Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
5.4
2.2
Journals
Symmetry
Special Issues
Symmetry in Acid-Base Chemistry
share announcement

Symmetry in Acid-Base Chemistry

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Chemistry: Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 17012

Special Issue Editor

Prof. Dr. Ewa Daniela Raczyńska

E-Mail Website
Guest Editor
Emeritus Professor, Department of Chemistry, Warsaw University of Life Sciences, 02-787 Warsaw, Poland
Interests: physical organic chemistry; structural chemistry; computational chemistry; gas-phase and solution acid-base equilibria; HB and metal cation adduct formation; tautomerism; substituent and solvent effects
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleague,

Symmetry plays a pivotal role in the permanently moving Univer and also in the continuously progressing life on the Earth. It can be found in the macro- and microworlds of plants, animals, and humans. Symmetry exists in human nature, and it reveals itself in human products of different constructive and artworks, as well as in scientific theories and laws. In acid-base chemistry, the symmetry concept has been introduced in structural studies on chemical compounds possessing an acid, base, or amphoteric character, and additionally in physicochemical, analytical, and spectroscopic investigations on their acid-base properties. Consequently, detailed analyses of internal (structural) and external (solvent) effects on these properties have led to formulating exciting structure–reactivity relationships that are very useful to design new mono- or polyfunctional molecules of desired acidity or basicity. They also help to understand the action of bioactive molecules and drugs in living organisms and to explain the mechanisms of various biochemical processes.

Prof. Dr. Ewa Daniela Raczyńska
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Symmetry in the structure of organic monofunctional and polyfunctional acids and bases, including biomolecules and drugs
  • Isomerization from unsymmetrical to symmetrical acid-base forms and vice versa
  • Electron and/or charge delocalization in relation to acid-base properties
  • Intra- and intermolecular neutral and ionic hydrogen-bonding
  • Proton-transfer reactions, including prototropy
  • Acid-base adducts formation
  • Similarities in substituent and solvent effects

Benefits of Publishing in a Special Issue

  • Ease of navigation: Grouping papers by topic helps scholars navigate broad scope journals more efficiently.
  • Greater discoverability: Special Issues support the reach and impact of scientific research. Articles in Special Issues are more discoverable and cited more frequently.
  • Expansion of research network: Special Issues facilitate connections among authors, fostering scientific collaborations.
  • External promotion: Articles in Special Issues are often promoted through the journal's social media, increasing their visibility.
  • e-Book format: Special Issues with more than 10 articles can be published as dedicated e-books, ensuring wide and rapid dissemination.

Further information on MDPI's Special Issue polices can be found here.

Published Papers (6 papers)

Download All Papers
Order results
Result details
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:

Editorial

Jump to: Research

3 pages, 175 KiB  
Editorial
Symmetry in Acid-Base Chemistry
by Ewa D. Raczyńska
Symmetry 2022, 14(8), 1643; https://doi.org/10.3390/sym14081643 - 10 Aug 2022
Viewed by 1076
Abstract
Most organic molecules, including natural products, drugs, and toxicants, contain functional groups that display acid-base properties [...] Full article
(This article belongs to the Special Issue Symmetry in Acid-Base Chemistry)

Research

Jump to: Editorial

23 pages, 10699 KiB  
Article
Push–Pull Effect on the Gas-Phase Basicity of Nitriles: Transmission of the Resonance Effects by Methylenecyclopropene and Cyclopropenimine π-Systems Substituted by Two Identical Strong Electron Donors
by Ewa D. Raczyńska, Jean-François Gal, Pierre-Charles Maria and Hamid Saeidian
Symmetry 2021, 13(9), 1554; https://doi.org/10.3390/sym13091554 - 24 Aug 2021
Cited by 12 | Viewed by 2140
Abstract
The gas-phase basicity of nitriles can be enhanced by a push–pull effect. The role of the intercalated scaffold between the pushing group (electron-donor) and the pulling (electron-acceptor) nitrile group is crucial in the basicity enhancement, simultaneously having a transmission function and an intrinsic [...] Read more.
The gas-phase basicity of nitriles can be enhanced by a push–pull effect. The role of the intercalated scaffold between the pushing group (electron-donor) and the pulling (electron-acceptor) nitrile group is crucial in the basicity enhancement, simultaneously having a transmission function and an intrinsic contribution to the basicity. In this study, we examine the methylenecyclopropene and the N-analog, cyclopropenimine, as the smallest cyclic π systems that can be considered for resonance propagation in a push–pull system, as well as their derivatives possessing two strong pushing groups (X) attached symmetrically to the cyclopropene scaffold. For basicity and push–pull effect investigations, we apply theoretical methods (DFT and G2). The effects of geometrical and rotational isomerism on the basicity are explored. We establish that the protonation of the cyano group is always favored. The push–pull effect of strong electron donor X substituents is very similar and the two π-systems appear to be good relays for this effect. The effects of groups in the two cyclopropene series are found to be proportional to the effects in the directly substituted nitrile series X–C≡N. In parallel to the basicity, changes in electron delocalization caused by protonation are also assessed on the basis of aromaticity indices. The calculated proton affinities of the nitrile series reported in this study enrich the gas-phase basicity scale of nitriles to around 1000 kJ mol−1. Full article
(This article belongs to the Special Issue Symmetry in Acid-Base Chemistry)
►▼ Show Figures

Figure 1

20 pages, 6517 KiB  
Article
Quantum-Chemical Search for Keto Tautomers of Azulenols in Vacuo and Aqueous Solution
by Ewa D. Raczyńska
Symmetry 2021, 13(3), 497; https://doi.org/10.3390/sym13030497 - 18 Mar 2021
Cited by 5 | Viewed by 2315
Abstract
Keto-enol prototropic conversions for carbonyl compounds and phenols have been extensively studied, and many interesting review articles and even books appeared in the last 50 years. Quite a different situation takes place for derivatives of biologically active azulene, for which only scanty information [...] Read more.
Keto-enol prototropic conversions for carbonyl compounds and phenols have been extensively studied, and many interesting review articles and even books appeared in the last 50 years. Quite a different situation takes place for derivatives of biologically active azulene, for which only scanty information on this phenomenon can be found in the literature. In this work, quantum-chemical studies have been undertaken for symmetrically and unsymmetrically substituted azulenols (constitutional isomers of naphthols). Stabilities of two enol (OH) rotamers and all possible keto (CH) tautomers have been analyzed in the gas phase {DFT(B3LYP)/6-311+G(d,p)} and also in aqueous solution {PCM(water)//DFT(B3LYP)/6-311+G(d,p)}. Contrary to naphthols, for which the keto forms can be neglected, at least one keto isomer (C1H, C2H, and/or C3H) contributes significantly to the tautomeric mixture of each azulenol to a higher degree in vacuo (non-polar environment) than in water (polar amphoteric solvent). The highest amounts of the CH forms have been found for 2- and 5-hydroxyazulenes, and the smallest ones for 1- and 6-hydroxy derivatives. The keto tautomer(s), together with the enol rotamers, can also participate in deprotonation reaction leading to a common anion and influence its acid-base properties. The strongest acidity in vacuo exhibits 6-hydroxyazulene, and the weakest one displays 1-hydroxyazulene, but all azulenols are stronger acids than phenol and naphthols. Bond length alternation in all DFT-optimized structures has been measured using the harmonic oscillator model of electron delocalization (HOMED) index. Generally, the HOMED values decrease for the keto tautomers, particularly for the ring containing the labile proton. Even for the keto tautomers possessing energetic parameters close to those of the enol isomers, the HOMED indices are low. However, some kind of parallelism exists for the keto forms between their relative energies and HOMEDs estimated for the entire molecules. Full article
(This article belongs to the Special Issue Symmetry in Acid-Base Chemistry)
►▼ Show Figures

Figure 1

15 pages, 792 KiB  
Article
The Acid-Base Through-the-Cage Interaction as an Example of an Inversion in a Cage Isomerism
by Jan Cz. Dobrowolski and Sławomir Ostrowski
Symmetry 2020, 12(8), 1291; https://doi.org/10.3390/sym12081291 - 3 Aug 2020
Cited by 3 | Viewed by 2695
Abstract
We define a new inversion in a cage isomerism (ic): X@C⋯Y₪icY@C⋯X, (₪ is the isomerism relation) as an isomerism in the three-component system of molecules X, Y [...] Read more.
We define a new inversion in a cage isomerism (ic): X@C⋯Y₪icY@C⋯X, (₪ is the isomerism relation) as an isomerism in the three-component system of molecules X, Y, and a cage C, in which one of the molecules is located inside and the other outside the cage. The ic isomerism is similar to the endo-exo one, which occurs only if either the interior or exterior of C is empty. By contrast, ic occurs only if neither the interior nor the exterior of C is empty. We also discuss the other closely related types of isomerisms are also discussed. Calculations of the XH⋯NH3@C60 and NH3⋯HX@C60ic isomers were performed at the ωB97XD/Def2TZVP level. The calculated energies demonstrated that the systems with the HX acid outside (X = F, Cl) and the NH3 base inside the cage, XH⋯NH3@C60, are more stable than their ic isomers, NH3⋯HX@C60, by about 4–8 kcal/mol. This is because NH3 is more stabilized inside the cage than HX (a matter of 6.5 kcal/mol). In the studied systems and subsystems, the HX molecules are Lewis acids and the NH3 molecule is always a Lewis base. The C60 molecule with HX inside or outside the cage is also an acid for the NH3 base positioned outside or inside the cage. On the other hand, the C60 cage is truly amphoteric because it is simultaneously an acid and a base. Full article
(This article belongs to the Special Issue Symmetry in Acid-Base Chemistry)
►▼ Show Figures

Graphical abstract

18 pages, 9431 KiB  
Article
Symmetric Potentiometric Cells for the Measurement of Unified pH Values
by Agnes Heering, Daniela Stoica, Filomena Camões, Bárbara Anes, Dániel Nagy, Zsófia Nagyné Szilágyi, Raquel Quendera, Luís Ribeiro, Frank Bastkowski, Rasmus Born, Jaak Nerut, Jaan Saame, Silvie Lainela, Lokman Liv, Emrah Uysal, Matilda Roziková, Martina Vičarová, Alan Snedden, Lisa Deleebeeck, Valentin Radtke, Ingo Krossing and Ivo Leitoadd Show full author list remove Hide full author list
Symmetry 2020, 12(7), 1150; https://doi.org/10.3390/sym12071150 - 9 Jul 2020
Cited by 14 | Viewed by 4483
Abstract
A unified pH scale of absolute values (pHabs scale) enables the comparison of acidities in different solvents. To date, very few different experimental setups have been used for the measurement of values on this scale. The article describes the design and performance [...] Read more.
A unified pH scale of absolute values (pHabs scale) enables the comparison of acidities in different solvents. To date, very few different experimental setups have been used for the measurement of values on this scale. The article describes the design and performance of the different symmetric cells used for unified pH measurement by several institutions. Well-established and reliable standard aqueous buffer solutions are the first step of method validation necessary to achieve a robust metrological level for more complex media. The pH of aqueous standard buffers was measured by differential potentiometry, where the potential between two glass electrodes is measured directly. All the tested electrochemical cells prove to be suitable for unified pH measurements. This validation highlights that the method is, to a large extent, independent of the used equipment, including the cell geometry. The inherent symmetry of the cell design helps to reduce the experimental workload and improve the accuracy of obtained results. Full article
(This article belongs to the Special Issue Symmetry in Acid-Base Chemistry)
►▼ Show Figures

Graphical abstract

47 pages, 17588 KiB  
Article
A Hidden Side of the Conformational Mobility of the Quercetin Molecule Caused by the Rotations of the O3H, O5H and O7H Hydroxyl Groups: In Silico Scrupulous Study
by Ol’ha O. Brovarets’ and Dmytro M. Hovorun
Symmetry 2020, 12(2), 230; https://doi.org/10.3390/sym12020230 - 3 Feb 2020
Cited by 6 | Viewed by 2972
Abstract
In this study at the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of quantum-mechanical theory it was explored conformational variety of the isolated quercetin molecule due to the mirror-symmetrical hindered turnings of the O3H, O5H and O7H hydroxyl groups, belonging to the A and C rings, around the [...] Read more.
In this study at the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of quantum-mechanical theory it was explored conformational variety of the isolated quercetin molecule due to the mirror-symmetrical hindered turnings of the O3H, O5H and O7H hydroxyl groups, belonging to the A and C rings, around the exocyclic C–O bonds. These dipole active conformational transformations proceed through the 72 transition states (TSs; C1 point symmetry) with non-orthogonal orientation of the hydroxyl groups relatively the plane of the A or C rings of the molecule (HO7C7C8/HO7C7C6 = ±(89.9–93.3), HO5C5C10 = ±(108.9–114.4) and HO3C3C4 = ±(113.6–118.8 degrees) (here and below signs ‘±’ corresponds to the enantiomers)) with Gibbs free energy barrier of activation ΔΔGTS in the range 3.51–16.17 kcal·mol−1 under the standard conditions (T = 298.1 K and pressure 1 atm): ΔΔGTSO7H (3.51–4.27) < ΔΔGTSO3H (9.04–11.26) < ΔΔGTSO5H (12.34–16.17 kcal mol−1). Conformational dynamics of the O3H and O5H groups is partially controlled by the intramolecular specific interactions O3H…O4, C2′/C6′H…O3, O3H…C2′/C6′, O5H…O4 and O4…O5, which are flexible and cooperative. Dipole-active interconversions of the enantiomers of the non-planar conformers of the quercetin molecule (C1 point symmetry) is realized via the 24 TSs with C1 point symmetry (HO3C3C2C1 = ±(11.0–19.1), HC2′/C6′C1′C2 = ±(0.6–2.9) and C3C2C1′C2′/C3C2C1′C6′ = ±(1.7–9.1) degree; ΔΔGTS = 1.65–5.59 kcal·mol−1), which are stabilized by the participation of the intramolecular C2′/C6′H…O1 and O3H…HC2′/C6′ H-bonds. Investigated conformational rearrangements are rather quick processes, since the time, which is necessary to acquire thermal equilibrium does not exceed 6.5 ns. Full article
(This article belongs to the Special Issue Symmetry in Acid-Base Chemistry)
►▼ Show Figures

Graphical abstract

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-6
Back to TopTop