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M E Munk

Publications and source records attributed to M E Munk.

61 records · Page 4Linked to original sources
PubMedDate not supplied

A novel formalism to characterize the degree of unsaturation of organic molecules.

The existing formalism to calculate the degree of unsaturation from the molecular formula of organic molecules cannot be applied to charged and/or disconnected species. Moreover, the calculated value depends on the assumed formal valence of each of the elements. In this work, we introduce a new formalism that eliminates these problems. The suggested property, degree of unsaturation, can be calculated from the molecular formula as well as from any structural representation of a molecule corresponding to that molecular formula.

Algorithms↗
PubMedDate not supplied

Stereoisomer generation in computer-enhanced structure elucidation.

The existence of stereoisomerism can be related to the presence of structural features referred to as stereocenters. On the basis of this relationship, computer software capable of generating all stereoisomers of a given constitutional isomer has been developed. Input to the program is a canonical connection table. In an initial step the stereocenters present in the structure are identified and characterized either as true-stereocenters or para-stereocenters. In the presence of n different true-stereocenters, structure generation is trivial and leads to 2n stereoisomers, each of which can be represented by a parity vector. In the presence of topological symmetry, the number of stereoisomers may be less than 2n; i.e., some of the 2n parity vectors correspond to equivalent configurations. An algorithm for determining equivalences among the set of 2n parity vectors is described. Program output includes the parity vector of each valid stereoisomer and the relationship between them, i.e., enantiomeric or diastereomeric. A simple procedure for representing the parity vector of the stereoisomer as a three-dimensional representation is given.

Chemistry, Organic↗
PubMedDate not supplied

HOUDINI: a new approach to computer-based structure generation.

A new method of structure generation called convergent structure generation has been developed to address limitations of earlier methods. The features of the program (HOUDINI) based on this method include the following: a single integrated representation of the collective substructural information; the use of parallel atom groups for efficient processing of families of alternative substructural inferences; and a managed structure generation procedure designed to build required structural features early in the process.

Algorithms↗
PubMedDate not supplied

Applications of a HOUDINI-based structure elucidation system.

SESAMI, a comprehensive program for the elucidation of the structure of complex compounds of carbon, incorporates a structure reduction-based structure genearator (COCOA). Observed limitations with this program in the solution of higher molecular weight unknowns prompted the development of a structure generator (HOUDINI) which embodies a new concept, convergent structure generation. A comparison of the performance of COCOA-based and HOUDINI-based SESAMI using a set of complex, naturally occurring compounds as a test set of unknowns revealed faster execution times and more efficient processing of ambiguous structural information for the latter.

Algorithms↗
PubMedDate not supplied

The neural network as a tool for multispectral interpretation.

A neural network which utilized data from the infrared spectra, carbon-13 NMR spectra, and molecular formulas of organic compounds was developed. The network, which had one layer of hidden units, was trained by backpropagation; network parameters were determined by a simplex optimization procedure. A database of 1560 compounds was used for training and testing. The trained network was able to identify with high accuracy the presence of a broad range of substructural features present in the compounds. The number of features identified and the accuracy were significantly greater as compared with networks using data from a single form of spectroscopy. The results have significance for the SESAMI computer-enhanced structure elucidation system.

Computers↗