scholarly journals 1H NMR Elucidation of Observed Stable Sugar-NaCl-water Complexes in Aqueous Solution

2021 ◽  
Author(s):  
Gan Zhu ◽  
Hui Li ◽  
Yiqun Li ◽  
Liuqun Gu
Keyword(s):  
1H Nmr ◽  
Direct Evidence ◽  
Aqueous Media ◽  
Hydroxyl Group ◽  
Chemical Transformations ◽  
New Findings ◽  
Pka Value ◽  
Different Types ◽  
Atom Level ◽  
Hydrogen Bondings

The solvation of sugars in aqueous media matters in the understanding of biological systems and carbohydrate transformations. Generally, 2 – 4 water units were proposed to interact with each hydroxyl group in monosaccharides via different types of hydrogen bondings at room temperature in previous studies. Presence of NaCl was known to perturb hydrogen bondings of sugar hydrates. However, direct evidence to elucidate mechanism at atom level is very rare even though “NaCl Effect” was well known in biomass chemical transformations. Here we report 1H NMR elucidation evidences of mono/disaccharides hydrates in different concentration of NaCl aqueous solutions. We here conclude two new findings: 1) under ideal usage of NaCl, different mono/disaccharides hydrates are likely to be converted into a stable sugar-NaCl-water form; 2) pKa value of different hydroxyls in mono/disaccharides has intangible influence on hydrate form change induced by NaCl. An ideal NaCl usage based on maximum of 1H NMR shift was proposed.

Cyanoacetylenic alcohols, molecules of interstellar origin in the biomimetic synthesis of life relevant heterocycles, amino acids, nucleobases and nucleosides: towards prebiotic chemistry

Synthesis ◽  
2021 ◽  
Author(s):  
Boris Trofimov ◽  
Anastasiya Mal’kina
Keyword(s):  
Amino Acids ◽  
Organic Synthesis ◽  
Prebiotic Chemistry ◽  
Aqueous Media ◽  
Biomimetic Synthesis ◽  
Hydroxyl Group ◽  
Chemical Transformations ◽  
Molecular Architecture ◽  
The Past ◽  
Derivatives Of

Cyanoacetylenic alcohols, R1R2C(OH)C≡C-CN, the closest derivatives of cyanoacetylene, an interstellar abundant molecule, are now becoming acknowledgeable in modern organic synthesis which tends to mimic nature. Highly reactive C≡C and C≡N bonds in close vicinity of the hydroxyl group makes these molecules a chemical trinity of mutually influencing functions ensuring an endless number of chemical transformations. All reactions of cyanoacetylenic alcohols parallel modern organic synthesis, being biomimetic. They do not need transition metals (and in most cases, the metals at all except for physiologically indispensible Na+, K+), proceed at ambient temperature and often in aqueous media. Fundamentally, these reactions are 100% atom-economic because they are almost exclusively addition processes. Usually, in the cyanoacetylenic alcohols, cyano, acetylene and hydroxyl functions behave as inseparable entity providing the multiple functionalizations of the forming molecules. This allows hydroxyl, carbonyl, carboxylic, imino, amino, amido, cyanoamido, cyano, various P-containing, ether and ester functions, along with the double bonds and different fundamental heterocycles (furans, furanones, pyrazoles, oxazoles, pyridines, pyrimidines, purins, etc.) and diverse polycyclic systems to be integrated in a one molecular architecture. This review focuses on analysis and generalization of the knowledge accumulated in the chemistry of these cyanoacetylenic alcohols, mostly over the past 15 years.

Point and planar defects in the iron sulfide compounds Fe1-xS

1984 ◽  
Vol 42 ◽  
pp. 434-435
Author(s):  
Thao A. Nguyen
Keyword(s):  
Low Temperatures ◽  
Direct Evidence ◽  
Iron Sulfide ◽  
Planar Defects ◽  
Selective Area ◽  
Vacancy Ordering ◽  
Different Types ◽  
Lattice Images ◽  
The Subject ◽  
Beam Lattice

It is well known that the large deviations from stoichiometry in iron sulfide compounds, Fe1-xS (0≤x≤0.125), are accommodated by iron vacancies which order and form superstructures at low temperatures. Although the ordering of the iron vacancies has been well established, the modes of vacancy ordering, hence superstructures, as a function of composition and temperature are still the subject of much controversy. This investigation gives direct evidence from many-beam lattice images of Fe1-xS that the 4C superstructure transforms into the 3C superstructure (Fig. 1) rather than the MC phase as previously suggested. Also observed are an intrinsic stacking fault in the sulfur sublattice and two different types of vacancy-ordering antiphase boundaries. Evidence from selective area optical diffractograms suggests that these planar defects complicate the diffraction pattern greatly.

Dissociation of imino proton(s) of a highly water-soluble metal-free phthalocyanine and determination of its pKa value in water

2013 ◽  
Vol 17 (06n07) ◽  
pp. 447-453 ◽  
Author(s):  
Hiroaki Isago ◽  
Harumi Fujita
Keyword(s):  
Aqueous Media ◽  
Thermal Reaction ◽  
Water Soluble ◽  
Acid Dissociation ◽  
Acid Dissociation Constant ◽  
Metal Free ◽  
Imino Proton ◽  
Pka Value ◽  
Triton X

Dissociation of imino proton(s) in the cavity of the macrocycle of a highly water-soluble, metal-free phthalocyanine ( H 2( H 4 tsppc ); where H 4 tsppc denotes tetrakis{(2′,6′-dimethyl-4′-sulfonic acid)phenoxy}phthalocyaninate) in ethanolic and aqueous solutions has spectrophotometrically been investigated. The spectral changes associated with reaction with NaOH have been found to involve one-proton transfer process in aqueous media while two-protons process in ethanolic media. The acid-dissociation constant of the first imino proton in water (in the presence of Triton X-100) has been determined to be 12.5 ± 0.2 (as pKa) at 25 °C. The doubly deprotonated species in EtOH has been easily converted to its corresponding cobalt(II) derivative by thermal reaction with anhydrous CoCl 2.

The pKa value of the proximal water molecule trans to a high-valent MnVO porphyrin: towards the control of reactivity by pH

2017 ◽  
Vol 46 (36) ◽  
pp. 12088-12094 ◽  
Author(s):  
Laurie Saint-Germes ◽  
Laure Bar ◽  
Jérôme Dejeu ◽  
Nicolas Spinelli ◽  
Eric Defrancq ◽  
...  
Keyword(s):  
Water Molecule ◽  
Hydroxyl Group ◽  
Protonation State ◽  
Pka Value ◽  
High Valent

In water, the protonation state of the proximal water molecule of a high-valent manganese-oxo porphyrin could be controlled by pH. While in interaction with DNA the porphyrin was able to cleave DNA, only when the proximal water molecule was in the form of a hydroxyl group.

scholarly journals Super Extended Calix[4]Pyrroles as Candidate for Binding Mercury

2018 ◽  
Vol 34 (6) ◽  
pp. 2789-2795
Author(s):  
Maan Al-Nuaim ◽  
H. N. K. AL-Salman ◽  
Hussein H. Hussein
Keyword(s):  
Thermodynamic Parameters ◽  
Organic Solvents ◽  
1H Nmr ◽  
Strong Interaction ◽  
Ester Group ◽  
Hydroxyl Group ◽  
Ester Derivative ◽  
Anion Complexation ◽  
Calorimetric Studies ◽  
Complexation Process

The binding of mercury Hg (II) by calix[4]pyrrole derivative; 2 has been much less discovered than anion complexation. The presence of hydroxyl group in the structure of meso-tetramethyl-tetrakis-[2(4-hydroxyphenyl)ethylcalix[4]pyrrole is important for further modifications in the next steps. The modification of the hydroxyl group by the substitution of ester group was carried out to produce the ester derivative for the modified calix[4]pyrrole 2. The ester group would be expected to deliver high electronic contributions in the complexation processes with the guests as well as to increase the solubility of the receptor in different organic solvents. 1H NMR and isothermal titration calorimetric studies revealed that the receptors exhibited strong interaction with mercury cation and the complexation process was driven enthalpically and entropically. Conductance measurements in acetonitrile were carried out to identify the composition of the formed complex. From Nano Isothermal Titration Calorimetric studies, the thermodynamic parameters for the complexation processes were calculated.

Preparation of Cellulose Stearate and Cellulose Acetate Stearate in 1-Butyl-3-Methylimidazolium Chloride

2013 ◽  
Vol 559 ◽  
pp. 105-110 ◽  
Author(s):  
Elvira Tarasova ◽  
Dmitri Šumigin ◽  
M. Kudrjašova ◽  
A. Krumme
Keyword(s):  
Ionic Liquid ◽  
Cellulose Acetate ◽  
1H Nmr ◽  
Hydroxyl Group ◽  
Cellulose Esters ◽  
Nmr Data

Cellulose stearates were prepared in a 1-butyl-3-metylimidazolium chloride ionic liquid. The addition of base pyridine as well as catalyst Tin octoate sufficiently increases the degree of hydroxyl group substitution. The new path for preparation of cellulose mixed esters, namely cellulose acetate stearate (CAS), is performed. The 1H NMR data confirmed the structure of obtained mono- and mix- cellulose esters.

Flavan derivatives. XVII. Epimerization of the benzylic 4-hydroxyl group in flavan-3,4-diols and the formation of 4-alkyl ethers by solvolysis

1967 ◽  
Vol 20 (10) ◽  
pp. 2151
Author(s):  
JW Clark-Lewis ◽  
LR Williams
Keyword(s):  
Aqueous Media ◽  
Cyclic Ether ◽  
Hydroxyl Group ◽  
Mechanism Of Formation ◽  
Enol Ether ◽  
Mild Conditions ◽  
Ethoxyl Group ◽  
Alkyl Ethers ◽  
By Products ◽  
Thermodynamic Factors

Epimerization and solvolysis of the benzylic 4-hydroxyl group is shown to be a general property of flavan-3,4-diols, and the diols give 4- ethoxyflavan-3-ols with ethanolic hydrochloric acid (1%). The diols are first converted into epimeric mixtures of 3,4-cis- and 3,4-trans-diols and in aqueous media cis-cis-flavan-3,4-diols yield mainly 2,3-cis-3,4- trans-diols. These 2,3-cis-3,4-diols undergo solvolysis to yield 2,3- cis-3,4-trans-4-ethoxyflavan-3-ols in which the 3,4-trans- stereochemistry is controlled by participation of the neighbouring 3ax- hydroxyl group. 2,3-trans-Flavan-3,4-diols give mixtures of trans- trans-diols and 2,3-trans-3,4-cis-diols and solvolysis first yields 2.3-trans-3,4-cis-4-ethoxyflavan-3-ols and then mixtures of the 3,4- cis- and 3,4-trans-ethers; the final proportion of these two ethers is controlled by thermodynamic factors. Solvolysis under mild conditions gives minor products considered to be 3-oxoflavans (or their enols) because of their immediate conversion into antho-cyanidins by cold acids in the presence of air, and from the formation of an enol-ether on prolonged solvolysis under more vigorous conditions. The relevance of these observations to the mechanism of formation of anthocyanidins from flavan-3,4-diols is discussed. Other by-products of solvolysis reactions include a dimeric cyclic ether (dioxan derivative) of 2,3- trans-3,4-cis-7,8,4?-trimethoxyflavan-3,4-diol. The structure and stereochemistry of solvolysis products were established by N.M.R. data; the 4-ethoxyl group in the ethers generally gave rise to an ABX3 multiplet.

scholarly journals Neurotransmitter organization of the nucleus of Edinger–Westphal and its projection to the avian ciliary ganglion

1991 ◽  
Vol 6 (5) ◽  
pp. 451-472 ◽  
Author(s):  
Anton Reiner ◽  
Jonathan T. Erichsen ◽  
John B. Cabot ◽  
Craig Evinger ◽  
Malinda E. C. Fitzerald ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Sole Source ◽  
Ciliary Ganglion ◽  
Choroidal Blood Flow ◽  
Different Types ◽  
Double Label ◽  
Ciliary Ganglion Neurons ◽  
Immunohistochemical Techniques ◽  
Ganglion Neurons ◽  
Immunohistochemical Studies

AbstractTwo morphologically distinct types of preganglionic endings are observed in the avian ciliary ganglion: boutonal and cap-like. Boutonal endings synapse on ciliary ganglion neurons (called choroidal neurons) innervating choroidal blood vessels, while cap-like endings synapse on ciliary ganglion neurons (called ciliary neurons) controlling the lens and pupil. Some of both types of preganglionic endings contain the neuropeptides substance P (SP) and/or leucine-enkephalin (LENK). Although both types of preganglionic terminals are also known to be cholinergic, there has been no direct evidence that SP and LENK are found in cholinergic endings in the ciliary ganglion. The present studies in pigeons, which involved the use of single- and double-label immunohistochemical techniques, were undertaken to examine this issue, as well as to (1) determine the relative percentages of the boutonal and cap-like endings that contain SP, LENK, or both SP and LENK; and (2) determine if the two different types of terminals in the ciliary ganglion arise from different subdivisions of the nucleus of Edinger-Westphal (EW).Single- and double-label immunohistochemical studies revealed that all neurons of EW, regardless of whether they contained immunohistochemically detectible amounts of SP or LENK, are cholinergic. In the medial subdivision of EW (EWM), which was found to contain approximately 700 neurons, 20.2% of these neurons were observed to contain both SP and LENK, while 11.6% were observed to contain SP only and 10.7% were observed to contain LENK only. In contrast, in lateral EW (EWL), which was found to contain approximately 500 neurons, 16.2% of the neurons were observed to contain both SP and LENK, while 19.2% of the neurons were observed to contain SP only and 12.6% were observed to contain LENK only. Retrograde-labeling studies involving horseradish peroxidase injections into the ciliary ganglion revealed that EW was the sole source of input to the ciliary ganglion and all, or nearly all, neurons in EW innervate the ciliary ganglion.Immunohistochemical labeling of the ciliary ganglion neurons with an antiserum against choline acetyltransferase revealed that approximately 900 choroidal neurons and approximately 600 ciliary neurons are present in the ganglion, all of which receive cholinergic preganglionic endings. Of the choroidal neurons, 94% receive butonal terminals containing both SP and LENK, while only 2% receive SP+ only boutonal endings and 2% receive LENK+ only butonal endings. Of the ciliary neurons, 25% receive cap-like endings containing both SP and LENK, 30% receive cap-like endings containing only SP and 3% receive cap-like endings containing only LENK. Total unilateral lesions of EW resulted in the loss of all SP+ or LENK+ terminals in the ipsilateral ganglion. Subtotal EW lesions that spared either part of EWM or part of EWL revealed that boutonal endings arise from EWM neurons and cap-like endings from EWL neurons.The present results suggest that the choroidal neurons, which regulate choroidal blood flow, may be relatively uniform in their functional properties since they nearly all receive boutonal endings from EWM that co-contain SP, LENK, and acetylcholine. In contrast, the ciliary neurons, which receive their preganglionic input from EWL, may consist of at least three major functionally distinct subgroups: (1) those receiving SP/LENK/acetylcholine-containing cap-like endings; (2) those receiving SP/acetylcholine-containing cap-like endings; and (3) those receiving acetylcholine-containing cap-like endings. The functional diversity of ciliary neurons may in part be related to the fact that some ciliary neurons innervate the iris and others the ciliary body.

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