Hindered Rotation in Carbamates: A Kinetic Anomaly

1972 ◽  
Vol 50 (10) ◽  
pp. 1594-1596 ◽  
Author(s):  
P. T. Inglefield ◽  
S. Kaplan
Keyword(s):  
High Resolution ◽  
Transition State ◽  
Shape Analysis ◽  
Line Shape ◽  
Energy Barriers ◽  
Hindered Rotation ◽  
Line Shape Analysis ◽  
Influence Of Solvent

The energy barriers to hindered rotation in two carbamate structures have been measured by total line-shape analysis of the high resolution n.m.r. spectrum. Conclusions are presented concerning the influence of solvent on the nature of the transition state in such processes and the existence of frequency factors outside the normal expected range for a unimolecular transformation.

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.

Zeeman-Effekt im Rotationsspektrum von Perdeuterodimethylsulfid / Rotational zeeman-effect of perdeuterodimethylsulfid

1972 ◽  
Vol 27 (7) ◽  
pp. 1159-1164 ◽  
Author(s):  
E. Hamer ◽  
D. H. Sutter ◽  
H. Dreizler
Keyword(s):  
Dipole Moment ◽  
High Resolution ◽  
Shape Analysis ◽  
Electric Dipole Moment ◽  
Sulfur Atom ◽  
Electric Dipole ◽  
Line Shape ◽  
Zeeman Effect ◽  
Line Shape Analysis

Abstract The rotational Zeeman effect of (CH3)2S and (CD3)2S has been observed under high resolution. Earlier measurements of BENSON and FLYGARE 2 on (CH3)2S were supplemented by the recording of two additional transitions. A line shape analysis was used to evaluate the data which led to the determination of the diagonal elements of the g-tensor and of the susceptibility anisotropies [in 10-6 erg/(G2 mole)] :From the change of the g-values upon deuteration it was possible to determine the sign of the electric dipole moment (negative end at the sulfur atom)

Internal rotation in the methyl esters of dimethylcarbamic acid and thio derivatives

1970 ◽  
Vol 48 (5) ◽  
pp. 824-829 ◽  
Author(s):  
Alberta E. Lemire ◽  
James C. Thompson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Shape Analysis ◽  
Line Shape ◽  
Resonance Line ◽  
Methyl Esters ◽  
Nuclear Magnetic Resonance Line ◽  
Hindered Rotation ◽  
Line Shape Analysis ◽  
Qualitative Picture

The kinetic parameters for hindered rotation about the C—N bond have been determined by total nuclear magnetic resonance line shape analysis for the methyl esters of N,N-dimethyldithiocarbamic acid, and N,N-dimethylmonothiocarbamic acid. A qualitative picture of the effect of substituents on the potential barrier in carbamate and thiocarbamate esters is presented.

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