Uncovering Individual Hydrogen Bonds in Rotaxanes by Frequency Shifts

2010 ◽  
Vol 132 (2) ◽  
pp. 484-494 ◽  
Author(s):  
Barbara Kirchner ◽  
Christian Spickermann ◽  
Werner Reckien ◽  
Christoph A. Schalley
Keyword(s):  
Hydrogen Bonds ◽  
Frequency Shifts

Spectral manifestations of strong hydrogen bonds in seven-membered rings of pyrazolecarboxylic acid derivatives

1979 ◽  
Vol 44 (3) ◽  
pp. 781-787 ◽  
Author(s):  
Emil Svátek ◽  
Viktor Zikán ◽  
Miroslav Semonský
Keyword(s):  
Hydrogen Bonds ◽  
Ir Spectra ◽  
Frequency Shift ◽  
Bond Order ◽  
Electronic System ◽  
Uv Spectra ◽  
Carboxyl Group ◽  
Opinion Formation ◽  
Frequency Shifts ◽  
Resonance Stabilization

Strong downward frequency shifts of ν(C=O) of benzoyl or carboxyl group have been found in IR spectra of some pyrazolecarboxylic acid derivatives, and bathochromic shifts of maximum of the first band of π-π* transition have been found in their UV spectra, which can be explained by the presence of strong hydrogen bonds in seven-membered rings. Considerable frequency shift of ν(C=O) indicates lowering of order of this bond which is comparable with the bond order lowering of C=O group in six-membered conjugated chelates of the type of enolized β-diketones. In our opinion, formation of strong hydrogen bonds in seven-membered rings in pyrazolecarboxylic acids is due to the presence of the adjoining five-membered aromatic ring, which enables resonance stabilization of the whole π-electronic system in a pseudo-azulene structure.

The covalence and infrared spectra of cationic hydrogen bonds and dihydrogen bonds

2014 ◽  
Vol 13 (07) ◽  
pp. 1450060 ◽  
Author(s):  
Boaz G. Oliveira
Keyword(s):  
Hydrogen Bonds ◽  
Bond Length ◽  
Infrared Spectra ◽  
Theoretical Study ◽  
Interaction Strength ◽  
Covalent Character ◽  
Frequency Shifts ◽  
Dihydrogen Bonds ◽  
Length Reduction ◽  
Ethyl Cation

A theoretical study of hydrogen bonds and dihydrogen bonds formed by ethyl cation, hydrocarbons and magnesium hydride is presented with calculations performed at the BHandHLYP/6-31G(d,p) level of theory. The structural results and IR analyses demonstrated great insights, mainly the strengthening and weakness of the CC bond of the ethyl cation and π or pseudo-π bonds, respectively. The interaction strength was measured through the supermolecule as well as by means of additional approaches. The QTAIM calculations were applied to characterize not only the intermolecular interactions but specifically the covalent character in the H + ⋯ π, H + ⋯ pseudo-π and H + ⋯ H contacts. The NBO calculations were useful to interpret the polarization on the CC bond and whether this effect is related with the bond length reduction as well as increase of charge density and frequency shifts.

A SPECTROSCOPIC STUDY OF HYDROGEN BONDING IN PERFORMIC AND PERACETIC ACIDS

1952 ◽  
Vol 30 (11) ◽  
pp. 821-830 ◽  
Author(s):  
Paul A. Giguère ◽  
A. Weingartshofer Olmos
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Spectroscopic Study ◽  
Infrared Spectra ◽  
Peracetic Acid ◽  
The Other ◽  
Frequency Shifts ◽  
Vapor State ◽  
Nonpolar Solvents ◽  
Intramolecular Hydrogen

The infrared spectra of concentrated performic and peracetic acids were measured in the rock-salt region. The most significant features are theO—H stretching frequency at 3310–3350 cm−1 and the OH bending frequency at 1450 cm−1 which, for both peracids, remain essentially the same in the vapor state as in the liquid or in solution in nonpolar solvents. This is attributed to intramolecular hydrogen bonds resulting in particularly stable five-membered rings,[Formula: see text]Steric conditions in the percarboxylic group are favourable to such ring formation or chelation. From the observed frequency shifts the energy of these hydrogen bonds is estimated to be about 7 kcal. per mole. No evidence for unchelated molecules was found even in very dilute solutions of peracetic acid in nonpolar solvent nor in the vapour at low pressure and moderate temperature. Tentative assignments of the other frequencies in the spectra of the peracids are made by comparison with those of formic and acetic acids.The danger involved in handling these peracids in concentrated form is emphasized.

Use of molecular overlap to predict intermolecular repulsion in N... H-O hydrogen bonds

1998 ◽  
Vol 95 (3) ◽  
pp. 525-537 ◽  
Author(s):  
I. NOBELI S. L. PRICE R. J. WHEATLEY
Keyword(s):  
Hydrogen Bonds
Sign in / Sign up

Export Citation Format

Share Document