The Barrier to Rotation About the N—N Bond in N-Nitrosamines as Determined by Nuclear Magnetic Resonance Total Line Shape Analysis

1974 ◽  
Vol 52 (17) ◽  
pp. 3028-3036 ◽  
Author(s):  
J. D. Cooney ◽  
S. K. Brownstein ◽  
J. W. ApSimon
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Energy Barrier ◽  
Activation Parameters ◽  
Substantial Contribution ◽  
Resonance Structure ◽  
Bond Rotation ◽  
Line Shape Analysis ◽  
Bond Character ◽  
Nitrogen Bond

The energy barrier to internal N—N bond rotation in five cyclic and two bicyclic N-nitrosamines [Formula: see text]has been determined using high temperature 100 MHz n.m.r. spectroscopy. A substantial contribution from the ionic resonance structure of [Formula: see text] produces considerable double bond character in the nitrogen–nitrogen bond and a concomitant increase in the rotational barrier about the N—N bond. The molecules were examined in the[Formula: see text]liquid state and had ring sizes varying from five to nine atoms. The Arrhenius and Eyring activation parameters for the energy barrier were determined using total line shape analysis and the intensity ratio approximation method. The energy barrier to N—N bond rotation was found to range from 23–29 kcal/mol depending on the molecular structure and the solvent.

Determination of the barrier to CN bond rotation in captopril: Application of reference deconvolution to line-shape analysis

1990 ◽  
Vol 28 (9) ◽  
pp. 820-823 ◽  
Author(s):  
Darren V. S. Green ◽  
Ian H. Hillier ◽  
Gareth A. Morris ◽  
Lesley Whalley
Keyword(s):  
Shape Analysis ◽  
Line Shape ◽  
Bond Rotation ◽  
Line Shape Analysis

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
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