Dynamic stereochemistry of 2,3,12,13-tetrathia- and -tetraselena[4,4]metacyclophanes

1983 ◽  
Vol 61 (7) ◽  
pp. 1598-1602 ◽  
Author(s):  
Keith R. Dixon ◽  
Reginald H. Mitchell
Keyword(s):  
Low Temperature ◽  
Shape Analysis ◽  
Line Shape ◽  
Thermodynamic Data ◽  
Nmr Spectra ◽  
Temperature Limit ◽  
Temperature Dependent ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Dynamic Stereochemistry

2,3,12,13-Tetrathia- and –tetraselena[4,4]metacyclophanes exhibit temperature dependent 1H nmr spectra in which the methylene resonances change from AB spectra in the low temperature limit to singlets at higher temperatures. Coalescence temperatures are 256 and 208 K, respectively, and a complete line-shape analysis yields [Formula: see text] and [Formula: see text]. The spectra and thermodynamic data are interpreted in terms of a mechanism involving interconversion of syn conformers with little or no involvement of the anti conformers previously assumed to dominate in this type of molecule.

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.

Quantification of 1H NMR spectra of human cerebrospinal fluid: a protocol based on constrained total-line-shape analysis

Metabolomics ◽  
2008 ◽  
Vol 4 (2) ◽  
pp. 150-160 ◽  
Author(s):  
Niko M. Jukarainen ◽  
Samuli-Petrus Korhonen ◽  
Mikko P. Laakso ◽  
Minna A. Korolainen ◽  
Matthias Niemitz ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
1H Nmr ◽  
Shape Analysis ◽  
Line Shape ◽  
Nmr Spectra ◽  
1H Nmr Spectra ◽  
Line Shape Analysis ◽  
Human Cerebrospinal Fluid
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