Redshift or Adduct Stabilization—A Computational Study of Hydrogen Bonding in Adducts of Protonated Carboxylic Acids

2009 ◽  
Vol 15 (2) ◽  
pp. 239-248 ◽  
Author(s):  
Solveig Gaarn Olesen ◽  
Steen Hammerum
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Bond Strength ◽  
Bond Length ◽  
Carboxylic Acids ◽  
Computational Study ◽  
Proton Affinities ◽  
Oh Groups ◽  
Hydrogen Bond Strength ◽  
Length Changes

It is generally expected that the hydrogen bond strength in a D–H•••A adduct is predicted by the difference between the proton affinities (Δ PA) of D and A, measured by the adduct stabilization, and demonstrated by the infrared (IR) redshift of the D–H bond stretching vibrational frequency. These criteria do not always yield consistent predictions, as illustrated by the hydrogen bonds formed by the E and Z OH groups of protonated carboxylic acids. The Δ PA and the stabilization of a series of hydrogen bonded adducts indicate that the E OH group forms the stronger hydrogen bonds, whereas the bond length changes and the redshift favor the Z OH group, matching the results of NBO and AIM calculations. This reflects that the thermochemistry of adduct formation is not a good measure of the hydrogen bond strength in charged adducts, and that the ionic interactions in the E and Z adducts of protonated carboxylic acids are different. The OH bond length and IR redshift afford the better measure of hydrogen bond strength.

scholarly journals Raman spectroscopy reveals variation in free OH groups and hydrogen bond strength in ultrahigh dilutions

2021 ◽  
Vol 15 (2) ◽  
pp. 2-9
Author(s):  
Atheni Konar ◽  
Tandra Sarkar ◽  
Indrani Chakraborty ◽  
Nirmal Chandra Sukul ◽  
Dipanwita Majumdar ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Raman Spectroscopy ◽  
Bond Strength ◽  
Relative Number ◽  
Laser Raman Spectroscopy ◽  
Wave Number ◽  
Oh Groups ◽  
Laser Raman ◽  
Hydrogen Bond Strength ◽  
Homeopathic Drugs

Objective: To decipher the nature of water structure in two ultrahigh diluted (UHD) homeopathic drugs by Laser Raman Spectroscopy. Method: Two homeopathic drugs Calcarea carbonica (Calc.) and Sepia officinalis (Sep.) in 8cH, 202cH, and 1002cH and their diluent medium 90% ethanol in 8cH and 202cH were used in the present study. Laser Raman spectra of all the samples were obtained in the wave number region of 2400 – 4200 cm-1. The intensity ratio at vibration frequencies between 3200 and 3420 (R1) and that between 3620 and 3420 (R2) were calculated for each UHD of the samples. Results: The spectra show a marked difference in intensities in the stretching vibrations of CH and OH groups of all the samples. R1 values for three UHDs of Calc. and Sep. show negative and positive relationships, respectively. In the case of R2 values, the relationship in three UHDs is 81002 for Calc., and 8> 202 < 1002 for Sep. In the case of control (ethanol UHDs) both R1 and R2 show a negative relationship. Conclusion: R1 denotes a relative number of OH groups with strong and weak hydrogen bonds. R2 indicates the relative number of OH groups with broken and weak H-bonds. Therefore, the UHDs of the two drugs and the control are different from each other with respect to hydrogen bond strength of OH groups and the number of free OH groups or non-hydrogen bonded water molecules.

scholarly journals Vibrational and Raman spectroscopy provide further evidence in support of free OH groups and hydrogen bond strength underlying difference in two more drugs at ultra high dilutions

2021 ◽  
Vol 15 (3) ◽  
pp. 2-10
Author(s):  
Tandra Sarkar ◽  
Atheni Konar ◽  
Nirmal Chandra Sukul ◽  
Achintya Singha ◽  
Anirban Sukul
Keyword(s):  
Hydrogen Bond ◽  
Bond Strength ◽  
Raman Spectra ◽  
Free Water ◽  
Wave Number ◽  
Water Molecules ◽  
Oh Groups ◽  
X Ray ◽  
Hydrogen Bond Strength ◽  
The Difference

Objective: To confirm that free water molecules and hydrogen bond strength of OH groups underlie difference between two homeopathic drugs at ultrahigh dilution (UHD). Method: FTIR and Laser Raman spectra of UHDs of X-ray and Magnetis Poli Ambo were obtained in the wave number regions of 2400-4000 cm-1 and 2400-4200 cm-1, respectively. Mother tincture (MT) were prepared by exposing ethanol water to X-radiation for X-ray and magnetic field for Magnetis. Spectra of the reference water and the three UHDs of Ethanol were also taken. All the samples were in water-ethanol solution in which the ethanol content was 25%. For FTIR the difference spectrum (absorbance of a UHD minus absorbance of reference water) was obtained after normalization of the spectrum at 3410 cm-1. For Raman spectra the intensity ratio at vibration frequencies between 3200 and 3420 cm-1 (R1), and that between 3620 and 3420 cm-1 (R2), were calculated for each UHD. The intensity at 3600 cm-1 in the difference spectra (FTIR) represents the number of free water molecules in UHDs. R2 values in Raman scattering suggest the same thing. Results: The data in both cases follow almost a similar pattern of difference among the UHDs studied here. For example, X-ray: FTIR 14

Hindered phenol-mediated damping of polyacrylate rubber: effect of hydrogen bonding strength on the damping properties

2019 ◽  
Vol 39 (7) ◽  
pp. 642-652
Author(s):  
Renbo Ma ◽  
Xuewei Zhang ◽  
Chao Liu ◽  
Wei Wu
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Bond Strength ◽  
Mechanical Analysis ◽  
Hydroxyl Group ◽  
Damping Properties ◽  
Scanning Calorimetry ◽  
Hydrogen Bond Strength ◽  
Hindered Phenols ◽  
Hindered Phenol

Abstract The loss factor (tanδ) and glass transition temperature (Tg) are two important parameters for evaluating damping properties. Hydrogen bonds (H bonds) play an important role in improving damping properties. In this work, the effect of the hydrogen bond strength and number on the damping properties was studied. Four hindered phenols with different steric hindrances were used to form hydrogen bonds with different strengths to mediate tanδ and Tg. Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) showed that hindered phenol content lower than 38 wt% led to a linear increase in tanδ and Tg because of the formation of H bonds. The Kwei equation was used to explain the relationship between H bonds and tanδ. When the content was higher than 38 wt%, the small molecule-hindered phenols can be divided into two categories: those that can maintain a good miscibility, thus continuously increasing the tanδ, and those that make tanδ increase slowly or decrease because of poor miscibility. These results demonstrated that tanδ is closely related to both hydrogen bond strength and number. The degree of hindrance of the hydroxyl group determines the hydrogen bond strength, whereas the miscibility determines the number.

Intramolecular Hydrogen Bonds and Fermi Resonance in N-Substituted N'-(2-Fluorobenzoyl)thiourea Derivatives

1994 ◽  
Vol 59 (4) ◽  
pp. 951-956 ◽  
Author(s):  
Oľga Hritzová ◽  
Dušan Koščík
Keyword(s):  
Hydrogen Bond ◽  
Perturbation Theory ◽  
Hydrogen Bonds ◽  
Bond Strength ◽  
Infrared Spectra ◽  
Fermi Resonance ◽  
Absorption Bands ◽  
Thiourea Derivatives ◽  
Hydrogen Bond Strength ◽  
Intramolecular Hydrogen

The presence of intramolecular NH...O=C bonds was proved in N-substituted N'-(2-fluorobenzoyl)thiourea derivatives by analysis of their infrared spectra. The intramolecular vibrational effects bring about a shift of the ν(NH) vibrational band to lower frequencies to the extent that the band gets into a vicinity to the δ(NH) overtone and Fermi resonance occurs between them. In addition, the ν(NH) vibration is also affected by Fermi resonance with the ν(CO) + δ(NH) combination. Double absorption bands were observed in the ν(CO) region for some of the derivatives. Based on perturbation theory applied to three-level interactions and using the Langseth and Lord equations, the band frequencies corrected for Fermi resonance were calculated and the hydrogen bond strength was examined in the compounds studied.

Non-covalent interactions in molecular systems: thermodynamic evaluation of the hydrogen bond strength in aminoalcohols

2021 ◽  
Author(s):  
Riko Siewert ◽  
Ralf Ludwig ◽  
Sergey P. Verevkin
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Bond Strength ◽  
Functional Groups ◽  
Thermodynamic Evaluation ◽  
Molecular Systems ◽  
Hydrogen Bond Strength ◽  
Non Covalent Interactions ◽  
Intramolecular Hydrogen ◽  
Covalent Interactions

In molecules with two functional groups that form hydrogen bonds, the strength of intramolecular hydrogen bonds does not depend significantly on the structure.

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