The effects of magnesium2+, hydrogen bonding, and steric factors on rate and equilibrium constants for phosphoryl transfer between carboxylate ions and pyridines

1990 ◽  
Vol 112 (5) ◽  
pp. 1942-1950 ◽  
Author(s):  
Daniel Herschlag ◽  
William P. Jencks
Keyword(s):  
Hydrogen Bonding ◽  
Equilibrium Constants ◽  
Phosphoryl Transfer ◽  
Steric Factors

Hydrogen bonding between phenols and cyanides

1966 ◽  
Vol 291 (1427) ◽  
pp. 460-468 ◽  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Carbon Tetrachloride ◽  
Equilibrium Constants ◽  
Lone Pair ◽  
Frequency Shifts ◽  
Tertiary Butyl ◽  
Group Frequency ◽  
Steric Factors ◽  
Lone Pair Electrons

The association between phenols and cyanides, dissolved in carbon tetrachloride, has been measured. The shifts of the bonded OH group frequency have been determined for a range of cyanides, and correlated with the Taft inductive factors of the groups concerned. Equilibrium constants for the formation of the complexes have been determined and correlated with the frequency shifts. The influence of steric factors has been studied, and it has been found that tertiary butyl groups in the ortho positions of phenol restrict the formation of the hydrogen bond. In most cases, the C≡N group frequency is displaced to higher frequency when bonded to a phenol. This effect is unusual, and suggests that the bonding occurs through the lone pair electrons on the nitrogen atom. Some data on the widths of the association bands have been given.

Hydrogen bonding in the gas phase: the thermodynamic properties of hydrogen fluoride-ether complexes and their far infrared spectra

1971 ◽  
Vol 322 (1548) ◽  
pp. 137-146 ◽  
Keyword(s):  
Hydrogen Bonding ◽  
Gas Phase ◽  
Infrared Spectra ◽  
Equilibrium Constants ◽  
Far Infrared ◽  
Methyl Ethyl ◽  
Rotational Contour ◽  
Stretching Vibration ◽  
Conformational Rearrangements ◽  
Far Infrared Spectra

The equilibrium constants of gas-phase complexes of HF with dimethyl, methyl ethyl and diethyl ether have been measured at several temperatures using the Benesi-Hildebrand approximation on the absorption band of the HF stretching vibration in the complex. From these, values of Δ H of — 43, — 38 and — 30 kJ mol -1 respectively, have been determined. They are interpreted in terms of conformational rearrangements of the ethers when they form hydrogen bonds. The far infrared spectra of the complexes with both HF and DF have also been recorded and in each case a band observed at around 180 cm -1 which is assigned to the intermolecular stretching mode of vibration. For the complex between HF and dimethyl ether a rotational contour has been observed at about 10 cm -1 .

Anion-molecule complexes in solution. II. The complexing of halide ions with acetylated β-D-glucopyranosyl derivatives

1968 ◽  
Vol 46 (20) ◽  
pp. 3263-3274 ◽  
Author(s):  
J. S. Martin ◽  
Jun-Ichi Hayami ◽  
R. U. Lemieux
Keyword(s):  
Hydrogen Bonding ◽  
Equilibrium Constants ◽  
Strong Dependence ◽  
Electrostatic Model ◽  
Halide Ions ◽  
Pyranose Ring

Tetra-O-acetyl-β-D-glucopyranosyl halides and phenoxides in solution in acetonitrile showed a specific deshielding of H-1, H-3, and H-5 on addition of tetraethylammonium halides. The shifts and equilibrium constants increased as the anion radius decreased. The ortho hydrogens of the phenoxide aglucons were also significantly deshielded. The strong dependence of the equilibrium constants of the phenoxide compounds on p-substituents indicated considerable involvement of the phenyl groups in a specific conformation. A simple electrostatic model was successful in correlating the energies and predicting the structures of the complexes. It was not necessary to postulate specific hydrogen bonding to account for association of the anion with an electrophilic region of the molecule. The calculations required specific orientations of acetoxy groups with respect to the pyranose ring which are consistent with those of related studies. In favorable circumstances, the method may be used as a probe for electrophilic regions in molecules.

scholarly journals Crystal structure and vibrational spectra of salts of 1H-pyrazole-1-carboxamidine and its protonation route

2020 ◽  
Author(s):  
Piotr Rejnhardt ◽  
Marek Daszkiewicz
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Vibrational Spectra ◽  
Theoretical Calculations ◽  
Equilibrium Constants ◽  
Tautomeric Equilibrium ◽  
Potential Energy Distribution ◽  
Distribution Analysis ◽  
Cationic Form ◽  
Inorganic Acids

Abstract Crystal structures of five salts of 1H-pyrazole-1-carboxamidine, PyCA, with various inorganic acids were determined, (HPyCA)Cl, (HPyCA)Cl·H2O, (HPyCA)Br, (HPyCA)2(I)I3, and (HPyCA)HSO4. Theoretical calculations of the protonation route of PyCA showed that the cationic form present in the studied crystals is energetically privileged. Tautomeric equilibrium constants indicated two isomers as the most stable neutral forms. Calculations for two other tautomers failed resulting in pyrazole and carbodiimid tautomer of cyanamide. Such decomposition is important in a view of guanylation reaction. Hydrogen bonding patterns were studied by means of the graph-set approach. Similarities of the patterns in different crystal structures were demonstrated by the algebraic relations between descriptors of the patterns. The strength of hydrogen bonding network in the crystals was assessed analyzing vibrational spectra. The bands were assigned on the basis of theoretical calculations for the complex [(HPyCA)2Cl4]2– ion and potential energy distribution analysis. The strength of hydrogen bonds was set in the following ascending series (HPyCA)2(I)I3 (4) < (HPyCA)Br (3) < (HPyCA)Cl (1) < (HPyCA)Cl·H2O (2) < (HPyCA)HSO4 (5).

Hydrogen bonding of alcohols with AOT in carbon tetrachloride: an infrared study

1985 ◽  
Vol 63 (12) ◽  
pp. 3367-3370 ◽  
Author(s):  
Pierre Ménassa ◽  
Camille Sandorfy
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectroscopy ◽  
Carbon Tetrachloride ◽  
Equilibrium Constants ◽  
Short Chain ◽  
Infrared Study ◽  
Free Band ◽  
Long Chain ◽  
Cyclic Alcohols ◽  
Aliphatic Chains

The interaction of the inverted micelles of AOT (sodium di(2-ethylhexyl)sulfosuccinate) with different alcohols due to hydrogen bonding has been studied by means of infrared spectroscopy. Spectra of solutions of the alcohols with increasing concentrations of AOT showed a decrease in the intensity of the free OH stretching band. At the same time a new OH band due to a H-bonded alcohol-inverted micelle complex appears and its intensity increases as the intensity of the free band decreases. Calculated values of the equilibrium constants for the formation of the complexes n-alcohol–AOT, showed a decrease in alcohol–AOT association with the increase of the length of the aliphatic chains in the n-alcohols. Surprisingly, cholesterol behaved like a short chain while other cyclic alcohols like long chain alcohols.

Liaison hydrogène des arylamines : compétition des sites π et N

2004 ◽  
Vol 82 (9) ◽  
pp. 1413-1422 ◽  
Author(s):  
Eric Marquis ◽  
Jérôme Graton ◽  
Michel Berthelot ◽  
Aurélien Planchat ◽  
Christian Laurence
Keyword(s):  
Hydrogen Bonding ◽  
Lone Pair ◽  
Molecular Electrostatic Potentials ◽  
Hydrogen Bond Donor ◽  
Complexation Constant ◽  
Steric Factors ◽  
Troger's Base ◽  
Nitrogen Lone Pair ◽  
Ir Study ◽  
Hydrogen Bonded

An IR study, in the region of OH stretching, of a reference hydrogen-bond donor, 4-fluorophenol, hydrogen bonded to primary, secondary, and tertiary arylamines differently substituted on the ring and on the nitrogen, shows the formation of two kinds of 1:1 complexes in CCl4 solution: an OH···π and an OH···N hydrogen-bonded complex. The IR method gives only access to a global complexation constant Kt. A method is proposed for separating Kt into a Kπ component for hydrogen bonding to the π system and a KN component for hydrogen bonding to the nitrogen atom. This method is validated by comparing the estimated Kπ and KN values to theoretically calculated descriptors of basicity: the nitrogen lone pair orientation towards the aromatic ring, the molecular electrostatic potentials around the nitrogen and the π cloud, and the enthalpy of hydrogen bonding of hydrogen fluoride with the π system of selected arylamines. The main electronic and steric factors governing the competition between π and N sites are analysed. The strongest π and N bases among the arylamines are julolidine and Tröger's base, respectively. Triphenylamine and diphenylamine, which are nitrogen Brønsted bases, become π bases in hydrogen bonding. Moreover, there is no correlation between the pKHB and the pKBH+ scales of basicity of arylamines. The use of the pKBH+ scale is therefore not recommended in hydrogen-bonding studies.Key words: hydrogen bonding, arylamines, pKHB scale, competition of π and N hydrogen-bonded sites.

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