Étude théorique (AM1) de l'affinité protonique des polyéthers cycliques (éthers couronnes) et non cycliques (glymes)

1991 ◽  
Vol 69 (12) ◽  
pp. 1970-1975 ◽  
Author(s):  
M'hamed Esseffar ◽  
Mohamed El Mouhtadi ◽  
José-Luis M. Abboud ◽  
José Elguero ◽  
Daniel Liotard
Keyword(s):  
Hydrogen Bonds ◽  
Key Words ◽  
Proton Affinity ◽  
Crown Ethers ◽  
Conformational Changes ◽  
Intramolecular Hydrogen Bonds ◽  
Angular Strain ◽  
Intramolecular Hydrogen ◽  
Semi Empirical ◽  
Oxygen Atoms

Semi-empirical calculations at the AM1 level have been used to study the proton affinity (PA) of polyether compounds (dioxane, glymes, and crown ethers). The calculated values, although systematically lower than the experimental ones, are linearly correlated with eight experimental PA's (r = 0.993). Taking into account the considerable conformational changes that take place upon protonation, the result is highly satisfactory and provides an estimate of proton affinity for 9-ether-crown-3 (206.5 kcal mol−1) and glyme-5 (231.1 kcal mol−1). Moreover, this work provides a rationale for the fact that, for the same number of oxygen atoms, glymes are more basic than crown ethers. For the crown ethers, the proton affinity depends on angular strain in the base and on intramolecular hydrogen bonds in the cation. Key words: protonation, reactivity, glymes, crown ethers, coordination.

The molecular and crystal structure of benzamidinium bromoacetate

1988 ◽  
Vol 53 (2) ◽  
pp. 294-300 ◽  
Author(s):  
Bohumil Kratochvíl ◽  
Jan Ondráček ◽  
Karel Malý ◽  
László Csordás
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Least Squares Method ◽  
Ion Pairs ◽  
Molecular And Crystal Structure ◽  
Monoclinic Space Group ◽  
Fourier Synthesis ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen ◽  
Oxygen Atoms

The molecular and crystal structure of benzamidinium bromoacetate was solved on the basis of Patterson and Fourier synthesis. The position of all the atoms were localized and the least squares method was employed to refine the coordinates of all the atoms together with their thermal vibration parameters. A final R factor value of 0.067 was obtained for 1 349 observed reflections (I 1.96 σ(I)). The substance crystallizes in the P21/n monoclinic space group with lattice parameters of a = 1 145.7(2), b = 1 571.3(3), c = 578.3(1) pm, γ = 90.65(1)°, Z = 4. Intramolecular hydrogen bonds form ion pairs in the structure between the nitrogen atoms of the amidinium group and the oxygen atoms of the bromoacetate. Intramolecular hydrogen bonds, also between nitrogen and oxygen atoms, connect the molecules in an infinite chain. The molecular chains are joined together by van der Waals forces. The N···O distance in the hydrogen bonds varies between 280.3(8) and 284.5(8) pm.

Influence of a hydrodynamic environment on chain rigidity, liquid crystallinity, absorptivity, and photoluminescence of hydrogen-bonding-assisted helical poly(phenylacetylene)

RSC Advances ◽  
2016 ◽  
Vol 6 (43) ◽  
pp. 36661-36666 ◽  
Author(s):  
Young-Jae Jin ◽  
Hyojin Kim ◽  
Mari Miyata ◽  
Guanwu Yin ◽  
Takashi Kaneko ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Conformational Changes ◽  
Liquid Crystallinity ◽  
Intramolecular Hydrogen Bonds ◽  
Chain Rigidity ◽  
Intramolecular Hydrogen ◽  
Hydrodynamic Environment

The chain rigidity, liquid crystallinity, absorptivity, and photoluminescence of a helical poly(phenylacetylene) derivative varied significantly depending on the solvent, owing to the conformational changes based on intramolecular hydrogen bonds.

Controlling emissive properties by intramolecular hydrogen bonds: alkyl and aryl meso‐substituted porphycenes

2021 ◽  
Author(s):  
Jacek Waluk ◽  
Arkadiusz Listkowski ◽  
Natalia Masiera ◽  
Michał Kijak ◽  
Roman Luboradzki ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen

Energies of intramolecular hydrogen bonds in some alcohols

1974 ◽  
Vol 20 (3) ◽  
pp. 414-415
Author(s):  
Ya. A. Shuster ◽  
V. A. Granzhan ◽  
P. M. Zaitsev
Keyword(s):  
Hydrogen Bonds ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen

Hydrogen bonds in derivatives of N-substituted N’-benzoyl- and N’-(2-chlorobenzoyl)thiourea

1991 ◽  
Vol 56 (4) ◽  
pp. 880-885 ◽  
Author(s):  
Oľga Hritzová ◽  
Dušan Koščík
Keyword(s):  
Hydrogen Bonds ◽  
Spectral Studies ◽  
Intramolecular Hydrogen Bonds ◽  
Tautomeric Forms ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

Intramolecular hydrogen bonds of the N-H···O=C type have been detected in the derivatives of N-substituted N’-benzoyl- and N’-(2-chlorobenzoyl)thiourea on the basis of IR spectral studies. The title compounds can exist in two tautomeric forms.

Spin-spin coupling via intramolecular hydrogen bonds

1985 ◽  
Vol 25 (5) ◽  
pp. 808-810
Author(s):  
L. N. Kurkovskaya ◽  
Yu. M. Chunaev ◽  
N. M. Przhiyalgovskaya
Keyword(s):  
Hydrogen Bonds ◽  
Spin Coupling ◽  
Intramolecular Hydrogen Bonds ◽  
Intramolecular Hydrogen ◽  
Spin Spin Coupling

3,3′-N,N′-Bis(amino)-2,2′-bipyridine — An unusually methylation-resistant amine

2011 ◽  
Vol 89 (8) ◽  
pp. 971-977
Author(s):  
Danielle M. Chisholm ◽  
Robert McDonald ◽  
J. Scott McIndoe
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Complex Mixtures ◽  
Amino Groups ◽  
Intramolecular Hydrogen Bonds ◽  
X Ray ◽  
Intramolecular Hydrogen

Methylation of aromatic amino groups is usually straightforward, but the formation of two intramolecular hydrogen bonds in 3,3′-N,N′-bis(amino)-2,2′-bipyridine and (or) the potential for ring methylation prevents the clean tetramethylation of this molecule. Numerous attempts to make 3,3′-N,N′-bis(dimethylamino)-2,2′-bipyridine produced only complex mixtures of variously methylated products, and the only isolated molecule was 3,3′-N,N′-bis(methylamino)-2,2′-bipyridine, for which an X-ray crystal structure was obtained.

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