Relationships between the proton donor capacity in hydrogen bonds and the CH acidity

1984 ◽  
Vol 20 (1) ◽  
pp. 29-33 ◽  
Author(s):  
T. B. Vishnyakova ◽  
V. K. Pogorelyi
Keyword(s):  
Hydrogen Bonds ◽  
Proton Donor ◽  
Donor Capacity

Theoretical study of hydrogen bonds between acetylene and selected proton donor systems

2004 ◽  
Vol 101 (2) ◽  
pp. 186-200 ◽  
Author(s):  
A. Bende ◽  
Á. Vibók ◽  
G. J. Halász ◽  
S. Suhai
Keyword(s):  
Hydrogen Bonds ◽  
Theoretical Study ◽  
Proton Donor

Intramolecular hydrogen bonds and the orientation of amino groupsin o-phenylenediamines

1967 ◽  
Vol 45 (19) ◽  
pp. 2135-2141 ◽  
Author(s):  
P. J. Krueger
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Infrared Absorption ◽  
Substituent Effect ◽  
Proton Donor ◽  
Proton Acceptor ◽  
Amino Groups ◽  
Intramolecular Hydrogen Bonds ◽  
Infrared Absorption Spectra ◽  
Intramolecular Hydrogen

The infrared absorption spectra of partially deuterated o-phenylenediamine and 4,5-di-methyl-, 4-methyl-, and 4-chloro-o-phenylenediamine in dilute CCl4 solution show double intramolecular [Formula: see text] hydrogen bonds in which the two NHD groups are equivalent and each group acts as both a proton donor and a proton acceptor. The ring substituent effect on this interaction in these compounds is small. In 4-methoxy-o-phenylenediamine, the amino groups are not equivalent, but double intramolecular hydrogen bonds are still present. In 4-nitro-o-phenylenediamine, only one intramolecular [Formula: see text] hydrogen bond appears to exist. The effect of N-substitution on some of these observations is discussed.

'Breaking' and formation of hydrogen bonds by proton donor anesthetics

1977 ◽  
Vol 55 (18) ◽  
pp. 3211-3217 ◽  
Author(s):  
Rachel Massuda ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Bonds ◽  
Electron Acceptor ◽  
Proton Donor ◽  
Point Of View ◽  
Mobile Hydrogen ◽  
Competitive Mechanism ◽  
Text Types ◽  
Anesthetic Potency ◽  
Mobile Hydrogen Atom

It has been shown previously that halofluorocarbons having anesthetic potency hinder the formation of hydrogen bonds (HB) of the [Formula: see text] types and it has been suggested that this is linked to a competitive mechanism involving another type of association. Since some of the most potent and widely used fluorocarbon anesthetics contain a mobile hydrogen atom the question arises if in such molecules the competitive mechanism involves the formation of HB's with the anesthetic as the proton donor instead of, or in addition to, association due to the electron acceptor properties of the higher halogens as seems to be the case for those fluorocarbon anesthetics which contain no hydrogen. Chloroform, halothane, methoxyflurane, enflurane, and 4,5-dichloro-2,2-difluoro-l,3-dioxolane have been studied from this point of view with the result that both mechanisms appear to operate.

Hydrogen Bonding Contribution to Lipophilicity Parameters. Hydrogen Acceptor and Hydrogen Acceptor Donor Parameters

2004 ◽  
Vol 69 (12) ◽  
pp. 2147-2173 ◽  
Author(s):  
Marvin Charton ◽  
Barbara I. Charton
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Reasonable Assumption ◽  
Hydrogen Acceptor ◽  
Donor Capacity ◽  
The Difference ◽  
Acceptor Capacity ◽  
Lipophilicity Parameters ◽  
Hydrogen Bond Energies

In our analysis of the composition of lipophilicity parameters by the intermolecular force (IMF) model we have made use of nH, the number of OH and/or NH bonds, as a measure of the hydrogen donor capacity of a substituent; and nn, the number of lone pairs on O and/or N atoms in the substituent, as a measure of the hydrogen acceptor capacity of the substituent. The basis of this method is the reasonable assumption that in 55.6 molar water hydrogen bonding is maximized. The method does not account however for differences in the energy of different types of hydrogen bonds, but further assumes that these differences are to a first approximation negligible. In order to improve the model we have defined a scale of group hydrogen bonding acceptor parameters, ηXHA, and overall hydrogen bond parameters ηXHAD from the water/1-octanol partition coefficients of AkX where Ak is alkyl. These parameters should account for both the extent of hydrogen bonding in water and for the difference in hydrogen bond energies of the various types of hydrogen bonds encountered. Correlations of log P values for Ph(CH2)nX, X1(CH2)X2, and substituted amino acids Xaa with the IMF equation using the ηXHA and ηXHAD parameters demonstrated their use. Correlation of log P values for PhX suggested that for many groups separate sets of ηXHA and ηXHAD values are required when they are bonded to sp2 hybridized carbon rather than sp3 hybridized carbon.

scholarly journals An analysis of the role of active site protic residues of cytochrome P-450s: mechanistic and mutational studies on 17α-hydroxylase-17,20-lyase (P-45017α also CYP17)

1998 ◽  
Vol 330 (2) ◽  
pp. 967-974 ◽  
Author(s):  
Peter LEE-ROBICHAUD ◽  
E. Monika AKHTAR ◽  
Muhammad AKHTAR
Keyword(s):  
Hydrogen Bonds ◽  
Active Site ◽  
Catalytic Properties ◽  
Active Form ◽  
Proton Donor ◽  
Wild Type ◽  
Cleavage Reaction ◽  
Acyl Carbon ◽  
Hydroxylation Reaction

Certain cytochrome P-450s involved in the transformation of steroids catalyse not only the hydroxylation process associated with the group of enzymes, but also an acyl-carbon cleavage reaction. The hydroxylation occurs using an iron-monooxygen species while the acyl-carbon cleavage has been suggested to be promoted by an iron peroxide. In this paper we have studied the role of active site protic residues, Glu305 and Thr306, in modulating the two activities. For this purpose, the kinetic parameters for the hydroxylation reaction (pregnenolone → 17α-hydroxypregnenolone) and two different versions of acyl-carbon cleavage (17α-hydroxypregnenolone → dehydroepiandrosterone and 3β-hydroxyandrost-5-ene-17β-carbaldehyde → 3β-hydroxyandrost-5,16-diene+androst-5-ene-3β,17α-diol) were determined using the wild-type human CYP17 and its eight different single and double mutants. In addition the propensity of the proteins to undergo a subtle rearrangement converting the 450 nm active-form into an inactive counterpart absorbing at 420 nm, was monitored by measuring the of the P-450 → P-420 conversion. The results are interpreted to draw the following conclusions. The functional groups of Glu305 and Thr306 do not directly participate in the two proton delivery steps required for hydroxylation but may be important participants for the provision of a net work of hydrogen bonds for ‘activating’ water that then acts as a proton donor. The loss of any one of these residues is, therefore, only partially debilitating. That the mutation of Thr306 impairs the hydroxylation reaction more than it does the acyl-carbon cleavage is consistent with the detailed mechanistic scheme considered in this paper. Furthermore attention is drawn to the fact that the mutation of Glu305 and Thr306 subtly perturbed the architecture of the active site, which affects the geometry of this region of the protein and therefore its catalytic properties.

Calorimetric and infrared study of methyl iodide and some monosubstituted butyl halides. Does methyl iodide form hydrogen bonds as a proton donor?

1996 ◽  
Vol 285 (2) ◽  
pp. 199-209 ◽  
Author(s):  
Mikhail D. Borisover ◽  
Andrey A. Stolov ◽  
Felix D. Baitalov ◽  
Alexander I. Morozov ◽  
Boris N. Solomonov
Keyword(s):  
Hydrogen Bonds ◽  
Methyl Iodide ◽  
Proton Donor ◽  
Infrared Study ◽  
Iodide Form

Spectroscopic conformational study of PMS 952, a specific imidazoline ligand. Experimental results

1999 ◽  
Vol 77 (12) ◽  
pp. 2015-2024 ◽  
Author(s):  
Marie-Hélène Baron ◽  
Sabine Halut-Desportes ◽  
Hai-Fen Ye ◽  
Jack Huet ◽  
Edith Favre
Keyword(s):  
Hydrogen Bonds ◽  
Tautomeric Form ◽  
Proton Donor ◽  
Coupling Constants ◽  
X Ray ◽  
H Nmr ◽  
Ftir Studies ◽  
Nmr Study ◽  
Imidazoline Ring ◽  
Imidazoline Derivative

X-ray analysis of PMS 952 displays two kinds of very strong hydrogen bonds, an intramolecular one stabilizing the conformer A and an intermolecular one that associates conformers A to form two infinite chains. The 1H NMR study of vicinal coupling constants based on dihedral angle values, evidences that PMS 952 takes up an eclipsed conformation, in CCl4 and CDCl3 solutions, closely related to the conformation in solid state. Deuterium exchange in methanol-d4 points out the presence of a tautomeric form. However, as there is spectral evidence neither from NMR nor from FTIR studies for such a tautomer, this specie cannot be taken into account to explain the complexity of the FTIR spectra. NMR data also reveal that the imidazoline ring freely rotates while FTIR analysis allows characterizing two conformers (A and B), with lifetime shorter than NMR time scale. These two conformers are stabilized by two different intramolecular H-bonds. Taking into account that conformer A could exist in two states (monomer A and (A)n-chains), an equilibrium between A, (A)n, and B entities allowed the assignment of all main bands of the IR spectra, assigned to vNH, vOH, vCH, and vCN modes. The strength of hydrogen bonds is solvent dependent. Polar solvents, either proton donor or acceptor stabilized the conformer A, while CCl4 favors the conformer B.Key words: hydrogen bonds, X-ray, NMR, FTIR, imidazoline derivative.

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