This document summarizes research on the solubility of tetraalkylammonium pertechnetate solutions and the influence of ion association. The key findings are:
1) The solubility of tetrabutylammonium pertechnetate depends strongly on the acidity of the solution due to equilibria involving association of pertechnetate ions with protons and tetrabutylammonium cations.
2) Analysis of solubility data using equilibrium equations yields association constants of around 4 for pertechnetate-proton complexes and 15 for pertechnetate-tetrabutylammonium complexes.
3) Methods such as spectroscopy and kinetics indicate complete dissociation of pertechnet
Shift of Reaction Pathway by Added Chloride Ions in the Oxidation of Aromatic...Ratnakaram Venkata Nadh
Role of added chloride ions on the shift of reaction pathway of oxidation of aromatic ketones (acetophenone,
desoxybenzoin) by dichloroisocyanuric acid (DCICA) was studied in aqueous acetic acid—perchloric
acid medium. Participation of enolic and protonated forms of ketones in the rate determining steps is
manifested from zero and first orders with respect to the oxidant in absence and presence of added chloride
ions, respectively. Positive and negative effects of acid and dielectric constant on the reaction rate were
observed. The observations deduce plausible mechanisms involving (i) rate-determining formation of enol
from the conjugate acid of the ketone (SH+) in the absence of added chloride ions and (ii) rapid formation of
molecular chlorine species from HOCl (hydrolytic species of DCICA) in the presence of added chloride ions,
which then interacts with SH+ in a rate-determining step prior to the rapid steps of product formation. The
order of Arrhenius parameters substantiate the proposed plausible mechanisms based on order of reactants
both in presence and absence of added chloride ions.
Synthesis and characterization of some metal complexes of 2- Phenyl-3,4-dihyd...IOSRJAC
2-Phenyl-3,4-dihydro-quinazolin-4-yloxy)-acetic acid (L1) metal complexes with Mn2+ , Co2+, Ni2+ Cu2+ , and Zn2+ ions were studied and the structure of the complexes were elucidated using elemental analyses, infrared (IR), 1H nuclear magnetic resonance (NMR), magnetic moment and thermal analysis measurements. Besides the characterization of complexes by physicochemical technique, Biological activities of the synthesized complexes were examined against some microbial strains for evaluation of antibacterial and antifungal activities.
Organic chemistry involves the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds, which include not only hydrocarbons but also compounds with any number of other elements, including hydrogen (most compounds contain at least one carbon–hydrogen bond), nitrogen, oxygen, halogens, phosphorus, silicon, and sulfur.
This branch of chemistry was originally limited to compounds produced by living organisms but has been broadened to include human-made substances such as plastics. The range of application of organic compounds is enormous and also includes, but is not limited to, pharmaceuticals, petrochemicals, food, explosives, paints, and cosmetics.
Shift of Reaction Pathway by Added Chloride Ions in the Oxidation of Aromatic...Ratnakaram Venkata Nadh
Role of added chloride ions on the shift of reaction pathway of oxidation of aromatic ketones (acetophenone,
desoxybenzoin) by dichloroisocyanuric acid (DCICA) was studied in aqueous acetic acid—perchloric
acid medium. Participation of enolic and protonated forms of ketones in the rate determining steps is
manifested from zero and first orders with respect to the oxidant in absence and presence of added chloride
ions, respectively. Positive and negative effects of acid and dielectric constant on the reaction rate were
observed. The observations deduce plausible mechanisms involving (i) rate-determining formation of enol
from the conjugate acid of the ketone (SH+) in the absence of added chloride ions and (ii) rapid formation of
molecular chlorine species from HOCl (hydrolytic species of DCICA) in the presence of added chloride ions,
which then interacts with SH+ in a rate-determining step prior to the rapid steps of product formation. The
order of Arrhenius parameters substantiate the proposed plausible mechanisms based on order of reactants
both in presence and absence of added chloride ions.
Synthesis and characterization of some metal complexes of 2- Phenyl-3,4-dihyd...IOSRJAC
2-Phenyl-3,4-dihydro-quinazolin-4-yloxy)-acetic acid (L1) metal complexes with Mn2+ , Co2+, Ni2+ Cu2+ , and Zn2+ ions were studied and the structure of the complexes were elucidated using elemental analyses, infrared (IR), 1H nuclear magnetic resonance (NMR), magnetic moment and thermal analysis measurements. Besides the characterization of complexes by physicochemical technique, Biological activities of the synthesized complexes were examined against some microbial strains for evaluation of antibacterial and antifungal activities.
Organic chemistry involves the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds, which include not only hydrocarbons but also compounds with any number of other elements, including hydrogen (most compounds contain at least one carbon–hydrogen bond), nitrogen, oxygen, halogens, phosphorus, silicon, and sulfur.
This branch of chemistry was originally limited to compounds produced by living organisms but has been broadened to include human-made substances such as plastics. The range of application of organic compounds is enormous and also includes, but is not limited to, pharmaceuticals, petrochemicals, food, explosives, paints, and cosmetics.
A ruthenium-carbamato-complex derived from a siloxylated amine and carbon dio...Pawan Kumar
The rutheniumcarbamate complex derived from3-trimethoxysilyl-1-
propyl amine and carbon dioxidewas found to be a novel catalyst for
the oxidative cyanation of aromatic and cyclic tertiary amines to
corresponding a-amino nitriles in high to excellent yields by using
hydrogen peroxide and molecular oxygen as enviro-economic
oxidants. The developed protocol suggested an efficient alternative
for recycling carbon dioxide.
Computer-assisted study on the reaction between pyruvate and ylide in the pat...Omar Alvarardo
n this study the formation of the lactyl–thia-
min diphosphate intermediate (L–ThDP) is addressed using
density functional theory calculations at X3LYP/6-
31??G(d,p) level of theory. The study includes potential
energy surface scans, transition state search, and intrinsic
reaction coordinate calculations. Reactivity is analyzed in
terms of Fukui functions. The results allow to conclude that
the reaction leading to the formation of L–ThDP occurs via
a concerted mechanism, and during the nucleophilic attack
on the pyruvate molecule, the ylide is in its AP form. The
calculated activation barrier for the reaction is 19.2 kcal/
mol, in agreement with the experimental reported value.
A ruthenium-carbamato-complex derived from a siloxylated amine and carbon dio...Pawan Kumar
The rutheniumcarbamate complex derived from3-trimethoxysilyl-1-
propyl amine and carbon dioxidewas found to be a novel catalyst for
the oxidative cyanation of aromatic and cyclic tertiary amines to
corresponding a-amino nitriles in high to excellent yields by using
hydrogen peroxide and molecular oxygen as enviro-economic
oxidants. The developed protocol suggested an efficient alternative
for recycling carbon dioxide.
Computer-assisted study on the reaction between pyruvate and ylide in the pat...Omar Alvarardo
n this study the formation of the lactyl–thia-
min diphosphate intermediate (L–ThDP) is addressed using
density functional theory calculations at X3LYP/6-
31??G(d,p) level of theory. The study includes potential
energy surface scans, transition state search, and intrinsic
reaction coordinate calculations. Reactivity is analyzed in
terms of Fukui functions. The results allow to conclude that
the reaction leading to the formation of L–ThDP occurs via
a concerted mechanism, and during the nucleophilic attack
on the pyruvate molecule, the ylide is in its AP form. The
calculated activation barrier for the reaction is 19.2 kcal/
mol, in agreement with the experimental reported value.
Bonita offre des fonctionnalités avancées pour la gestion des processus au sein des entreprises et des organisations.
Alors c’est un logicielle qui gère un enchaînement de tâches suivant une procédure prédéfinie, permettant ainsi de coordonner les activités de différentes personnes dont le but d'atteindre un objectif global
Study of the Densities of Some R4NI - Solutions in Water - Isopropyl Alcohol ...IJAEMSJORNAL
Based on Masson’s equation we study the molecular interactions between the compositions of the binary solution mixtures for different (%) compositions of Water– Isopropyl alcohol by adding tetraalkyl ammonium iodide at 313.15K. The densities of the solution mixtures (ρ¬s)have been measured very accurately by using Magnetic float Densitometer. The densitometer works on the electrostatic attraction force developed by the passage of current through a solenoid .using this technique, the densities (d¬0¬) of Water – Isopropyl alcohol solvent and mixtures of some tetra alkyl ammonium iodide, viz. Et4NI, Pr4NI, But¬4NI, Pen4NI at 0, 20, 40, 60, 80, 100% compositions (v/v) have been determined experimentally. The apparent molar volumes have been calculated from density data using Masson’s equation and graph plotted between ϕv vs √c . The slopes of curves shows that in low dielectric constant medium (i.e, 20% water, =30.76 and 40% water, ∈=42.74 for all the four tetraalkyl ammonium iodide salts have positive slope. But as the dielectric constant of the solvent medium is increased by adding Water – Isopropyl alcohol, further additions of salts in the solution will start contributing towards the volume so the volume will increase on increasing the salt concentration therefore the plot ϕ¬¬¬v+ vs √c curves will give a positive and negative slope the data have been explained on the basis of dielectric constant of the solvent mixtures and size of the electrolyte ion.
Partial Molar Volumes of Tetra alkyl ammonium salts in 10%(W/W) 2-(Ethoxy) et...Premier Publishers
In this article densities and apparent molar volumes of Tetra alkyl ammonium bromide salts ( ) in 10% (W/W) 2-(Ethoxy) ethanol-water mixture is studied at 30o, 35o and 40oC. Partial molar volumes are divided into ionic components using different methods such as Conway et al. and Jolicoeur et al. The results are compared with the values of partial molar volumes of ions reported in literature for pure water. Decrease in hydrophobic hydration is noticed. This may be due to the addition of co-solvent 2-(Ethoxy) ethanol (confirming the conclusions drawn from our viscosity studies that in 2-(Ethoxy) ethanol-water mixture, the structuredness of water is reduced by the breaking of hydrogen bonds). The values are divided into and . Making use of the Padova’s equation values of salts are calculated. These are also divided into ionic contributions. Dimensions of ions have been calculated to understand solvation behavior. It is shown that the classification of salts into structure makers and structure breakers on the basis of the sign of is not valid for the present water rich mixed solvent system.
Its related to Study of gene metal-ligand stability constant of cefadroxil with cu2+ metal ion ph metrically at 0.1 m ionic strength. Also describe another Parameters.
Bis-perfluorocycloalkenyl (PFCA) aryl ether monomers towards a versatile clas...Babloo Sharma, Ph.D.
A unique class of perfluorocycloalkenyl (PFCA) aryl ether monomers was synthesized from commercially available perfluorocycloalkenes (PFCAs) and bisphenols in good yields. This facile one pot reaction of perfluorocycloalkenes, namely, octafluorocyclopentene (OFCP), and decafluorocyclohexene (DFCH), with bisphenols occurs at room temperature via an addition–elimination reaction in the presence of a base. The synthesis of PFCA monomers and their condensation with bisphenols lead to perfluorocycloalkenyl (PFCA) aryl ether homopolymers and copolymers with random and/or alternating polymer architectures.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
Influence of Tetra Alkyl Ammonium Cation and Temperature on Molecular Interac...IOSRJAC
Ultrasonic velocity (u), density (ρ), viscosity (η) and related acoustical parameters such as adiabatic compressibility (β), free energy (∆G), internal pressure (πi), relaxation time (τ) and acoustic impedance (z) have been computed using standard relation for tetra alkyl ammonium cation (Et4N + , Pr4N + , Bu4N + , and Pen4N + ) in binary liquid mixtures of 1, 4 - Dioxane and N, N – Dimethyl Formamide was prepared of 0.14M on different percentage compositions over the temperature range from 303.15K to 323.15K with the interval of 10K under room pressure to investigate inter - ionic interactions. The densities were measured by Magnetic Float Densitometer. Transport properties provide a deep and meaningful insight of various interactions taking place. It has been observed that the influence of small as well as large alkyl chain length of tetra alkyl ammonium cations (R4N + ), in terms of shape and ionic size with the DMF solvent in the presence of Dioxane, is helpful in investigating the molecular interactions, molecular rearrangement, molecular association etc
MACROMOLECULAR COMPOUNDS AND GELS. A manual for students and graduate students of biotechnology training and medical universities (in Russian) Authors: Belova EV, German KE, Afanasyev AV, Slyusar OI, Solodova EV
2018 History of technetium studies in Russia Anna KuzinaKonstantin German
Lecture is about the History of technetium studies in Russia and Anna Kuzina 100 anniversary of birthday
Technetium separation in milligram, gram and kilogram ammounts 1957 - 1993
Proceedings and selected lectures 10th intern symp technetium rheniumKonstantin German
Proceedings and selected lectures of the 10th International Symposium on Technetium and Rhenium – Science and Utilization, October 3-6, 2018 - Moscow – Russia, Eds: K. German, X. Gaona, M. Ozawa, Ya. Obruchnikova, E. Johnstone, A. Maruk, M. Chotkowski, I. Troshkina, A. Safonov. Moscow: Publishing House Granica, 2018, 518 p.
ISBN 978-5-9933-0132-7 December 2018
Aleksey Buryak. WELCOME ADDRESS FROM IPCE - RUSSIAN ACADEMY OF SCIENCES Andrey Romanov. WELCOME ADDRESS FROM THE MINISTRY OF SCIENCE AND HIGHER EDUCATION OF RUSSIAN FEDERATION Mikhail Igorevich Panasyuk. ANNA KUZINA: BIOGRAPHY. K.E. German. PROF. ANNA FEDOROVNA KUZINA – 100TH ANNIVERSARY OF BIRTHDAY T. Yoshimura, M. Seike, H. Ikeda, K. Nagata, A. Ito, E. Sakuda, N. Kitamura, A. Shinohara PHOTOLUMINESCENCE SWITCHING OF NITRIDORHENIUM(V) COMPLEXES B. Grambow, X. Gaona, W. Runde, R. Konings, A.V. Plyasunov, L. Rao, A.L. Smith, E. Moore, M.-E. Ragoussi, J. Martinez-Gonzalez, I. Grenthe. CHEMICAL THERMODYNAMICS OF TECHNETIUM IN THE OECD/NEA UPDATE VOLUME E.S. Kulikova, Zh.K. Majed, D.V. Drobot, E.I. Efremova. HIGHLY SELECTIVE CATALYSTS BASED ON BIMETALLIC RHENIUM-RUTHENIUM COMPLEXES OBTAINED BY ALKOXYTECHNOLOGY E.S. Kulikova, D.V. Drobot, E.I. Efremova. THE FIRST EXAMPLE OF BI AND THREEMETALLIC ALKOXIDES CONTAINING RHENIUM AND RUTHENIUM T. Matsuzaki, H. Sakurai. A NEW PRODUCTION METHOD OF 99Mo BY MUON NUCLEAR TRANSMUTATION N. Budantseva, G. Andreev, A. Fedoseev THE U(VI), NP(VI) AND PU(VI) COMPLEXES WITH TcO4-, ReO4-. THE DIFFICULTIES IN ASSIGNING OF AnO22+ GROUPS VIBRATIONAL FREQUENCIES. J.S. McCloy, C. Soderquist, J. Weaver, Jason Lonergan. SPECTROSCOPIC STUDIES OF ALKALI PERTECHNETATES
Молекулы белков лежат в основе почти всех биологических процессов. Ученым всегда были любопытны как белки, участвующие в метаболических путях, так и молекулярные основы их функционирования. Однако в эру системной биологии еще больше внимание уделяется полному пониманию работы всей совокупности белков организма, его протеома. Все более важно, что мы не только понимаем все стороны данной функции, или функций, какого-либо белка, но и то, что наше знание распространяется на все компоненты изучаемой системы или организма и так далеко, насколько это возможно. Без всестороннего анализа информации попытки синтеза и расчетов не смогут выйти за рамки приближенной реальности.
Книга "Структура и функционирование белков: Применение методов биоинформатики" представляет собой уникальный обзор современного состояния вопросов моделирования структуры белков и предсказания их функции. Книга написана ведущими специалистами в своей области, прекрасно иллюстрирована и содержит ссылки на доступные серверы и другие ресурсы, которые читатель, возможно, захочет использовать в своей научной работе. В конце каждой главы описываются перспективы развития и наиболее актуальные проблемы соответствующих областей науки.
Физико-химические методы исследования в медицине и биологии: Учебное пособие / Медицинский университет Реавиз. Москва, Издательство «Граница», 2016. 120 с.
Данное учебное пособие написано в соответствии с содержанием Государственных образо-вательных стандартов и программой дисциплины “Физико-химические методы анализа” по специальности “Медицина”, направлению и программой большого практикума (раздел “Физикохимические методы анализа”), который выполняется студентами по специальности “Биология”.
В нем изложены основы физико-химических методов анализа. Рассмотрены условия и области применения методов, их достоинства и недостатки, ограничения, перспективы развития и другие особенности и характеристики.
В конце каждой главы дано описание практических работ, приведены контрольные вопросы.
Предназначено для студентов-медиков, биологов, химиков, аспирантов, научных работников и учителей школ.
2016 rsc-advance-tc-c-qinggao wang - 6 pp 16197-16202Konstantin German
We analyze the formation of transition metal (TM) carbides, as determined by the strength of TM–TM and
TM–C bonds, as well as lattice distortions induced by C interstitials. With increasing filling of the d-band of
TMs, TM–C bonds become increasingly weak from the left of the periodic table to the right, with fewer and
fewer C atoms entering the TMs lattice. Technetium (Tc) turns out to be a critical point for the formation of
carbides, guiding us to resolve a long-standing dispute. The predicted Tc carbides, agreeing with measured
X-ray absorption spectra, should decompose to cubic Tc and graphite above 2000 K. Consequently, we
show that what has been claimed as TcC (with rocksalt structure) is actually a high-temperature cubic
phase of elemental technetium.
своевременная диагностика и терапия данного заболевания до сих пор являются нерешенной клинической задачей. По данным на 2011 г., заболе-
ваемость раком простаты в России составила 10,7% (40 тыс. первичных случаев) мужского населения, причем в 60% случаев заболевание диа-
гностировали на поздней (III–IV) стадии, когда неизбежен процесс активного роста и распространения метастазов. Методы анатомической
визуализации при диагностике данного заболевания имеют низкую чувствительность и специфичность. Методы метаболической визуализации,
использующие в качестве маркера простатспецифический антиген (ПСА), также малоэффективны. В качестве маркера для диагностики и
лечения метастатического рака простаты предлагается рассматривать простатспецифический мембранный антиген (ПСМА). За рубежом
проходят клинические испытания наиболее перспективные диагностические радиофармпрепараты на основе малых пептидных молекул, моди-
фицированных мочевиной, которые отличаются наибольшим сродством к ПСМА. Отличительной особенностью этих соединений является их
благоприятная фармакокинетика, высокое и длительное накопление в опухоли и метастазах, быстрое выведение из организма.
Ключевые слова: метастатический рак предстательной железы, простатспецифический мембранный антиген, радиофармпрепараты.
(Для цитирования: Власова О.П., Герман К.Э., Крылов В.В., Петриев В.М., Эпштейн Н.Б. Новые радиофармпрепараты для диагности-
ки и терапии метастатического рака предстательной железы на основе ингибиторов простатспецифического мембранного антигена.
Вестник РАМН. 2015; 70 (3): 360–365. Doi: 10.15690/vramn.v70i3.1334)
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
Azure Interview Questions and Answers PDF By ScholarHat
1988 soubility bu4 n-tco4
1. Journal of R adioanalytical and Nuclear Chemistry, Articles VoL 121, No. 2 (1988) 515-521
ION ASSOCIATION IN TETRAALKYLAMMONIUM
PERTECHNETATE SOLUTIONS
K. E. GERMAN, S. V. KRJUCHKOV,L. L BELYAEVA,V. I. SP1TSYN
Institute of PhysiCal Chemistry, USSR Academy of Sciences,
Moscow (USSR)
(Received November 19, 1987)
The solubility of tetraalkylammonium perteehnetates in aqueous deetrolyte solutions
has been studied. It does not practically depend on ionic strength of the solution when
specific interaction of own ions and ions of the dissolved electrolyte (e.g. LiNO~ up to 5
tool/l) does not occur. A remarkable dependence of Bu~NTeO~ solubility on acidity of the
solution has been found. The influence of ion association on the solubility is discussed.
Introduction
Some properties of substances under consideration make us to take into account
ion association. Such are solubility and its variation while a solution composition is
varied. There are some ions in solutions taking part in complexation equilibria (such
as-association with protons or c6-ions). It influences the solubility values enabling
us to get information on the corresponding equilibrium constants.
Experimental and discussion
We studied the influence of solution acidity and tetrabutyl-ammonium concentration on the solubility of Bu4NTcO4. Solubility was determined by ~-counting of
99Tc. Solubility values obtained are shown in Table I.
Experimental data show that solubility of tetra-n-butyl-ammonium pertechnetate
does not practically depend on the ionic strength of the solution in the absence of
specific interaction of own ions and ions of the dissolved electrolyte (e.g. LiNO3) up
to 5 mol/1. Suffice it to note the practical identity of Bu4NTcO4 solubility in constant ionic strength solutions consisting of LiNO3 and HNO3 and solubility in pure
nitric acid solutions of corresponding concentration.
Solubility measurements for Bu4NTcO4 in nitric acid and in mixtures of HNO3
and IANO3 showed the unexpected remarkable dependence of solubility values on
acidity of the solution.
Elsevier Sequoia S. A., Lausanne
A kad~miat Kiad6, Budapest
2. K. E. GERMAN et al.: ION ASSOCIATION
Table 1
Solubility of Bu4NTeO4 in aqueous
electrolyte solutions at 20 ~
Electrolyte
concentration,
moll1
H~O
_
LiNOs
0.25
0.50
1.00
2.00
5.00
HNO~
0.25
0.50
L00
2.00
3.00
4.00
5.00
Bu4NOH
0.0042
0.010
0.097
0.210
LiNO~ + HNO3
4.50 0.50
4.00 1.00
3.00 2.00
2.00 "3.00
1.00 4.00
Solubility,
mmol/l
4.220.2
4.2 • 0.2
4.3 +-0.2
4.3 • 0.2
4.2 • 0.2
4.3 • 0.2
5.2•
6.220.3
8.1 • 0.3
12.7 • 0.4
15.9 • 0.5
25.9 • 0.8
34.0 • 1.5
4.2 • 0.2
1.3 20.1
0.39 • 0.03
0.24 • 0.02
6.3 •
8.3 •
12.0x0.5
16.0 • 0.5
25.8 • 0.8
To o u r m i n d , o n e o f t h e e x p l a n a t i o n m a y be t h e l o w e r i n g o f H T c O 4 dissociat i o n d u e t o t h e following equilibria:
K1
Bu4NTc04 ~
B u r N § -v TcO~-
K1 = SP,
(1)
K2 = K - 1
diss"
(2)
K2
H+ + TcO~
516
HTcO4
3. ICE. GERMANet al.: ION ASSOCIATION
In such a case it is possible to linearize solubility as follows:
2
2
Cs/Cs, ~ -
1 = K2 "
(A)
aHNO~
C$
- solubility of Bu4 NTc04, mol/1,
C2
= SP -- true product of solubilities of Bu4NTc04,
K2
where
- effective association constant of HTc04,
St 0
aHN03 -
activity of nitric acid, mol/1 (2), anNO, < 3.
The value of 4.1 was computed from this equation for the constant 1(2. Such a
calculation does not take into account the possibility of association of pertechnetate
ion with tetra-n-butyl ammonium, which follows from Table 1, where reduction of
concentration [TeO~ in solutions with different [Bu4N§ is lower than expected
(calculated from the solubility product).
K3
Bu4 Naq + TcO~'aq
+
r
Bu4 NTc04 aq
(3)
A simultaneous consideration of Eqs (1)-(3) leads us to the equation:
-Ks
/
* SP = 1+K2
9
aHNOs
(B)
It is possible to determine Ka by means of extrapolation ufing solubility values of
Bu4NTc04 at large concentration of Bu4NOH (Table 1).
Ca = [Bu4NTcO4]aq "
I
1t
1 + Ka[Bu4 N+]
(c)
Rearranging Eq. (C) we obtain
SP
Cs -
C s , o = [ B u 4 N +]
(D)
517
4. K. E. GERMAN et al.: ION ASSOCIATION
So far as graphical extrapolation in terms of Eq. (D) leads to the value of Cs,o =
= (0.2 • 0.02) X 10-3tool/I, the value K3, calculated using equation D is K3 = 15 • 3
l/mol.
It should be noted that the values measured for RANTcO4 (0.13 tool/1 for R = CH3,
and 0.012 tool/1 for R = C2Hs and 0.0042 mol/l for R = C4H9) are significantly
larger than expected for the salts of univalent cations because of the monotonic reduction of solubility among the alkali metal pertechnetates (Fig. 1).
A
,I-
:
r olLi" ~
/ rt'b
N
Oata r/Z
bNSu~.
~-3
Fig. 1. Solubility of pertechnetates
The latter is at leasI partly connected with the influence of association of [RAN]
[TcO4] in aqueous solutions. The usage of the expression for concentration of TcO,~
according to Eqs. ( I ) and (3) shows that the concentration of the associated salt in
the solution can be introduced as a product of two constants:
Cs,o = [Bu4NTcO4]a q = SP 9 K3
(4)
where from the value of the true solubility product, corrected for association of acid
in the mixture will be introduced as SP = (1.3 -+ 0.5) 9 10 -s mol 2 9 1-2 .
The values obtained enabled us to calculate the correct value of the association constant of the ion TcO~ with protons (K2) using Eq. (B).
As a result, we obtained the value K2 = 4.0 -+ 0.9 mol-1 being almost identical to
the value determined from Eq. (A).
The values of the association constant show that the association of TcOi ions with
Bu4N + and protons should be taken into account in evaluation of the solubility of
518
5. K. E. GERMAN et al.: ION ASSOCIATION
Table 2
Assodation constants of pertechnetate - ion with proton
Determination method
log K
Ionic force
References
Solubility of salt
Potentiometry
Calculation frcm liquid
extraction
Anion e~change
Liquid extraction
Raman spectroscopy
Kinetics
0.60
0.30
0-3
1-4
New data
4
0. 20
0.033
-0.3
-8.0
-8.0
1-4
5
5
0-6
6
7
8
9
-
Bu4NTcO4. Papers devoted to investigations of ion exchange, potentiometry, liquid
extraction, equilibrium work on solutions containing TcO~ ions pointed to the great
importance of taking into account association of pertechnetate ions with protons.
Association constant obtained in this work is compared with literature data in Table 2.
Table 2 shows that methods such as Raman spectroscopy and kinetics lead to pKa
values that conform to PAULING'sI 0 and RICCI'sI 1 hypothesis and indicate complete HTcO4 dissociation in aqueous solutions, while works based on study of real
equilibria in the solution point to a significant decrease of activity of TcO~ ions in
the acid solutions.
The hypothesis introduced in Reference 6 is evidently true. It indicates the presence of a weak outer-sphere (coritact ion pair) complex as well as a strong innersphere one (associate HTcO4). The Observation of this or that complex depends on
the method applied,
i
X
V"
Z
*
Fig. 2. Structure of Bu4NTcO4 ! 2
519
6. K. E. G E R M A N et al.: ION ASSOCIATION
A
O c~
@ c2
0 c3
@c4
|
N~
|
N2
Oo
Fig. 3. Structure of Me, NTcO4 ~~
The problem of the thermodynamic stability o f such weak outer-sphere complexes
is still under discussion. The stability of such associates is evidently connected with
the results of X-ray single crystal analysis showing pseudo-JAHN-TELLER distortion
of the d~
TcOg It was found that TcO4 ion in the structure of tetrabutylammonium pertechnetate has C3v. symmetry (as a result o f shortening of three
T c - O bonds to 1.58 A 12 (Fig. 2). Almost the same structure (Fig. 3) but with one
shorter bond was noted in the course of work with tetramethylammonium. 13 If it
were possible to show that the formation of ion pairs in the mixture is accompanied
by analogous changes, we would have one more argument for enhanced thermodynamic stability o f such associates.
References
1. E. YU. YANSON, YA. K. PUTININ, Teoreticheskie osnovy analiticheskoi khimii, Vyssh.
Shkola, Moscow, 1980, p. 114.
2. V. I. SPITSIN, A. F. KUZINA, Tekhnetsii, Nauka, Moscow, 1981, p. 60.
3. L. I. ZAITSEVA, A. V. VELICHKO, I. V. VINOGRADOV, Soedineniya tekhnetsiya i oblast ikh
prirneneniya, Vol. 9. VINITI, Moscow, 1984, p. 119.
520
7. IC E. GERMAN et al.: ION ASSOCIATION
4. C. L. RUFS, R. F. HIRSCH, R. A. PACER, Nature, 199 (1963) 66.
5. K. H. LIESER, R. N. SINGH, Radiochim. Acta, 32 (1983) 203.
6. T. NAKASHIMA, K. H. LIESER, Radiochira. Acta, 38 (1985) 203.
7. E. VIALARD, M. GERMAIN, Intern. Conf. on Nuclear and Radiochemistry, Lindau, October
1984.
8. G. E. BOYD,Inorg. Chem., 17 (1978) 1808.
9. C. L. RULFS, R. F. HIRSCHER, J. PACER, J. Inor~ Nucl. Chem., 29 (1967) 681.
10. L. PAULING, General Chemistry, San Francisco, Calif., 1947, p. 394.
11. J. E. RICCI, J. Amer. Chem. Soc., 70 (1948) 109.
12. V. I. SPITSIN, A. F. KUZINA, K. E. GERMAN, M. S. GRIGOREV, Dokl. Akad. Nank, SSSR,
Set Kristallografii I., 293 (1987) 101.
13. K. E. GERMAN, M. S. GRIGOREV, A, F. KUZINA, B. F. GUI.~V, V~ I. SPITSIN, Dokl.
Akad. Nauk. SSSR, 287 (1986) 650.
19
521