Entropy in dissimilarity and chirality measures |
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Authors: | Remi Chauvin |
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Institution: | (1) Laboratoire de Chimie de Coordination du CNRS, Unité 8241, liée par conventions à l'Université Paul Sabatier et à l Institut National Polytechnique, 205 Route de Narbonne, 31077 Toulouse Cedex, France |
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Abstract: | Within the prospect of quantifying the geometrical dissimilarity of molecular models on the basis of a thermodynamical formalism, the algebra of stereogenic pairing equilibria is reviewed and applied to molecular geometry: developing Rassat's proposition, an interaction energy of two figures F and F is taken as proportional tod
H
Emphasis>/2
(F, F ), whered
H denotes the Hausdorff distance. IfG is a group of rotations in E
n
the geometrical version of the general equation (E) of the chemical algebra defines a distance extensionD
p(F,F ) ofd
H(F,F ), which is independent of the orientations of F and F , and where the coefficientp is interpreted as the reciprocal of a temperature-like parameter:p 1/T. At K (p = ), no formal entropy contributes to the definition of the uniform distanceD
. At K (p = 0), the discrimination between homo- and hetero-pairing of figures by the harmonic distance Do is averaged over orientation states. Temperature-dependent chirality measuresc
p are derived fromD
p, andc
is analogous to Mislow's chirality measure. If T and oT are normalized enantiomorphic triangles with coincident centroids inE
2,c
p(T) =D
p (T, T) is calculated forp = 0 andp = , and discussed for 0 <p < . Finally, the Hausdorff interaction model is putatively related to energy profiles versus dihedral angle inmeso- anddl-molecules. |
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Keywords: | |
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