- Solvent effects on kinetics of an aromatic nucleophilic substitution reaction in mixtures of an ionic liquid with molecular solvents and prediction using artificial neural networks
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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
- Habibi-Yangjeh, Aziz,Jafari-Tarzanag, Yahya,Banaei, Ali Reza
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Read Online
- Aggregation effects in the reactions of 2,4-dinitrochlorobenzene with aniline in aprotic solvents
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The kinetics of the reaction of 2,4-dinitrochlorobenzene with aniline have been studied in toluene and in toluene-methanol binary solvents and compared with the reactions in benzene and chloroform. The reactions in aprotic solvents exhibit a rate dependence that is third-order in amine consistent with aggregates of the aniline acting as the nucleophile. Molecular complexes between the aniline and the substrate were also detected spectrophotometrically. Additionally, an inhibitory effect of toluene complexes was observed, which is similar to the previously reported effect of benzene in the reaction of the same substrate with n-butylamine. The reaction in the presence of pyridine shows an amine dependence which indicates formation of 'mixed aggregates' between aniline and pyridine. All the above results, as well as recently reported studies of other reactions different from SNAr, are fully interpreted within the 'dimer nucleophile' mechanism.
- Nudelman, N. Sbarbati,Alvaro, Cecilia E. S.,Yankelevich, Jeanette S.
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- Reaction of 2,4-dinitrochlorobenzene with aniline. Solvent effects and molecular complex formation
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The kinetics of the reaction of aniline with 2,4-dinitrochlorobenzene (2,4-DNC1B) were studied in several benzene-n-hexane mixtures at 40 °C in the presence of variable amounts of aniline. A linear dependence of the second-order rate coefficients, kA, with [B] is observed, with a null intercept. Taking into account the non-polar character of the solvent, and the excellent nucleofugacity of chlorine, this kinetic behaviour is interpreted as evidence of the aggregation of aniline, the hydrogen-bonded dimer acting as the nucleophile. Consistent with this interpretation, when the solvent is changed to THF, a good hydrogen-bond acceptor (HBA), the kA is no longer dependent on [B]. Electron donor-acceptor (EDA) molecular complexes of 2,4-DNC1B with benzene and with aniline, and also between aniline and the product, were clearly recognized and the stability constants of each one of these complexes were determined.
- Nudelman, N. Sbarbati,Savini, Monica,Alvaro, C. E. Silvana,Nicotra, Viviane,Yankelevich, Jeanette
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Read Online
- Incorporation of: N -phenyl in poly(benzimidazole imide)s and improvement in H2O-absorbtion and transparency
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5-Amine-2-(4-amino-benzene)-1-phenyl-benzimidazole (N-PhPABZ) was successfully synthesized and polymerized with 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) to obtain a novel N-phenyl-poly(benzimidazole imide) (N-Ph-PBII). The successful incorporation of N-phenyl addressed the issue of high H2O-absorption of traditional PBIIs while retained the superheat resistance property. The resulting N-Ph-PBII possessed a high glass-transition temperature (Tg) up to 425 °C and a low affinity for water of 1.4%. Furthermore, the loose molecular packing and noncoplanar structures led to an increase in optical transparency for the modified PBII.
- Qian, Guangtao,Dai, Fengna,Chen, Haiquan,Wang, Mengxia,Hu, Mengjie,Chen, Chunhai,Yu, Youhai
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p. 3770 - 3776
(2021/02/03)
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- Benzimidazole diamine monomer and preparation method thereof
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The invention relates to a benzimidazole diamine monomer and a preparation method thereof. The preparation method comprises the steps that a benzimidazole intermediate with the structural formula shown in the formula (III) is reduced, a reduction product of the benzimidazole intermediate is mixed with a compound with the structural formula shown in the formula (IV), a substitution reaction and a reduction reaction are conducted in sequence, and the benzimidazole diamine monomer is obtained; the benzimidazole intermediate with the structural formula as shown in the formula (III) is prepared byfirstly carrying out partial reduction reaction on a compound with the structural formula as shown in the formula (I), then a partial reduction product of the compound is mixed with a compound with the structural formula as shown in the formula (II), and then the substitution reaction and a cyclization reaction are sequentially carried out. The structural formulas of the formula (I), the formula (II), the formula (III) and the formula (IV) are shown in the specification. The preparation method is simple and feasible, the prepared benzimidazole diamine monomer is used for preparing polyimide, and the heat resistance and solubility of polyimide can be improved.
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Paragraph 0057-0060
(2020/07/21)
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- Prodrugs for nitroreductase-based cancer therapy-3: Antitumor activity of the novel dinitroaniline prodrugs/Ssap-NtrB enzyme suicide gene system: Synthesis, in vitro and in silico evaluation in prostate cancer
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Prodrugs for targeted tumor therapies have been extensively studied in recent years due to not only maximising therapeutic effects on tumor cells but also reducing or eliminating serious side effects on healthy cells. This strategy uses prodrugs which are safe for normal cells and form toxic metabolites (drugs) after selective reduction by enzymes in tumor tissues. In this study, prodrug candidates (1-36) containing nitro were designed, synthesized and characterized within the scope of chemical experiments. Drug-likeness properties of prodrug candidates were analyzed using DS 2018 to investigate undesired toxicity effects. In vitro cytotoxic effects of prodrug canditates were performed with MTT assay for human hepatoma cells (Hep3B) and prostate cancer cells (PC3) and human umbilical vein endothelial cells (HUVEC) as healthy control. Non-toxic compounds (3, 5, 7, 10, 12, 15, 17, 19 and 21–23), and also compounds (1, 2, 5, 6, 9, 11, 14, 16, 20 and 24) which had low toxic effects, were selected to examine their suitability as prodrug canditates. The reduction profiles and kinetic studies of prodrug/Ssap-NtrB combinations were performed with biochemical analyses. Then, selected prodrug/Ssap-NtrB combinations were applied to prostate cancer cells to determine toxicity. The results of theoretical, in vitro cytotoxic and biochemical studies suggest 14/Ssap-NtrB, 22/Ssap-NtrB and 24/Ssap-NtrB may be potential prodrug/enzyme combinations for nitroreductase (Ntr)-based prostate cancer therapy.
- Tokay, Esra,Güng?r, Tu?ba,Hac?o?lu, Nelin,?nder, Ferah C?mert,Gülhan, ünzile Güven,Tok, Tu?ba Ta?k?n,?elik, Ayhan,Ay, Mehmet,K??kar, Feray
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- URJC-1-MOF as New Heterogeneous Recyclable Catalyst for C-Heteroatom Coupling Reactions
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Guillermo Calleja and co-workers from @urjc describe URJC-1-MOF as a new heterogeneous recyclable catalyst for c-heteroatom coupling reactions. The capacity of copper-based URJC-1-MOF as a MOF catalyst in cross-coupling reactions has been evaluated, focusing on the Chan-Lam-Evans arylation-type reactions on amines and alcohols without extra additives or ligands. The extraordinary chemical and structural stability of URJC-1-MOF and its good specific surface, make this material a promising alternative to homogeneous Cu (II) catalysts for cross-coupling reactions. URJC-1-MOF showed a remarkable catalytic activity for cross-coupling C?N and C?O reactions, higher than other heterogeneous and homogeneous copper-based catalyst, such as CuO, HKUST-1, Cu?MOF-74, Cu(OAc)2 and CuSO4?5H2O. Moreover, its easy recovery by simple filtration and reusability in successive runs without any loss of activity and stability, demonstrates the potential of URJC-1-MOF as an alternative catalyst for this kind of reactions in different chemical media of industrial interest.
- Mu?oz, Antonio,Leo, Pedro,Orcajo, Gisela,Martínez, Fernando,Calleja, Guillermo
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p. 3376 - 3380
(2019/07/04)
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- Recyclable bimetallic CuMoO4 nanoparticles for C-N cross-coupling reaction under mild conditions
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Herein we disclosed inexpensive copper(ii) bimetallic CuMoO4 nanoparticles for the C-N cross-coupling reaction of alkyl and aryl amines with haloarenes. The reaction proceeds under mild and ligand free conditions. The catalyst is recyclable and effective for a wide range of amines and haloarenes. Here, the efficiency of the Cu(ii) catalyst is increased by doping molybdenum metal. The bimetallic nanoparticles are anticipated to proceed via normal oxidative addition and reductive eliminations.
- Panigrahi, Reba,Panda, Subhalaxmi,Behera, Pradyota Kumar,Sahu, Santosh Kumar,Rout, Laxmidhar
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supporting information
p. 19274 - 19278
(2019/12/24)
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- Neutral Cyclometalated Iridium(III) Complexes Bearing Substituted N-Heterocyclic Carbene (NHC) Ligands for High-Performance Yellow OLED Application
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The synthesis, crystal structure, and photophysics of a series of neutral cyclometalated iridium(III) complexes bearing substituted N-heterocyclic carbene (NHC) ancillary ligands ((CN)2Ir(R-NHC), where CN and NHC refer to the cyclometalating ligand benzo[h]quinoline and 1-phenylbenzimidazole, respectively) are reported. The NHC ligands were substituted with electron-withdrawing or -donating groups on C4′ of the phenyl ring (R = NO2 (Ir1), CN (Ir2), H (Ir3), OCH3 (Ir4), N(CH3)2 (Ir5)) or C5 of the benzimidazole ring (R = NO2 (Ir6), N(CH3)2 (Ir7)). The configuration of Ir1 was confirmed by a single-crystal X-ray diffraction analysis. The ground- and excited-state properties of Ir1-Ir7 were investigated by both spectroscopic methods and time-dependent density functional theory (TDDFT) calculations. All complexes possessed moderately strong structureless absorption bands at ca. 440 nm that originated from the CN ligand based 1π,π*/1CT (charge transfer)/1d,d transitions and very weak spin-forbidden 3MLCT (metal-to-ligand charge transfer)/3LLCT (ligand-to-ligand charge transfer) transitions beyond 500 nm. Electron-withdrawing substituents caused a slight blue shift of the 1π,π*/1CT/1d,d band, while electron-donating substituents induced a red shift of this band in comparison to the unsubstituted complex Ir3. Except for the weakly emissive nitro-substituted complexes Ir1 and Ir6 that had much shorter lifetimes (≤160 ns), the other complexes are highly emissive in organic solutions with microsecond lifetimes at ca. 540-550 nm at room temperature, with the emitting states being predominantly assigned to 3π,π*/3MLCT states. Although the effect of the substituents on the emission energy was insignificant, the effects on the emission quantum yields and lifetimes were drastic. All complexes also exhibited broad triplet excited-state absorption at 460-700 nm with similar spectral features, indicating the similar parentage of the lowest triplet excited states. The highly emissive Ir2 was used as a dopant for organic light-emitting diode (OLED) fabrication. The device displayed a yellow emission with a maximum current efficiency (ηc) of 71.29 cd A-1, a maximum luminance (Lmax) of 32747 cd m-2, and a maximum external quantum efficiency (EQE) of 20.6%. These results suggest the potential of utilizing this type of neutral Ir(III) complex as an efficient yellow phosphorescent emitter.
- Liu, Bingqing,Jabed, Mohammed A.,Guo, Jiali,Xu, Wan,Brown, Samuel L.,Ugrinov, Angel,Hobbie, Erik K.,Kilina, Svetlana,Qin, Anjun,Sun, Wenfang
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p. 14377 - 14388
(2019/11/03)
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- Deep eutectic solvent as an operative media on structure-reactivity relationships
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Deep eutectic solvents seem to be environmentally friendly solvents, particularly because they are prepared easily and have very low-vapor pressures under ambient conditions. They are suitable candidates as green solvents for reaction media with special properties. To present this behavior, substitution reactions of some para- and meta-substituted anilines with 1-fluoro-2,4-dinitrobenzene have been spectrophotometrically investigated in varying mole fractions of ethaline as a deep eutectic solvent in dimethyl sulfoxide (DMSO). The measured rate coefficients of the reaction demonstrated a noticeable variation with the increasing mole fraction of ethaline in ethaline-DMSO mixtures. The linear free energy relationship (LFER) of second-order rate coefficients based on Hammett's substituent constants demonstrates a reasonably linear straight line with a negative slope in different mole fractions of ethaline-DMSO mixtures. Another LFER investigation based on the polarity parameters of the media showed a good agreement with hydrogen bond donor and acceptor abilities of the solvent. Non-LFER assay according to the preferential solvation model confirmed differences between the microsphere solvation of the solute molecules and the bulk composition of the solvents.
- Harifi-Mood, Ali Reza,Khorshahi, Hasan
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p. 511 - 519
(2019/04/14)
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- “Zero VOC” Synthetic Strategy – Aromatic Amination Reactions in Deep Eutectic Solvents
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Rising concern for environment hazards resulting from the use of volatile organic compounds (VOCs) is prompting many chemists to use “green” solvents like water, polyethylene glycol, ionic liquids and deep eutectic solvents (DES). With a few notable exceptions, many of these processes still need to use volatile organic solvents for the workup and isolation of products. In the present report, we demonstrate a “zero VOC” protocol which eliminates the need to use organic solvents for any stage of the reaction. As a proof of concept, nucleophilic aromatic substitution reactions of 1-halo-2,4-dinitrobenzene with secondary amines were carried out in deep eutectic solvents. The reaction workup involved the addition of water for separating the product from the DES. Evaporation of water led to recovery of the DES, which exhibited good recyclability. The reaction in deep eutectic solvents was much faster than that in many other solvents, as confirmed by the kinetic studies. An attempt was made to elucidate the origin of this rate enhancement based on analysis activation parameters and correlation with the polarity parameters. The results show that use of deep eutectic solvents can take chemists a step closer towards the “zero VOC” synthetic strategy.
- Valvi, Arun,Tiwari, Shraeddha
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p. 4933 - 4939
(2018/09/11)
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- Deep Eutectic Solvent/Lipase: Two Environmentally Benign and Recyclable Media for Efficient Synthesis of N-Aryl Amines
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Abstract: Deep eutectic solvent (DES)/lipase catalyzed efficient synthesis of N-aryl amines from electron deficient aryl chlorides and amines at ambient temperature is reported. Its significant features include excellent yields of products, use of biodegradable, non-toxic and recyclable catalysts, thereby avoiding toxic metal catalyst/solvents making these protocols environmentally benign. Graphical Abstract: [Figure not available: see fulltext.].
- Pant, Preeti Lalit,Shankarling, Ganapati Subray
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p. 1371 - 1378
(2017/08/29)
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- Efficient synthetic route to aromatic secondary amines: Via Pd/RuPhos/TBAB-catalyzed cross coupling
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Herein, C-N cross coupling methodology was developed for the synthesis of a diverse range of nitro-substituted secondary amines. A variety of strained, aliphatic, and aromatic precursors were effectively used, with low catalyst and ligand loading ratios resulting in product formation in good yield. This method can act as an alternative to nucleophilic addition reactions. To cross couple electron-donating, electron-withdrawing, neutral, and aliphatic primary amines with alkyl/aryl halides, a combination of RuPhos and TBAB was carefully tuned. Further, characterization of these molecules was carried out using FT-IR, 1H-NMR, 13C-NMR, 19F-NMR, single crystal XRD, and C, H, and N elemental analyses.
- Gaur, Pinki,Durga Bhaskar Yamajala,Banerjee, Shaibal
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p. 6523 - 6529
(2017/07/17)
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- Synthesis and Anti-Staphylococcal Activity of 2,4-Disubstituted Diphenylamines
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Infections caused by Staphylococcus aureus are ubiquitous and life threatening. Evolution of resistant strains has necessitated the need to continuously discover new drugs to combat such organisms. Diphenyl ethers, such as triclosan, have recently shown potential as antibacterial agents. In this study, a series of diphenyl amines were synthesized and evaluated for in vitro antibacterial activity against Gram-positive (Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Pseudomonas putida) bacteria. Preliminary results showed that six of the twelve synthesized molecules were active against Staphylococcus aureus. Most notable amongst them were compounds 2(2,4-dinitrophenylamino) phenol and 2(2-dinitrophenylamino)phenol having minimum inhibitory concentration (MIC) in the range of 7.8-15.6 μg mL-1 and 7.8-62.5 μg mL-1 respectively for all the eight selected organisms. Five active compounds from the preliminary results were further screened against resistant S. aureus cultures where compounds 2(2,4-dinitrophenylamino)phenol, 2(2-dinitrophenylamino)phenol and 2-chloro-N-(2-(2,4-dichlorophenylamino)phenyl)acetamide gave encouraging results having MIC in the range 3.9-7.8 μg mL-1 for most of the organisms. Results obtained above for the selected organisms and the resistant S. aureus strains conclude that hydroxyl group at 2-position of ring B potentiates the antibacterial activity and overcomes the antibiotic resistance.
- Mehton, Ramandeep K.,Meshram, Vineet,Saxena, Sanjai,Chhibber, Manmohan
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p. 1236 - 1244
(2016/08/16)
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- Cooperatively assisted N-arylation using organic ionic base-Br?nsted acid combination under controlled microwave heating
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A new synthetic strategy is developed for the construction of C-N bond through the assistance of Br?nsted acid/[DBU][HOAc] without adding any metal catalyst. This is the first efficient SNAr methodology utilizing fluoro, chloro, bromo, and iodoarenes as coupling partners, which offers excellent yield up to 94% within a very short time.
- Singh, Rahul,Allam, Bharat Kumar,Raghuvanshi, Dushyant Singh,Singh, Krishna Nand
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p. 1038 - 1042
(2013/02/23)
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- NiCl2·6H2O as recyclable heterogeneous catalyst for N-arylation of amines and NH-heterocycles under microwave exposure
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NiCl2·6H2O has been proven to be an effective catalyst for the coupling of amines with aryl iodides without ligand under solvent-free conditions employing microwave irradiation. Reactions cleanly result in coupled products in a short reaction time. The catalyst, being heterogeneous, is recovered by filtration and is recyclable.
- Gupta, Amit Kumar,Tirumaleswara Rao,Singh, Krishna Nand
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experimental part
p. 2218 - 2221
(2012/05/19)
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- Oxidative arylamination of 1,3-dinitrobenzene and 3-nitropyridine under anaerobic conditions: The dual role of the nitroarenes
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1,3-Dinitrobenzene and 3-nitropyridine react with lithium arylamides under anaerobic conditions to produce N-aryl-2,4-dinitroanilines and N-aryl-5-nitropyridin-2-amines, respectively, in 8-42% yields. ARKAT-USA, Inc.
- Gulevskaya, Anna V.,Tyaglivaya, Inna N.,Verbeeck, Stefan,Maes, Bert U.W.,Tkachuk, Anna V.
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experimental part
p. 238 - 251
(2011/08/22)
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- Reaction kinetics investigation of 1-fluoro-2,4-dinitrobenzene with substituted anilines in ethyl acetate-methanol mixtures using linear and nonlinear free energy relationships
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Aromatic nucleophilic substitution reaction of 1-fluoro-2,4-dinitrobenzene with para-substituted and meta-substituted anilines was kinetically investigated in the mixtures of ethyl acetate and methanol at room temperature. The correlation of second-order rate coefficients with Hammett's substituent constants yields a fairly linear straight line with negative slope in different mole fractions of ethyl acetate-methanol mixtures. The measured rate coefficients of the reaction demonstrated a dramatic variation in ethyl acetate-methanol mixtures with the increasing mole fraction of ethyl acetate. Linear free energy relationship (LFER) investigations confirm that polarity has a major effect on the reaction rate whereas the hydrogen-bonding ability of the media has a slight effect on it. Nonlinear free energy relationship based on preferential solvation hypothesis showed differences between the microsphere solvation of the solute and the bulk composition of the solvents, and non-ideal behavior is observed in the trend of the rate coefficients, which cover the LFER results. Copyright
- Jamali-Paghaleh, Javad,Harifi-Mood, Ali Reza,Gholami, Mohammad Reza
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experimental part
p. 1095 - 1100
(2012/02/15)
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- The "dimer nucleophile mechanism" for reactions with rate-determining first step: Derivation of the whole kinetic law and further treatment of kinetic results
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Overwhelming evidence has been previously reported for the existence of the so-called "dimer nucleophile mechanism" in aromatic nucleophilic substitutions by amines in aprotic solvents, for which the most prominent feature is the fourth-order kinetics (third order in amine) that has been observed with many different substrate-nucleophile systems, especially those in which departure of the nucleofuge is the rate-determining step. The mechanism has been confirmed by several other features, although other alternative mechanisms were suggested to explain the fourth-order kinetics, no one has been able to explain the other above-mentioned features. The present paper affords additional experimental evidence and derivation of the kinetic expressions for reactions with good nucleofugues, where the first step is rate determining. The work involves studies of the reactions of 2,4-dinitrofluorobenzene and 2,4-dinitrochlorobenzene with aniline and with alkyldiamines in toluene. The novelty of this work lies in the selection of substrate-nucleophile systems exhibiting kinetic behavior that allows estimations of the different k's involved. The satisfactory agreement between the quotients of k's calculated from sets of data obtained under different reaction conditions hereby reported indicates that the assumptions made are correct and that the whole treatment applied to the kinetic data is justified. All together, the results fit well with the reaction scheme involving the dimer nucleophile mechanism, adding new evidence to this mechanism that it is well established in the current literature.
- Alvaro, Cecilia E. Silvana,Nudelman, Norma Sbarbati
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scheme or table
p. 735 - 742
(2011/07/29)
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- SMALL MOLECULE COMPOUNDS FOR STEM CELL DIFFERENTIATION
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Methods and small molecule compounds for stem cell differentiation are provided. One example of a class of compounds that may be used is represented by the compound having the structure IA or IB in the form of free base or a pharmaceutically acceptable salt, hydrate, solvate or N-oxide thereof. R1 is independently hydrogen or (C1-C6)alkyl; R2 is independently hydrogen, (C1-C6)alkyl, aryl, or heteroaryl; R2' is independently hydrogen, (C1-C6)alkyl, CF3 or C2F5; R3 is independently (C1-C6)alkyl, aryl, 2-tetrahydrofuryhnethyl, an aliphatic tertiary amine, or 4-methoxybenzyl; or R2 and R3 may be joined together to form a 5 or 6 member ring lactone; R4 is independently hydrogen, (C1-C6)alkyl, a 2- or 4-R5-substituted aromatic ring selected from a 4-R5-phenyl or a 2-R5-5-pyridyl, aryl, heteroaryl, aliphatic tertiary amine or halogen; and R5, R5', R6, R6', R7, R7' are each independently hydrogen, (C1-C6)alkyl, aryl, optionally substituted phenyl, heteroaryl, a heterocyclic ring, an aliphatic tertiary amine, or halogen.
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Page/Page column 53
(2010/04/25)
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- Nitropyrazoles 15.* Synthesis and some transformations of 1-(2,4-dinitrophenyl)-4-methyl-3,5-dinitropyrazole
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The method for preparation of 1-(2,4-dinitrophenyl)-4-methyl-3,5- dinitropyrazole has been developed. Due to the larger CH-acidity of 4-Me-group compared to 1,4-dimethyl-3,5-dinitropyrazole, 1-(2,4-dinitrophenyl)-4-methyl-3, 5-dinitropyrazole is capable of reacting with substituted benzaldehydes to afford 4-[(E)-2-arylvinyl]-1-(2,4-dinitrophenyl)-3,5-dinitropyrazoles. Under the action of nucleophiles, dinitrophenyl group is detached from the former compounds leading to previously unknown N-unsubstituted 4-[(E)-2-arylvinyl]-3,5- dinitropyrazoles.
- Zaitsev,Vatsadze,Dalinger,Kachala,Nelyubina,Shevelev
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p. 2109 - 2117
(2011/01/11)
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- ANTIVIRAL DRUGS FOR TREATMENT OF ARENAVIRUS INFECTION
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Compounds, methods and pharmaceutical compositions for treating viral : infections, by administering certain novel compounds in therapeutically effective "'" amounts are disclosed. Methods for preparing the compounds and method’s using the compounds and pharmaceutical compositions thereof are also disclosed. In particular, the treatment and prophylaxis of viral infections such as caused by hemorrhagic fever viruses is disclosed, i.e., including but not limited to, Arenaviridae (Junin, Machupo, Guanarito, Sabia, Lassa, Tacaribe, Pichinde, and LCMV), Filoviridae (Ebola and Marburg viruses), Flaviviridae (yellow fever, Omsk hemorrhagic fever and Kyasanur Forest disease viruses), and Bunyaviridae (Rift Valley fever).
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Page/Page column 39-40
(2008/06/13)
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- Novel benzimidazole-based MCH R1 antagonists
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The identification of an MCH R1 antagonist screening hit led to the optimization of a class of benzimidazole-based MCH R1 antagonists. Structure-activity relationships and efforts to optimize pharmacokinetic properties are detailed along with the demonstration of the effectiveness of an MCH R1 antagonist in an animal model of obesity.
- Carpenter, Andrew J.,Al-Barazanji, Kamal A.,Barvian, Kevin K.,Bishop, Michael J.,Britt, Christy S.,Cooper, Joel P.,Goetz, Aaron S.,Grizzle, Mary K.,Hertzog, Donald L.,Ignar, Diane M.,Morgan, Ronda O.,Peckham, Gregory E.,Speake, Jason D.,Swain, Will R.
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p. 4994 - 5000
(2007/10/03)
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- Direct coupling of nucleophiles with nitroaromatic compounds via fluoride-promoted oxidative nucleophilic aromatic substitution for hydrogen
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Useful yields are achieved in the regioselective direct coupling of amines, amides, and ketones with m-dinitrobenzene, 1-nitronaphthalene, and 1,3-dinitronaphthalene, through oxidatively activated nucleophilic aromatic substitution for hydrogen promoted by fluoride anions.
- Huertas, Inma,Gallardo, Iluminada,Marquet, Jordi
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p. 3439 - 3441
(2007/10/03)
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- Direct formation of aromatic C-N bonds. Regioselective amination of m- dinitrobenzene via fluoride promoted nucleophilic aromatic photosubstitution for hydrogen
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Useful yields are achieved in the regioselective direct formation of anilines and aromatic amides through hydrogen nucleophilic aromatic photosubstitution of m-dinitrobenzene with primary amines and amides, promoted by fluoride anion.
- Huertas, Inma,Gallardo, Iluminada,Marquet, Jordi
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p. 279 - 281
(2007/10/03)
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- 15N NMR and FTIR studies of 2,4-dinitroanilines and their salts
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Twenty-two 2,4-dinitroanilines were synthesised and their pK(a) values were determined. The 2,4-dinitroanilines and their protonated forms were studied by 15N NMR spectroscopy. The relations between the 15N NMR chemical shifts and the pK(a) values of the 2,4-dinitroanilines and their salts were found to be linear. The deprotonation reaction of N-methyl-2,4- dinitroanilines and N-methyl-2,4,6-trinitroaniline by MTBD was successful only for the latter and yielded protonated MTBD molecule and the anion in which the electrons are strongly delocalised. The kinetic parameters of the 2,4-dinitroanilines in reactions with hydroxide ions in mixed solvent DMSO:water (95:5, v/v) were determinated and discussed. (C) 2000 Elsevier Science B.V.
- Gierczyk,Leska,Nowak-Wydra,Schroeder,Wojciechowski,Bartl,Brzezinski
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p. 217 - 225
(2007/10/03)
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- Effects of the nucleophile structure on the mechanisms of reaction of 1-chloro-2,4-dinitrobenzene with aromatic amines in aprotic solvents
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The kinetics of reactions of 1-chloro-2,4-dinitrobenzene with aniline and several substituted aromatic amines, B, in toluene shows a quadratic dependence of the second-order rate constant, kA, on [B], which is preserved even in the presence of increasing amounts of dimethylaniline, while the reaction with N-methylaniline shows a linear dependence of kA vs [B]. All these results are interpreted by the "dimer nucleophile" mechanism, and confirmed by the effects of a non-nucleophilic hydrogen bond acceptor tertiary amine which show the relevance of the structure of the nucleophile and the role of mixed aggregates in defining the mechanisms of aromatic nucleophilic substitutions with amines in aprotic solvents.
- Nudelman, Norma Sbarbati,Silvana Alvaro, Cecilia E.,Savini, Monica,Nicotra, Viviana,Yankelevich, Jeannette
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p. 1583 - 1593
(2007/10/03)
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- Photochemical Reaction of 2,4-Dinitrodiphenylacetamide and Related Compounds: Spectroscopic and Chemical Identification of Intermediates
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2,4'-Dinitrodiphenylacetamide 1b reacts via the triplet state to give 3-nitrophenazine 5-oxide 2b.The initial step is addition of the nitro group to the C=O bond.This intermediate 7 rearranges in the ms time scale to yield an O-acylnitro derivative 8.This, in turn, undergoes heterocyclic cleavage (rate dependent upon solvent polarity) and the aminium cation thus formed cyclizes to 2b.Intermediate 7 is sensitive to acid-catalysed hydrolysis, and the cleavage of 8 and subsequent cyclization are influenced by various additives.Thus, with triphenylphosphine a phosphoranylidenamino derivative is obtained, and 2,6-di-tert-butylphenol gives 4-nitro-2-nitrosodiphenylamine.Two other amides are compared.
- Fasani, Elisa,Mella, Mariella,Albini, Angelo
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p. 2689 - 2692
(2007/10/02)
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- THE PHOTOCYCLIZATION OF N-ACYL-2-NITRODIPHENYLAMINES TO PHENAZINE N-OXIDES: SCOPE AND MECHANISM
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The photocyclization of N-acyl-2-nitridiphenylamines to phenazine N-oxides is extended to several dinitro derivatives and a pyridine analogue obtaining N-oxides of otherwise difficult access.In the presence of some additives, the reaction takes a different course.Thus, with acids deacylation occurs, with triphenylphosphine a N-phosphoranylidene amine is formed and with 2,6-di-tert-butylphenol the corresponding nitrosodiphenylammine is obtained.A mechanism starting from the nitroamide triplet and involving several discrete intermediates is proposed in order to account for such observations.
- Fasani, Elisa,Pietra, Silvio,Albini, Angelo
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p. 573 - 584
(2007/10/02)
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- The Reaction of 2,4-Dinitrofluorobenzene with Aniline, Cyclohexylamine, and 1,2-Diaminocyclohexanes in Aprotic Solvents. A New Approach to the 'imer Mechanism'
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The reaction of 2,4-dinitrofluorobenzene (DNF) with aniline in toluene and in chloroform at 35 deg C shows a third-order kinetic dependence on .In hydrogen-bond acceptor (HBA) solvents an important rate increase, and a second-order dependence on , are observed.Finally, the reaction shows a second-order dependence on non-nucleophilic tertiary amines.All these results are fully consistent with the previously proposed 'dimer nucleophile mechanism'.Another approach towards confirming the mechanism was designed: a system where an 'intramolecular dimer nucleophile' is possible.The reactions of DNF with cyclohexylamine, and with cis- and trans-1,2-diaminocyclohexane, were studied in toluene, and also in toluene-methanol mixtures in some cases.The kinetic order observed, as well as the enhanced reactivity of the cis isomer and the solvent effects are new evidence in favour of the 'dimer nucleophile' mechanism.The results cannot be explained by other, alternative mechanisms.
- Nudelman, Norma S.,Montserrat, Javier M.
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p. 1073 - 1076
(2007/10/02)
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- REACTIVITY OF NUCLEOPHILES IN DIMETHYL SULFOXIDE AND ITS COMPARISON WITH NUCLEOPHILIC REACTIVITY IN PROTIC MEDIUM
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Reactions of 2,4-dinitrophenyl acetate and 2,4-dinitrofluorobenzene as model substrates with 12 nucleophiles have been studied in dimethyl sulfoxide.The rate constants obtained have been discussed with regard to the nucleophilic reactivity differences in dimethyl sulfoxide and protic solvents inclusive of the different manifestations of the charge of nucleophiles.The applicability of an earlier-suggested correlation equation to the data obtained has been verified.The reaction medium markedly affects the reactivity of nucleophiles, the effect of charge being substantially greater in aprotic solvents (electrostatic interaction) than in protic ones (solvation).In spite of these differences the correlation with application of an empirical nucleophilicity scale suggested earlier is satisfactory, the regression coefficients obtained reflect changes in the nature of medium.
- Zima, Vitezslav,Pytela, Oldrich,Kavalek, Jaromir,Vecera, Miroslav
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p. 2715 - 2720
(2007/10/02)
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- KINETICS OF THE REACTION OF 2-(2,4-DINITROPHENOXY)-N-ETHYLPYRIDINIUM TETRAPHENYLBORATE WITH AROMATIC AMINES IN ACETONITRILE
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The reactions of 2-(2,4-dinitrophenoxy)-N-ethylpyridinium salts with arylamines take place by nucleophilic substitution at a carbon atom of the benzene ring with the formation of 2,4-dinitrodiphenylamine derivatives.The sensitivity coefficient (ρ0) to the induction effect of the substituents in the arylamine does not depend on the temperature in the range of 10-55 deg C and is equal to -6.89.The constant of the leaving group (τAr) for the 2-hydroxy-N-ethylpyridinium cation amounts to 1.66.
- Titskii, G. D.,Mitchenko, E. S.,Dubovaya, A. A.
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p. 1945 - 1949
(2007/10/02)
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- A STUDY OF NUCLEOPHILICITY IN SELECTED SYSTEMS
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Kinetic studies have been carried out of the reactions of 15 nucleophiles with 2,4-dinitrophenyl acetate and 14 nucleophiles with 2,4-dinitrofluorobenzene in 52percent (w/w) methanol at 25 deg C.The rate constant values obtained and literature data have been treated by the factor analysis.It has been found that the description of nucleophilicity at least needs two factors.The nucleophiles studied are divided into two groups (ionic and nitrogen-containing ones).In each group, the nucleophilic properties are affected by linear combination of both factors.
- Zima, Vitezslav,Pytela, Oldrich,Vecera, Miroslav
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p. 814 - 821
(2007/10/02)
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- REACTIONS OF IMIDIC ACID DERIVATIVES WITH NUCLEOPHILIC REAGENTS. MECHANISM OF THE ALKALINE HYDROLISIS OF ARYL N-ARYLARENECARBOXIMIDATES
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In the kinetics of the alkaline hydrolysis of aryl-N-phenylbenzimidates PhC(OArX) =NPh(I) in a water-dioxane mixture (1:1 by volume) and with a constant ionic strength in 0.2 M sodium perchlorate first order is observed in each of the reagents.The Hammett ρ and Bronsted β parameters with variation of the substituent in the leaving group are 1.6 and -0.35 respectively.The products from the hydrolysis of compounds (I) (X = 2,4-(NO2)2, 2-NO2-4-COCH3) are benzoic acid and substituted diphenylamines and, in the case of the derivatives of (I) benzanilide and the corresponding phenol.In spite of the different qualitative composition of the hydrolysis products the data for all the substituents (including the ortho substituents) satisfy the Hammett and Bronsted equations.The results are explained in terms of an addition-elimination stage mechanism with the formation of a tetrahedral intermediate product in the rate-determining stage.
- Prudchenko, A. P.,Drizhd, L. P.,Savelova, V. A.
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p. 1715 - 1719
(2007/10/02)
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- REACTION OF ANILINE WITH 2,4-DINITROCHLOROBENZENE AT A SOLUTION-GAS INTERFACE ACTIVATED BY CATIONIC SURFACTANTS
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The catalytic action of cationic surfactants on the reaction of aniline with 2,4-dinitrochlorobenzene at a liquid-gas interface was investigated.The reaction rate constant in the surface films of alkylpyridinium chloride lies in the range of (0.5-3.5)*E-3 m3/mole.sec and is higher than the rate constant of this reaction in a micellar solution of the surfactant (2.7*E-5 m3/mole.sec).The effect of the concentration of the surfactant and electrolytes on the rate constant was investigated.The highest rate constant is obtained with the surfactant at a concentration of 0.3 mole percent, which corresponds to saturation of the surface layer.The reaction is inhibited by increase in the concentration and in the charge of the anions of the electrolytes (NaCl, Na2SO4).
- Azarova, V. I.,Panyukova, M. A.,Sviridov, V. V.
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p. 1525 - 1527
(2007/10/02)
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- CATALYSIS BY AMINE SALTS OF SOME AROMATIC NUCLEOPHILIC SUBSTITUTION REACTIONS
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The reaction of 1-chloro-2,4-dinitrobenzene with aniline in acetonitrile is catalysed by R4NY where Y is Cl, Br, I, or toluene-p-sulphonate, but not by 1,4-diazabicyclooctane (DABCO).When the nucleophile is changed to n-butylamine or morpholine, addition of tetraethylammonium chloride has only a small effect; the reactions of all three nucleophiles are not catalysed by tetraethylammonium perchlorate.The reaction of 1-fluoro-2,4-dinitrobenzene with aniline is strongly catalysed by tetraethylammonium chloride, to a lesser extent by the bromide and toluene-p-sulphonate and also by trimethylamine hydrochloride, but not by tetraethylammonium perchlorate.The reactions of morpholine with 1-fluoro-2,4-dinitrobenzene and piperidine with 2,4-dinitrophenyl phenyl ether are not catalysed by amine salts.The results are consistent with the formation and stabilisation of the intermediate formed in aromatic nucleophilic substitution reactions by the anions of the salts, when the nucleophile is aniline
- Hirst, Jack,Onyido, Ikenna
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p. 711 - 716
(2007/10/02)
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- Kinetic study and analytical application of the hexadecyltrimethylammonium bromide-catalyzed reaction of 1-fluoro-2,4-dinitrobenzene with amines
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Arylation of amines by reaction with 1-fluoro-2,4-dinitrobenzene is catalyzed by micelles of cetrimonium bromide. This catalysis has been exploited to reduce the analysis time in the spectrophotometric determination of amines as their dinitrophenyl derivatives. The kinetics of the catalysis were studied for the five amines: alanine, phenylalanine, aniline, 4-methylaniline, and 4-methoxyaniline. The dependence of rate constant on surfactant concentration can be quantitatively accounted for by Berezin's model, in which uptake of the amine and the 1-fluoro-2,4-dinitrobenzene by the micelle is described as a partitioning phenomenon for both species. An alternative model is developed in which one reactant partitions into the micellar phase and the other binds to the micelle with 1:1 stoichiometry; the two models are formally equivalent. Intrinsic catalytic rate constants and binding constants were evaluated. About one-third to one-half of the maximum observed micellar acceleration is attributed to a true micellar catalysis, the remainder being ascribed to an increase in local reactant concentrations in the micelle.
- Wong,Connors
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p. 146 - 150
(2007/10/02)
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- REACTIONS BETWEEN 1-HALOGENO-2,4-DINITROBENZENES AND SUBSTITUTED ANILINES: KINETICS AND EVIDENCE FOR THE PRESENCE OF A MOLECULAR COMPLEX
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The title reactions (halogen = F or Cl) have been studied in benzene and in chloroform.The experimental reaction order in aniline is higher than 2 in every case (the value 3 is reached for the fluoro derivative in both solvents).Spectroscopic evidence (1H NMR and UV) indicates the presence of a molecular complex the formation of which (together with a base-catalysed step) is probably responsible for the observed kinetic features.The substituent effect (in aniline) is discussed.
- Forlani, Luciano
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p. 205 - 212
(2007/10/02)
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- Base Catalysis of Aromatic Nucleophilic Substitution Reactions in Aprotic and Dipolar Aprotic Solvents
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For base-catalysed aromatic nucleophilic substitution reactions in benzene, catalysis by added base is observed irrespective of whether the catalyst is a stronger or a weaker base than the nucleophile.In acetonitrile, catalysis is only observed if the catalyst has either approximately the same strength or is a stronger base than the nucleophile.These observations are shown to indicate a difference in the mechanism of catalysis in the two solvents.
- Bamkole, Titus O.,Hirst, Jack,Onyido, Ikenna
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p. 889 - 894
(2007/10/02)
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- Water-soluble trisazo 8-amino-naphthol-1 dyes
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Very effective direct dyeing of cotton and other hydroxyl- or nitrogen-containing fibers is effected with water-soluble triasazo dyes having the formula: where A is a radical of a diazoconstituent and A3 is a radical of a coupling constituent STR1 and A1 or A2 or both can have their azo linkages reversed. These dyes are very fast particularly to washing and to perspiration, and are so effective with cotton that dye baths for such use are rapidly exhausted and the disposal of used bath is less of a problem.
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