THEORETICAL-STUDY OF IONIZATION-POTENTIALS IN MONOSUBSTITUTED BENZENES

• Type: Article in International Scientific Journal
• Date: 1993

Authors

MELO, A (Author) FCUP; GOMES, JANF (Author) FCUP

Journal

Title: International Journal of Quantum Chemistry

Vol. 46

Pages: 651-669

ISSN: 0020-7608

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 2 Citations

Scopus - 2 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-001-NMS

DOI: 10.1002/qua.560460506

Abstract (EN): Monosubstituted benzenes, in which the substituents participate in the pi-electron system, are studied following a classification in two classes according to the pi-electronic structure of the substituent. For this type of molecule, a relation is established between the nature of the substituent and, on the one hand, the energies of the two highest occupied molecular orbitals and, on the other hand, their respective differences. The two orbitals referred to above have pi-character and belong to the a2 and b1 species if a C2v point group is assumed. Simple symmetry arguments lead to the conclusion that the a2 Orbitals have, essentially, an intraring character, whereas the pi-orbitals of the substituents do give an important contribution to the b1 orbitals. Therefore, an a2 electron must have a larger interaction with the benzene ring and a smaller kinetic energy, whereas a b1 electron must have a larger interaction with the substituent and a larger kinetic energy. It is also expected that the changes in the pi-electronic structure of the substituent must much more influence the variations on the b1 energies and on the components of orbital energies associated with the substituent than the variations on the a2 energies and on the intraring components of the orbital energies. A modified version of the MOPAC program was prepared to perform the decomposition of the orbital energies in their kinetic and potential energy components and these in their monocentric and bicentric terms. MNDO calculations on nine monosubstituted benzenes, using the modified MOPAC program, give good confirmation of the symmetry predictions and prove the consistency of the classification of the substituents that is introduced.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 19