution Reaction with Tertiary Aromatic Amines.CHEMINFORM, Issue 30 2002Hiroyasu Takahashi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Highly Regio- and Stereo-Controlled Pd(0)-Catalyzed Nucleophilic Substitution Reaction for the Synthesis of Optically Active ,-Fluoroalkylated Allylic Alcohols.CHEMINFORM, Issue 4 2001Tsutomu Konno Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Nucleophilic Substitution Reaction of p -Dinitrobenzene by a Carbanion: Evidence for Electron Transfer MechanismCHINESE JOURNAL OF CHEMISTRY, Issue 11 2002You-Cheng Liu Abstract On the basis of investigation of cyclic voltammetry, EPR spectroscopy and competition experiments, the nucleophilic substitution reaction of p - dinitrobenzene with the sodium salt of ethyl ,-cyanoacetate carbanion in dimethyl sulfoxide giving ethyl ,-cyano-,- (p-nitrophenyl) acetate is shown to take place via the intermediacy of p -dinitrobenzene radical anion. The reaction rate goes faster than that between p -nitrohalobenzenes and the same sodium salt of ethyl ,-cyanoacetate carbanion. There is an evidence for a single electron transfer mechanism. [source] Nucleophilic Substitution Reactions of meso -5,10,15-Tris(pentafluorophenyl)corrole; Synthesis of ABC-Type Corroles and Corrole-Based OrganogelsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2010Takaaki Hori Abstract Nucleophilic substitution reactions of 5,10,15-tris(pentafluorophenyl)corrole (1) with amines were examined as a post-modification route to functional corroles. Reaction of 1 with an excess of amine nucleophiles led to exclusive formation of 5,10,15-tris(4-amino-2,3,5,6-tetrafluorophenyl)-substituted corroles. In this nucleophilic reaction, 5- and 15-pentafluorophenyl substituents were found to be more reactive than the substituent at the 10-position. This substitution reaction was applied for the preparation of ABC-type corroles and corrole-based organogels. The latter exhibited a blue-shifted Soret band and small fluorescence quantum yields in nonpolar hydrocarbon solvents due to the formation of H-type aggregates. [source] ChemInform Abstract: tert-Alcohol-Functionalized Imidazolium Ionic Liquid: Catalyst for Mild Nucleophilic Substitution Reactions at Room Temperature.CHEMINFORM, Issue 10 2010Sandip S. Shinde Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: From DMF to Isatin: A Novel and General One-Pot Synthesis of Isatin and Its N-Unsubstituted Derivatives via Nucleophilic Substitution Reactions on 1,2-Bis(dimethylamino)-1,2-dichloroethene.CHEMINFORM, Issue 41 2009Stefan M. Huber Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Regioselective Alkyl and Alkynyl Substitution Reactions of Epoxy Alcohols by the Use of Organoaluminum Ate Complexes: Regiochemical Reversal of Nucleophilic Substitution Reactions.CHEMINFORM, Issue 39 2001Minoru Sasaki Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] The ,-effect in micelles: Nucleophilic substitution reaction of p -nitrophenyl acetate with N -phenylbenzohydroxamate ion,INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2006Kallol K. Ghosh Pseudo-first-order rate constants have been determined for the nucleophilic substitution reactions of p -nitrophenyl acetate with p -chlorophenoxide (4-ClC6H4O,) and N -phenylbenzohydroxamate (C6H5CON(C6H5)O,) ions in phosphate buffer (pH 7.7) at 27°C. The effect of cationic, (CTAB, TTAB, DTAB), anionic (SDS), and nonionic (Brij-35) surfactants has been studied. The kobs value increases upon addition of CTAB and TTAB. The effect of DTAB and other surfactants on the reaction is not very significant. The micellar catalysis and ,-effect shown by hydroxamate ion have been explained. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 26,31, 2006 [source] Nucleophilic Substitution Reactions of meso -5,10,15-Tris(pentafluorophenyl)corrole; Synthesis of ABC-Type Corroles and Corrole-Based OrganogelsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2010Takaaki Hori Abstract Nucleophilic substitution reactions of 5,10,15-tris(pentafluorophenyl)corrole (1) with amines were examined as a post-modification route to functional corroles. Reaction of 1 with an excess of amine nucleophiles led to exclusive formation of 5,10,15-tris(4-amino-2,3,5,6-tetrafluorophenyl)-substituted corroles. In this nucleophilic reaction, 5- and 15-pentafluorophenyl substituents were found to be more reactive than the substituent at the 10-position. This substitution reaction was applied for the preparation of ABC-type corroles and corrole-based organogels. The latter exhibited a blue-shifted Soret band and small fluorescence quantum yields in nonpolar hydrocarbon solvents due to the formation of H-type aggregates. [source] Solvent and substituent effects on the reaction of 2- and 4-chloro-3,5-dinitrobenzotrifluorides with substituted anilinesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2009Basim H. M. Asghar The solvent effect on a nucleophilic substitution reaction of 2- and 4-chloro-3,5-dinitrobenzotrifluoride with substituted anilines was studied in methanol, acetonitrile, and toluene at 25°C. This reaction is of second order, except 2-chloro-3,5-dinitrobenzotrifluoride in toluene shows third order. The kA values are found to be dependent on the substituent in aniline and give good Hammett correlations. The obtained , values are ,4.07 and ,4.62, for the reaction of anilines with 2-chloro-3,5-dinitrobenzotrifluoride in methanol and acetonitrile, respectively. The , values for the reaction of the anilines with 4-chloro-3,5-dinitrobenzotrifluoride are ,3.38, ,4.11, and ,4.34 in methanol, acetonitrile, and toluene, respectively. The reaction of the former compound with anilines in toluene shows a second order in aniline. The dependence of the reaction on the external base such as DABCO suggests a proton transfer controlling step. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 777,786, 2009 [source] Solvent effects on kinetics of an aromatic nucleophilic substitution reaction in mixtures of an ionic liquid with molecular solvents and prediction using artificial neural networksINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2009Aziz Habibi-Yangjeh Kinetics of the reaction between 1-chloro-2,4-dinitrobenzene and aniline was studied in mixtures of 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) with methanol, chloroform, and dimethylsulfoxide at 25°C. Single-parameter correlations of log kA versus normalized polarity parameter (ENT), hydrogen-bond acceptor basicity (,), hydrogen-bond donor acidity (,), and dipolarity/polarizability (,*) of media do not give acceptable results. Multiparameter linear regression (MLR) of log kA versus the solvatochromic parameters demonstrates that the reaction rate constant increases with ENT, ,*, and , and decreases with , parameter. To predict accurately solvent effects on the rate constant, optimized artificial neural network with three inputs (including ,, ,*, and , parameters) was applied for prediction of the log kA values in the prediction set. It was found that properly selected and trained neural network could fairly represent the dependence of the reaction rate constant on solvatochromic parameters. Mean percent deviation of 5.023 for the prediction set by the MLR model should be compared with the value of 0.343 by the artificial neural network model. These improvements are due to the fact that the reaction rate constant shows nonlinear correlations with the solvatochromic parameters. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 153,159, 2009 [source] A linear three-center four electron bonding identity nucleophilic substitution at carbon, boron, and phosphorus.INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 7 2010A theoretical study in combination with van't Hoff modeling Abstract We studied various identity nucleophilic substitution reactions based on an SN2 reaction profile. With calculations and experimental geometries concerning the nature of the various complexes indicated as stable, intermediate, and transition state we were able to show the additional value of van't Hoff 's tetrahedron by changing its geometry via a trigonal pyramid into a trigonal bipyramid. The ratio of the apical and the corresponding tetrahedral bond distance is then 1.333. This value has been used in general as a calibration point for the understanding of the (in)stabilities of the complex formation on the SN2 reaction coordinate. The relevance of this approach has been also proved for enzymatic reactions focused on carbon and phosphorus substrates. Furthermore, it could be established that identity proton-in-line displacements are fully comparable with the relocation of carbon in a nucleophilic substitution reaction as Cl, + CH3Cl. The significance of this information will afford new insight in the dynamics of a linear three-center four-electron complex. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Mechanism of the Nucleophilic Substitution of Acyl Electrophiles using Lithium OrganocupratesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2008Naohiko Yoshikai Abstract The mechanism of nucleophilic substitution reaction at an sp2 carbon center of a thioester or an acid chloride with a lithium organocuprate reagent has been investigated. Density functional calculations indicated that the thioester undergoes oxidative addition of the CS bond to the copper(I) atom through a three-centered transition state to afford an organocopper(III) intermediate, which gives the product through reductive elimination of the alkyl and the acyl groups. On the other hand, the acid chloride loses a chloride anion very easily when it interacts with the cuprate, because the chloride anion is captured by a lithium(I) cation rather than a copper(I) atom. 13C kinetic isotope effect (KIE) experiments showed excellent agreement with computational predictions for the thioester reaction, but suggested that the nucleophilic displacement transition state of the acid chloride occurs much more advanced than the calculations predict. [source] Substitution-reduction: an alternative process for the [18F]N -(2-fluoroethylation) of anilinesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2004Emmanuelle Briard Abstract Substitution of a halo atom (chloro or bromo) in easily prepared N -haloacetyl-anilines with no-carrier added (NCA) cyclotron-produced [18F]fluoride ion (18F, t1/2= 109.8 min; ,+=96.9%), followed by reduction with borane,tetrahydrofuran (BH3,THF), provides an alternative route to NCA [18F]N -(2-fluoroethyl)-anilines. This two-step and one-pot process is rapid (,50 min) and moderately high yielding (,40% decay-corrected radiochemical yield (RCY) overall). In the nucleophilic substitution reaction, 18-crown-6 is preferred to Kryptofix® 222 as complexing agent for the solubilization of the counter-ion (K+), derived from an added metal salt, in acetonitrile. Weakly basic potassium bicarbonate is preferred as the added metal salt. Inclusion of a small amount of water, equating to 4,5 molar equivalents relative to 18-crown-6, base or precursor (held in equimolar ratio), is beneficial in preventing the adsorption of radioactivity onto the wall of the glass reaction vessel and for achieving high RCY in the nucleophilic substitution reaction. BH3,THF is effective for the rapid reduction of the generated [18F]N -fluoroacetyl-aniline to the [18F]N -(2-fluoroethyl)-aniline. Copyright © 2004 John Wiley & Sons, Ltd. [source] Synthesis of [18F]3-[1-(3-fluoropropyl)-(S)-pyrrolidin-2-ylmethoxy]pyridine ([18F]NicFP): a potential ,4,2 nicotinic acetylcholine receptor radioligand for PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2003Filip Dumont Abstract Nicotinic acetylcholine receptors are widely distributed throughout the human brain and are believed to play a role in several neurological and psychiatric disorders. In order to identify an effective PET radioligand for in vivo assessment of the ,4,2 subtype of nicotinic receptor, we synthesized [18F]3-[1-(3-fluoropropyl)-(S)-pyrrolidin-2-ylmethoxy]pyridine (NicFP). The in vitro KD of NicFP was determined to be 1.1 nM, and the log P value obtained by HPLC analysis of the unlabelled standard was found to be 2.2. The radiosynthesis of [18F]NicFP was carried out by a nucleophilic substitution reaction of anhydrous [18F]fluoride and the corresponding mesylate precursor. After purification by HPLC, the radiochemical yield was determined to be 11.3±2.1% and the specific activity was 0.47±0.18 Ci/,mol (EOS, n = 3). The time of synthesis and purification was 99±2 min. The final product was prepared as a sterile saline solution suitable for in vivo use. Copyright © 2003 John Wiley & Sons, Ltd. [source] Resistive switching polymer materials based on poly(aryl ether)s containing triphenylamine and 1,2,4-triazole moietiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2008Kun-Li Wang Abstract A series of poly(aryl ether)s were successfully prepared via aromatic nucleophilic substitution reaction from various bisphenols and a novel bipolar aryl difluoride monomer containing electron-donor triphenylamine and electron-acceptor 1,2,4-triazole moieties. The poly(aryl ether)s exhibited excellent solubility in organic solvents such as dimethylformamide, chloroform, and tetrahydrofuran at room temperature. The poly(aryl ether)s showed high thermal stability with Td10 higher than 500 °C and glass transition temperatures (Tg) higher than 187 °C. The thin films of the poly(aryl ether)s indicated bistable resistive switching behavior with ON/OFF current ratios as high as 103. The switching on and switching off bias voltages of the poly(aryl ether)s were affected by the bisphenol moiety. The good resistive switching behavior of the poly(aryl ether)s made them promising candidates for future nonvolatile memory applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6861,6871, 2008 [source] Synthesis, properties, and sulfonation of novel dendritic multiblock copoly(ether-sulfone)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2008Sumiko Matsumura Abstract Multiblock copoly(ether-sulfone)s (PESs) bearing anchor units for the construction of dendritic blocks were synthesized by two-step reactions: (1) synthesis of PES block with both phenoxide end-groups; (2) chain extension and end-capping of the block by use of excess novel hexafunctional agent, hexakis(4-(4-fluorophenylsulfonyl)phenyl)benzene. The optimum average block length (n) and amount (x) of the hexafunctional agent used for the synthesis of high-molecular-weight PES without crosslinking were n = 26 and x = 2.6 equiv, respectively. The dendritic blocks in the PES were constructed by the aromatic nucleophilic substitution reaction of the activated aromatic fluoride groups on the anchor units using 4-tritylbenzenethiol. The clean substitution of the fluoride groups in the PES was confirmed by 1H NMR and 19F NMR. Three sulfonic acid groups were introduced on the pendant phenyl rings of the trityl groups in the PES by the reaction with chlorosulfonic acid. This is the first example of a dendritic PES bearing clusters of sulfonic acid groups only on the dendritic blocks. Cast films of presulfonated dendritic PES were strong and flexible, however, the membranes of sulfonated dendritic PES were brittle so that the conductivity measurements were not performed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6365,6375, 2008 [source] Synthesis and properties of fluorinated polyimides based on 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2,5-di- tert -butylbenzene and various aromatic dianhydridesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2004Chin-Ping Yang Abstract A novel fluorinated diamine monomer, 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2,5-di- tert -butylbenzene (2), was prepared through the nucleophilic substitution reaction of 2-chloro-5-nitrobenzotrifluoride and 2,5-di- tert -butylhydroquinone in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C. Fluorinated polyimides (5a,5f) were synthesized from diamine 2 and various aromatic dianhydrides (3a,3f) via thermal or chemical imidization. These polymers had inherent viscosities of 0.77,1.01 dL/g. The 5 series polyimides were soluble in N -methyl-2-pyrrolidone, N,N -dimethylacetamide, and N,N -dimethylformamide and were even soluble in dioxane, tetrahydrofuran, and dichloromethane. 5(C) showed cutoff wavelengths between 363 and 404 nm and yellowness index (b*) values of 6.5,40.2. The polyimide films had tensile strengths of 93,114 MPa, elongations to break of 9,12%, and initial moduli of 1.7,2.1 GPa. The glass-transition temperatures were 255,288 °C. The temperatures of 10% weight loss were all above 460 °C in air or nitrogen atmospheres. In comparison with a nonfluorinated polyimide series based on 1,4-bis(4-aminophenoxy)-2,5-di- tert -butylbenzene, the 5 series showed better solubility and lower color intensity, dielectric constants, and moisture absorption. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2272,2284, 2004 [source] Polyimides based on 2,5-bis(4-aminophenoxy)biphenylJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2002Chin-Ping Yang Abstract A diamine monomer II, 2,5-bis(4-aminophenoxy)biphenyl, was prepared through a nucleophilic substitution reaction of phenylhydroquinone and p -chloronitrobenzene in the presence of potassium carbonate in N,N -dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. A series of all-aromatic, organosoluble polyimides bearing pendent phenyl groups were synthesized from the diamine with six kinds of commercial dianhydrides via a conventional two-stage process. For improving solubility of polypyromellitimide, copolypyromellitimides with arbitrary solubilities were prepared from II and a pair of dianhydrides, which were mixed at certain molar ratios. These polymers showed good solubilities in N -methyl-2-pyrrolidone and m -cresol. The softening temperatures of these polyimides were recorded between 206 and 269 °C. Polymers had glass-transition temperatures at 230,286 °C and 10% weight-loss temperatures above 521 °C in air or nitrogen atmospheres. Their films had high tensile moduli and strengths. Excellent properties of these polyimides are attributed to the incorporation of the pendent phenyl group in diamine II. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 429,438, 2002; DOI 10.1002/pola.10116 [source] Synthesis of Well-Defined Telechelic Macrophotoinitiator of Polystyrene by Combination of ATRP and Click ChemistryMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19 2009Mustafa Degirmenci Abstract A new well-defined telechelic macrophotoinitiator of polystyrene was synthesized by combination of ATRP and click chemistry. The ATRP of styrene by means of 2-oxo-1,2-diphenylethyl-2-bromopropanoate (PI-Br) initiator with CuBr/2,2,-bipyridine yields polystyrene with photoactive benzoin (PI) and bromine (Br) group (PI-PSt-Br). Subsequently, PI-PSt-Br was converted to PI-PSt-N3 by simple nucleophilic substitution reaction. Alkyne functionalized benzoin (PI-alkyne) was synthesized by using benzoin photoinitiator and propargyl bromide. Then the coupling reaction between PI-PSt-N3 and PI-alkyne was performed by Cu(I) catalysis. The spectroscopic studies revealed that low-polydispersity polystyrene with desired photoinitiator functionality at both end of the chain, PI-PSt-PI, was obtained. [source] Synthesis of poly(cyclohexene oxide)- block -polystyrene by combination of radical-promoted cationic polymerization, atom transfer radical polymerization and click chemistryPOLYMER INTERNATIONAL, Issue 6 2010Mustafa Degirmenci Abstract The combination of radical-promoted cationic polymerization, atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of poly(cyclohexene oxide)- block -polystyrene (PCHO- b -PSt). Alkyne end-functionalized poly(cyclohexene oxide) (PCHO-alkyne) was prepared by radical-promoted cationic polymerization of cyclohexene oxide monomer in the presence of 1,2-diphenyl-2-(2-propynyloxy)-1-ethanone (B-alkyne) and an onium salt, namely 1-ethoxy-2-methylpyridinium hexafluorophosphate, as the initiating system. The B-alkyne compound was synthesized using benzoin photoinitiator and propargyl bromide. Well-defined bromine-terminated polystyrene (PSt-Br) was prepared by ATRP using 2-oxo-1,2-diphenylethyl-2-bromopropanoate as initiator. Subsequently, the bromine chain end of PSt-Br was converted to an azide group to obtain PSt-N3 by a simple nucleophilic substitution reaction. Then the coupling reaction between the azide end group in PSt-N3 and PCHO-alkyne was performed with Cu(I) catalysis in order to obtain the PCHO- b -PSt block copolymer. The structures of all polymers were determined. Copyright © 2010 Society of Chemical Industry [source] Preparation of new membranes based on sulfonated aromatic copolyimidesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2008Ahmad Rabiee Abstract New sulfonated aromatic copolyimides with controlled degree of sulfonation were prepared via polycondensation reactions of a sulfonated diamine and two unsulfonated diamines with 1,4,5,8-naphthalene tetracarboxylic dianhydride (NDA). The sulfonated diamine 3,3,-disulfonic acid- bis[4-(5-amino-1-naphthoxy)phenyl]sulfone (DANPS) was synthesized through nucleophilic substitution reaction of 5-amino-1-naphthol with disodium-3,3,-disulfonate-4,4,-dichlorodiphenysulfone (SDCDPS) and subsequent acidification. Two unsulfonated diamines 4,4,-(5-amino-1-naphthoxy)diphenylsulfone (ANDS) and 4,4,-(4-aminophenoxy)diphenylsulfone (APDS) were prepared by nucleophilic reaction of 5-amino-1-naphthol and 4-aminophenol with 4,4,-dichlorodiphenylsulfone in the presence of potassium carbonate, respectively. After characterization of the monomers and polymers with common methods, the physical properties of the polymers including thermal behavior and stability, viscosity, molecular weight, and ion exchange capacity (IEC) were studied. The polymers showed high thermal stability and ion exchange capacity which were the basic requirements for application as fuel cell membranes. Copyright © 2008 John Wiley & Sons, Ltd. [source] Nucleophilic Substitution Reaction of p -Dinitrobenzene by a Carbanion: Evidence for Electron Transfer MechanismCHINESE JOURNAL OF CHEMISTRY, Issue 11 2002You-Cheng Liu Abstract On the basis of investigation of cyclic voltammetry, EPR spectroscopy and competition experiments, the nucleophilic substitution reaction of p - dinitrobenzene with the sodium salt of ethyl ,-cyanoacetate carbanion in dimethyl sulfoxide giving ethyl ,-cyano-,- (p-nitrophenyl) acetate is shown to take place via the intermediacy of p -dinitrobenzene radical anion. The reaction rate goes faster than that between p -nitrohalobenzenes and the same sodium salt of ethyl ,-cyanoacetate carbanion. There is an evidence for a single electron transfer mechanism. [source] Tuning the Optoelectronic Properties of Carbazole/Oxadiazole Hybrids through Linkage Modes: Hosts for Highly Efficient Green ElectrophosphorescenceADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Youtian Tao Abstract A series of bipolar transport host materials: 2,5-bis(2-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o -CzOXD) (1), 2,5-bis(4-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (p -CzOXD) (2), 2,5-bis(3-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (m -CzOXD) (3) and 2-(2-(9H -carbazol-9-yl)phenyl)-5-(4-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (op -CzOXD) (4) are synthesized through simple aromatic nucleophilic substitution reactions. The incorporation of the oxadiazole moiety greatly improves their morphological stability, with Td and Tg in the range of 428,464,°C and 97,133,°C, respectively. The ortho and meta positions of the 2,5-diphenyl-1,3,4-oxadiazole linked hybrids (1 and 3) show less intramolecular charge transfer and a higher triplet energy compared to the para-position linked analogue (2). The four compounds exhibit similar LUMO levels (2.55,2.59,eV) to other oxadiazole derivatives, whereas the HOMO levels vary in a range from 5.55,eV to 5.69,eV, depending on the linkage modes. DFT-calculation results indicate that 1, 3, and 4 have almost complete separation of their HOMO and LUMO levels at the hole- and electron-transporting moieties, while 2 exhibits only partial separation of the HOMO and LUMO levels possibly due to intramolecular charge transfer. Phosphorescent organic light-emitting devices fabricated using 1,4 as hosts and a green emitter, Ir(ppy)3 or (ppy)2Ir(acac), as the guest exhibit good to excellent performance. Devices hosted by o -CzOXD (1) achieve maximum current efficiencies (,c) as high as 77.9,cd A,1 for Ir(ppy)3 and 64.2,cd A,1 for (ppy)2Ir(acac). The excellent device performance may be attributed to the well-matched energy levels between the host and hole-transport layers, the high triplet energy of the host and the complete spatial separation of HOMO and LUMO energy levels. [source] Solvent hydrogen bonding and structural effects on nucleophilic substitution reactions: Part 3.INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2007Reaction of benzenesulfonyl chloride with anilines in benzene/propan-2-ol mixtures Substitution reactions of 13 para- and meta-substituted anilines with benzenesulfonyl chloride in varying mole fractions of benzene in propan-2-ol have been investigated conductometrically. The second-order rate constants correlate well with pKa values of anilines and with the Hammett's equation. The negative Hammett reaction constant indicates the formation of an electron-deficient transition state. The rate data correlate satisfactorily with macroscopic solvent parameters such as relative permittivity, ,r, and polarity, ETN. Correlation of rate data with Kamlet,Taft solvatochromic parameters (,, ,, ,*) suggests that both the specific and nonspecific solute,solvent interactions influence the reactivity. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 657,663, 2007 [source] The ,-effect in micelles: Nucleophilic substitution reaction of p -nitrophenyl acetate with N -phenylbenzohydroxamate ion,INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2006Kallol K. Ghosh Pseudo-first-order rate constants have been determined for the nucleophilic substitution reactions of p -nitrophenyl acetate with p -chlorophenoxide (4-ClC6H4O,) and N -phenylbenzohydroxamate (C6H5CON(C6H5)O,) ions in phosphate buffer (pH 7.7) at 27°C. The effect of cationic, (CTAB, TTAB, DTAB), anionic (SDS), and nonionic (Brij-35) surfactants has been studied. The kobs value increases upon addition of CTAB and TTAB. The effect of DTAB and other surfactants on the reaction is not very significant. The micellar catalysis and ,-effect shown by hydroxamate ion have been explained. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 26,31, 2006 [source] Kinetics and mechanism of the reaction of para -chlorophenyl aryl chlorophosphates with anilines in acetonitrileINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2002Hai Whang Lee The kinetics and mechanism of the nucleophilic substitution reactions of p -chlorophenyl aryl chlorophosphates (2) with anilines are investigated in acetonitrile at 55°C. Relatively large magnitudes of ,X and ,X values are indicative of a large degree of bond making in the TS. Smaller magnitudes of ,X (0.20 for X = H) and ,XY (,0.30) than those for the corresponding reactions with phenyl aryl chlorophosphates (1) (,X = 0.54 for X = H and ,XY = ,1.31) are interpreted to indicate partial electron loss, or shunt, towards the electron acceptor equatorial ligand (p -ClC6H4O-) in the bipyramidal pentacoordinated transition state. The inverse secondary kinetic isotope effects (kH/kD = 0.64,0.87) involving deuterated aniline (ND2C6H4X) nucleophiles, and small ,H, and large negative ,S, are obtained. These results are consistent with a concerted nucleophilic substitution mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 632,637, 2002 [source] A linear three-center four electron bonding identity nucleophilic substitution at carbon, boron, and phosphorus.INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 7 2010A theoretical study in combination with van't Hoff modeling Abstract We studied various identity nucleophilic substitution reactions based on an SN2 reaction profile. With calculations and experimental geometries concerning the nature of the various complexes indicated as stable, intermediate, and transition state we were able to show the additional value of van't Hoff 's tetrahedron by changing its geometry via a trigonal pyramid into a trigonal bipyramid. The ratio of the apical and the corresponding tetrahedral bond distance is then 1.333. This value has been used in general as a calibration point for the understanding of the (in)stabilities of the complex formation on the SN2 reaction coordinate. The relevance of this approach has been also proved for enzymatic reactions focused on carbon and phosphorus substrates. Furthermore, it could be established that identity proton-in-line displacements are fully comparable with the relocation of carbon in a nucleophilic substitution reaction as Cl, + CH3Cl. The significance of this information will afford new insight in the dynamics of a linear three-center four-electron complex. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Energy landscapes of nucleophilic substitution reactions: A comparison of density functional theory and coupled cluster methodsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2007Marcel Swart Abstract We have carried out a detailed evaluation of the performance of all classes of density functional theory (DFT) for describing the potential energy surface (PES) of a wide range of nucleophilic substitution (SN2) reactions involving, amongst others, nucleophilic attack at carbon, nitrogen, silicon, and sulfur. In particular, we investigate the ability of the local density approximation (LDA), generalized gradient approximation (GGA), meta-GGA as well as hybrid DFT to reproduce high-level coupled cluster (CCSD(T)) benchmarks that are close to the basis set limit. The most accurate GGA, meta-GGA, and hybrid functionals yield mean absolute deviations of about 2 kcal/mol relative to the coupled cluster data, for reactant complexation, central barriers, overall barriers as well as reaction energies. For the three nonlocal DFT classes, the best functionals are found to be OPBE (GGA), OLAP3 (meta-GGA), and mPBE0KCIS (hybrid DFT). The popular B3LYP functional is not bad but performs significantly worse than the best GGA functionals. Furthermore, we have compared the geometries from several density functionals with the reference CCSD(T) data. The same GGA functionals that perform best for the energies (OPBE, OLYP), also perform best for the geometries with average absolute deviations in bond lengths of 0.06 Å and 0.6°, even better than the best meta-GGA and hybrid functionals. In view of the reduced computational effort of GGAs with respect to meta-GGAs and hybrid functionals, let alone coupled cluster, we recommend the use of accurate GGAs such as OPBE or OLYP for the study of SN2 reactions. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] | |||||||||||||||||||||||||