Ensino de estereoquímica: construção e aplicação de um modelo em sala de aula

Abstract

In classes that deal with the concept of Stereochemistry, the students' greatest difficulty is the visualization of the molecules in their spatial conformations. In order to reduce or remedy these difficulties, teachers use methodologies that help students visualize molecules, such as the use of molecular handheld models such as ball and rod, games, multimedia, and software. For the development of this methodology, a study was conducted with teachers of the content of Stereochemistry, through a questionnaire, in order to know what were the main difficulties that they face during the teaching of this content. A semi-structured interview was also conducted on this issue. The difficulties reported by teachers are those related to the three-dimensional visualization of molecules and their different conformations. Thus, a didactic strategy was elaborated to represent Fischer and Perspectives formula stereoisomers. These structures were elaborated using ChemSketch software (ACD / ChemSketch Freeware, 2010), printed on A4 sheets and transparencies, so that the student can visualize the spatial forms of the molecules and the changes in the configuration of the isomers. The methodological proposal was collected and applied to students of the third year of the Integral Integrated Chemistry Technician course at the Federal Institute of Science and Technology of Goiás (IFG), Itumbiara Campus. The students also answered a questionnaire about the strategy applied in the classroom, besides solving an activity in which the transition between the two-dimensional and threedimensional structures was requested. In the analysis of the answers, it can be evidenced that the methodology fulfills its purpose, since it helped the students to understand the Stereochemistry visualizing the three-dimensional structures. It is noteworthy that students still had difficulties in transposing two-dimensional structures into three-dimensional (and vice versa). The results also showed that, among the models used in the classroom (printed and molecular), the printed model is preferred by students to improve their understanding in the study of isomerism. The teachers who participated in this research evaluated the model as viable and that can be used in the classroom.