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The induced magnetic field (IMF) of naphthalene, biphenyl, biphenylene, benzocyclobutadiene, and pentalene is dissected to contributions from the total π system, canonical π-molecular orbitals (CMO), and HOMO→π* excitations, to evaluate and interpret relative global and local diatropicity and paratropicity. Maps of the IMF of the total π system reveal its relative strength and topology that corresponds to global and local diatropic and paratropic ring currents. The total π magnetic response is determined by this of canonical HOMOs and particularly by paratropic contributions of rotational excitations from HOMOs to unoccupied π* orbitals. Low energy excitations and similar nodal structure of HOMO and π* induce strong paratropic fields that dominate on antiaromatic rings. High energy excitations and different nodal structures lead to weak paratropic contributions of canonical HOMOs, which are overwhelmed by diatropic response of lower energy canonical orbitals in aromatic rings. CMO-IMF analysis is found in agreement with ring current analysis. © 2017 Wiley Periodicals, Inc.

Students’ understanding of molecular structure through the use of two dimensional diagrammatic representations is essential for chemistry learning. However, several researches suggest that students exhibit difficulties in achieving representational competence with molecular diagrams. This study is focused on three forms of diagrammatic representations: Newman projections (NP), Fisher projections (FP) and Dash-Wedge diagrams (DW). Three computer based diagram matching tests were designed, developed and implemented to 33 undergraduates from our chemistry department. Students’ visuospatial skills and prior chemistry knowledge were also assessed. The findings of this pilot study were derived from the analysis of participants’ performance (scores and response times) in the matching diagrams tests, the spatial tests and the Chemistry test. Statistical analysis was performed in order to investigate the relationships between the examined cognitive factors and students’ performance in matching diagrams.