Line notation, Wiswesser

The Wiswesser Line Notation (WLN) was introduced in 1946, in order to organize and to systematically describe the cornucopia of compounds in a more concise manner. A line notation represents a chemical structure by an alphanumeric sequence, which significantly simplifies the processing by the computer [9-11], (n many cases the WLN uses the standard symbols for the chemical elements. Additionally, functional groups, ring systems, positions of ring substituents, and posi- 

The simple WLN uses 40 symbols from the following character sets [12]  

The great advantage of WLN codes is their compactness. Both compactness and unambiguity are achieved only by a complex set of rules, which make the notation difficult to code and error-prone. Since much information had been stored in the WLN code (functional groups, fragments, etc.), much effort was spent in the devel- 

The WLN was applied to indexing the Chemical Structure Index (CSI) at the Institute for Scientific Information (ISI) [13] and the Ituiex Chemicus Registry System (ICRS) as well as the Crossbow System of Imperial Chemical Industries (ICl). With the introduction of connection tables in the Chemical Abstracts Service (CAS) in 1965 and the advent of molecular editors in the 1970s, which directly produced connection tables, the WLN lost its importance. 

The Wiswesser line notation was already invented in 1938, i.e., before the advent of computers that could effectively use it [10-14], In 1960, the Institute for Scientific Information (ISI) developed the Index Chemicus, based on the Wiswesser line notation. The Wiswesser line notation is based on sequences of letters, numbers, and other characters as shown in Table 14.5. Numbers refer to the number of carbon atoms. For example, QV refers to acetic acid, and Q2 refers to ethyl alcohol. 

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Wiswesser line notation The Wiswesser line-formula notation (WLN) is a method for expressing the more usual graphical structure of a chemical compound as a linear string of symbols. The resulting alternative notation is unambiguous, short and particularly suitable for computer processing and retrieval but can also be understood easily by chemists after minimal training in its use. 

WLN Wiswesser line notation, wolfram An alternative name for tungsten. 

An alternative way to represent molecules is to use a linear notation. A linear notation uses alphanumeric characters to code the molecular structure. These have the advantage of being much more compact than the connection table and so can be particularly useful for transmif-ting information about large numbers of molecules. The most famous of the early line notations is the Wiswesser line notation [Wiswesser 1954] the-SMILES notation is a more recent example that is increasingly popular [Weininger 1988]. To construct the Wiswesser... 

The above is based on the calculation of a collective r for the whole molecule. This value changes the HOMO of either the diene or dienophile, as is necessary. This equation is accurate to about 0.5 eV on either side of the known values [15]. The value of ttotal is inserted into the HOMO-LUMO calculation as the parameter r Y), Note that in its pure form, this equation only yields values for the HOMO orbitals. Corrections are used for the calculation of the LUMO values. Table 1 contains examples of the Wiswesser Line Notation and the raw r values used in the computation of orbital energies. 

Fritts, Lois E., Margaret Mary Schwind, Using the Wiswesser Line Notation (WLN) for Online, Interactive Searching of Chemical Structures, J. Chem. Inf. Comput. Sci., 22, (1982), pp. 106-109. 

Figure 4. Representation using Wiswesser line notation...

Eakin [13] describes the chemical structure information system at Imperial Chemical Industries Ltd., where registration is based on Wiswesser Line Notation. For connection tables, the unique, unambiguous representation is derived automatically, i.e., a single, invariant numbering of the connection table is algorithmically derived. 

Programs now exist to convert Wiswesser Line Notation [29], Hayward [30], and IUPAC [18] linear notations to connection tables. Because fragment codes alone do not provide the complete description of all structural detail, conversion to other representations is typically not possible. 

Ebe, Tommy, and Antonio Zamora, "PATHFINDER II, A Computer Program That Generates Wiswesser Line Notations for Polycyclic Structures," Journal of Chemical Information and Computer Sciences, 16( 1), 36-39 (1976). 

This column gives the name and, below it, the Wiswesser Line Notation (WIN) designation of each compound included. Some of the names are the simplest and shortest trivial names for the compounds they denote others follow Chemical Abstracts nomenclature. The WLN designation is given only once for each compound when an entry continues onto the following pair of pages the name of the compound is repeated but the WIN designation is not. 

Atlas of Spectral Data and Physical Constants for Organic Compounds (1975), 2nd edn. Eds J. G. Grassell and W. M. Ritchey. Cleveland, Ohio CRC Press. Six volumes containing the following data on 21 000 compounds Wiswesser Line Notation, i.r., u.v., lH and l3C n.m.r. and m.s. data. 

The Pesticide Index (ref. 14) lists the following categories of pesticides acaricides, attractants, chemosterilants, defoliants, fungicides, herbicides, insecticides, molluscicides, nematicides, plant regulators, repellents, and rodenticides. Listings are in alphabetical order with structural and molecular formulae for single chemical entities. Other data include CAS nomenclature and number Wiswesser Line Notation LD-50 and test animal data when available physical appearance and safety information. Also provided are a CAS nomenclature index separate molecular (line) formulae of chemicals identified by their common names a separate section of Wiswesser line notations, also with common names an appendix of manufacturers, and an appendix of recent publications dealing with pesticide names. 

Until the late 1970s, the Wiswesser Line Notation (WLN) was the only widely recognized format in which to code chemical structures in a computer-readable linear format. It was invented by William J. Wiswesser (1952), and his work was recognized and honored with the Skolnik Award for outstanding contributions to and achievements in the theory and practice of chemical information science by the American Chemical Society in 1980. The WLN was quickly adopted by major chemical companies to store and retrieve machine-readable, 3D-chemical structure information in a 2D, linear array, and is still in use today. 

There are several linear canonical notations for the input of chemical structures into the computer notable among these are the Wiswesser line notation [226] and the IUPAC notation [227], which are used in industrial information systems. In order to achieve a canonical notation, a large number of rules are necessary, more than three hundred in the Wiswesser line notation [226]. Furthermore, the resulting notation is quite arbitrary and very far from the usual practice of a chemist for example, acetone is 1V1 in the Wiswesser notation. In conclusion, both coding a formula and reading a coded formula in the Wiswesser notation require highly trained chemists. 

There are two main problems to consider. One is the formulation of quantitative relationships using physicochemical parameters and regression analysis. As such equations are derived, the problem of organization of the mass of data must be solved. The most suitable, relatively inexpensive method for dealing with the structures of organic compounds via computers is the Wiswesser Line Notation method. This notation and the proper computer program can be of great help in comparative pharmacodynamics. 

These identifiers were developed as an lUPAC project in 2000-2004. They are the most recent technology aimed at an unambiguous text-string representation of chemical structures. (Earlier technologies included Wiswesser line notation, which is not described here, and SMILES, described below.)... 

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