Hindered rotation about C–N bonds: equilibration of diastereomeric rotational isomers

1970 ◽  
Vol 0 (16) ◽  
pp. 974-974 ◽  
Author(s):  
W. E. Bentz ◽  
L. D. Colebrook ◽  
J. R. Fehlner ◽  
A. Rosowsky
Keyword(s):  
Hindered Rotation ◽  
Rotational Isomers

scholarly journals Synthesis and dynamic behaviour of zwitterionic [M(η6-C6H5-BPh3)(coe)2] (M = Rh, Ir) cyclooctene complexes

2014 ◽  
Vol 43 (39) ◽  
pp. 14778-14786 ◽  
Author(s):  
Jesús J. Pérez-Torrente ◽  
Marta Angoy ◽  
Daniel Gómez-Bautista ◽  
Adrián Palacios ◽  
M. Victoria Jiménez ◽  
...  
Keyword(s):  
Dynamic Behaviour ◽  
Hindered Rotation ◽  
Rotational Isomers ◽  
Zwitterionic Complexes

Hindered rotation about the metal–cyclooctene bond in bis-cyclooctene zwitterionic complexes results in an unusual equilibrium between two rotational isomers.

Hindered rotation around the amide bond in a series of derivatives of 2-acetamidothiophenes

1991 ◽  
Vol 88 ◽  
pp. 689-707 ◽  
Author(s):  
P Andriamadio ◽  
D Nicole ◽  
A Cartier ◽  
M Wierzbicki ◽  
G Kirsch
Keyword(s):  
Amide Bond ◽  
Hindered Rotation ◽  
Derivatives Of

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.

Hindered rotation in N-acyl-1,2,4-triazoles

1978 ◽  
Vol 27 (7) ◽  
pp. 1463-1465
Author(s):  
I. D. Kalikhman ◽  
P. V. Makerov ◽  
E. F. Shibanova ◽  
Zh. N. Fidler ◽  
V. A. Pestunovich ◽  
...  
Keyword(s):  
Hindered Rotation

scholarly journals Spectroscopic, X-ray Diffraction and Density Functional Theory Study of Intra- and Intermolecular Hydrogen Bonds in Ortho-(4-tolylsulfonamido)benzamides

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 926
Author(s):  
Malose J. Mphahlele ◽  
Eugene E. Onwu ◽  
Marole M. Maluleka
Keyword(s):  
Density Functional Theory ◽  
Solid State ◽  
Hydrogen Bonds ◽  
Density Functional ◽  
Tetrahedral Geometry ◽  
Hindered Rotation ◽  
Hydrogen Bond Acceptor ◽  
Functional Theory ◽  
Vis Spectroscopy ◽  
Hydrogen Bonded

The conformations of the title compounds were determined in solution (NMR and UV-Vis spectroscopy) and in the solid state (FT-IR and XRD), complemented with density functional theory (DFT) in the gas phase. The nonequivalence of the amide protons of these compounds due to the hindered rotation of the C(O)–NH2 single bond resulted in two distinct resonances of different chemical shift values in the aromatic region of their 1H-NMR spectra. Intramolecular hydrogen bonding interactions between the carbonyl oxygen and the sulfonamide hydrogen atom were observed in the solution phase and solid state. XRD confirmed the ability of the amide moiety of this class of compounds to function as a hydrogen bond acceptor to form a six-membered hydrogen bonded ring and a donor simultaneously to form intermolecular hydrogen bonded complexes of the type N–H···O=S. The distorted tetrahedral geometry of the sulfur atom resulted in a deviation of the sulfonamide moiety from co-planarity of the anthranilamide scaffold, and this geometry enabled oxygen atoms to form hydrogen bonds in higher dimensions.

Stable cis and trans rotational isomers of 1,8-di-o-tolylnaphthalene

1976 ◽  
Vol 98 (4) ◽  
pp. 1018-1020 ◽  
Author(s):  
Roger L. Clough ◽  
John D. Roberts
Keyword(s):  
Rotational Isomers ◽  
Cis And Trans

scholarly journals Characteristic infrared frequencies of rotational isomers of alkyl chlorides

1962 ◽  
Vol 18 (12) ◽  
pp. 1603-1613 ◽  
Author(s):  
J.J. Shipman ◽  
V.L. Folt ◽  
S. Krimm
Keyword(s):  
Rotational Isomers ◽  
Infrared Frequencies

Strongly hindered rotation in α,α,2,6-terrachlorotoluene. Stereospecific five-bond coupling. Hyperconjugative contributions to long-range sidechain-ring proton coupling constants

1968 ◽  
Vol 46 (12) ◽  
pp. 2187-2188 ◽  
Author(s):  
T. Schaefer ◽  
R. Schwenk ◽  
C. J. Macdonald ◽  
W. F. Reynolds
Keyword(s):  
Free Energy ◽  
Resonance Spectrum ◽  
Coupling Constants ◽  
Proton Resonance ◽  
Kcal Mole ◽  
Hindered Rotation ◽  
Ring Proton ◽  
Meta Position ◽  
Proton Coupling ◽  
Free Energy Of Activation

At −40 °C the C—H bond of the dichloromethyl group of α,α,2,6-tetrachlorotoluene lies in the plane of the ring. The proton resonance spectrum demonstrates a stereospecific five-bond coupling between the C—H proton and the ring proton in the meta position. The coupling to the para proton is essentially zero as expected from a hyperconjugative mechanism. The free energy of activation of rotation of the dichloromethyl group is about 15 kcal/mole at 25 °C.

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