Relative basicity of nitrogen, oxygen, and sulfur bases. The site of protonation in sulfenamides and sulfinamides determined by nitrogen-14 NMR relaxation

1994 ◽  
Vol 59 (1) ◽  
pp. 232-233 ◽  
Author(s):  
Alessandro Bagno ◽  
Stephen J. Eustace ◽  
Lena Johansson ◽  
Gianfranco Scorrano
Keyword(s):  
Nmr Relaxation ◽  
Relative Basicity

Mononucleotides 31P NMR relaxation measurement

1983 ◽  
Vol 80 ◽  
pp. 831-832 ◽  
Author(s):  
A.M. Avedikian ◽  
D. Besserre ◽  
M. Delepierre
Keyword(s):  
31P Nmr ◽  
Nmr Relaxation ◽  
Relaxation Measurement

1H-NMR RELAXATION STUDIES ON THE NATURE OF THE SEMICONDUCTING STATE OF (TMTTF)2Br AND (TMTTF)2PF6: MAGNETISM

1983 ◽  
Vol 44 (C3) ◽  
pp. C3-1095-C3-1097
Author(s):  
T. Takahashi ◽  
F. Creuzet ◽  
D. Jérôme ◽  
J. M. Fabre
Keyword(s):  
1H Nmr ◽  
Nmr Relaxation ◽  
Relaxation Studies

Structure and Dynamics of Spherical and Rodlike Alkyl Ethoxylate Surfactant Micelles Investigated Using NMR Relaxation and Atomistic Molecular Dynamics Simulations

2019 ◽  
Author(s):  
Allison Edwards ◽  
Abdolreza Javidialesaadi ◽  
Katie Weigandt ◽  
George Stan ◽  
Charles Eads
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Nmr Relaxation ◽  
Cross Relaxation ◽  
Relaxation Rates ◽  
Surfactant Micelles ◽  
Cylindrical Micelles ◽  
Spherical Micelles ◽  
Dynamics Simulations ◽  
Relative Motions

We study molecular arrangements and dynamics in alkyl ethoxylate nonionic surfactant micelles by combining high field (600 and 700 MHz) NMR relaxation measurements with large-scale atomistic molecular dynamics simulations. For spherical micelles, but not for cylindrical micelles, cross relaxation rates are positive only for surfactant alkyl tail atoms connected to the hydrophilic head group. All cross relaxation rates are negative for cylindrical micelles. This effect is reproducible either by changing composition (ratios of the nonionic surfactants) or changing temperature of a single surfactant in order to change the micelle shape. We validate the micelle shape by SANS and use the results as a guide for our simulations. We calculate parameters that determine relaxation rates directly from simulated trajectories, without introducing specific functional forms. Results indicate that relative motions of nearby atoms are liquid-like, in agreement with 13C T1 measurements, though constrained by micelle morphology. Relative motions of distant atoms have slower components because the relative changes in distances and angles are smaller when the moving atoms are further apart. The slow, long-range motions appear to be responsible for the predominantly negative cross relaxation rates observed in NOESY spectra. The densities of atoms from positions 1 and 2 in the boundary region are lower in spherical micelles compared to cylindrical micelles. Correspondingly, motions in this region are less constrained by micelle morphology in the spherical compared to the cylindrical cases. The two effects of morphology lead to the unusual occurrence of positive cross relaxation involving positions 1 and 2 for spheres.

The effects controlling the oxygen basicity in alkoxysilanes (RO)nSi(CH3)4-n. The mutual polarizability effect of alkoxy groups attached to silicon

1979 ◽  
Vol 44 (3) ◽  
pp. 750-755 ◽  
Author(s):  
Josef Pola ◽  
Marie Jakoubková ◽  
Václav Chvalovský
Keyword(s):  
Regression Analysis ◽  
Linear Regression ◽  
Electronic Effect ◽  
Linear Regression Analysis ◽  
Effect Of Substituents ◽  
Relative Basicity ◽  
Polarizability Effect ◽  
Alkoxy Groups ◽  
Individual Series

Relative basicity of the oxygen in alkoxysilanes (RO)nSi(CH3)3-n having n = 1-4 and various electrondonating and electronwithdrawing groups R measured as Δν(OH) of phenol due to its interaction with these compounds in CCl4 is shown to be chiefly controlled by the electronic effect of substituents R. Linear regression analysis of the Δν(OH) vs n relatioship for individual series (RO)nSi(CH3)4-n suggests the operation of the polarizability effect of RO groups becoming more important with increasing electronwithdrawing nature of R.

The effect of solvation by acetone on the basicity of silylalkylamines

1979 ◽  
Vol 44 (9) ◽  
pp. 2828-2831 ◽  
Author(s):  
Zlata Papoušková ◽  
Vlasta Fialová ◽  
Václav Chvalovský
Keyword(s):  
Potentiometric Titration ◽  
Electronic Interaction ◽  
Relative Basicity

The relative basicity of fifteen methylethoxysilylalkylamines of the type (CH3)3-m(C2H5O)m.Si(CH2)nNH2 in acetone has been studied by potentiometric titration. For n 1 the basicity increases with increasing m, which is likely due to increasing electronic interaction of the oxygen of acetone with the silicon of silylalkylamines. The basicity of silylmethylamines (n = 1) changes nonsystematically, probably as a consequence of the competing action of opposite effects.

Acid-base properties of metals and glasses of Na2O.P2O5-xB2O3 system

1984 ◽  
Vol 49 (10) ◽  
pp. 2355-2362 ◽  
Author(s):  
Juraj Leško ◽  
Marie Dorušková ◽  
Jan Tržil
Keyword(s):  
Boron Oxide ◽  
A Priori ◽  
Optical Basicity ◽  
Galvanic Cell ◽  
Acid Base ◽  
Tetrahedral Configuration ◽  
Relative Basicity ◽  
Base Theory ◽  
Base Properties

Boron oxide in the Na2O.P2O5-x B2O3 system behaves as a Lux base. Its addition to Na2O.P2O5 brings about transformation of a Co(II) indicator from octahedral to tetrahedral configuration, increase in the optical basicity ΛPb(II), increase in the relative basicity of the melt as determined by means of a galvanic cell, and depolymerization reactions releasing PO43- ions. In the Na2O-B2O3 system free of P2O5, boron oxide behaves as a Lux acid. The amphoretic nature of B2O3 is explained in terms of Lux's acid-base theory extended in analogy with the protolysis theory. The theoretical optical basicity values do not indicate the amphoretic behaviour of B2O3 because in this approach boron oxide is a priori regarded as more acidic than Na2O.P2O5.

Temperature Dependence of Molecular Conformation, Dynamics, and Chemical Shift Anisotropy of α,α-Trehalose in D2O by NMR Relaxation

1997 ◽  
Vol 119 (6) ◽  
pp. 1336-1345 ◽  
Author(s):  
Gyula Batta ◽  
Katalin E. Kövér ◽  
Jacquelyn Gervay ◽  
Miklós Hornyák ◽  
Gareth M. Roberts
Keyword(s):  
Chemical Shift ◽  
Temperature Dependence ◽  
Molecular Conformation ◽  
Chemical Shift Anisotropy ◽  
Nmr Relaxation
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