scholarly journals COORDINATION PROPERTIES OF NITRO-SUBSTITUTED 5,15-DIPHENYL-3,7,13,17-TETRAMETHYL-2,8,12,18-TETRAETHYLPORPHYRIN WITH MANGANESE ACETATE IN PYRIDINE AND ACETIC ACID

2020 ◽  
Vol 63 (9) ◽  
pp. 49-55
Author(s):  
Elizaveta M. Kuvshinova ◽  
Olga V. Gornukhina ◽  
Alexander S. Semeikin ◽  
Irina A. Vershinina ◽  
Sergey A. Syrbu
Keyword(s):  
Acetic Acid ◽  
Transition State ◽  
Reaction Rate ◽  
Planar Structure ◽  
Manganese Complexes ◽  
Manganese Acetate ◽  
Resonance Spectroscopy ◽  
Electron Absorption Spectroscopy ◽  
Phenyl Rings ◽  
Tetrapyrrole Macrocycle

The synthesis of 5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphyrin and its nitro substituted was carried out. Nitro groups are located in meso-positions of the tetrapyrrole macrocycle and (or) para-positions of the phenyl rings. The synthesized porphyrins are characterized by a set of modern research methods: electron absorption spectroscopy; IR and nuclear magnetic resonance spectroscopy 1H. The reactions of the formation of manganese complexes with nitro-substituted 5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphyrin and their stability in organic solvents are studied. It was found that the rate of reactions of formation of manganese complexes in pyridine with the introduction of nitrogroups in 5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphine grows as the degree of deformation of the tetrapyrrole macrocycle increases. Obviously, in this case, not only the stretching of NH bonds, due to the presence of electron-withdrawing substituents (NO2) in the para positions of the phenyl rings, makes a decisive contribution to the energy of the transition state, but also the increase in the basicity of tertiary nitrogen atoms, which form strong bonds in the transition state with a solvated cation of salt. In acetic acid, the macrocycle deformation effect leads to a decrease in the reaction rate, which is due to the specific solvation of the porphine reaction center by acetic acid molecules. It was found that steric distortions of the planar structure of porphyrins have relatively little effect on the kinetic parameters of the solvoprotolytic dissociation of manganese complexes of 5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphyrin and its nitro-substituted ones. This is probably due to the fact that the coordination of the manganese cation results in a more planar structure of the porphyrin macrocycle. The decrease in the dissociation reaction rate with an increase in the number of nitrogroups in 5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphyrine is due to the influence of the negative inductive effect of nitrogroups, which reduces the effective charge in the macrocycle on nitrogen atoms that are attacked by a solvated proton.

scholarly journals SYNTHESIS AND COORDINATION PROPERTIES OF COBALT COMPLEXES OF 5-PHENYL-2,3,7,8,12,18-HEXAMETHYL-13,17-DIETHYLPORPHYRIN AND ITS NITRO-SUBSTITUTED IN ORGANIC SOLVENTS

2018 ◽  
Vol 61 (7) ◽  
pp. 44 ◽  
Author(s):  
Elizaveta M. Kuvshinova ◽  
Maria A. Bykova ◽  
Irina A. Vershinina ◽  
Olga V. Gornukhina ◽  
Tatyana V. Lyubimova ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Organic Solvents ◽  
Reaction Rate ◽  
Bathochromic Shift ◽  
Cobalt Complexes ◽  
Electronic Effects ◽  
Metal Porphyrin ◽  
Absorption Bands ◽  
Coordination Properties ◽  
Tetrapyrrole Macrocycle

5-Phenyl-2,3,7,8,12,18-hexamethyl-13,17-diethylporphyrin (1), 5-phenyl-10,20-dinitro-2,3,7,8,12,18-hexamethyl -13,17-diethylporphyrin (2), 5- (p-nitrophenyl) -2,3,7,8,12,18-hexamethyl-13,17-diethylporphyrin (3) weresynthesized. The kinetics of formation and dissociation of their cobalt complexes in pyridine and acetic acid was studied. It was found that the change in reactivity upon transition from porphyrin 1 to 2 during complexation in acetic acid is due to an increase in the degree of deformation of the tetrapyrrole aromatic nucleus and the electronic effect of nitro groups. This is manifested by a strong bathochromic shift of all absorption bands in electronic spectra. It is shown that the opposite effect of the deformation effect and the i-effect of nitro groups on the rate of the reaction of formation of metal porphyrin leads to an insignificant change in the kinetic parameters. In pyridine, which has weakly basic properties, the reaction rate increases sharply with the introduction of nitro groups at position of 10, 20 of the porphyrin core. This is due to the fact that the deviation of the tetrapyrrole macrocycle from planarity leads to an increase in the reaction rate. It was found that a spherical distortion of the planar structure of porphyrins (1-3) in the series 1<3<2 relatively slightly influence on the rate of dissociation of their cobalt complexes. Apparently, this is due to the fact that coordination of the cobalt cation leads to a more flat structure of the tetrapyrrole macrocycle and the electronic effects of the nitro groups is the main contribution to the rate of the dissociation reaction of porphyrins (1-3).Forcitation:Kuvshinova E.M., Bykova M.A., Vershinina I.A., Gornukhina O.V., Lyubimova T.V., Semeikin A.S. Synthesis and coordination properties of cobalt complexes of 5-phenyl-2,3,7,8,12,18-hexamethyl-13,17-diethylporphyrin and its nitro-substituted in organic solvents. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 43-48

Nucleophilic cleavage of diaryl disulphides

1973 ◽  
Vol 26 (1) ◽  
pp. 121 ◽  
Author(s):  
DAR Happer ◽  
JW Mitchell ◽  
GJ Wright
Keyword(s):  
Transition State ◽  
Reaction Rate ◽  
Substituent Effects ◽  
Butyl Alcohol ◽  
Sulphur Atom ◽  
Cyanide Ion ◽  
Benzene Rings ◽  
Nucleophilic Cleavage ◽  
Rapid Equilibrium ◽  
Electron Withdrawal

The rates of cleavage of 14 symmetrically substituted diaryl disulphides by cyanide ion have been measured in 60% aqueous t-butyl alcohol at pH 9.2. A plot of log k against σ� shows that while the reaction rate is accelerated by inductive electron withdrawal from the benzene rings, substituents capable of conjugative interaction are not correlated by their σ� parameters. +R substituents cause reaction to occur much faster than predicted on the basis of their σ� values, while -R substituents react more slowly than predicted. Measurement of rates of cleavage of three series of unsymmetrically substituted disulphides by cyanide or hydroxide shows that these unusual substituent effects arise from substituents in the thiocyanate-forming aryl ring. This behaviour is explained in terms of a change in the electronic behaviour of the thio- cyanate-forming sulphur atom from -I, + R in the disulphide to -I,-R in the rate-determining transition state for the reaction. The study does not show whether the cleavage involves an SN2 process or rapid equilibrium formation of a pentacovalent intermediate.

scholarly journals Perborate Oxidation of Substituted 5-Oxoacids in Aqueous Acetic Acid Medium: A Kinetic and Mechanistic Study

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. Shree Devi ◽  
B. Muthukumaran ◽  
P. Krishnamoorthy
Keyword(s):  
Acetic Acid ◽  
Acid Medium ◽  
Reaction Rate ◽  
Reaction Medium ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Mechanistic Study ◽  
Aqueous Acetic Acid ◽  
Sodium Perborate ◽  
Acetic Acid Medium

Kinetics and mechanism of oxidation of substituted 5-oxoacids by sodium perborate in aqueous acetic acid medium have been studied. The reaction exhibits first order both in [perborate] and [5-oxoacid] and second order in [H+]. Variation in ionic strength has no effect on the reaction rate, while the reaction rates are enhanced on lowering the dielectric constant of the reaction medium. Electron releasing substituents in the aromatic ring accelerate the reaction rate and electron withdrawing substituents retard the reaction. The order of reactivity among the studied 5-oxoacids is p-methoxy ≫ p-methyl > p-phenyl > –H > p-chloro > p-bromo > m-nitro. The oxidation is faster than H2O2 oxidation. The formation of H2BO3+ is the reactive species of perborate in the acid medium. Activation parameters have been evaluated using Arrhenius and Eyring’s plots. A mechanism consistent with the observed kinetic data has been proposed and discussed. Based on the mechanism a suitable rate law is derived.

scholarly journals A microwave-catalyzed rapid, efficient and ecofriendly synthesis of substituted pyrazol-5-ones (Short communication)

2003 ◽  
Vol 68 (10) ◽  
pp. 723-727 ◽  
Author(s):  
Vijay Dabholkar ◽  
Rahul Gavande
Keyword(s):  
Acetic Acid ◽  
Carboxylic Acid ◽  
Microwave Irradiation ◽  
Reaction Rate ◽  
Short Communication ◽  
Acid Hydrazide ◽  
Acetoacetic Ester ◽  
Carboxylic Acid Hydrazide ◽  
Conventional Methods

A series of 1-(3,4-dihydro-3-oxo-2H-1,4-benzoxazine-2-carbonyl)-3-methyl-4-(substituted phenylhydrazono)-2-pyrazolin-5-ones have been synthesized by the reaction of 2H-3,4-dihydro-3-oxo-1,4-benzoxazine-2-carboxylic acid hydrazide with substituted acetoacetic ester derivatives using acetic acid as solvent under microwave irradiation (MWI), as well as by conventional methods. The reaction rate is enhanced tremendously and the yields are improved under MWI as compared to conventional methods.

scholarly journals The Limitation of the Combination of Transition State Theory and Thermodynamics for the Reactions of Proteins and Nucleic Acids

Biomolecules ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 28
Author(s):  
Nobuo Shimamoto
Keyword(s):  
Nucleic Acids ◽  
Transition State ◽  
Stationary State ◽  
Transition State Theory ◽  
Reaction Rate ◽  
State Theory

When a reaction is accompanied by a change with the speed close to or slower than the reaction rate, a circulating reaction flow can exist among the reaction states in the macroscopic stationary state. If the accompanying change were at equilibrium in the timescale of the relevant reaction, the transition-state theory would hold to eliminate the flow.

scholarly journals Study of UiO-66 and UiO-66 Modulated with Acetic Acid as the Adsorbent for Eriochrome Black T Dye

2021 ◽  
Vol 8 (3) ◽  
pp. 183-193
Author(s):  
M. Anugrah Rizky Pambudi ◽  
Nanda Prayogo ◽  
Muhammad Nadjib ◽  
Ratna Ediati
Keyword(s):  
Acetic Acid ◽  
Reaction Rate ◽  
Metal Organic Framework ◽  
X Ray Diffraction ◽  
Adsorption Selectivity ◽  
X Ray ◽  
Langmuir Adsorption ◽  
Eriochrome Black T ◽  
Metal Organic ◽  
Pseudo Second Order

UiO-66, as one of the metal-organic framework (MOF) compounds, has been used to treat some anionic and cationic dye waste. In order to determine the adsorption selectivity decisively, the synthesis of UiO-66 and UiO-66 modulated with acetic acid had been carried out, along with their adsorption tests for Eriochrome Black T (EBT) dye solution. The synthesis was performed by utilizing a solvothermal method with the reaction mixtures of zirconium (IV) chloride (ZrCl4) and terephthalic acid (H2BDC) as a ligand heated at 120 oC for 24 hours. Both UiO-66 (without acetic acid) and acetic acid modulated UiO-66 were obtained as a white powder. Acetic acid as a modulator was added and being investigated for the adsorption capability compared to the normal UiO-66. This study showed that normal UiO-66 exhibited better adsorption than acetic acid modulated UiO-66 with a mmol ratio of acetic acid:ligand varied from 50:1, 100:1, and 150:1. Acetic acid modulated UiO-66 with a mmol ratio of 50 exhibited the best crystallinity as observed by using x-ray diffraction. It can be concluded that the adsorption of EBT using normal and acetic acid modulated UiO-66 obeyed the pseudo-second-order reaction rate law as well as the Langmuir adsorption isotherm pattern.

scholarly journals Improvement of acid solutions for stimulation of compacted high-temperature carbonate collectors

2021 ◽  
Vol 6 (3(62)) ◽  
pp. 11-14
Author(s):  
Oleh Zimin
Keyword(s):  
Surface Tension ◽  
Acetic Acid ◽  
High Temperature ◽  
Reaction Rate ◽  
Methyl Acetate ◽  
Surface Tension Coefficient ◽  
Gradual Transition ◽  
Acid Solutions ◽  
Hydrocarbon Production ◽  
Low Viscosity

The object of research in this work is the intensification of hydrocarbon production. The most problematic task of the study is the efficiency of intensification of compacted high-temperature carbonate reservoirs. Despite the gradual transition to renewable energy sources, natural gas and oil will play a dominant role in the world's energy balance in the next 20–30 years. Carbonate rocks have significant mining potential, but low filtration properties require intensification to improve reservoir permeability. High temperatures and pressures at great depths require the improvement of existing hydrocarbon production technologies. The most popular method for treating reservoirs containing carbonates is acid treatments in different variations, but for effective treatment it is necessary to achieve deep penetration of the solution into the formation. The study solves the problem of selection of effective carrier liquids for the preparation of acid solutions for the treatment of compacted high-temperature reservoirs with high carbonate content. To ensure quality treatment, acid solutions must have low viscosity and surface tension coefficient, low reaction rate, their chemical properties must ensure the absence of insoluble precipitates in the process of reactions with fluids and rocks, as well as be environmentally friendly. To select the most optimal carrier liquid, experiments were conducted to determine which candidate liquids provide the minimum reaction rate of acidic solutions with carbonates. Based on the analysis of industrial application data and literature sources, water, nephras, methanol, ethyl acetate, and methyl acetate were selected for further research. Widely studied acetic acid was chosen as the basic acid. Studies have shown that methyl acetate has a number of advantages, namely low reaction rate, low viscosity and surface tension coefficient. As well as the possibility of hydrolysis in the formation with the release of acetic acid, which significantly prolongs the reaction time of the solution with the rock and the depth of penetration of the active solution into the formation.

Ligand Substitution Reactions

2007 ◽  
Author(s):  
Robert B. Jordan
Keyword(s):  
Transition State ◽  
Coordination Number ◽  
Reaction Rate ◽  
Ligand Substitution ◽  
Substitution Reactions ◽  
Definite Evidence ◽  
Oxidation Reduction ◽  
Leaving Group ◽  
Group 2 ◽  
Ligand Substitution Reactions

In ligand substitution reactions, one or more ligands around a metal ion are replaced by other ligands. In many ways, all inorganic reactions can be classified as either substitution or oxidation-reduction reactions, so that substitution reactions represent a major type of inorganic process. Some examples of substitution reactions follow: The operational approach was first expounded in 1965 in a monograph by Langford and Gray. It is an attempt to classify reaction mechanisms in relation to the type of information that kinetic studies of various types can provide. It delineates what can be said about the mechanism on the basis of the observations from certain types of experiments. The mechanism is classified by two properties, its stoichiometric character and its intimate character. The Stoichiometric mechanism can be determined from the kinetic behavior of one system. The classifications are as follows: 1. Dissociative (D): an intermediate of lower coordination number than the reactant can be identified. 2. Associative (A): an intermediate of larger coordination number than the reactant can be identified. 3. Interchange (I): no detectable intermediate can be found. The intimate mechanism can be determined from a series of experiments in which the nature of the reactants is changed in a systematic way. The classifications are as follows: 1. Dissociative activation (d): the reaction rate is more sensitive to changes in the leaving group. 2. Associative activation (a): the reaction rate is more sensitive to changes in the entering group. This terminology has largely replaced the SN1, SN2 and so on type of nomenclature that is still used in physical organic chemistry. These terminologies are compared and further explained as follows: Dissociative [D = SN1 (limiting)]: there is definite evidence of an intermediate of reduced coordination number. The bond between the metal and the leaving group has been completely broken in the transition state without any bond making to the entering group. Dissociative interchange (1d= SN1): there is no definite evidence of an intermediate. In the transition state, there is a large degree of bond breaking to the leaving group and a small amount of bond making to the entering group.

Sign in / Sign up

Export Citation Format

Share Document