نتایج جستجو برای: intramolecular hydrogen bond

تعداد نتایج: 210500  

Journal: :Molecules 2017
Malose Jack Mphahlele Marole Maria Maluleka Lydia Rhyman Ponnadurai Ramasami Richard Mokome Mampa

The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (¹H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)-NH₂ single bond resulted in non-equivalence of the amide protons and therefore two distinct re...

2008
Oney Ramírez-Rodríguez Maximiliano Martínez-Cifuentes Andres Ibañez Andrés Vega Ramiro Araya-Maturana

In the title mol-ecule, C(16)H(16)O(3), the ring system is planar and an intramolecular hydrogen bond is present. The mol-ecular packing is dominated by an inter-molecular hydrogen bond and by π-stacking inter-actions [inter-planar separation 3.8012 Å].

Journal: :iranian journal of science and technology (sciences) 2004
b. etemadi

the crystal structure of the compound c20 h24 n2 o24 was determined by direct methods. thecrystals are monoclinic, space group p21/n, and unit cell parameters are: a= 10.2342 (9), b=4.8763 (5),c=19.3578 (11) a, β =98.9632 (10) o ,v=956.6 (5) a3, z=2, dc=1.239grm-3, dm=1.22grm-3. the final rfactorsare converged to r=0.059 and rw=0.056 for 553 independent observed reflections. themolecules are li...

2015
Daniel J. Sprague Benjamin M. Nugent Ryan A. Yoder Brandon A. Vara Jeffrey N. Johnston

Chiral diamine-derived hydrogen-bond donors were evaluated for their ability to effect stereocontrol in an intramolecular hetero-Diels-Alder (HDA) reaction hypothesized in the biosynthesis of brevianamides A and B. Collectively, these results provide proof of principle that small-molecule hydrogen-bond catalysis, if even based on a hypothetical biosynthesis construct, holds significant potentia...

Journal: :Acta crystallographica. Section C, Crystal structure communications 2005
Isabelle Sylvestre Colin A Kilner Malcolm A Halcrow

The title compound, C23H24N4OS, contains a highly asymmetric bifurcated intramolecular hydrogen bond between the hydroxy group and two pyrazole N atoms. The compound associates into centrosymmetric dimers in the crystal through two unique C-H...pi interactions, which are in turn linked into a (6,3)-network through an additional intermolecular C-H...N hydrogen bond.

Journal: :Chemical communications 2012
Xin Su Märt Lõkov Agnes Kütt Ivo Leito Ivan Aprahamian

A "V"-shaped Hammett plot shows that resonance-assisted hydrogen bonding does not dictate the strength of the intramolecular hydrogen bond in the E isomers of hydrazone-based switches because it involves an aromatic pyridyl ring.

Journal: :Chemistry 2010
Sirivipa Piyamongkol Yong M Ma Xiao L Kong Zu D Liu Mutlu D Aytemir Dick van der Helm Robert C Hider

The synthesis and physicochemical properties of a range of 2- and 6-amido-3-hydroxypyridin-4-ones are described. All the amido-substituted 3-hydroxypyridin-4-ones have lower pK(a) values than 1,2-dimethyl-3-hydroxypyridin-4-one (deferiprone). This is due to the inductive effect of the amido group. Furthermore, the pK(a) values of the 3-hydroxy group in 1-nonsubstituted pyridinones are dramatica...

Journal: :Molecules 2014
Carlos Z Gómez-Castro Itzia I Padilla-Martínez Efrén V García-Báez José L Castrejón-Flores Ana L Peraza-Campos Francisco J Martínez-Martínez

Intramolecular hydrogen bond (HB) formation was analyzed in the model compounds N-(2-benzoylphenyl)acetamide, N-(2-benzoylphenyl)oxalamate and N1,N2-bis(2-benzoylphenyl)oxalamide. The formation of three-center hydrogen bonds in oxalyl derivatives was demonstrated in the solid state by the X-ray diffraction analysis of the geometric parameters associated with the molecular structures. The solven...

Journal: :The journal of physical chemistry letters 2016
Ralph Welsch Eric Driscoll Jahan M Dawlaty Thomas F Miller

A previously unexplained effect in the relative rate of excited-state intramolecular proton transfer (ESIPT) in related indole derivatives is investigated using both theory and experiment. Ultrafast spectroscopy [ J. Phys. Chem. A, 2015, 119, 5618-5625 ] found that although the diol 1,3-bis(2-pyridylimino)-4,7-dihydroxyisoindole exhibits two equivalent intramolecular hydrogen bonds, the ESIPT r...

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