- Intramolecular base catalysed hydrolysis of ortho-hydroxyaryl esters: The anomalous position of methyl 3,5-dinitrosalicylate on the Linear Free Energy Relationship plot
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The pKa of the ortho-hydroxy group in methyl 3,5-dinitrosalicylate, HMDNS, is 2.45. Rate constants for the reaction of its conjugate base, MDNS- with hydroxide anion and water are 5.3 × 10-2 mol dm-3 s-1 and 6.6 × 10-6 s-1, respectively at 25°C. The rate constant for the uncatalysed reaction of HMDNS and water is 6.5 × 10-6 s-1 and so there is no evidence for intramolecular general base catalysis of the water reaction with MDNS- by the weakly basic ortho-O-. By means of Bronsted plots the water reaction of MDNS- is compared with that of a group of other salicylate esters (β = 0) and also a structurally different group of esters (β = 0.4), both of which undergo intramolecular base catalysed hydrolysis. Although the title ester structurally belongs to the first set of compounds, its anomalous position on the plot clearly corresponds to the trend of the second set. This is explained in terms of differences in resonance stabilisation and hydrogen bonding in the transition state.
- Moozyckine, Alexei U.,Davies, D. Martin
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- NOVEL WATER SOLUBLE POLYIMIDE RESIN, ITS PREPARATION AND USE
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The present invention relates to a novel water soluble polyimide resin, which contains a hydrophilic functional group such as —OH, —COOH to increase the solubility of the polyimide resin in alkali aqueous solution, and is suitable for using as an insulation film in electronic and photoelectric products. The present invention also relates to preparation and use of the above polyimide.
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- INHIBITORS OF STEAROYL-COA DESATURASE
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Provided herein are compounds of the formula (I): as well as pharmaceutically acceptable salts thereof, wherein the substituents are as those disclosed in the specification. These compounds, and the pharmaceutical compositions containing them, are useful for the treatment of diseases such as, for example, obesity.
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- Process for the synthesis of hydroxy aromatic acids
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Hydroxy aromatic acids are produced in high yields and high purity (>95%) from halogenated aromatic acids in a reaction mixture containing a copper source and a ligand that coordinates to copper.
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Page/Page column 20-21
(2008/06/13)
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- Cold microwave chemistry: synthesis using pre-cooled reagents
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A novel experimental procedure for chemical reactions has been devised that involves mixing and then freezing the reagents (organic solvent-free) to a sub-zero temperature such as -30 °C. This frozen mixture is exposed to microwave irradiation for a brief period of time. The use of pre-cooled reagents may give a single product not obtained by traditional microwave irradiation at room temperature. Interestingly, such a product may provide information about mechanisms by identifying the first step of a multiple step reaction.
- Bose, Ajay K.,Ganguly, Subhendu N.,Manhas, Maghar S.,He, William,Speck, Jeffrey
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p. 3213 - 3215
(2007/10/03)
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- Nitration of aromatic compounds by Zn(NO3)2· 2N2O4 and its charcoal-supported system
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Zn(NO3)2·N2O4 and its charcoal supported system were found to be efficient nitrating agents. Mononitration of aromatic compounds such as benzene, alkyl benzenes, halobenzenes, nitrobenzene, anisol, and the highly selective mono-, di-, and trinitration of phenol, and dinitraion of substituted phenols were also performed in the presence of these reagents.
- Iranpoor, Nasser,Firouzabadi, Habib,Heydari, Reza,Shiri, Morteza
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p. 263 - 270
(2007/10/03)
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- Synthesis of salicylic acid derivatives from the corresponding 2-chlorobenzoic acid using water as solvent
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An improved synthesis of salicylic acid using water as solvent can be achieved using the Ullmann-Goldberg reaction conditions in presence of pyridine as cocatalyst. A number of salicylic acids were prepared in good yield.
- Pellon Comdom, Rolando F.,Docampo Palacios, Maite L.
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p. 2055 - 2059
(2007/10/03)
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- Pseudopolymorphs of 3,5-dinitrosalicylic acid
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Seven pseudopolymorphs of 3,5-dinitrosalicylic acid are studied. Four of these (A-D) are obtained from dioxane and their formation is rationalised on the basis of simultaneous O-H ... O and C-H ... O bond formation between the donor-rich solute molecule a
- Kumar, V. S. Senthil,Kuduva, Srinivasan S.,Desiraju, Gautam R.
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p. 1069 - 1073
(2007/10/03)
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- Micellar ctalysis of organic reactions. XXXVIII:. A study of the catalytic effect of micelles of 3-hydroxymethyl-1-tetradecylpyridinium bromide on amide hydrolysis and nucleophilic aromatic substitution
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The preparation of 3-hydroxymethyl-1-tetradecylpyridinium bromide and its use as a catalyst of nucleophilic aromatic substitution and also amide hydrolysis are reported. It was found that the hydroxydehalogenation of nitro-activated aryl halides was much faster in these micelles than in the presence of cetyl(2-hydroxyethyl)dimethylammonium bromide. It was concluded that the increased catalysis of nucleophilic aromatic substitution by this micelle was due to a faster decomposition of the aryl micellar ether which must occur before the phenolate product is released. No such difference in the two micelles was found for amide or thioamide hydrolysis since in these reactions the product amine is produced in the first step of the reaction and decomposition of the acylated micelle is not required in the rate-determining step of the reaction.
- Broxton, Trevor J.
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p. 541 - 543
(2007/10/03)
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- The Effects of Single- and Twin-Tailed Ionic Surfactants on the Hydroxy- dehalogenation of Charged Substrates
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Reactions of OH- with 4-chloro-3,5-dinitrobenzoic and 2-chloro-3,5-dinitrobenzoic acids have been examined in solutions of cetyltrimethylammonium chloride, bromide and hydroxide, bis(dodecyl)dimethylammonium chloride, and bis(tetradecyl)dimethylammonium chloride.Rate effects were analysed quantitatively in terms of the distribution of reactants between water and the colloidal particles.It has been found that twin-tailed ionic surfactants better distinguish between favourable and unfavourable orientations of substrate molecules within micellar aggregates than do single-tailed ionic surfactants.
- Cipiciani, Antonio,Primieri, Stefania
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p. 1505 - 1509
(2007/10/02)
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- Micellar Catalysis of Organic Reactions. 29. SNAr Reactions with Neutral Nucleophiles
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The reaction of a number of nitroactivated halobenzoates (1-4) with some primary and tertiary amines has been studied in the presence of micelles of cetyltrimethylammonium bromide (CTAB) and in water.With primary amines aminodehalogenation was observed, and it was found that if the reaction center of the aromatic substrate was located at the micelle water interface (compounds 1 and 2) the reaction was catalyzed by CTAB, but if the reaction center was more deeply buried into the micelle interior the reaction with aniline was inhibited by micelles of CTAB (compounds 3 and 4), while CTAB had little effecton the reaction of n-propylamine with compound 4.With the more sterically bulky tertiary amines, hydroxydehalogenation was observed rather than aminodehalogenation, and the reactions were all catalyzed by CTAB, but for the substrate with a more deeply buried reaction center (compound 4), the catalysis was stronger than for that with a reaction center at or near the interface (compound 2).The mechanism of hydroxydehalogenation was found to be specific base catalysis by the tertiary amine.Thus, the observation of micellar catalysis or inhibition of these reactions depends on the orientation of the organic substrate within the micellar aggreagate and the reaction product, amine or phenol, depends on the streric bulk of the amine at least for the compounds investigated here which contain two substituents ortho to the reaction center.
- Broxton, Trevor J.,Marcou, Victor
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p. 1041 - 1044
(2007/10/02)
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- Nucleophilic Aromatic Substitution with Elimination in a Dinitrosalicylic Lactone or Ester via Meisenheimer Intermediates
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The dinitro lactone 1b and dinitro ester 2b derived from salicylic acid undergo SNAr reactions in the presence of a variety of N-,O-, and S-nucleophiles.Substitution is accompanied by elimination of the β-ethylenoxy group, the ester group in no
- Jones, Paul R.,Rothenberger, Scott D.
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p. 3016 - 3023
(2007/10/02)
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- Synthesis and Spectral Characterization of Blue Dyes of the Benzene Series
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53 Donor-acceptor substituted azo dyes of the benzene series were prepared by diazonium-coupling reactions (1a-s) or halogen-cyanide exchange (->2a-x, 3a-j).Described are the preparation of the amines 4a-m and the coupling compounds 5a-t and the procedure of diazotizing and coupling.The colouristic and spectroscopic data show that compounds of the general formula 1 are excellent brilliant blue azo dyes usefull for dyeing polyester material.
- Thiel, W.,Mayer, R.,Jauer, E.-A.,Modrow, H.,Dost, H.
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p. 497 - 514
(2007/10/02)
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- The Influence of Intramolecular Hydrogen Bonding on Proton-Transfer Reactions. A Temperature-Jump Study of Acid-Base Reactions Involving Substituted Salicylic Acids
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The temperature-jump relaxation technique has been used to study the kinetics of proton transfer between salicylic acid derivatives (3,5-dinitrosalicylic acid, DNSA, and thiosalicylic acid, TSA) and a second donor/acceptor system (ammonia or cacodylic acid).Depending on the system, the investigations have been carried out between pH 6.0 and 9.0.The concentration dependencies of the observed relaxation time demonstrate that not only the direct proton-transfer process but also the hydrolytic or protolytic pathway, respectively, contribute to the overall reaction under the given conditions.The rate constants for proton transfer from the monoprotonated salicylate anions to the acceptors NH3, cacodylate-, and OH- are far below the diffusion-controlled values, even if these reactions are thermodinamically favored.This decrease in reactivity indicates that the proton to be transferred is engaged in an internal H bond in the mononegative salicylate anions.The strength of the internal H bond is much lower in TSA than in DNSA.
- Diebler, H.,Secco, F.,Venturini, M.
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p. 4229 - 4232
(2007/10/02)
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