scholarly journals Water-Activated Semiquinone Formation and Carboxylic Acid Dissociation in Melanin Revealed by Infrared Spectroscopy

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4403
Author(s):  
Zakhar V. Bedran ◽  
Sergey S. Zhukov ◽  
Pavel A. Abramov ◽  
Ilya O. Tyurenkov ◽  
Boris P. Gorshunov ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Gradual Increase ◽  
Acid Dissociation ◽  
Spectral Features ◽  
Proton Current ◽  
Carboxylic Groups ◽  
The Common ◽  
First Time

Eumelanin is a widespread biomacromolecule pigment in the biosphere and has been widely investigated for numerous bioelectronics and energetic applications. Many of these applications depend on eumelanin’s ability to conduct proton current at various levels of hydration. The origin of this behavior is connected to a comproportionation reaction between oxidized and reduced monomer moieties and water. A hydration-dependent FTIR spectroscopic study on eumelanin is presented herein, which allows for the first time tracking the comproportionation reaction via the gradual increase of the overall aromaticity of melanin monomers in the course of hydration. We identified spectral features associated with the presence of specific “one and a half” C𝌁O bonds, typical for o-semiquinones. Signatures of semiquinone monomers with internal hydrogen bonds and that carboxylic groups, in contrast to semiquinones, begin to dissociate at the very beginning of melanin hydration were indicated. As such, we suggest a modification to the common hydration-dependent conductivity mechanism and propose that the conductivity at low hydration is dominated by carboxylic acid protons, whereas higher hydration levels manifest semiquinone protons.

Hydrogen Bonds in "Carboxyoximes": the Case of Bomane Derivatives

2000 ◽  
Vol 55 (8) ◽  
pp. 677-684 ◽  
Author(s):  
Maciej Kubicki ◽  
Teresa Borowiak ◽  
Wiesław Z. Antkowiak
Keyword(s):  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Carboxylic Acids ◽  
Supramolecular Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carboxylic Groups ◽  
Acid Function

Abstract The tendency of forming mixed carboxyl-to-oxime hydrogen bonds was tested on the series of bornane derivatives: one with the acid function only (bornane-2-endo-carboxylic acid), one with the oxime function (2,2′-diethylthiobomane-3-oxime), and one with both oxime and carboxylic functions (bornane-2-oxime-3-endo-carboxylic acid). The crystal structures of these compounds were determined by means of X-ray diffraction. In bornane-2-endo-carboxylic acid and 2,2′-diethylthiobornane-3-oxime 'homogenic' hydrogen bonds were found, and these hydrogen bonds close eight-and six-membered rings, respectively. By contrast, in bornane-2-oxime-3-endo-carboxylic acid 'heterogenic' hydrogen bonds between carboxylic and oxime bonds were found. This carboxylic-oxime, or 'carboxyoxime' system is almost always present in compounds which have both oxime and carboxylic groups; therefore it can be regarded as an element of supramolecular structures (synthon). The presence of such synthons can break the tendency of carboxylic acids and oximes towards crystallizing in centrosymmetric structures.

Vibrational Spectroscopic Investigation of Glycine Binding in a Zirconium—Aluminum—Glycine Antiperspirant Material

1979 ◽  
Vol 33 (2) ◽  
pp. 114-118
Author(s):  
Richard P. Oertel ◽  
Rhonda M. Rush
Keyword(s):  
Spectral Analysis ◽  
Infrared Spectroscopy ◽  
Spectroscopic Investigation ◽  
Spectral Features ◽  
Vibrational Modes ◽  
Infrared Band ◽  
Raman And Infrared Spectroscopy ◽  
Almost All ◽  
First Time ◽  
Inhibiting Property

Through use of Raman and infrared spectroscopy, we have determined the mode of incorporation of glycine, a gelation inhibitor, in a complex antiperspirant material (ZAG) containing zirconium and aluminum hydroxy chlorides. Most of the vibrational modes of glycine are affected upon inclusion of this component in ZAG. Our spectral analysis indicates that the glycine in ZAG exists as the dipolar ion, coordinated to metal ions through the COO− end and hydrogen bonded to various constituents through the NH3+ end. Almost all of the glycine in solid ZAG is bound in this fashion, as is more than half of the glycine in a 50% (by wt.) aqueous ZAG solution. This binding could well contribute to the gelation-inhibiting property of the glycine in aqueous ZAG by interfering with the extended hydroxy and oxy bridging that commonly exists in solutions containing Zr(IV) and Al(III). Several spectral features of the bound glycine dipolar ion, most especially a prominent Raman and infrared band near 1475 cm−1, are discussed in detail for the first time.

scholarly journals Crystal structure of 7,7-dimethyl-6-methylidenetricyclo[6.2.1.01,5]undecane-2-carboxylic acid

2015 ◽  
Vol 71 (2) ◽  
pp. o94-o94
Author(s):  
Noureddine Beghidja ◽  
Samir Benayache ◽  
Fadila Benayache ◽  
David W. Knight ◽  
Benson M. Kariuki
Keyword(s):  
Crystal Structure ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Rotation Axis ◽  
Chair Conformation ◽  
Membered Ring ◽  
Envelope Conformation ◽  
Compound C ◽  
Carboxylic Groups

In the title compound, C15H22O2, both five-membered rings display an envelope conformation whereas the six-membered ring displays a chair conformation. In the crystal, pairs of O—H...O hydrogen bonds between carboxylic groups link molecules, related by a twofold rotation axis, into supramolecular dimers.

scholarly journals NEW TRANS-1,2- CYCLOHEXYLDIAMINO-NN,N’N’ (CH2CO2)(CH2CO2H)3 ANION CONTAINING ADDUCTS AND DERIVATIVES: SYNTHESIS AND INFRARED STUDY

2018 ◽  
Vol 23 (4) ◽  
Author(s):  
GORGUI AWA SECK ◽  
ABOUBACRY SENE ◽  
LIBASSE DIOP
Keyword(s):  
Infrared Spectroscopy ◽  
Hydrogen Bonds ◽  
Infrared Study ◽  
Supramolecular Architectures ◽  
Trigonal Bipyramidal ◽  
Carboxylic Groups ◽  
Mercury Halides

<p>Five Cyclohexyldiamino-NN, N’N’(CH<sub>2</sub>CO<sub>2</sub>)(CH<sub>2</sub>CO<sub>2</sub>H)<sub>3</sub> anion containing adducts and derivatives with tin, antimony and mercury halides  have been synthesized and characterized by infrared spectroscopy. The suggested structures are discrete, the anion behaving as a monodentate or a monochelating ligand: the environments around the metallic centres are trigonal bipyramidal or octahedral.The carboxylic groups and the cation, when involved in extra OH---O, OH----Cl or NH---Cl or O hydrogen bonds may lead to supramolecular architectures.</p>

scholarly journals NEW TRANS-1,2- CYCLOHEXYLDIAMINO-NN,N’N’ (CH2CO2)(CH2CO2H)3 ANION CONTAINING ADDUCTS AND DERIVATIVES: SYNTHESIS AND INFRARED STUDY

2017 ◽  
Vol 23 (4) ◽  
pp. 32-36
Author(s):  
GORGUI AWA SECK ◽  
ABOUBACRY SENE ◽  
LIBASSE DIOP
Keyword(s):  
Infrared Spectroscopy ◽  
Hydrogen Bonds ◽  
Infrared Study ◽  
Supramolecular Architectures ◽  
Trigonal Bipyramidal ◽  
Carboxylic Groups ◽  
Mercury Halides

Five Cyclohexyldiamino-NN, N’N’(CH2CO2)(CH2CO2H)3 anion containing adducts and derivatives with tin, antimony and mercury halides have been synthesized and characterized by infrared spectroscopy. The suggested structures are discrete, the anion behaving as a monodentate or a monochelating ligand: the environments around the metallic centres are trigonal bipyramidal or octahedral.The carboxylic groups and the cation, when involved in extra OH---O, OH----Cl or NH---Cl or O hydrogen bonds may lead to supramolecular architectures.

scholarly journals The role of hydrogen bonds in diluted ethanol solutions of cyclohexane and dimethylformamide

2021 ◽  
pp. 44-47
Keyword(s):  
Hydrogen Bond ◽  
Refractive Index ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Hydrogen Bonds ◽  
Ethanol Solution ◽  
Pure Ethanol ◽  
First Time ◽  
Formed Hydrogen

The aim of this work is to determine molecular association in solutions of cyclohexane-ethanol and dimethylformamide-ethanol. The refractometric method and Fourier transform infrared spectroscopy used to determine the optical features of the concentration characteristics of diluted ethanol solutions of cyclohexane and dimethylformamide. It was found for the first time that at some concentrations the hydrogen bond is stronger than for a pure ethanol solution. The first maximum of the excess refractive index of solutions is formed at a concentration of 0.02 mole fraction of cyclohexane and dimethylformamide, which is in good correlation with IR spectroscopy, indicating the largest number of formed hydrogen bonds.

Preparation of potassium selenites, their solubility and bonding conditions

1986 ◽  
Vol 51 (12) ◽  
pp. 2741-2750 ◽  
Author(s):  
Zdeněk Mička ◽  
Miroslav Ebert ◽  
Pavel Ptáček
Keyword(s):  
Infrared Spectroscopy ◽  
Hydrogen Bonds ◽  
Point Of View ◽  
Effect Of Temperature ◽  
Solubility Diagrams ◽  
Preparation Conditions ◽  
First Time ◽  
Acid Salts

The solubility diagrams of a K2SeO3-H2SeO3-H2O system were studied at 293 and 303 K for the first time. The effect of temperature on the character of the studied system from the point of view of the transition from hydrogenselenite to diselenite was studied. The results were used to refine the preparation conditions for K5H3(SeO3)4, KHSeO3, KH3(SeO3)2, and K2Se2O5. The compounds obtained were studied using thermoanalytical methods and infrared spectroscopy. The behaviour of protons in the hydrogen bonds of the acid salts was described.

(±)-2,2-Dimethyl-5-oxotetrahydrofuran-3-carboxylic acid (terebic acid): a racemic layered structure

2012 ◽  
Vol 68 (8) ◽  
pp. o294-o297
Author(s):  
L. M. Santos ◽  
A. O. Legendre ◽  
P. C. M. Villis ◽  
C. Viegas Jr ◽  
A. C. Doriguetto
Keyword(s):  
Crystal Structure ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Layered Structure ◽  
Chemical Compound ◽  
Crystalline Form ◽  
Double Layers ◽  
Industrial Chemical ◽  
First Time

A racemic crystalline form of terebic acid, C7H10O4, which is an important industrial chemical compound, is reported for the first time. The crystal structure is stabilized by O—H...O and C—H...O hydrogen bonds which form racemic double layers parallel to (001).

Peculiarities of the juvenile period of the native Chechen genotypes of willow leaf pear (Pyrus salicifolia Pall.)

2020 ◽  
Vol 62 ◽  
pp. 32-38
Author(s):  
E. A. Dolmatov ◽  
R. B. Borzayev ◽  
A. N. Shaipov
Keyword(s):  
Chestnut Soil ◽  
Crop Breeding ◽  
Juvenile Period ◽  
Period 2 ◽  
Russian Research Institute ◽  
The Common ◽  
One Year ◽  
First Time ◽  
Selection Of ◽  
Creative Cooperation

The results of the study of the duration of the juvenile period of indigenous Chechen willow leaf pear genotypes (Pyrus salicifolia Pall.) are given in connection with the acceleration of the breeding process and the use of selected forms in pear breeding for high precocity. The studies were carried out in 2016-2019 at OOO “Orchards of Chechnya” in accordance with the Agreement on creative cooperation with the Russian Research Institute of Fruit Crop Breeding. The work was carried out in accordance with generally accepted programs and methods. The objects of the study were one-year and two-year-old pear seedlings obtained from sowing seeds of selected dwarf and low-growing local Chechen forms of willow pear (P. salicifolia Pall.), laying fruit buds on annual growths and seedlings of Caucasian pear (P. caucasica Fed.), 20 500 pcs. of each specie. The aim of the research was to study the potential of precocity of willow pear seedlings and to reveal of selected forms with the greatest degree of this trait. Stratified seeds were sown in the sowing department of the OOO “Orchards of Chechnya” production nursery in April, 2017. The seedlings were grown according to the common technology in dryland conditions on the plot with chestnut soil. The first fl owering of plants was noted in the spring, 2019. As a result of the research, for the first time on a large number of the experimental material it was found that in the off spring of the indigenous Chechen willow leaf pear genotypes, the selection of a little more than 2% of seedlings with a very short juvenile period (2 years) was possible. They are of great interest in accelerating the breeding process and in the selection of new pear varieties with high precocity. 20 willow leaf pear genotypes were selected for the further use in breeding for high precocity and as sources of the trait of short juvenile period.

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