NMR evidence for free rotation of coordinated tetracyanothylene in its square pyramidal adducts with tetrakis(arylisocyanide)rhodium(I) perchlorates

Structural studies are largely performed without taking into account vibrational effects or with incorrectly taking them into account. The paper presents a first-order perturbation theory analysis of the problem. It is shown that vibrational effects introduce errors on the order of 0.02 Å or larger (sometimes, up to 0.1-0.2 Å) into the results of diffraction measurements. Methods for calculating the mean rotational constants, mean-square vibrational amplitudes, vibrational corrections to internuclear distances, and asymmetry parameters are described. Problems related to low-frequency motions, including torsional motions that transform into free rotation at low excitation levels, are discussed. The algorithms described are implemented in the program available from the author (free).

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Free rotation dimensions of linear polyesters and polyamides

European Polymer Journal ◽

10.1016/0014-3057(91)90120-d ◽

1991 ◽

Vol 27 (1) ◽

pp. 21-25 ◽

Cited By ~ 5

Author(s):

Malcolm B. Huglin ◽

Jose M. Rego

Keyword(s):

Free Rotation

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Single particle dynamics in an anharmonic potential with translation-rotation coupling: crossover from weak localisation via chaos to free rotation

Zeitschrift für Physik B Condensed Matter ◽

10.1007/s002570050430 ◽

1997 ◽

Vol 104 (1) ◽

pp. 137-145 ◽

Cited By ~ 12

Author(s):

P. Schiebel ◽

W. Prandl

Keyword(s):

Single Particle ◽

Particle Dynamics ◽

Free Rotation ◽

Anharmonic Potential

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Free rotation and the electric moment of organic molecules

Transactions of the Faraday Society ◽

10.1039/tf9343000804 ◽

1934 ◽

Vol 30 ◽

pp. 804 ◽

Cited By ~ 11

Author(s):

C. T. Zahn

Keyword(s):

Organic Molecules ◽

Free Rotation ◽

Electric Moment

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Hydrogen exchange and isomerization in ortho substituted benzamides. On the question of free rotation in an N-protonated amide

Canadian Journal of Chemistry ◽

10.1139/v79-473 ◽

1979 ◽

Vol 57 (22) ◽

pp. 2896-2901 ◽

Cited By ~ 2

Author(s):

Robert A. McClelland ◽

William F. Reynolds

Keyword(s):

Exchange Reaction ◽

Rate Constants ◽

Hydrogen Exchange ◽

Isomerization Reaction ◽

Free Rotation ◽

Bond Rotation ◽

Diffusion Limited ◽

Deprotonation Reaction ◽

Substituted Benzamides ◽

Acid Catalyzed

Rate constants have been obtained for the acid-catalyzed N–H exchange of N-methyl, 2,N-dimethyl, and 2,4,6,N-tetramethylbenzamide and the acid-catalyzed isomerization of the three corresponding N,N-dimethylbenzamides. The ratio [Formula: see text] increases significantly with increased number of ortho methyl substituents. This is explained in terms of a suggestion of Perrin, that C—N bond rotation is not completely free in the N-protonated amide, since it must compete with a diffusion limited deprotonation reaction. The isomerization reaction, which requires such a rotation, is therefore slowed by ortho methyl substituents which hinder rotation, relative to the exchange reaction, which does not require rotation.

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