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Michael I Page - One of the best experts on this subject based on the ideXlab platform.
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Micelle Formation in Liquid Ammonia.
The Journal of organic chemistry, 2015Co-Authors: Joseph M. Griffin, John H Atherton, Michael I PageAbstract:Perfluorinated long chain alkyl amides aggregate in Liquid Ammonia with increasing concentration which reflects micelle-type formation based on changes in 19F NMR chemical shifts. The critical micelle concentrations (cmc) decrease with increasing chain length and give Kleven parameters A = 0.18 and B = 0.19. The micelles catalyze the ammonolysis of esters in Liquid Ammonia. The corresponding perfluorinated long chain alkyl carboxylates form ion pairs in Liquid Ammonia, but the equilibrium dissociation constants indicate favorable interactions between the chains in addition to the electrostatic forces. These perfluorinated carboxylates form micelles in aqueous solution, and their cmc’s generate a Kleven B-value = 0.52 compared with 0.30 for the analogous alkyl carboxylates. The differences in hydrophobicity of CH2 and CF2 units in water and Liquid Ammonia are discussed, as is the possible relevance to life forms in Liquid Ammonia.
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The ammonolysis of esters in Liquid Ammonia
Journal of Physical Organic Chemistry, 2013Co-Authors: Joseph M. Griffin, John H Atherton, Michael I PageAbstract:The rates of ammonolysis of alkyl benzoate and phenylacetate esters in Liquid Ammonia increase with the acidity of the leaving group alcohol and show relatively large Bronsted βlg values of −1.18 and −1.34, respectively, when plotted against the aqueous pKa of the alcohol. The Bronsted βlg obtained using the pKa of the leaving group alcohol in Liquid Ammonia is significantly reduced to ~ −0.7, which indicates that the rate-limiting step involves a reaction of the tetrahedral intermediate with little C–OR bond fission in the transition state. The solvolysis reaction is subject to significant catalysis by ammonium ion, which, surprisingly, generates a similar Bronsted βlg indicating little interaction between the ammonium ion and the leaving group. It is concluded that the rate-limiting step for the ammonium-ion-catalysed solvolysis of alkyl esters in Liquid Ammonia is the diffusion-controlled protonation of the zwitterionic tetrahedral intermediate T+- to give T+, which is rapidly deprotonated to give T0 which is compatible with the rate-limiting step for the uncatalysed reaction being the formation of the neutral T0 by a ‘proton switch
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Copper catalysed azide–alkyne cycloaddition (CuAAC) in Liquid Ammonia
Organic & biomolecular chemistry, 2012Co-Authors: John H Atherton, Michael I PageAbstract:Copper(I) catalysed azide–alkyne cycloaddition reactions (CuAAC) occur smoothly in Liquid Ammonia (LNH3) at room temperature to give exclusively 1,4-substituted 1,2,3-triazoles with excellent yields (up to 99%). The CuAAC reactions in Liquid Ammonia require relatively small amounts of copper(I) catalyst (0.5 mole%) compared with that in conventional solvents. The product can be obtained conveniently by simply evaporation of Ammonia, indicating its potential application in industry. The rate of the CuAAC reaction in Liquid Ammonia shows a second order dependence on the copper(I) concentration and the reaction occurs only with terminal alkynes. Deuterium exchange experiments with phenyl acetylene-d1 show that the acidity of the alkyne is increased at least 1000-fold with catalytic amounts of copper(I) in Liquid Ammonia. The mechanism of the CuAAC reaction in Liquid Ammonia is discussed.
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copper i catalyzed amination of aryl halides in Liquid Ammonia
Journal of Organic Chemistry, 2012Co-Authors: John H Atherton, Michael I PageAbstract:The amination of aryl halides in Liquid Ammonia (LNH(3)) is catalyzed by a copper(I) salt/ascorbate system to yield primary aromatic amines in good to excellent yields. The low concentrations of catalyst required and the ease of product isolation suggest that this process has potential industrial applications. Commonly used ligands for analogous metal-catalyzed reactions are not effective. The rate of amination of iodobenzene in Liquid Ammonia is first order in copper(I) catalyst concentration. The small Hammett ρ = 0.49 for the amination of 4-substituted iodobenzenes in Liquid Ammonia at 25 °C indicates that the C-I bond is not significantly broken in the transition state structure and that there is a small generation of negative charge in the aryl ring, which is compatible with the oxidative addition of the copper ion being rate limiting.
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Organic reactivity in Liquid Ammonia
Organic & biomolecular chemistry, 2012Co-Authors: John H Atherton, Michael I PageAbstract:Liquid Ammonia is a useful solvent for many organic reactions including aliphatic and aromatic nucleophilic substitution and metal-ion catalysed reactions. The acidity of acids is modified in Liquid Ammonia giving rise to differences from conventional solvents. The ionisation constants of phenols and carbon acids are the product of those for ion-pair formation and dissociation to the free ions. There is a linear relationship between the pKa of phenols and carbon acids in Liquid Ammonia and those in water of slope 1.68 and 0.7, respectively. Aminium ions exist in their unprotonated free base form in Liquid Ammonia. The rates of solvolysis and aminolysis by neutral amines of substituted benzyl chlorides in Liquid Ammonia show little or no dependence upon ring substituents, in stark contrast with the hydrolysis rates of substituted benzyl halides in water which vary 107 fold. However, the rates of the reaction of phenoxide ions and amine anions with 4-substituted benzyl chlorides gives a Hammett ρ = 1.1 and 0.93, respectively. The second order rate constants for the substitution of benzyl chlorides by neutral and anionic amines show a single Bronsted βnuc = 0.21 whereas those for substituted phenoxide ions generate a Bronsted βnuc = 0.40. The rates of aromatic nucleophilic substitution reactions in Liquid Ammonia are much faster than those in protic solvents indicating that Liquid Ammonia behaves like a typical dipolar aprotic solvent in its solvent effects on organic reactions. Nitrofluorobenzenes (NFB) readily undergo solvolysis in Liquid Ammonia but oxygen nucleophiles, such as alkoxide and phenoxide ions, displace the fluorine of 4-NFB in Liquid Ammonia to give the corresponding substitution product with little or no competing solvolysis product. The Bronsted βnuc for the reaction of 4-NFB with para-substituted phenoxides is 0.91, indicative that the decomposition of the Meisenheimer σ-intermediate is rate limiting. The aminolysis of 4-NFB occurs without general base catalysis by the amine and the second order rate constants generate a Bronsted βnuc of 0.36, which is also interpreted in terms of rate limiting breakdown of the Meisenheimer σ-intermediate.
John H Atherton - One of the best experts on this subject based on the ideXlab platform.
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Micelle Formation in Liquid Ammonia.
The Journal of organic chemistry, 2015Co-Authors: Joseph M. Griffin, John H Atherton, Michael I PageAbstract:Perfluorinated long chain alkyl amides aggregate in Liquid Ammonia with increasing concentration which reflects micelle-type formation based on changes in 19F NMR chemical shifts. The critical micelle concentrations (cmc) decrease with increasing chain length and give Kleven parameters A = 0.18 and B = 0.19. The micelles catalyze the ammonolysis of esters in Liquid Ammonia. The corresponding perfluorinated long chain alkyl carboxylates form ion pairs in Liquid Ammonia, but the equilibrium dissociation constants indicate favorable interactions between the chains in addition to the electrostatic forces. These perfluorinated carboxylates form micelles in aqueous solution, and their cmc’s generate a Kleven B-value = 0.52 compared with 0.30 for the analogous alkyl carboxylates. The differences in hydrophobicity of CH2 and CF2 units in water and Liquid Ammonia are discussed, as is the possible relevance to life forms in Liquid Ammonia.
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The ammonolysis of esters in Liquid Ammonia
Journal of Physical Organic Chemistry, 2013Co-Authors: Joseph M. Griffin, John H Atherton, Michael I PageAbstract:The rates of ammonolysis of alkyl benzoate and phenylacetate esters in Liquid Ammonia increase with the acidity of the leaving group alcohol and show relatively large Bronsted βlg values of −1.18 and −1.34, respectively, when plotted against the aqueous pKa of the alcohol. The Bronsted βlg obtained using the pKa of the leaving group alcohol in Liquid Ammonia is significantly reduced to ~ −0.7, which indicates that the rate-limiting step involves a reaction of the tetrahedral intermediate with little C–OR bond fission in the transition state. The solvolysis reaction is subject to significant catalysis by ammonium ion, which, surprisingly, generates a similar Bronsted βlg indicating little interaction between the ammonium ion and the leaving group. It is concluded that the rate-limiting step for the ammonium-ion-catalysed solvolysis of alkyl esters in Liquid Ammonia is the diffusion-controlled protonation of the zwitterionic tetrahedral intermediate T+- to give T+, which is rapidly deprotonated to give T0 which is compatible with the rate-limiting step for the uncatalysed reaction being the formation of the neutral T0 by a ‘proton switch
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Copper catalysed azide–alkyne cycloaddition (CuAAC) in Liquid Ammonia
Organic & biomolecular chemistry, 2012Co-Authors: John H Atherton, Michael I PageAbstract:Copper(I) catalysed azide–alkyne cycloaddition reactions (CuAAC) occur smoothly in Liquid Ammonia (LNH3) at room temperature to give exclusively 1,4-substituted 1,2,3-triazoles with excellent yields (up to 99%). The CuAAC reactions in Liquid Ammonia require relatively small amounts of copper(I) catalyst (0.5 mole%) compared with that in conventional solvents. The product can be obtained conveniently by simply evaporation of Ammonia, indicating its potential application in industry. The rate of the CuAAC reaction in Liquid Ammonia shows a second order dependence on the copper(I) concentration and the reaction occurs only with terminal alkynes. Deuterium exchange experiments with phenyl acetylene-d1 show that the acidity of the alkyne is increased at least 1000-fold with catalytic amounts of copper(I) in Liquid Ammonia. The mechanism of the CuAAC reaction in Liquid Ammonia is discussed.
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copper i catalyzed amination of aryl halides in Liquid Ammonia
Journal of Organic Chemistry, 2012Co-Authors: John H Atherton, Michael I PageAbstract:The amination of aryl halides in Liquid Ammonia (LNH(3)) is catalyzed by a copper(I) salt/ascorbate system to yield primary aromatic amines in good to excellent yields. The low concentrations of catalyst required and the ease of product isolation suggest that this process has potential industrial applications. Commonly used ligands for analogous metal-catalyzed reactions are not effective. The rate of amination of iodobenzene in Liquid Ammonia is first order in copper(I) catalyst concentration. The small Hammett ρ = 0.49 for the amination of 4-substituted iodobenzenes in Liquid Ammonia at 25 °C indicates that the C-I bond is not significantly broken in the transition state structure and that there is a small generation of negative charge in the aryl ring, which is compatible with the oxidative addition of the copper ion being rate limiting.
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Organic reactivity in Liquid Ammonia
Organic & biomolecular chemistry, 2012Co-Authors: John H Atherton, Michael I PageAbstract:Liquid Ammonia is a useful solvent for many organic reactions including aliphatic and aromatic nucleophilic substitution and metal-ion catalysed reactions. The acidity of acids is modified in Liquid Ammonia giving rise to differences from conventional solvents. The ionisation constants of phenols and carbon acids are the product of those for ion-pair formation and dissociation to the free ions. There is a linear relationship between the pKa of phenols and carbon acids in Liquid Ammonia and those in water of slope 1.68 and 0.7, respectively. Aminium ions exist in their unprotonated free base form in Liquid Ammonia. The rates of solvolysis and aminolysis by neutral amines of substituted benzyl chlorides in Liquid Ammonia show little or no dependence upon ring substituents, in stark contrast with the hydrolysis rates of substituted benzyl halides in water which vary 107 fold. However, the rates of the reaction of phenoxide ions and amine anions with 4-substituted benzyl chlorides gives a Hammett ρ = 1.1 and 0.93, respectively. The second order rate constants for the substitution of benzyl chlorides by neutral and anionic amines show a single Bronsted βnuc = 0.21 whereas those for substituted phenoxide ions generate a Bronsted βnuc = 0.40. The rates of aromatic nucleophilic substitution reactions in Liquid Ammonia are much faster than those in protic solvents indicating that Liquid Ammonia behaves like a typical dipolar aprotic solvent in its solvent effects on organic reactions. Nitrofluorobenzenes (NFB) readily undergo solvolysis in Liquid Ammonia but oxygen nucleophiles, such as alkoxide and phenoxide ions, displace the fluorine of 4-NFB in Liquid Ammonia to give the corresponding substitution product with little or no competing solvolysis product. The Bronsted βnuc for the reaction of 4-NFB with para-substituted phenoxides is 0.91, indicative that the decomposition of the Meisenheimer σ-intermediate is rate limiting. The aminolysis of 4-NFB occurs without general base catalysis by the amine and the second order rate constants generate a Bronsted βnuc of 0.36, which is also interpreted in terms of rate limiting breakdown of the Meisenheimer σ-intermediate.
Lina Lin - One of the best experts on this subject based on the ideXlab platform.
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Cationic modification of ramie fibers in Liquid Ammonia
Cellulose, 2018Co-Authors: Yingjie Cai, Su Siwei, Rahul Navik, Shu Wen, Xiongyi Peng, Nahid Pervez, Lina LinAbstract:Anhydrous Liquid Ammonia was used as a solvent for the cationic modification of ramie fiber using 2, 3-epoxypropytrimethylammonium chloride (EPTAC). The processing parameters, including treatment temperature, treatment time, concentration of EPTAC, and concentration of NaOH were schematically investigated in order to control the properties of the fibers. The optimum parameters for cationic modification in Liquid Ammonia were analyzed through zeta potential measurement. The modified fibers were dyed in different conditions after modification, and the dyeing behaviors such as exhaustion and fixation properties were carefully examined. The modified fiber in Liquid Ammonia consisted of a higher number of cationic groups on the fibers compared to the fibers modified in water. The cationization reaction in Liquid Ammonia significantly decreased the crystallinity and the crystallite orientation of the resultant fibers. The decreased crystallinity slightly decreased the thermal resistance and tensile strength but increased the elongation ability of the fibers. The Liquid Ammonia cationic modification process turned the appearance of fibers from rough to smooth and lustrous due to swelling of fibers in the solvent. The exhaustion, fixation and wash fastness property of the fibers were improved after the cationic modification in Liquid Ammonia.
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Reactive dyeing of ramie yarn washed by Liquid Ammonia
Cellulose, 2017Co-Authors: Yingjie Cai, Su Siwei, Rahul Navik, Xiongyi Peng, Lou Kankan, Qiang Wang, Ping Zhang, Lina LinAbstract:The washing efficiency of water, nonionic soap solution, reflux solution, pure Liquid Ammonia (99.99%), and solvated Liquid Ammonia was studied on dyed ramie yarns. The ramie yarn samples were dyed with a 2% on weight of fiber (o.w.f) shade with five types of reactive dye by the classical exhaustion method. The washing performances of these solvents were quantified by the dye removal rate, the color uniformity, and the color fastness properties (washing, rubbing, and lightness). Furthermore, the influence of these wash methods on the physical properties of the final yarn samples including shrinkage, tensile strength, and elongation was schematically examined. The results of these measurements revealed that the dye removal rates during the washing in pure Liquid Ammonia and solvated Liquid Ammonia were lower than the yarn washed in water, soap solutions, or reflux solutions. The color uniformity (expressed as the standard deviation of K/S values for all dyed ramie yarns) was within the acceptable limits with the satisfactory color fastness levels. The shrinkage values of yarns that were washed in the pure Liquid Ammonia and the solvated Liquid Ammonia were both similar (9.0%) and considerably higher than the samples washed in water (1.8%), soap solution (2.4%), or reflux solution (2.6%). The tensile strength and the elongation of the resultant yarns improved significantly when the samples washed in pure Liquid Ammonia. The yarns that were washed in the solvated Liquid Ammonia solutions had decreased tensile strength and elongation. The cause of the decrease was determined by the XRD measurements, which confirmed that the crystallinity, and the orientation of these fibers decreased dramatically after being washed in the Ammonia system solutions. The samples that were washed in the Liquid Ammonia had a smoother surface morphology than the other washing processes.
Yingjie Cai - One of the best experts on this subject based on the ideXlab platform.
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Cationic modification of ramie fibers in Liquid Ammonia
Cellulose, 2018Co-Authors: Yingjie Cai, Su Siwei, Rahul Navik, Shu Wen, Xiongyi Peng, Nahid Pervez, Lina LinAbstract:Anhydrous Liquid Ammonia was used as a solvent for the cationic modification of ramie fiber using 2, 3-epoxypropytrimethylammonium chloride (EPTAC). The processing parameters, including treatment temperature, treatment time, concentration of EPTAC, and concentration of NaOH were schematically investigated in order to control the properties of the fibers. The optimum parameters for cationic modification in Liquid Ammonia were analyzed through zeta potential measurement. The modified fibers were dyed in different conditions after modification, and the dyeing behaviors such as exhaustion and fixation properties were carefully examined. The modified fiber in Liquid Ammonia consisted of a higher number of cationic groups on the fibers compared to the fibers modified in water. The cationization reaction in Liquid Ammonia significantly decreased the crystallinity and the crystallite orientation of the resultant fibers. The decreased crystallinity slightly decreased the thermal resistance and tensile strength but increased the elongation ability of the fibers. The Liquid Ammonia cationic modification process turned the appearance of fibers from rough to smooth and lustrous due to swelling of fibers in the solvent. The exhaustion, fixation and wash fastness property of the fibers were improved after the cationic modification in Liquid Ammonia.
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Reactive dyeing of ramie yarn washed by Liquid Ammonia
Cellulose, 2017Co-Authors: Yingjie Cai, Su Siwei, Rahul Navik, Xiongyi Peng, Lou Kankan, Qiang Wang, Ping Zhang, Lina LinAbstract:The washing efficiency of water, nonionic soap solution, reflux solution, pure Liquid Ammonia (99.99%), and solvated Liquid Ammonia was studied on dyed ramie yarns. The ramie yarn samples were dyed with a 2% on weight of fiber (o.w.f) shade with five types of reactive dye by the classical exhaustion method. The washing performances of these solvents were quantified by the dye removal rate, the color uniformity, and the color fastness properties (washing, rubbing, and lightness). Furthermore, the influence of these wash methods on the physical properties of the final yarn samples including shrinkage, tensile strength, and elongation was schematically examined. The results of these measurements revealed that the dye removal rates during the washing in pure Liquid Ammonia and solvated Liquid Ammonia were lower than the yarn washed in water, soap solutions, or reflux solutions. The color uniformity (expressed as the standard deviation of K/S values for all dyed ramie yarns) was within the acceptable limits with the satisfactory color fastness levels. The shrinkage values of yarns that were washed in the pure Liquid Ammonia and the solvated Liquid Ammonia were both similar (9.0%) and considerably higher than the samples washed in water (1.8%), soap solution (2.4%), or reflux solution (2.6%). The tensile strength and the elongation of the resultant yarns improved significantly when the samples washed in pure Liquid Ammonia. The yarns that were washed in the solvated Liquid Ammonia solutions had decreased tensile strength and elongation. The cause of the decrease was determined by the XRD measurements, which confirmed that the crystallinity, and the orientation of these fibers decreased dramatically after being washed in the Ammonia system solutions. The samples that were washed in the Liquid Ammonia had a smoother surface morphology than the other washing processes.
Rahul Navik - One of the best experts on this subject based on the ideXlab platform.
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Cationic modification of ramie fibers in Liquid Ammonia
Cellulose, 2018Co-Authors: Yingjie Cai, Su Siwei, Rahul Navik, Shu Wen, Xiongyi Peng, Nahid Pervez, Lina LinAbstract:Anhydrous Liquid Ammonia was used as a solvent for the cationic modification of ramie fiber using 2, 3-epoxypropytrimethylammonium chloride (EPTAC). The processing parameters, including treatment temperature, treatment time, concentration of EPTAC, and concentration of NaOH were schematically investigated in order to control the properties of the fibers. The optimum parameters for cationic modification in Liquid Ammonia were analyzed through zeta potential measurement. The modified fibers were dyed in different conditions after modification, and the dyeing behaviors such as exhaustion and fixation properties were carefully examined. The modified fiber in Liquid Ammonia consisted of a higher number of cationic groups on the fibers compared to the fibers modified in water. The cationization reaction in Liquid Ammonia significantly decreased the crystallinity and the crystallite orientation of the resultant fibers. The decreased crystallinity slightly decreased the thermal resistance and tensile strength but increased the elongation ability of the fibers. The Liquid Ammonia cationic modification process turned the appearance of fibers from rough to smooth and lustrous due to swelling of fibers in the solvent. The exhaustion, fixation and wash fastness property of the fibers were improved after the cationic modification in Liquid Ammonia.
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Reactive dyeing of ramie yarn washed by Liquid Ammonia
Cellulose, 2017Co-Authors: Yingjie Cai, Su Siwei, Rahul Navik, Xiongyi Peng, Lou Kankan, Qiang Wang, Ping Zhang, Lina LinAbstract:The washing efficiency of water, nonionic soap solution, reflux solution, pure Liquid Ammonia (99.99%), and solvated Liquid Ammonia was studied on dyed ramie yarns. The ramie yarn samples were dyed with a 2% on weight of fiber (o.w.f) shade with five types of reactive dye by the classical exhaustion method. The washing performances of these solvents were quantified by the dye removal rate, the color uniformity, and the color fastness properties (washing, rubbing, and lightness). Furthermore, the influence of these wash methods on the physical properties of the final yarn samples including shrinkage, tensile strength, and elongation was schematically examined. The results of these measurements revealed that the dye removal rates during the washing in pure Liquid Ammonia and solvated Liquid Ammonia were lower than the yarn washed in water, soap solutions, or reflux solutions. The color uniformity (expressed as the standard deviation of K/S values for all dyed ramie yarns) was within the acceptable limits with the satisfactory color fastness levels. The shrinkage values of yarns that were washed in the pure Liquid Ammonia and the solvated Liquid Ammonia were both similar (9.0%) and considerably higher than the samples washed in water (1.8%), soap solution (2.4%), or reflux solution (2.6%). The tensile strength and the elongation of the resultant yarns improved significantly when the samples washed in pure Liquid Ammonia. The yarns that were washed in the solvated Liquid Ammonia solutions had decreased tensile strength and elongation. The cause of the decrease was determined by the XRD measurements, which confirmed that the crystallinity, and the orientation of these fibers decreased dramatically after being washed in the Ammonia system solutions. The samples that were washed in the Liquid Ammonia had a smoother surface morphology than the other washing processes.