scholarly journals Proton Abstraction Mediates Interactions between the Super Photobase FR0-SB and Surrounding Alcohol Solvent

2019 ◽  
Vol 123 (40) ◽  
pp. 8448-8456 ◽  
Author(s):  
Jurick Lahiri ◽  
Mehdi Moemeni ◽  
Jessica Kline ◽  
Babak Borhan ◽  
Ilias Magoulas ◽  
...  
Keyword(s):  
Proton Abstraction ◽  
Alcohol Solvent

Supramolecular fibrous gels with helical pitch tunable by polarity of alcohol solvents

Soft Matter ◽  
2021 ◽  
Author(s):  
Rika Iwaura ◽  
Shiro Komba ◽  
Takahito Kajiki
Keyword(s):  
Helical Pitch ◽  
Alcohol Solvent ◽  
Alcohol Solvents

The pitch of supramolecular helical fibers formed from palmitoylated 1,5-anhydro-d-glucitol was able to be tuned by controlling the polarity of alcohol solvent.

scholarly journals Kinetics and Mechanism of the Change of the 4-Nitrobenzylthio-System into 4,4′-Diformylazoxybenzene in Alkaline Dioxane-Water Media

1985 ◽  
Vol 40 (11) ◽  
pp. 1128-1132
Author(s):  
Y. Riad ◽  
Adel N. Asaad ◽  
G.-A. S. Gohar ◽  
A. A. Abdallah
Keyword(s):  
Acetic Acid ◽  
Sodium Hydroxide ◽  
Rate Constants ◽  
Main Product ◽  
Reaction Medium ◽  
Aqueous Dioxane ◽  
Proton Abstraction ◽  
First Order ◽  
Water Media ◽  
Different Temperatures

Sodium hydroxide reacts with α -(4-nitrobenzylthio)-acetic acid in aqueous-dioxane media to give 4,4'-diformylazoxybenzene as the main product besides 4,4'-dicarboxyazoxybenzene and a nitrone acid. This reaction was kinetically studied in presence of excess of alkali in different dioxane-water media at different temperatures. It started by a fast reversible a-proton abstraction step followed by two consecutive irreversible first-order steps forming two intermediates (α -hydroxy, 4-nitrosobenzylthio)-acetic acid and 4-nitrosobenzaldehyde. The latter underwent a Cannizzaro's reaction, the products of which changed in the reaction medium into 4,4'-diformylazoxybenzene and 4,4'-dicarboxyazoxybenzene. The rate constants and the thermodynamic parameters of the two consecutive steps were calculated and discussed. A mechanism was put forward for the formation of the nitrone acid.Other six 4-nitrobenzyl, aryl sulphides were qualitatively studied and they gave mainly 4,4'-diformylazoxybenzene beside 4,4'-dicarboxyazoxybenzene or its corresponding azo acid.

The Mechanism of Sugar C−H Bond Oxidation by a Flavoprotein Oxidase Occurs by a Hydride Transfer Before Proton Abstraction

2019 ◽  
Vol 25 (17) ◽  
pp. 4460-4471 ◽  
Author(s):  
Thanyaporn Wongnate ◽  
Panida Surawatanawong ◽  
Litavadee Chuaboon ◽  
Narin Lawan ◽  
Pimchai Chaiyen
Keyword(s):  
Hydride Transfer ◽  
Proton Abstraction

scholarly journals l-mandelate dehydrogenase from Rhodotorula graminis: comparisons with the l-lactate dehydrogenase (flavocytochrome b2) from Saccharomyces cerevisiae

1993 ◽  
Vol 290 (1) ◽  
pp. 103-107 ◽  
Author(s):  
O Smékal ◽  
M Yasin ◽  
C A Fewson ◽  
G A Reid ◽  
S K Chapman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactate Dehydrogenase ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Dimensional Structure ◽  
Striking Difference ◽  
Kinetic Properties ◽  
Proton Abstraction ◽  
Rate Determining Step ◽  
Kinetic Isotope

L-Lactate dehydrogenase (L-LDH) from Saccharomyces cerevisiae and L-mandelate dehydrogenase (L-MDH) from Rhodotorula graminis are both flavocytochromes b2. The kinetic properties of these enzymes have been compared using steady-state kinetic methods. The most striking difference between the two enzymes is found by comparing their substrate specificities. L-LDH and L-MDH have mutually exclusive primary substrates, i.e. the substrate for one enzyme is a potent competitive inhibitor for the other. Molecular-modelling studies on the known three-dimensional structure of S. cerevisiae L-LDH suggest that this enzyme is unable to catalyse the oxidation of L-mandelate because productive binding is impeded by steric interference, particularly between the side chain of Leu-230 and the phenyl ring of mandelate. Another major difference between L-LDH and L-MDH lies in the rate-determining step. For S. cerevisiae L-LDH, the major rate-determining step is proton abstraction at C-2 of lactate, as previously shown by the 2H kinetic-isotope effect. However, in R. graminis L-MDH the kinetic-isotope effect seen with DL-[2-2H]mandelate is only 1.1 +/- 0.1, clearly showing that proton abstraction at C-2 of mandelate is not rate-limiting. The fact that the rate-determining step is different indicates that the transition states in each of these enzymes must also be different.

Kinetic and Equilibrium Studies of the Reactions of 2,4,6-Trinitrotoluene and 2,4,6-Trinitrotoluene-d3 with Sodium and Potassium t-Butoxide in t-Butanol

1974 ◽  
Vol 52 (12) ◽  
pp. 2306-2315 ◽  
Author(s):  
Erwin Buncel ◽  
Albert Richard Norris ◽  
Kenneth Edwin Russell ◽  
Harold Wilson
Keyword(s):  
Initial Rate ◽  
Forward Rate ◽  
Specific Rate ◽  
Equilibrium Studies ◽  
Proton Abstraction ◽  
Kinetic Isotope ◽  
Forward Rate Constant ◽  
Hydrogen Deuterium ◽  
Reaction In Solution ◽  
Sodium And Potassium

The reactions of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrotoluene fully deuterated at the methyl position (TNT-d3) with sodium and potassium t-butoxide in t-butanol have been studied. With TNT as the substrate, proton abstraction by ion-paired sodium or potassium t-butoxide appears to be the predominant reaction in solution. With sodium t-butoxide as base, the forward rate constant for proton abstraction at 30.0 °C (Kf,ip) is 6000 ± 400 M−1 s−1 while ΔH≠ and ΔS≠ for the reaction are 4.2 ± 0.3 kcal mol−1 and −27 ± 2 cal deg−1 mol−1, respectively. With TNT-d3 as the substrate, formation of a TNT-d3-t-butoxide ion σ-complex occurs simultaneously with deuteron abstraction. Specific rate constants for the two processes have been determined at 30.0 °C. Initial rate studies establish a hydrogen-deuterium kinetic isotope effect of 8 ± 1 for the formation of the anion in t-butanol.

Enhanced adsorption performance for antibiotics by alcohol-solvent mediated boron nitride nanosheets

Rare Metals ◽  
2021 ◽  
Author(s):  
Hao-Feng Wu ◽  
Yan-Hong Chao ◽  
Guo-Hua Xia ◽  
Jing Luo ◽  
Duan-Jian Tao ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Adsorption Performance ◽  
Boron Nitride Nanosheets ◽  
Alcohol Solvent ◽  
Enhanced Adsorption

Fragmentation of alkoxide ions following collisional activation. An energy-resolved study

1988 ◽  
Vol 66 (11) ◽  
pp. 2947-2953 ◽  
Author(s):  
Roger S. Mercer ◽  
Alex G. Harrison
Keyword(s):  
Kinetic Energy ◽  
Collisional Activation ◽  
Collision Energy ◽  
Relative Importance ◽  
Elimination Reaction ◽  
Proton Abstraction ◽  
Relative Stabilities ◽  
Collisionally Activated Dissociation ◽  
Reaction Channels ◽  
Alkane Elimination

The collisionally activated dissociation reactions of the C2 to C5 alkoxide ions have been studied for collisons occurring at 8 keV kinetic energy and also over the range 5 to 100 eV kinetic energy. The alkoxide ions fragment by 1,2-elimination of H2 and/or an alkane. Thus, primary alkoxide ions fragment by elimination of H2 only, secondary alkoxide ions show elimination of H2 and alkane molecules, while tertiary alkoxide ions show elimination of alkanes only. In alkane elimination, loss of CH4 is much more facilie than loss of larger alkanes. For secondary alkoxide ions, where more than one elimination reaction occurs, the energy dependence of fragmentation has been explored over the collision energy range 5 to 100 eV. The results are interpreted in terms of a step-wise mechanism involving formation of an anion-carbonyl compound ion-dipole complex, followed by proton abstraction by the H− or alkyl anion leading to the final products. The relative importance of the reaction channels is determined by the relative stabilities of these ion-dipole complexes.

scholarly journals Pemanfaatan kulit singkong sebagai bahan baku pembuatan Natrium Karbosimetil Selulosa

2018 ◽  
Vol 11 (3) ◽  
pp. 124
Author(s):  
Shella Permatasari Santoso ◽  
Niko Sanjaya ◽  
Aning Ayucitra
Keyword(s):  
Sodium Hydroxide ◽  
Carboxymethyl Cellulose ◽  
Isopropyl Alcohol ◽  
Degree Of Substitution ◽  
Raw Material ◽  
Sodium Carboxymethyl Cellulose ◽  
Carboxymethyl Cellulose Sodium ◽  
Alcohol Solvent ◽  
Cassava Peels ◽  
Cassava Peel

The use of cassava peels as raw material for Sodium Carboxymethyl Cellulose productionCassava peels are abundantly available and may be used as an lowcost cellulose source (80-85% cellulose per weight cassava peel). the study was to evaluate the effect of the concentration of sodium hydroxide, sodium chloroacetate, and temperature reaction on the sodium carboxymethyl cellulose (sodium-CMC) characteristics i.e. yield, purity, and degree of substitution in sodium-CMC preparation.  Sodium-CMC functional group was determined using FTIR spectrophotometer. Cassava peels was dried and grounded to 50 mesh. Lignin was eliminated from cassava peel by extraction of grounded cassava peel with 10% NaOH at 35 °C for 5 h. Cassava peel free lignin was then re-extracted using 10% of acetic acid and sodium chloride at 75 °C for 1 h, thus cellulose free hemicellulose was obtained. Alkalization at 30 °C for 90 min was performed by adding sodium hydroxyde at 10-40% to cellulose using isopropyl alcohol solvent. Following this, etherification was conducted by adding sodium chloroacetate of 1-5 g at 50-80 °C for 6 h. As result, the highest purity of sodium-CMC (96.20%) was obtained from alkalization using 20% of sodium hydroxide and etherification using 3 g sodium chloroacetate at 70 °C. Sodium-CMC yield was 22% and degree of substitution 0.705.Keywords: cassava peel, carboxymethyl cellulose, sodium-CMC, etherification AbstrakKulit singkong merupakan sumber selulosa yang berlimpah dan murah, dengan kadar selulosa 80-85% dari berat kulit singkong. Tujuan penelitian ini adalah memanfaatkan selulosa dalam kulit singkong sebagai bahan baku pembuatan natrium karboksimetil selulosa (Na-CMC), mempelajari pengaruh natrium hidroksida, natrium kloroasetat serta suhu pada karakteristik Na-CMC seperti perolehan, kemurnian, dan derajat substitusi, serta menentukan kondisi operasi optimum untuk pembuatan Na-CMC berdasarkan kemurnian Na-CMC terbesar. Gugus fungsi Na-CMC ditentukan menggunakan Fourier Transform Infrared Spectra. Mula-mula, kulit singkong dikeringkan dan dihancurkan sehingga berukuran 50 mesh. Kulit singkong diekstraksi dengan NaOH 10% di suhu 35 °C selama 5 jam, untuk melarutkan lignin. Kulit singkong bebas lignin diekstrak dengan asam asetat 10% dan natrium klorida dengan pemanasan 750 °C selama 1 jam untuk melarutkan hemiselulosa sehingga didapatkan selulosa. Alkalisasi dilakukan dengan mereaksikan selulosa dengan NaOH 10-40% dengan pelarut isopropil alkohol pada suhu 30 °C selama 90 menit, dilanjutkan eterifikasi dengan natrium kloroasetat 1-5 g pada suhu 50-80 °C selama 6 jam. Berdasarkan hasil penelitian, karakteristik Na-CMC terbaik didapatkan dari alkalisasi selulosa menggunakan NaOH 20% serta eterifikasi menggunakan 3 g natrium kloroasetat pada suhu 70 °C. Perolehan Na-CMC yang didapat adalah sebesar 22%, kemurnian 96,20%, derajat substitusi 0,705; termasuk dalam grade kedua menurut SNI 06-3736-1995.Kata kunci: kulit singkong, karboksimetil selulosa, Na-CMC, eterifikasi

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