Fischer symbol

The Fischer symbol was created for the description of different packings of identical spheres and is consequently only applicable to uninodal nets. It has the format p/n/JU. 

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Net Fischer symbol Vertex symbol Genus Planarityf Angles Chiral... 

The (8,3)-a and (8,3)-b nets (8 -cta and 8 -ctb) are the two uninodal (8,3) nets and they can both be constructed with perfect symmetry around the vertex, that is angles of 120 and equal lengths of the connectors [211. Wells labelled the first (8,3)-a and the second (8,3) b. The corresponding three letter codes are eta and etb (Fischer symbol 3/8/h2 and 3/8/hl). Unfortunately, they have both the same vertex symbol 8-8 8j, and genus 4, which could make it difficult to distinguish between them. However, eta is chiral, and etb not this should make the identification easier. The nets are shown in Figure 6.11 and Figure 6.12. 

Numbering and naming of the parent structure 2-Carb-3. The Fischer projection of the acyclic form 2-Carb-4. Configurational symbols and prefixes... 

Anna Seelig Ewa Landwojtowicz, Holger Fischer, and Xiaochun Li Blatter Abbreviations 461 Symbols 461... 

Fig. 4 Effect of added water on the C5 + selectivity (filled symbols) and CH4 selectivity (open symbols) as a function of CO conversion at different conditions for Co/A1203 (A), CoRe/Al203 (B), Co/Si02 (C), CoRe/Si02 (D), Co/Ti02 (E), and CoRe/Ti02 (F). Before water addition ( , ), 20% water added ( , O), 33% water added (A, A) and after water addition ( , O).19 Reprinted from Journal of Catalysis, Vol. 231, S. Storsaeter, 0. Borg, E. A. Blekkan and A. Holmen, Study of the effect of water on Fischer-Tropsch synthesis over supported cobalt catalysts, pp. 405-419. Copyright (2005), with permission from Elsevier.

Usually in Fischer projections the earbon atoms of the main chain are omitted [4]. In general, in the area of maeromolecular chemistry, element symbols are not omitted in the backbone and are usually shown in the rotated Fischer projection [3]. 

The Cahn-Ingold-Prelog rules (1956) are used to designate the configuration of each chiral C in a molecule in terms of the symbols R and S. These symbols come from the Latin, R from rectus (right) and S from sinister (left). Once told that the configuration of a chiral C is R or S, a chemist can write the correct projection or Fischer structural formulas. In our statement of the three rules the numerals 1, 2, 3, and 4 are used some chemists use letters a, b, c. and d in their place. 

Fig- 35. The in-plane magnetostriction Ay, coercivity HqHc and Curie temperature Tq as a function of the annealing temperature Ta for TbDyFe + Zr/Nb multilayers. Open square symbols indicate the phase transition temperature of an amorphous rest phase. After Fischer et al. (1999). 

At the turn of the twentieth century, Emil Fischer was studying the stereochemistry of sugars (Chapter 23), which contain as many as seven asymmetric carbon atoms. To draw these structures in perspective would have been difficult, and to pick out minor stereochemical differences in the drawings would have been nearly impossible. Fischer developed a symbolic way of drawing asymmetric carbon atoms, allowing them to be drawn rapidly. The Fischer projection also facilitates comparison of stereoisomers, holding them in their most symmetric conformation and emphasizing any differences in stereochemistry. 

D- and L- are older configurational descriptors used to denote the configuration of chiral molecules, especially carbohydrates and a-amino acids. Fischer projections are used to assign the symbols D- and L-. 

The preceding formulas VII and XI to XVI have been written purposely without the use of d and I symbols for distinguishing the members of a pair of enantiomorphs in order to emphasize that the mechanical models and Fischer s conventional formulas for representing them are quite independent of any plan of nomenclature. Recognizing this independence, let us consider next the historical origin and development of systematic nomenclature for such models and stereo-formulas in the carbohydrate group. 

Fischer projections, used for naturally occulting amino acids and sugars, are associated with symbols d and l. The former indicates the same configuration as the standard, d(+)-glyceraldehyde (3),... 

The average Karl Fischer moisture content as determined by Laboratory I and Laboratory 2. Symbols have same meaning as in Table I. 

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