Difficulties in Organic Chemistry Learning at University

FARRÉ, A.; LORENZO, M.G.

Roma

Conferencia; 22nd International Conference on Chemistry Education, 11th European Conference on Research in Chemical Education; 2012

Research and practice in chemical education in advanced courses are a new realm of study, and organic chemistry is a noteworthy component (1). Mechanistic explanation is a key topic for learning Organic Chemistry and it requires the knowledge of different specific representational systems. Particularly, the Electrophilic Aromatic Substitution (EAS) mechanism is explained by using resonances structures just because the intermediate is a resonance hybrid. In addition, to explain the product distribution of an EAS carried out on substituted benzene requires explaining why the intermediate of the faster transformation is lower in energy than the intermediate of the slower, competing transformation (2). The aim of the present work is to detect and analyse the main difficulties and the types of mistakes that students make when they solve different types of exercises/problems about EAS mechanism in a first course of Organic Chemistry. A sample of 236 students of Pharmacy and Biochemistry participated in this research. Four open paper-andpencil tasks were designed with two questions complex enough for data gathering: 1) low order cognitive demand (LOCD), and 2) high order cognitive demand (HOCD). Both questions had two independent variables (reactant and substituent) in a 2x2 design (table 1). Answers were checked first with chemical criteria; then, the number and type of errors were analysed using qualitative and statistical approach. For all analysed examples students had difficulties (wrong answers: 38% and 77% for LOCD and HOCD, respectively). Main errors were: structures of intermediate (54.2%), the location of the new substituent (39.6%), nomenclature of the products (23.1%). Students usually require to rote memory to solve LOCD, but it is not enough to solve complex questions because of saturation of work memory and conceptual difficulties to reach an integrated view of Organic Chemistry network.