Asymmetry and Dissymmetry

Sometimes the terms asymmetry, dissymmetry, and antisymmetry are confused in the literature although the scientific meaning of these 

Pierre Curie suggested a broad application of the term dissymmetry. He called a crystal dissymmetric in case of the absence of those elements of symmetry upon which depends the existence of one or another physical property in that crystal. In Pierre Curie s original words Dissymmetry creates the phenomenon ( C est la dissymetrie qui cree le phenomene ) [51], Namely, a phenomenon exists and is observable due to dissymmetry, i.e., due to the absence of some symmetry elements from the system. Finally, Shubnikov called dissymmetry the falling out of one or another element of symmetry from a given group [52], He argued that to speak of the absence of elements of symmetry makes sense only when these symmetry elements are present in some other structures. 

from the point of view of chirality any asymmetric figure is chiral, but asymmetry is not a necessary condition for chirality. All dissymmetric figures are also chiral if dissymmetry means the absence of usually a plane of reflection. In this sense, dissymmetry is synonymous with chirality. 

Is it not necessary and sufficient to admit that at the moment of the elaboration of the primary principles in the vegetable organism, [a dissymmetric] force is present . .. Do these [dissymmetric] actions, possibly placed under cosmic influences, reside in light, electricity, in magnetism, or in heat  

Can they be related to the motion of the earth, or to the electric currents by which physicists explain the terrestrial magnetic poles  

Sometimes, the terms asymmetry, dissymmetry, and antisymmetry are confused in the literature although the scientific meaning of these terms is in complete conformity with the etymology of these words. Asymmetry means the complete absence of symmetry, dissymmetry means the derangement of symmetry. and antisymmetry means the symmetry of opposites (see Section 4.6). 

Incidentally, Pierre Curie s teachings on symmetry are probably not so widely known as they should be, considering their fundamental and general importance. The fact that his works on symmetry were characterized by extreme brevity may have contributed to this. Marie Curie and Aleksei V. Shubnikov [2-42, 2-43] have considerably facilitated the dissemination of Curie s teachings. Our discussion also relies on their works. There is also a critical and fascinating discussion of Pierre Curie s symmetry teachings by Stewart and Golubitsky [2-44]. 

Pierre Curie s above-quoted statement concerning the role of dissymmetry in creating a phenomenon is part of a broader formulation. It states that in every phenomenon there may be elements of symmetry compatible with, though not required by, its existence. What is necessary is that certain elements of symmetry shall not exist. In other words, it is the absence of certain symmetry elements that is a necessary condition for the phenomenon to exist. 

Another important statement of Pierre Curie s is that when several phenomena are superposed in the same system, the dissymmetries are added together. As a result, only those symmetry elements which were common to each phenomenon will be characteristic of the system. 

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This problem is designed to illustrate chirality, asymmetry, and dissymmetry with simple models or common objects. 

Structural asymmetry and dissymmetry can be made amenable to theoretical treatment by showing in a general way that electromagnetic waves can perturb charged particles, of which molecules are constructed, so as to produce rotatory phenomena. A charged particle, which we may take to be a loosely bound electron for the reason that rotatory power originates almost entirely from electronic rather than nuclear motions, will oscillate... 

In 1964, Cahn, Ingold, and Prelog (see p. 130) proposed that chemists use the terms chiral and chirality as defined by Kelvin. Based on the Greek word for hand (cheir), chirality means handedness, in reference to that pair of non-supcrimposablc mirror images we constantly-have before us our two hands. There has been wide-spread acceptance of Kelvin s terms, and they have largely displaced the earlier dissymmetric and dissymmetry (and the still earlier—and less accurate— asymmetric and asymmetry ), although one must expect to encounter the older terms in the older chemical literature. 

The term of Pasteur was translated into German and English as asymmetry and then came back as asymmetry in the works of Teilhard de Chardin (e.g., 1955, p. 98), Vernadsky used the term in its oiiginal form (dissymmetry). Therefor, we will refer to this phenomenon as dissymmetry iffi both cases to escape further confusion. Without doubt, Teilhard and Vernadsky were using two words to describe the same phenomenon. Teilhard (1961, p. 74) wrote ... 

Molecules of inheient structural asymmetry aie anisotropic they are optically active and exhibit optical rotation in solution. The typical optically active center is a carbon atom with four different substituents. In addition, any structural dissymmetry that results in a spatial left- and right-handedness will cause optical activity. Compounds of these types of come in a right-hand l R) and left-hand (L) form. When equal amounts of these two forms are mixed (racemic mixtures) there is no optical rotation because the activity of the two forms exactly cancel. Internal compensation of optically active centers m complex molecules is also found. Left- and right-handed optical isomers were first studied by Pasteur well over 100 years ago. and extensive surveys are found in most organic chemical texts. 

The asymmetric hydrosilylation of a-methylstyrene with methyldi-chlorosilane has been catalyzed by (/ )-benzylmethylphenylphosphine complexes of platinum(II) 302) or nickel(II) 304) to give a 5 or 17.6% excess of one enantiomer in the addition product, 2-phenylpropyl-methyldichlorosilane. The corresponding palladium(II) complexes were, however, only slightly useful for asymmetric synthesis in hydrosilylation of olefins. Nevertheless, palladium(II) complexes of methyldiphenyl-phosphine or epimeric neomethyldiphenylphosphine, where the dissymmetry is remote from the phosphorus, are especially useful for the induction of asymmetry in the hydrosilylation of styrene and some cyclic conjugated dienes 199). A similar procedure has been used for... 

A more subtle way to generate a chiral calixarene is to create dissymmetry or asymmetry within the molecule itself One of the means for doing this with a calix[4]arene is to establish a substitution pattern of AABC or ABCD on the upper or lower rim, producing a compound that is inherently chiral in all possible conformations. Tabulations of the cone, partial cone, 1,2-alternate, and... 

Vernadsky proposed a principle, which he called the Curie (or Pasteur-Curie, or dissymmetry principle , J>issymmetrical effects (phenomena) can be brought about only by a dissymmetrical cause". He realised that, if space is a kind of intelligible reality, then the causes and their effects must find themselves in the same state of space, i.e. they must be embraced by a certain state of space (Vernadsky, 1965, p.l82). As E. Eliseev (1989, p. 196) remarked later, the addition made by Vernadsky is so important that the latter principle should be called the Curie-Vernadsky principle. This is also correct, Vernadsky s dissymmetry is only a special case of Curie s asymmetry. 

Although Pasteur believed that there is a sharp gap between vital and nonliving processes, he attributed the asymmetry of living matter to the asymmetry of the structure of the universe and not to a vital force. Pasteur himself wrote that he was inclined to think that life, as it appears to us, must be a product of the dissymmetry of the universe (see Ref. [2-48]). 

Bromination of I yielded diastereoisomerides II and IV, which were separated by fractionation and then oxidized individually. The antipodal substances, III and V, respectively, were isolated, in which the induced asymmetry of the original olefinic group has been fixed by bromination, but the original dissymmetric secondary alcoholic grouping has been oxidized to a symmetrical carbonyl group. It remains a part of the final molecule, but with its classical dissymmetry destroyed, though it probably still contributes to the total optical activity of the product through asymmetric induction. 

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