Bonds symbols

The ROSDAL syntax is characterized by a simple coding of a chemical structure using alphanumeric symbols which can easily be learned by a chemist [14]. In the linear structure representation, each atom of the structure is arbitrarily assigned a unique number, except for the hydrogen atoms. Carbon atoms are shown in the notation only by digits. The other types of atoms carry, in addition, their atomic symbol. In order to describe the bonds between atoms, bond symbols are inserted between the atom numbers. Branches are marked and separated from the other parts of the code by commas [15, 16] (Figure 2-9). The ROSDAL linear notation is rmambiguous but not unique. 

The hypothesis that electron-pair donation from the a atom will stabilize this transition state leads to the difficulty that the attacking atom must carry more bonds than conventional valence bond symbolism admits. Despite this problem, the general idea is expressed by 7 and its relationship to 6 by resonance. It is possible that transition state stabilization can be obtained in this way by rehybridization of the entire molecule. Klopman et al. suggest that the a effect arises from... 

This approach is useful because it allows quantitative analysis via Walsh correlation diagrams to be made without extensive calculations. Figure 5.11 may clarify the approach. Initially the extra half-plane is at x = 0 and atom C is covalently bonded to atom A. When the half plane moves to the mid-glide position, x = b/2, the activation complex, ACB forms (Figure 5.10). Finally, when the half-plane moves to x = b, the pair CB forms a new covalent bond. Symbolically ... 

Where appropriate, the cu prebonds in the structure diagram can be indicated by distinctive bond symbols ( —, —i)... 

As anticipated by its ML2X2 formulation (Table 4.52), the computed structure of singlet nickelocene approximates a square-planar di-allylic coordination mode. We can deconstruct each r 3-Cp to Ni interaction into an electron-pair bond (M—X) with the radical carbon and a dative interaction (M—L) with the 7icc bond, symbolized as shown below with a half-filled circle ( >) to represent the radical site and a filled circle ( ) to represent the dative 7t-bond site ... 

Figure 11.16 The Kekule structures of benzene (C6H6) (upper structures), showing the two possible arrangements of the double bonds around the ring. Below is the aromatic resonance structure with the rotation of the double bonds symbolized by a ring, and the hydrogen atoms assumed to be present at each of the six corners .

The dipeptide A-a-glutamylglycine is abbreviated as Glu-Gly. A-y-Glutamyl-glycine is represented by the bond symbol... 

Bond specification Single, double, triple, and aromatic bonds are represented by the symbols —, =,, and , respectively, for example, CC=0 for acetaldehyde. Generally, single and aromatic bond symbols are omitted. 

A structural formula that shows all valence electrons, with the bonds symbolized by dashes ( —) or by pairs of dots, and nonbonding electrons symbolized by dots. (p. 7)... 

Note the dashed bond symbol is used here to indicate the continuation of a polymer chain. 

The second rule defines simple chains in molecules. A simple chain of atoms is represented by atomic symbols interspersed with their respective bond symbols. For example, CC represents ethane C-=C ethene and CCCCCO, n-pentanol. 

The third rule defines simple branches in molecules. A branch from the main chain is enclosed in parentheses. The string in parentheses is placed directly after the symbol for the atom to which the branch is connected. If it is connected by a multiple bond, the bond symbol immediately follows the left parenthesis. More than one... 

All of the substructure match algorithms described so far rely entirely on the topology of 2-D molecular structures. These algorithms can be further extended to compare query-target pairs of structures containing stereochemistry [42]. It is in this area where atom coordinates of 2-D structures play a certain role The configuration of double bonds and tetrahedral centers can be computed from atom display coordinates and bond symbols [42],... 

Carbon atoms readily form covalent bonds with other carbon atoms and with atoms of other nonmetals, especially hydrogen, nitrogen, oxygen, phosphorus, sulfur, and the halogens. Carbon atoms form these bonds by sharing pairs of electrons with atoms of other elements. When two atoms share two electrons, the bond is called a single bond (symbolized in a structural formula by a single dash - ). When four electrons are shared, the bond is called a double bond (symbolized by a double dash = ). When six electrons are shared, the bond is called a triple bond (symbolized by a triple dash <=> ). A carbon atom will... 

Structural Three-dimensional Large units (molecules) Large character set (over 100 different atom and bond symbols Exact or inexact match Whole or part unit match i. e. substructure search) with multidirectional pathtracing 1... 

The nomenclature in this work Ph represents phenyl, Y(A) represents a cyclic structure (e.g. Y(C5) is cyclopentadiene), D is a double bond (CDO is C=0), A or AJ represent a radical site on the structure. In some abbreviated nomenclature the double bond symbol (= or D) is omitted in the name, e g. CH2=CHCH=CHC =0 is named C4C DO. There are often several resonant structures for a given species. 

SRSG bond symbol the connectivity table type record of an average SRSG such as (2) will take 36 bytes. 

Figure 5.4. Band maximum of TO stretching mode of Si-O-Si bonds symbols — experiment solid line — caicuiation from Eq. (5.7). Reprinted, by permission, from H. Ono, T. Ikarashi, K. Ando, and T. Kitano, J. Appl. Phys 84, 6064 (1998). Copyright 1998 American Institute of Physics.

To summarize this exercise, we show in Scheme 2.8 the correct molecule H-F that can exist under the Law of Nirvana. It has an electron-pair bond symbolized by a line... 

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