Polarographic reduction of 3-O-methylpyridoxal 5'-phosphate

1980 ◽  
Vol 45 (6) ◽  
pp. 1662-1668 ◽  
Author(s):  
Enrique López-Cantarero ◽  
Juan Llor ◽  
Manuel Cortijo
Keyword(s):  
Carbonyl Group ◽  
Aldehyde Group ◽  
The Other ◽  
Polarographic Reduction ◽  
Acid Base ◽  
Proton Transfers

The polarographic reduction of 3-O-methyl-pyroxidal 5'-phosphate has been studied as a function of pH. The reduction of the aldehyde group by a two electrons process occurs in all conditions studied. The rate of interconversion between the free and hydrate forms of the carbonyl group has been computed. This reaction is acid-base catalyzed. The other reactions (proton transfers) that precede the electrodic reaction are very much faster. The results are compared with those previously obtained for pyridoxal 5'-phosphate.

Polarographic reduction of α-(4-ethylbenzoyl)-α,β-dibromopropionic acid on mercury dropping electrode

1979 ◽  
Vol 44 (4) ◽  
pp. 1318-1323
Author(s):  
Miloslava Počtová
Keyword(s):  
Electrochemical Reduction ◽  
Carbonyl Group ◽  
Polarographic Reduction ◽  
Polarographic Wave ◽  
Intermediate Products ◽  
Active Intermediate

A mechanism of the electrochemical reduction of β-(4-ethylbenzoyl)-α,β-dibromopropionic acid is suggested based on the results of classical polarography and polarography with Kalousek's switch and on the identification of the polarographically active intermediate products. The substance converts to β-4-ethylbenzoylacrylic acid on the electrochemical elimination of the bromine atoms, and the latter acid is reduced further to β-4-ethylbenzoylpropionic acid. The most negative polarographic wave corresponds to the reduction of the carbonyl group in the benzoyl part of the last acid.

scholarly journals Complexation of 2,6-helic[6]arene and its derivatives with 1,1′-dimethyl-4,4′-bipyridinium salts and protonated 4,4'-bipyridinium salts: an acid–base controllable complexation

2019 ◽  
Vol 15 ◽  
pp. 1795-1804 ◽  
Author(s):  
Jing Li ◽  
Qiang Shi ◽  
Ying Han ◽  
Chuan-Feng Chen
Keyword(s):  
Association Constants ◽  
The Other ◽  
Acid Base ◽  
Polar Solvents ◽  
X Ray ◽  
H Nmr ◽  
Hydrogen Bonding Interactions ◽  
Acids And Bases ◽  
Multiple Hydrogen Bonding ◽  
Nmr Titrations

2,6-Helic[6]arene and its derivatives were synthesized, and their complexation with 1,1′-dimethyl-4,4′-bipyridinium and protonated 4,4'-bipyridinium salts were investigated in detail. It was found that the helic[6]arene and its derivatives could all form 1:1 complexes with both 1,1′-dimethyl-4,4'-bipyridinium salts and protonated 4,4'-bipyridinium salts in solution and in the solid state. Especially, the helic[6]arene and its derivatives containing 2-hydroxyethoxy or 2-methoxyethoxy groups exhibited stronger complexation with the guests than the other helic[6]arene derivatives for the additional multiple hydrogen bonding interactions between the hosts and the guests, which were evidenced by 1H NMR titrations, X-ray crystal structures and DFT calculations. Moreover, it was also found that the association constants (K a) of the complexes could be significantly enhanced with larger counteranions of the guests and in less polar solvents. Furthermore, the switchable complexation between the helic[6]arene and protonated 4,4'-bipyridinium salt could be efficiently controlled by acids and bases.

Ab initio Calculations of the Nuclear Quadrupole Coupling Constants of BHn = 2,4X+ (X = NH3, PH3, H2O, H2S)

2005 ◽  
Vol 60 (1-2) ◽  
pp. 37-40
Author(s):  
Tayyebe Partovi ◽  
Marjan A. Rafieea
Keyword(s):  
Electronic Structure ◽  
Electric Field Gradient ◽  
Coupling Constants ◽  
The Other ◽  
Quadrupolar Nuclei ◽  
Donor Atom ◽  
Acid Base ◽  
Donor And Acceptor ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

The electronic structure and strength of acid-base bonding in the protonated boron-Lewis complexes BHn=2,4X+ (X = NH3, PH3, H2O, H2S) and their neutral parents were studied. The results showed that in the H2BX+ monocations the electron releasing from the donor atom in X to BH3 is significant and more complete than in the other studied complexes. Therefore the bonding between the donor and acceptor in H2BX+ is strongest. To obtain these data, the electric field gradient (EFG) at the quadrupolar nuclei in each complex was calculated. The EFG’s of the boron atom and other quadrupolar nuclei were calculated by the Gaussian 98 program, using the MP2/6-31G** method.

Haemodialysis or Haemoperfusion in Severe Salicylate Poisoning?

1988 ◽  
Vol 7 (2) ◽  
pp. 161-163 ◽  
Author(s):  
D. Jacobsen ◽  
E. Wiik-Larsen ◽  
J.E. Bredesen
Keyword(s):  
Blood Flow ◽  
Plasma Levels ◽  
The Other ◽  
Blood Pump ◽  
Supportive Treatment ◽  
Acid Base ◽  
Electrolyte Disturbances ◽  
Salicylate Poisoning ◽  
Maximal Plasma ◽  
Theoretical Advantage

Two cases of severe salicylate poisoning with maximal plasma levels of 6.9 and 8.9 mmol/l are described. In addition to supportive treatment and forced alkaline diuresis, one case was treated with haemoperfusion and the other with haemodialysis. The use of the same blood pump and blood flow allowed us to compare directly the effect of these methods in removing salicylate. There was a non-significant higher dialysance (mean 86 ml/min, s.d. ± 8) than haemoperfusion clearance (mean 81 ml/min s.d. ± 17) at a blood flow of 200 ml/min. As haemodialysis offers the theoretical advantage of correcting acid-base and electrolyte disturbances, does not trap platelets and has a lower heparin requirement, the present comparison indicates that haemodialysis is preferable when extracorporal elimination is indicated in salicylate poisoning.

The Placental Transfer and Fetal Effects of Levobupivacaine, Racemic Bupivacaine, and Ropivacaine

1999 ◽  
Vol 90 (6) ◽  
pp. 1698-1703. ◽  
Author(s):  
Alan C. Santos ◽  
Barry Karpel ◽  
George Noble
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Local Anesthetics ◽  
Placental Transfer ◽  
Well Being ◽  
The Other ◽  
Uterine Blood Flow ◽  
Acid Base ◽  
Fetal Serum ◽  
Acid Base Status

Background The purposes of this study were to assess the effects of levobupivacaine on uterine blood flow and fetal well-being and to compare its placental transfer with that of bupivacaine and ropivacaine. Methods After a control period, pregnant ewes that were fitted with instruments for long-term monitoring were randomized to receive a two-step intravenous infusion of levobupivacaine, bupivacaine, or ropivacaine, in a blinded manner, for 1 h. Maternal and fetal hemodynamics were monitored during the study. Arterial blood samples were drawn at 30 and 60 min of infusion from the mother and fetus to determine the acid-base status (60 min only) and serum drug concentrations. The fetal brain, heart, liver, lungs, adrenal glands, and kidneys were obtained to measure tissue drug levels. Results Maternal blood pressure, central venous and intraamniotic pressures, acid-base status and uterine blood flow were unaffected by any drug infusion. In contrast to the other two local anesthetics, the infusion of bupivacaine was associated with a small but significant decrease in the ewe's heart rate. At the end of the study, the heart rate in the bupivacaine-treated animals was significantly less than in the animals treated with the other two drugs. All fetuses were in good condition at the start of study, and none of the local anesthetics affected fetal well-being. No significant differences were found among the three drugs in the maternal serum, fetal serum, fetal tissue concentrations, and tissue:serum concentration ratios. Conclusions Levobupivacaine was similar to bupivacaine and ropivacaine in causing no important hemodynamic changes in the pregnant ewe and fetus. There were no significant differences in the fetal serum and tissue levels of the drugs.

The mechanisms of α-H and proton transfers of glycine induced by Mg2+

2015 ◽  
Vol 14 (02) ◽  
pp. 1550008
Author(s):  
Qing Zhang ◽  
Xiang-Jun Meng
Keyword(s):  
Energy Barrier ◽  
Inductive Effect ◽  
Covalent Bond ◽  
Electron Cloud ◽  
Chemical Activity ◽  
The Other ◽  
Single Bond ◽  
Substitution Reactions ◽  
Neutral Complex ◽  
Proton Transfers

A MP2/6-31++G(d,p)//B3LYP/6-31++G(d,p) method was used to investigate the mechanisms of α- H and proton transfers of glycine induced by Mg 2+. Eight complexes were obtained, six of which were neutral and the other two were zwitterionic. Among them, the zwitterion with a binding energy of 159.4 kcal/mol was the most stable structure. Conformation transformations of the complexes caused by the rotation of single bond and the transfers of α- H and proton were completed via seven transition states. The inductive effect of Mg 2+ made the electron cloud of glycine deviate to Mg 2+, which activated the covalent bond involving the transferred proton. The neutral complex can be turned into the zwitterionic one by the transfers of both carboxyl hydrogen and α- H , and the energy barrier of each reaction was less than 9.2 kcal/mol. After the transfer of α- H , a delocalized π bond was formed in glycine skeleton and the α- C atom took 0.19 positive charges. So the chemical activity of the glycine enhanced, and glycine was readily available for addition and nucleophilic substitution reactions. The path from the most stable glycine conformer G1 to the zwitterionic conformation I is G1 → G1–G3 → G3 → G3–G4 → G4 → G2–G4 → G2 → VI → I–VI → I, and the highest energy barrier of this path is 9.2 kcal/mol.

scholarly journals Analysis of acid-base misconceptions using modified certainty of response index (CRI) and diagnostic interview for different student levels cognitive

2017 ◽  
Vol 1 (2) ◽  
pp. 91 ◽  
Author(s):  
Satya Sadhu ◽  
Maria Tensiana Tima ◽  
Vika Puji Cahyani ◽  
Antonia Fransiska Laka ◽  
Desfi Annisa ◽  
...  
Keyword(s):  
Data Analysis ◽  
Content Knowledge ◽  
Diagnostic Interview ◽  
The Other ◽  
Science Students ◽  
Acid Base ◽  
Response Index ◽  
Base Theory ◽  
The One ◽  
Descriptive Method

<p class="Abstract">The authors in this paper draw attention to the importance of an instrument that can analyze student’s misconception.This study described the kind of the misconception in acid-base theory, and the percentage students’ misconception occur in every subconcept of acid-base theory. The design of this study is a descriptive method, involved 148 of 11<sup>th</sup> grade science students from Senior High School, which divided into two classes are high cognitive and low cognitive. Further analysis of using Modified Certainty of Response Index (CRI) as a diagnostic instrument is used to explore misconception which in that test included evaluating only content knowledge with considering the reason behind the students' choice of response and their certainty of response in every question. The result of data analysis has shown that misconception occurred in high cognitive class, gained 43,86% and misconception occurred in low cognitive class, gained 24,63%. Based on the diagnostic interview has shown that misconception occurred in students due to students does not understand the concept well and they related the one concept to the other concepts with partial understanding, the result students make the failed conclusions. The type of misconception occurred is a conceptual misunderstanding.  According to the data analysis showed that Modified Certainty of Response Index (CRI) is effective used to analyze students’ misconceptions and the diagnostic interview is effective used to know the reasons that caused students which having misconceptions.</p>

Coupling constants nitrogen-15-nitrogen-15 and nitrogen-15-hydrogen in phenylhydrazones forming hydrogen bond

1981 ◽  
Vol 46 (4) ◽  
pp. 892-897 ◽  
Author(s):  
Antonín Lyčka ◽  
Dobroslav Šnobl
Keyword(s):  
Hydrogen Bond ◽  
Carbonyl Group ◽  
Ester Group ◽  
Natural Abundance ◽  
Coupling Constants ◽  
The Other ◽  
A Value ◽  
Proton Signal ◽  
Hydrazone Form

Absolute values of the coupling constants 1J(15N15N), 1J(15NH) of six phenylhydrazones forming hydrogen bond, 2J(15N15NH) of four, and 4J(15NH) of two phenylhydrazones have been determined. Three coupling constants 1J(15N15N) have been obtained from the nitrogen-15 monolabelled compounds by measuring the other nitrogen at natural abundance. The coupling constants 2J(15N15NH) have been measured with the nitrogen-15 doubly labelled compounds, because in the arrangement 15N14NH there exists a broadening of the proton signal due to nitrogen-14. Absolute values of the coupling constants 1J(15N15N) of the phenylhydrazones forming hydrogen bond to the ester group are smaller ( 10.8 Hz) than those of the phenylhydrazones having hydrogen bond to carbonyl group ( 11.1 Hz). The coupling constants 2J(15N15NH) have a value 2.4 ± 0.2 Hz. The value of 1J(15N15N) of 1-phenylazo-2-naphthalenol decreases with increasing content of hydrazone form. The values of 2J(15N15NH) of this compound are within 1.2 to 1.6 Hz.

Determination Methods of Dialdehyde Celluloses from Bacterial Cellulose

2007 ◽  
Vol 361-363 ◽  
pp. 507-510
Author(s):  
Yu Hong Feng ◽  
Jia Cheng Li ◽  
Qiang Lin ◽  
Su Juan Pang ◽  
Meng Ying Zhang ◽  
...  
Keyword(s):  
Bacterial Cellulose ◽  
Amino Nitrogen ◽  
Aldehyde Group ◽  
Acid Base ◽  
Titration Method ◽  
Cannizzaro Reaction ◽  
Acid Base Titration ◽  
Determination Methods ◽  
Oxidation System

This paper addresses the determination of aldehyde group (% of dialdehyde units) in dialdehyde cellulose (DACs) oxidized from bacterial cellulose (BC). With 4 determination methods, the oxidation degrees of DACs were studied: Automatic potential titration method through Schiff base reaction, Acid-base titration in Cannizzaro reaction, Metaperiodate consumption determination, and Measurement of amino nitrogen content in DAC derivatives. By comparing determination results of these methods, we found out the proper way suitable for this metaperiodate oxidation system of BC to measure the dialdehyde unit content of the DACs.

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