Model molecules to classify CH⋯O hydrogen-bonds

2018 ◽  
Vol 54 (36) ◽  
pp. 4629-4632 ◽  
Author(s):  
Amol M. Vibhute ◽  
U. Deva Priyakumar ◽  
Arthi Ravi ◽  
Kana M. Sureshan
Keyword(s):  
Hydrogen Bonds ◽  
Bond Strength ◽  
Downfield Shift ◽  
H Nmr

A set of molecules locked in the CH⋯O H-bonding conformation has been used to correlate the magnitude of the downfield shift of the 1H NMR signal due to the bridging hydrogen with the hybridization state of the acceptor oxygen and the CH⋯O H-bond strength.

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.

1H NMR studies of proton transfer equilibria in hydrogen bonds – the role of the entropy

2001 ◽  
Vol 79 (9) ◽  
pp. 1376-1380 ◽  
Author(s):  
Roland Langner ◽  
Georg Zundel
Keyword(s):  
Hydrogen Bonds ◽  
Proton Transfer ◽  
Nmr Studies ◽  
H Nmr

Anionenaktivierung, III. Zur Bedeutung von Wasserstoffbrückenbindungen für das reaktive Verhalten von Kronenäthern und Aminopolyäthern / Anionactivation, III. Anionactivation, III1 Concerning the Significance of Hydrogen-Bonding for the Reactivity of Crown Ethers and Aminopolyethers

1976 ◽  
Vol 31 (9) ◽  
pp. 1192-1200 ◽  
Author(s):  
A. El Basyony ◽  
J. Klimes ◽  
A. Knöchel ◽  
J. Oehler ◽  
G. Rudolph
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Shift ◽  
Hydrogen Bonds ◽  
Crown Ethers ◽  
Organic Molecules ◽  
Substitution Reactions ◽  
Macrocyclic Polyethers ◽  
H Nmr ◽  
Acidic Compounds ◽  
Nmr Signals

Adducts of macrocyclic polyethers (crown ethers) and aminopolyethers1,2 having hydrogen bonds with polar organic molecules, especially with CH-acidic compounds, are described. These can be isolated as solids, and are, as a rule, stoichiometrically consistent. The chemical shift of the 1H NMR signals of the adducts of malononitrile with various crown ethers corresponds to the anionic reactivity of potassium complexes of the crown ethers in the course of nucleophilic substitution reactions.

Zusammensetzung von Rohsulfan, Nachweis der Sulfane H2S9 bis H2S35 Composition of Crude Sulfane Oil, Identification of the Sulfanes H2S9 to H2S35

1985 ◽  
Vol 40 (2) ◽  
pp. 263-272 ◽  
Author(s):  
Josef Hahn
Keyword(s):  
Narrow Range ◽  
Benzene Solution ◽  
Chemical Shifts ◽  
Upfield Shift ◽  
Downfield Shift ◽  
H Nmr ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bondings ◽  
Nmr Signals

In benzene solution the position of the 1H NMR signals of sulfanes, H2Sn, strongly depends on the sulfur chain length and on the sulfane concentration. Under proper conditions all sulfanes in a mixture are characterized by well-resolved NMR signals showing a downfield shift with increasing length of the sulfur chain. The shift differences between the higher homologues ( n > 8 ) remain nearly constant, thus allowing the assignment of the signals up to H2S35 and the determination of the complete sulfane distribution in crude oils. In sulfane mixtures without solvent as well as in CS2 and CCl4 solutions, however, H2S8 shows the largest downfield shift. The signals of the higher sulfanes overlap in a narrow range at slightly higher field and cannot be characterized except for the CCl4 solution where an assignment up to H2S11 is possible. The chemical shifts are interpreted in terms of inter- and intramolecular hydrogen bondings. The upfield shift caused by benzene is attributed to the formation of H2Sn · benzene complexes.

Preparation and Crystal Structure of Genistein Benzenesulfonate Prodrugs

2008 ◽  
Vol 2008 (10) ◽  
pp. 555-558 ◽  
Author(s):  
You Peng ◽  
Zeyuan Deng ◽  
Shaojie Lang ◽  
Yawei Fan
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Sulfonic Acid ◽  
Nmr Spectra ◽  
High Yield ◽  
X Ray Diffraction ◽  
Aromatic Rings ◽  
X Ray ◽  
H Nmr ◽  
Ester Prodrugs

In order to improve bioavailability and anticancer activity of genistein, a series of novel sulfonic acid ester prodrugs of the isoflavone genistein were synthesised in high yield with excellent regioselectivity. Their structures were characterised by IR, MS, elemental analysis and 1H NMR spectra. The crystal structure was examined by X-ray diffraction. X-ray structure determination revealed that all the aromatic rings in the compound are not coplanar. In the crystal structure, molecules are linked through intermolecular C-H···O hydrogen bonds, forming layers parallel to the ab plane.

(3E)-5-Hydroxy-3-[5-(hydroxymethyl)furan-2-ylmethylene]-1-benzofuran-2(3H)-one

2007 ◽  
Vol 63 (11) ◽  
pp. o4354-o4354
Author(s):  
Hong-Yan Ma ◽  
Ji Shi ◽  
Chang-Hong Wang ◽  
Zheng-Tao Wang
Keyword(s):  
Hydrogen Bonds ◽  
Spectroscopic Data ◽  
Furan Ring ◽  
Crystallographic Analysis ◽  
Relative Configuration ◽  
X Ray ◽  
H Nmr ◽  
Compound C ◽  
A Chain ◽  
C Nmr

The title compound, C14H10O5, was isolated from Senecio cannabifolius Less var. integrifolius aqueous extract. The structure was elucidated on the basis of spectroscopic data, including MS, 1H NMR and 13C NMR, and the relative configuration was confirmed by X-ray crystallographic analysis. The benzofuran ring is almost coplanar with the furan ring [dihedral angle = 10.47 (15)°]. A chain is formed through supramolecular R 2 2(10) synthons and three-centre hydrogen bonds.

Estimating the energy of intramolecular hydrogen bonds from1H NMR and QTAIM calculations

2016 ◽  
Vol 14 (47) ◽  
pp. 11199-11211 ◽  
Author(s):  
Andrei V. Afonin ◽  
Alexander V. Vashchenko ◽  
Mark V. Sigalov
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Critical Point ◽  
Intramolecular Hydrogen Bond ◽  
Bond Energy ◽  
Bond Critical Point ◽  
Hydrogen Bond Energy ◽  
H Nmr ◽  
Nmr Data ◽  
Intramolecular Hydrogen

Novel equations have been derived for the assessment of the E intramolecular hydrogen bond energy based on the experimental1H NMR data and the calculated QTAIM topologicalVandρparameters of the hydrogen bond critical point.

Tizanidine and tizanidine hydrochloride: on the correct tautomeric form of tizanidine

2011 ◽  
Vol 68 (1) ◽  
pp. o28-o32 ◽  
Author(s):  
Sándor L. Bekö ◽  
Silke D. Thoms ◽  
Martin U. Schmidt ◽  
Michael Bolte
Keyword(s):  
Hydrogen Bonds ◽  
Structure Determination ◽  
Tautomeric Form ◽  
Asymmetric Unit ◽  
Free Base ◽  
Adrenergic Agonist ◽  
Acta Cryst ◽  
Hydrochloride Salt ◽  
H Nmr

A crystallization series of tizanidine hydrochloride, used as a muscle relaxant for spasticity acting centrally as an α2-adrenergic agonist, yielded single crystals of the free base and the hydrochloride salt. The crystal structures of tizanidine [systematic name: 5-chloro-N-(imidazolidin-2-ylidene)-2,1,3-benzothiadiazol-4-amine], C9H8ClN5S, (I), and tizanidine hydrochloride {systematic name: 2-[(5-chloro-2,1,3-benzothiadiazol-4-yl)amino]imidazolidinium chloride}, C9H9ClN5S+·Cl−, (II), have been determined. Tizanidine crystallizes with two almost identical molecules in the asymmetric unit (r.m.s. deviation = 0.179 Å for all non-H atoms). The molecules are connected by N—H...N hydrogen bonds forming chains running along [2\overline{1}1]. The present structure determination corrects the structure determination of tizanidine by Johnet al.[Acta Cryst.(2011), E67, o838–o839], which shows an incorrect tautomeric form. Tizanidine does not crystallize as the usually drawn 2-amino–imidazoline tautomer, but as the 2-imino–imidazolidine tautomer. This tautomer is present in solution as well, as shown by1H NMR analysis. In tizanidine hydrochloride, cations and anions are connected by N—H...Cl hydrogen bonds to form layers parallel to (100).

Effects of ultrasonic wave pretreatment on the fibrillation of cellulose fiber

TAPPI Journal ◽  
2014 ◽  
Vol 13 (4) ◽  
pp. 37-43 ◽  
Author(s):  
YONGJIAN XU ◽  
YING YAN ◽  
XIAOPENG YUE ◽  
ZHENFENG ZHU ◽  
DINGJUN ZHANG ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Bond Strength ◽  
Ftir Spectroscopy ◽  
Ultrasonic Wave ◽  
Internal Bond ◽  
Cellulose Fiber ◽  
Ultrasonic Waves ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
X Ray

Pinus massoniana Lamb. was used as the raw cellulose fiber material to investigate effects of ultrasonic wave pretreatment and PFI pretreatment on fiber bonding and absorbability. Influences of ultrasonic wave pretreatment on fiber crystalline structure and hydrogen bonds were also analyzed by wide-angle X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy. The absorption and internal bond strength of fiber pretreated by ultrasonic waves increased by 23.49% and 4.07%, respectively, in comparison with those of virgin fiber, which would result in the improvement of weak bonding and absorbability. Instead, when fiber was pretreated by PFI, absorption decreased in comparison with virgin fiber and internal bond strength increased as much as 1.33 times than that of virgin fiber. The analysis of wide-angle X-ray diffraction curves and FTIR spectroscopy curves revealed that the crystallinity of fiber decreased by 20.59% in comparison with that of virgin fiber when treated by ultrasonic waves. Moreover, the effect of ultrasonic wave pretreatment on intramolecular hydrogen bonds was rather stronger than that of intermolecular hydrogen bonds. Therefore, the optimal swelling ability of fiber would be obtained.

Synthesis and X-Ray Crystal Structure of Two Novel Ester Ferrocenophanes

2007 ◽  
Vol 62 (4) ◽  
pp. 605-609 ◽  
Author(s):  
Li Tao ◽  
Yang Bingqin ◽  
Gao Bo
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Elemental Analysis ◽  
3D Structure ◽  
Spectroscopic Methods ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Carbonyl Chloride ◽  
Tof Ms

Two novel ester ferrocenophanes have been prepared by esterification of 1,1′-ferrocenedi(carbonyl chloride) with glycol and 1,4-butanediol, respectively. Both of them have been characterized by IR, elemental analysis, MALDI-TOF MS and 1H NMR spectroscopic methods, and their structures have been elucidated by X-ray diffraction. The intermolecular associations based on C-H···O hydrogen bonds have also been discussed. These molecules are assembled into chains, and the chains are further assembled into a 3D structure through several hydrogen bonds.

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