Commentary on the NMR apparent phase transition effect in natrolite, fluor-montmorillionite and other systems: Generalizations when the Arrhenius law applies

1976 ◽  
Vol 54 (3) ◽  
pp. 295-300 ◽  
Author(s):  
H. A. Resing ◽  
D. W. Davidson
Keyword(s):  
Phase Transition ◽  
Water Molecule ◽  
Shape Analysis ◽  
Line Shape ◽  
Activation Enthalpy ◽  
Arrhenius Law ◽  
Transition Effect ◽  
Line Shape Analysis ◽  
Mobile Fraction ◽  
The Mean

In situations where the NMR apparent phase transition effect occurs and the Arrhenius rate law is applicable, it has been shown that the mean activation enthalpy is roughly 37 times the temperature at which the mobile fraction is one-half. This and further generalizations have been applied to proton NMR line-shape analysis of water in natrolite and other systems; the mean activation enthalpy for water molecule diffusion in natrolite is estimated to be 18 kcal/mol.

A study of internal rotation in 2-furaldehyde through 13C relaxation times in the rotating frame

1987 ◽  
Vol 52 (2) ◽  
pp. 541-546 ◽  
Author(s):  
Vladimír Mlynárik
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Activation Enthalpy ◽  
Relaxation Times ◽  
Rotating Frame ◽  
Line Shape Analysis ◽  
13C Relaxation Times ◽  
Free Activation Energy ◽  
13C Relaxation ◽  
Good Agreement

Carbon-13 relaxation times in the rotating frame were used to study the exchange between unequally populated rotamers of 2-furaldehyde. Calculated free activation energy and activation enthalpy are in good agreement with the results of 1H line shape analysis. Accuracy and reliability of this method in comparison with the line shape analysis is discussed.

Line Shape Analysis of Spin Echo Signals in Cubic Solids

1969 ◽  
Vol 24 (5) ◽  
pp. 768-774 ◽  
Author(s):  
M. Mehring ◽  
O. Kanert
Keyword(s):  
Distribution Function ◽  
Shape Analysis ◽  
Line Shape ◽  
Rotation Angle ◽  
Pulse Sequence ◽  
Spin Echo ◽  
Distribution Functions ◽  
Echo Signal ◽  
Line Shape Analysis ◽  
The Mean

Abstract In the case of static magnetic dipolar and electric quadrupolar interactions (inhomogenous broadening) the dependency of the spin echo height at time t = 2τ after a π/2-τ-β pulse sequence on the rotation angle ß of the second rf-pulse is calculated for the spins I=3/2, 5/2, 7/2, 9/2. For each spin I an optimum rotation angle βopt is found out for which the spin echo signal has a maxi­mum. From the measured spin echo lineshape the distribution function of the quadrupole distortion in a solid can be determined. The mean quadrupole distortion can be obtained from the echo width. Detailed calculations in the case of Gaussian and Lorentzian distribution functions are presented.

Determination of the Accurate Values of the Rate Constant and Thermodynamic Parameters for the Rotation About the C(sp2)-C(aryl) Bond; Adamantan-1-yl 3-Bromo-2,4,6-trimethylphenyl Ketone

1998 ◽  
Vol 63 (7) ◽  
pp. 955-966
Author(s):  
Eva Přibylová ◽  
Miroslav Holík
Keyword(s):  
Thermodynamic Parameters ◽  
Shape Analysis ◽  
Rate Constants ◽  
Line Shape ◽  
Microsoft Excel ◽  
Hindered Rotation ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Coalescence Temperature

Four programs for the 1H NMR line shape analysis: two commercial - Winkubo (Bruker) and DNMR5 (QCPE 165) and two written in our laboratory - Newton (in Microsoft Excel) and Simtex (in Matlab) have been tested in order to get highly accurate rate constants of the hindered rotation about a single bond. For this purpose four testing criteria were used, two of them were also developed by us. As supplementary determinations the rate constants obtained for the coalescence temperature and for the thermal racemization of chromatographically separated enantiomers were used which fitted well the temperature dependence of the rate constants determined by the line shape analysis. As a test compound adamantan-1-yl 3-bromo-2,4,6-trimethylphenyl ketone was prepared and studied. It was shown that supermodified simplex method used in our algorithm (Simtex), though time consuming, gives the most accurate values of the rate constants and consequently the calculated thermodynamic parameters Ea, ∆H≠, and ∆S≠ lay in relatively narrow confidence intervals.

Cope rearrangement of 9-methylenebarbaralane. Complete line shape analysis

1973 ◽  
Vol 38 (6) ◽  
pp. 1210-1215 ◽  
Author(s):  
Linda G. Greifenstein ◽  
Joseph B. Lambert ◽  
Michael J. Broadhurst ◽  
Leo A. Paquette
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Cope Rearrangement ◽  
Line Shape Analysis

First line shape analysis and spectroscopic parameters for the ν11 band of 12C2H4

2016 ◽  
Vol 184 ◽  
pp. 297-307 ◽  
Author(s):  
Et-touhami Es-sebbar ◽  
John Mantzaras ◽  
Yves Benilan ◽  
Aamir Farooq
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
First Line ◽  
Spectroscopic Parameters ◽  
Line Shape Analysis

scholarly journals Determination of Effective Linewidth Using FMR Line Shape Analysis

1997 ◽  
Vol 07 (C1) ◽  
pp. C1-443-C1-444
Author(s):  
A. K. Srivastava ◽  
M. J. Patni ◽  
B. K. Chaturvedi
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Line Shape Analysis
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