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.

scholarly journals Hydrogen Bond Arrangement Is Shown to Differ in Coexisting Phases of Aqueous Two-Phase Systems

Biomolecules ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1787
Author(s):  
Pedro P. Madeira ◽  
Amber R. Titus ◽  
Luisa A. Ferreira ◽  
Alexander I. Belgovskiy ◽  
Elizabeth K. Mann ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Hydrogen Bonds ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Two Phase ◽  
Coexisting Phases ◽  
Aqueous Two Phase Systems ◽  
Phase Systems

Analysis by attenuated total reflection–Fourier transform infrared spectroscopy shows that each coexisting phase in aqueous two-phase systems has a different arrangement of hydrogen bonds. Specific arrangements vary for systems formed by different solutes. The hydrogen bond arrangement is shown to correlate with differences in hydrophobic and electrostatic properties of the different phases of five specific systems, four formed by two polymers and one by a single polymer and salt. The results presented here suggest that the arrangement of hydrogen bonds may be an important factor in phase separation.

Insight into structure, stability and hydrogen bond in complexes of guanine and thymine at the molecular level using computational chemical method

2021 ◽  
Vol 11 (1) ◽  
pp. 127-134
Author(s):  
Nhung Ngo Thi Hong ◽  
Huong Dau Thi Thu ◽  
Trung Nguyen Tien
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Energy Surface ◽  
Covalent Bond ◽  
Electrostatic Energy ◽  
Substantial Contribution ◽  
Structure Stability ◽  
Dispersion Terms ◽  
Insight Into

Nine stable structures of complexes formed by interaction of guanine with thymine were located on potential energy surface at B3LYP/6-311++G(2d,2p). The complexes are quite stable with interaction energy from -5,8 to -17,7 kcal.mol-1. Strength of complexes are contributed by hydrogen bonds, in which a pivotal role of N−H×××O/N overcoming C−H×××O/N hydrogen bond, up to to 3.5 times, determines stabilization of complexes investigated. It is found that polarity of N/C−H covalent bond over proton affinity of N/O site governs stability of hydrogen bond in the complexes. The obtained results show that the N/C−H×××O/N red-shifting hydrogen bonds occur in all complexes, and a larger magnitude of an elongation of N−H compared C-H bond length accompanied by a decrease of its stretching frequency is detected in the N/C−H×××O/N hydrogen bond upon complexation. The SAPT2+ analysis indicates the substantial contribution of attractive electrostatic energy versus the induction and dispersion terms in stabilizing the complexes.

scholarly journals Study on the unsaturated hydrogen bond behavior of bio-based polyamide 56

e-Polymers ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 23-31
Author(s):  
Shouyun Zhang ◽  
Jinghong Ma
Keyword(s):  
Hydrogen Bond ◽  
Infrared Spectroscopy ◽  
Hydrogen Bonds ◽  
Metal Oxides ◽  
Significant Influence ◽  
Polymer Chains ◽  
Experimental Results ◽  
Bond Behavior ◽  
Unit Structure

AbstractIn this paper, the unsaturated hydrogen bonds (H-bonds) of the bio-based polyamide 56 (PA56) with an odd-even unit structure were analyzed by infrared spectroscopy. It was proved that the bio-based PA56 had less saturated H-bonds, which became attenuated and blue-shifted at the temperature exceeding 260°C. Besides, as H-bond was decayed and broken, new unsaturated H-bonds readily formed. Moreover, the experimental results obtained strongly indicate that the unsaturated H-bonds of bio-based polyamide 56 could react with polar metal oxides. Besides, the intercalation of montmorillonite was found to have a significant influence on the hydrogen bond between polymer chains.

scholarly journals New insight into single phase formation of capric acid/menthol eutectic mixtures by Fourier-transform infrared spectroscopy and differential scanning calorimetry

2020 ◽  
Vol 19 (2) ◽  
pp. 361-369 ◽  
Author(s):  
Hiba H. Ali ◽  
Mowafaq M. Ghareeb ◽  
Mayyas Al-Remawi ◽  
Faisal T. Al-Akayleh
Keyword(s):  
Differential Scanning Calorimetry ◽  
Hydrogen Bond ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Fourier Transform Infrared Spectroscopy ◽  
Bond Formation ◽  
Capric Acid ◽  
Fourier Transform Infrared ◽  
Scanning Calorimetry ◽  
Hydrogen Bond Formation

Purpose: To examine the structural changes of a eutectic mixture comprising capric acid and menthol which are commonly used in pharmaceutical applications. Methods: A phase diagram was constructed by quantitative mixing of capric acid and menthol under controlled conditions until a single liquid phase was formed. Eutectic mixtures of capric acid: menthol at the ratios of 3:2, 1:4, 1:1, 2:3, and 1:4 were prepared. Hydrogen bond formation and conformational changes were analyzed using Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Microscopic imaging was carried out to capture phase change events upon increasing temperature. Results: Menthol confirmed the intact structure of a hexagonal ring. The high degree of broadening of the menthol O-H groups indicates hydrogen bond formation. FTIR band changes related to capric acid suggest a break-up of the methylene arrangement structure due to changes in the C-H band frequencies. The red shift encountered in C=O stretching band emphasizes hydrogen bond formation taking place between the oxygen atom of the hydroxyl group comprising the carboxylic moiety of capric acid and the hydrogen atom of menthol hydroxyl group. DSC results indicate the presence of two polymorphs of the capric acid/ menthol complex. Both exhibited crystallization and conformational change exotherms in addition to two melting endotherms as result of transformation of crystalline components to become partially crystalline due to hydrogen bond formation. Conclusion: The interaction between capric acid and menthol results in a typical preparation of deep eutectic systems that can act as natural-based solvents in numerous pharmaceutical applications. Keywords: Eutectic system, Capric acid, Menthol, Differential scanning calorimetry, DSC, Fourier transform infrared spectroscopy, FTIR

scholarly journals Integrated Band Intensities of Ethylene (C212H4) by Fourier Transform Infrared Spectroscopy

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
G. B. Lebron ◽  
T. L. Tan
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Ambient Temperature ◽  
Ftir Spectroscopy ◽  
Fourier Transform Infrared ◽  
Vapor Pressures ◽  
Infrared Band ◽  
Combination Bands ◽  
First Time ◽  
Absorbance Spectra

The integrated band intensities of ethylene (12C2H4) in the 640–3260 cm−1 region were determined by Fourier transform infrared (FTIR) spectroscopy. The infrared absorbance spectra of the ν7 and ν10, ν12, ν7+ν8, ν6+ν10, v11, and ν9 and ν2+ν12 bands of ethylene recorded at a resolution of 0.5 cm−1 were measured at an ambient temperature of 296 K at various vapor pressures ranging from 3×10−5 to 1×10−3 atm to obtain respective Beer-Lambert's law plots. The measured integrated band intensities in cm−1/cm atm were S(ν9andν2+ν12)=112.20±0.24, S(ν11)=55.35±0.14, S(ν12)=41.22±0.30, and S(ν7andν10)=328.66±16.55. In addition, the measured infrared band intensities of the ν7+ν8 and ν6+ν10 combination bands of ethylene are reported for the first time: S(ν7+ν8)=21.701±0.028 cm−1/cm atm and S(ν6+ν10)=2.568±0.025 cm−1/cm atm.

Structural polymorphism of pyrazinium hydrogen sulfate: extending chemistry of the pyrazinium salts with small anions

2010 ◽  
Vol 66 (4) ◽  
pp. 451-457 ◽  
Author(s):  
Armand Budzianowski ◽  
Mariana Derzsi ◽  
Piotr J. Leszczyński ◽  
Michał K. Cyrański ◽  
Wojciech Grochala
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bond ◽  
Dipole Moment ◽  
Hydrogen Bonds ◽  
Dft Calculations ◽  
Density Functional ◽  
Hydrogen Sulfate ◽  
Structural Polymorphism ◽  
Functional Theory ◽  
First Time

Two polymorphs (α, β) of pyrazinium hydrogen sulfate (pyzH+HSO_4^-, abbreviated as PHS) with distinctly different hydrogen-bond types and topologies but close electronic energies have been synthesized and characterized for the first time. The α-polymorph (P212121) forms distinct blocks in which the pyzH+ and HSO_4^- ions are interconnected through a network of NH...O and OH...O hydrogen bonds. The β-form (P\bar 1) consists of infinite chains of alternating pyzH+ and HSO_4^- ions connected by NH...O and OH...N hydrogen bonds. Density functional theory (DFT) calculations indicate the possible existence of a hypothetical polar P1 form of the β-polymorph with an unusually high dipole moment.

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