- Quantitative Assessment of Solvent-Sorting Effects. 1. Menschutkin Reaction in Mixed Solvents
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The second-order rate constant kapp for the reaction between (C2H5)3N and CH3I has beeen determined at 30.0 deg C in cyclohexane and in mixtures of cyclohexane with variable amounts (up to ca. 0.3 M) of the following cosolvents (S): N,N-dimethylacetamide, cyclohexanecarbonitrile, cyclohexyl methyl ketone, butanone, tetrahydrofuran, ethyl acetate, cyclohexyl chloride, methyl cyclohexanecarboxylate, cyclohexyl methyl ether, dibutyl ether, nitrobenzene, N,N-dimethylbenzamide, benzonitrile, acetophenone, benzophenone, methyl benzoate, diphenylmethane, anisole, chlorobenzene, fluorobenzene, 1,2-diphenylethane, triphenylmethane, benzene, 1,4-dichlorobenzene, toluene, and p-xylene.Within the limits of experimental error, the following have been found: (1) The activity coefficients of the reagents are practically unaffected by the added cosolvent. (2) For low cosolvent concentrations, kapp is related to the concentration of S by the equation kapp = k0 + kc, where k0 is the reaction rate in pure cyclohexane. (3) In all cases, the catalytic effect of S is quite large: it amounts to ca. 50percent of the lowering of the activation free energy of the reaction, observed on going from pure cyclohexane to pure S. (4) This major effect is largely underestimated by the Onsager-Kirkwood model. (5) The catalytic efficiency of aromatic cosolvents of low or zero dipolarity is over 1 order of magnitude larger than predicted by this model.This is traced to electrostatic interactions involving higher multipoles and to London forces. (6) Although a fraction of the catalytic effect can be attributed to a "general dielectric" contribution, these and other results strongly suggest that this reaction can proceed through a true termolecular channel.
- Abboud, Jose-Luis M.,Douhal, Abderrazzak,Arin, Maria Jesus,Diez, Maria Teresa,Homan, Hamid,Guiheneuf, Georges
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Read Online
- Method of producing oxyborate Tetracyanobicyclo (by machine translation)
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PROBLEM TO BE SOLVED: To provide a method for efficiently producing a tetracyanoborate compound (VI). SOLUTION: A boron compound (for example, boron trichloride) and an ammonium derivative having a halogenide ion as a counter anion are mixed in xylol; then, a trialkylsilyl cyanide is added and reacted; the reaction system is subjected to a treatment with hydrogen peroxide, and an extraction treatment with butyl acetate; and butyl acetate is distilled out to obtain a tetracyanoborate compound represented by formula (VI) wherein [Kt]m+ is an ammonium cation; and m=1. In the formula, [Kt]m+ denotes an organic cation or an inorganic cation; and m denotes an integer of 1 to 3. COPYRIGHT: (C)2012,JPO&INPIT
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Paragraph 0080
(2016/12/26)
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- A new synthesis of Entacapone and report on related studies
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A new synthesis of the catechol-O-methyltransferase (COMT) inhibitor, entacapone (E-isomer) has been achieved under mild conditions by amine-mediated demethylation of the precursor 2-Cyano-3-(3- hydroxy-4-methoxy-5-nitrophenyl) prop-2-eneamide, wherein the methoxyl group adjacent to a nitro group gets demethylated under nucleophilic attack. Similar demethylation was achieved on ethyl 2-cyano-3-(3, 4-dimethoxy-5-nitrophenyl) prop-2-enoate, 2-cyano-3-(3,4-dimethoxy-5-nitrophenyl)-N,N-diethylprop-2-enamide, ethyl 2-cyano-3-(3-hydroxy-4-methoxy-5-nitrophenyl) prop-2-enoate and ethyl 2-cyano-3-(4-methoxy-3-nitrophenyl) prop-2-enoate. The scope of demethylation has been studied. Analogues of ethyl 2-cyano-3-(3, 4-dimethoxy-5-nitrophenyl) prop-2-enoate wherein a methoxyl group is not adjacent to a NO 2 group are unaffected and phenolic derivatives yield the amine salts. Entacapone has been converted to salts with organic bases. The crystal structure of the isomer of entacapone (Z-isomer), a significant human metabolite of E-isomer has been established. NMR methods for deriving E and Z geometry and other similar molecules have been successfully established, mainly by studying the proton coupled 13C spectra. Preliminary studies reveal in vitro activity for some compounds against tuberculosis (TB) and dengue. [Figure not available: see fulltext.]
- Harisha, Attimogae Shivamurthy,Nayak, Suresh Parameshwar,Pavan,Shridhara,Sundarraja Rao,Rajendra,Pari, Koteppa,Sivaramkrishnan,Guru Row,Nagarajan, Kuppuswamy
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p. 1977 - 1991
(2015/12/30)
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- The potential of methylsiloxanes as solvents for synthetic chemistry applications
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The potential use of volatile methylsiloxanes (VMSs) as solvents for chemicals synthesis has been explored. Assessment of the environmental impact of these VMS solvents is made and found to be significantly lower than those of the non-polar organic solvents that they have the potential to replace. The polarities of the VMSs, as expressed by empirical polarity measurements, and miscibilities with other liquids are found to be similar to those of alkane solvents. Finally, some uses of VMSs as solvents for both organic and inorganic transformations are described. The VMSs provide environmentally more sustainable (greener) alternatives to the nonpolar solvents that they have the potential to replace.
- Ab Rani, Mohd Azri,Borduas, Nadine,Colquhoun, Victoria,Hanley, Robert,Johnson, Henry,Larger, Solene,Lickiss, Paul D.,Llopis-Mestre, Veronica,Luu, Selina,Mogstad, Martin,Oczipka, Philipp,Sherwood, James R.,Welton, Tom,Xing, Jun-Yi
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p. 1282 - 1296
(2014/03/21)
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- Quaternary ammonium ions can externally block voltage-gated K+ channels. Establishing a theoretical and experimental model that predicts KDS and the selectivity of K+ over Na+ ions
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The physicochemical basis for the high ion selectivity of potassium channels is poorly understood. In the present studies, external blockade of cloned voltage-gated potassium channels with alkyl quaternary ammonium ions are analyzed from a model derived from theory and experimental data. Atomic mass units, electrostatic potential residing on the nitrogen atom, the COSMO van der Waals solvent accessible surface, the Onsager solvation model, and the isodensity PCM solvation model are computed at the semi-empirical and the ab initio levels of theory. A structure-activity relationship (SAR) exists between the calculated values and the experimentally obtained KD (mM). The SAR model gives us KD predictions and when K+ and Na+ are incorporated into the model, it dramatically predicts the selectivity of K+ over Na+ ions.
- Wempe
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- Pressure effect on the rate and equilibrium constants of the Diels- Alder reaction 9-chloroanthracene with tetracyanoethylene
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The pressure effect on the forward and backward rate constants and equilibrium constants of the Diels-Alder reaction of 9-chloroanthracene with tetracyanoethylene has been investigated in 1,2-dichloroethane up to 1000 kgcm-2 at 298.15 K. The reaction volume obtained from the pressure effect on equilibrium (-20.6 ±1.5 cm3 mol-1) and as difference of activation volumes of forward (-28.5±1.5) and backward (-6.5 ± 0.5) reaction (- 22.0±1.5 cm3 mol-1) are in agreement with partial molar volume difference of adduct (255.5±1.5) {diene (170.7±0.5) and dienophile (107.8±0.2)} giving -23.0 ±2 cm3 mol-1.
- Kiselev, Vladimir D.,Kashaeva, Elena A.,Konovalov, Alexander I.
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p. 1153 - 1162
(2007/10/03)
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- Synthesis of bridgehead nitrogen heterocycles via cyclization of α- ammonio 5-hexenyl radicals
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Ring-closure of the 2,2-dimethyl-2-azonia-5-hexenyl radical (4) proceeds smoothly and efficiently to give the 5-exo isomer essentially quantitatively, in accordance with predictions based on MP4SDTQ/6-31G* ab initio calculations on the thermodynamic stability of α-ammonio radicals. The corresponding 5-hexynyl radical species 15 and its 6-phenyl derivative 19 display similar behavior affording the analogous 5-exo-3- methylenepyrrolidinium salts in high yield. In none of these cases were the products of reduction were detected. All of the radical intermediates were generated conveniently by treatment of the iodomethyl and/or phenylselenomethyl salts with tributyltin hydride. Application of this procedure to monocyclic precursors such as 1-methyl-1-iodomethyl-4-methylene- 1-azoniacyclohexyl iodide (31) provided an attractive entry into quaternary derivatives of the 1-azabicyclo[2.2.1]heptyl system in good yield via a three-step sequence from 1-methylpiperidone. Dequaternization of the bicyclic salts so obtained unexpectedly leads to rupture of one of the rings rather than loss of the N-methyl group. The 1-azabicyclo[2.2.1]heptane could be accessed readily via tin hydride-induced cyclization of the corresponding N- phenylethylammonium salt 54, followed by Hofmann elimination with potassium tert-butoxide.
- Della, Ernest W.,Smith, Paul A.
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p. 1798 - 1806
(2007/10/03)
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- SIGNIFICANCE TEST OF REFRACTIVE INDEX OF SOLVENT IN EVALUATION OF EFFECT OF MEDIUM ON RATES OF QUATERNIZATION REACTIONS OF METHYL IODIDE WITH AMINES
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The rate constants have been measured of the reactions of methyl iodide with triethylamine (I) and tributylamine (III) at 293 K in twelve aprotic solvents, methyl iodide with tripropylamine (II) at 293, 313, 323, and 333 K in fifteen solvents differing greatly in their dipole moments, relative permittivities, and refractive indexes, and diiodomethane with tripropylamine in diiodomethane at 293 K (k1 = 2.1 * 10-5 s-1).The aprotic solvents predominantly affect the activation entropy which for the reaction of II varies from -200 J mol-1 s-1 (in cyclohexane) to-108 J mol-1 s-1 (in diiodomethane).The activation enthalpy of the reaction of methyl iodide with tripropylamine (II) is only little affected by aprotic solvents, a significant increase in activation enthalpy has been observed in the case of amphiprotic solvents.The evaluation of effect of medium on the rate constants of the above-mentioned reactions by means of the Kirkwood functions of relative permittivity and refractive index has shown a significant contribution of the refractive index of solvent which is comparable with the effect of relative permittivity.
- Nevecna, Tat'jana,Bekarek, Vojtech
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p. 180 - 184
(2007/10/02)
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- Reaction of Triphenylphosphine with Methyl Iodide. Transfer Thermodynamic Quantities and Various Extended Broensted Treatments
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The enthalpies of solution and the apparent molar volumes have been determined in various solvents for the reactants and products of the reaction of triphenylphosphine with methyl iodide in various solvents.The rate constants, activation enthalpies, activation volumes, and the reaction enthalpies have also been determined for these reactions.Three types of extended Broensted plots,i.e., ΔV(excit.) versus ΔV0, δΔH(excit.) versus δΔH0 with solvent variation, and ΔH(excit.) versus ΔH0 with variation of the nucleophile, do not show any general pattern of behaviour.The physical meaning of the various Broensted slopes is discussed.
- Kondo, Yasuhiko,Zanka, Atsuhiko,Kusabayashi, Shigekazu
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p. 827 - 832
(2007/10/02)
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- Menschutkin Reaction of Triethylamine and of Pyridine with Methyl Iodide. Activation Enthalpy versus Activation Entropy Correlations and Extended Broensted Treatments in Acetonitrile-Methanol Mixtures
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The rate constants and activation parameters for the reaction of triethylamine with methyl iodide and for pyridine with methyl iodide have been determined in acetonitrile-methanol mixtures.Enthalpies of solution have also been determined for triethylamine, pyridine, triethylmethylammoniun iodide, and methylpyridinium iodide in the same solvent mixtures.Transfer enthalpies of amines and of quaternary ammonium iodide have been split into constituent terms, i.e., 'more physical' interaction and specific interaction enthapies.Correlations involving activation enthalpy versus activation entropy plots, and extended Broensted plots, yielded straight lines only when corrected for the specific interaction term.
- Kondo, Yasuhiko,Ogasa, Masao,Kusabayashi, Shigekazu
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p. 2093 - 2098
(2007/10/02)
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