Fischer rules

The /8-monoglycerides are optically inactive substitution on the a-C-atom results in an optically active monoglyceride. According to the Baer-Fischer rule (1939) this structure has a-D-configuration because oxidation of the molecule, barring hydrolysis of the substituent in a-position of the molecule, will yield a derivative of D-glyceraldehyde ... 

As a general rule esterification by the Fischer-Speier method should be carried out using absolute cthanob in the following preparation of ethyl benzoate, however, the yield is not sensibly affected by the use of the cheaper rectified spirit. 

At the present time, use of the Fischer convention is almost entirely restricted to carbohydrates, amino acids, and biologically important molecules of closed related structural types. The problem with more general use is that there are no adequate rules for deciding whether a diiral atom is like D-glyceraldehyde or L-glyceraldehyde when the structures are not closely similar to the reference molecules. This relationship is clear for carbohydrates and amino acids. 

No single factor can be identified as determining the outcome of radical addition. Nonetheless, there is a requirement for a set of simple guidelines to allow qualitative prediction. This need was recognized by Tedder and Walton,2 17 Beckwith ei ah, Giese. and, most recently, Fischer and Radom.4 With the current state of knowledge, any such rules must be partly empirical and, therefore, it is to be expected that they may have to be revised from time to time as more results become available and further theoretical studies are carried out. 1 lowever, this does not diminish their usefulness. 

This is our Fischer projection. All of the configurations can be seen on this drawing, because we are able to picture in our minds what the 3D shape is. So the rule is that all horizontal lines are coming out at us, and all vertical lines are going away from us ... 

Fermi golden rule, 268 Filipescu, N., 291 Fisch, M. H., 307 Fischer, F., 379 Flash photolysis, 80-92 of aromatic hydrocarbons, 89, 90 determination of jsc, 228-230 determination of triplet lifetime, 240-242 energy of higher triplet levels, 219-220 flash kinetic spectrophotometry, 82, 83 measurement of triplet spectra, 81,82 nanosecond flash kinetic apparatus, 89 nanosecond flash spectrographic apparatus, 88... 

Pohl-Ruling, J., P. Fischer, and E. Pohl, The Effect of Radon and Decay Products on Peripheral Blood Chromosomes, this volume (1987). 

J. Pohl-Ruling, P. Fischer, and E. Fohl Division of Biophysics, University of Salzburg, A-5020 Salzburg, Austria... 

Pohl-Ruling, J. and P. Fischer, The Dose Effect Relationship of Chromosome Aberrations to Alpha and Gamma Irradiation in a Population Subjected to an Increased Burden of Natural Radioactivity, Radiation Research 80 61-81 (1979)... 

Pohl-Ruling, J. and P. Fischer, Chromosome Aberrations in Inhabitants of Areas With ELevated Natural Radioactivity, in Radiation-Induced Chromosome Damage in Man (T. Ishihara and M.S. Sasaki, ed) pp. 527-560, A.R. Liss, Inc., New York (1982). 

Pohl-RUling, J., P. Fischer, 0. Haas, G.Obe, A.T. Natarajan, P.P.W. van Buul, K.E. Buckton, N.0. Bianchi, M. Larramendy, M. KufcerovA, Z. PolikovA, A. Leonard, L. Fabry, F. Palitti, T.Sharma, W. Binder, R.N. Mukherjee, and U. Mukherjee, Effect of Low-Dose Acute X-Irradiation on the Frequencies of Chromosomal Aberrations in Human Peripheral Lymphocytes in Vitro, Mutation Research 110 7182 (1983) ... 

For the depiction of structural formulas of hexofuranoses, a combination of a three-dimensional, Haworth-perspective tetrahydrofuran ring with a Fischer projection of the C-5-C-6 side-chain is commonly used, as exemplified by formulas 3 and 6. With the formal closure of the second ring and formation of a 2,6-dioxabicyclo[3.3.0]octane system, however, the depiction of the C-6-C-3 ring, as in formula 7, also assumes three-dimensional geometry, and this does not correspond to the Fischer projection rule.11 Consequently, structural representations of such bicyclic molecules should be as close as possible to the actual steric situation, as shown by structures 4 and 8. 

Following these rules, D-glyceraldehyde 6 in Fischer s convention can be assigned an ( -configuration. 

The (I ,S)-nomenclature still reminds the user of the right and left handed helical pattern arising from Fresnel s 29> interpretation of optical activity. These patterns are characterized by the combination of a translational and a rotational direction. The Ta skeletal symmetry of tetracoordinate systems submits itself to the pictorial models not applicable to other configurational types. The CIP rules may as well be used to define a configurational nomenclature on the basis of the Fischer projection. If one specified that in such a projection of an (R)-... 

In the a-donating (zwitterionic) resonance form of the latter heteroatom-cumu-lated free ligands, all the atoms satisfy the octet rule. Two kinds of all-carbon versions can be distinguished those that are 71-conjugated to a remote heteroatom and those that are not [14—19]. The former are largely exemplified by aminoalle-nylidenes, in which the a-donating resonance form of the free ligand is also stabilized by the octet rule (they are functional carbo-m cs of the Fischer-type aminocarbenes). The second kind is represented by C-substituted allenylidenes. 

U. Wachsmarm, R. F. H. Fischer, and J. B. Hnber, Mnltilevel Codes Theoretical Concepts and Practical Design Rules, ... 

From what was plarmed as a straightforward displacement of the chloride atom in 36 with hydrazine followed by a condensation with 2-tetralone and Fischer indolization to produce 39, dihydrazone 38 was isolated as an intermediate, resulting fi om dihydrazine 37 <99JHC441>. Subsequent Fischer indole cyclization and aminolysis of 38 produced 39 a mono-hydrazone intermediate (as opposed to 38) was ruled out by the authors on the basis of H NMR. 

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. 

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