Pregledni rad

Fragment Molecular Orbitals for Molecules and Interacting Systems

Martin Klessinger ; Organisch-Chemisches Institut der Universitat, D-4400 Munster, W. Germany

Sažetak

Different approaches to describe the structure and properties
of molecules as well as reactions between molecules in terms of
localized fragment orbitals and their interactions are briefly reviewed
and the method of fragments-in-molecules (FIM) is delineated:
The FIM method is formulated entirely in terms of strictly transfera<
ble fragment orbitals (FO's) which makes it possible to reduce
the basis set in order to simplify the calculations, to save computer
time and to make the results even more visual. Calculations within
the CND0/2 approximation on CH3-S molecules with S = CH3,
NH2, OH, F, CN, CH=CH2 and CH=O are used to demonstrate the
effect of limiting the number of virtual orbitals taken into account
and to an that the same orbital interactions between occupied and virtual
FO's of different fragments which are responsible for the rotational
barrier also have the largest effect on the total energies of the
systems under consideration. A partitioning of the energy of interaction
between molecular fragments based on the formulation of
the FIM approach yields definitions of inductive and mesomeric
effects which are in good accord with chemical experience and is
closely connected with other energy partitioning schemes.

Ključne riječi

Hrčak ID:

194062

URI

https://hrcak.srce.hr/194062

Datum izdavanja:

14.1.1985.

Posjeta: 821 *