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Microwave-aided reactions of aniline derivatives with formic acid : inquiry-based learning experiments

Mycak Michael, Doležal Rafael, Bílek Martin, Kolář Karel

Chemistry-Didactics-Ecology-Metrology

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2022

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R. 27, NR 1-2

135--151

EN

The synthesis of amides belongs to traditional experimental tasks not only in organic chemistry exercises at universities but also at chemically focused secondary schools or in special practices at general high schools. An example of such a synthesis may be the preparation of acetanilide via reaction of aniline with acetic acid or acetic anhydride. However, both of these reactions are associated with a rather long reaction time and certain hazards that limit their straightforward use in pedagogical practice. Conveniently, the reaction of aniline with acetic acid may be significantly optimised if it is performed under solvent-free conditions in the presence of microwaves, which reduces considerably the reaction time and provides very good yield, compared to traditional heating by a heating nest. In this study, the main pedagogical aim of the experimental design is elucidation of the influence of the structure of the amines on the course of the reaction with formic acid through inquiry-based learning. Specifically, the proposed experiments consist in investigation of the chemical yield achieved in microwave assisted reactions of aniline and its derivatives with formic acid in such a way that is adequate for constructive learning of undergraduate chemistry students. The selected series of amines involves aniline, 4-methoxyaniline, 4-chloroaniline, and 4-nitroaniline. In accordance with the chemical reactivity principles, students gradually realise that the influence of the substituent is reflected in the reaction yield, which grows in the following order: N-(4-nitrophenyl)formamide ˂ N-(4-chlorophenyl)formamide ˂ N-phenylformamide ˂ N-(4-methoxyphenyl)formamide. Therefore, the results of the experiments enable students to discover that stronger basicity of the amine increases the yield of the amide. In order to deepen the students’ chemical knowledge and skills, the concept of the experiments was transformed to support inquiry-based student learning. The proposed experiments are intended for experimental learning in universities educating future chemistry teachers, but they may be also utilised in the form of workshops for students at secondary schools of a general educational nature.

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Molecular models in chemistry education at university and upper secondary school - structure of amides

Kolář Karel, Doležal Rafael, Karásková Natálie, Maltsevskaya Nadezhda V., Křížková Šárka

Chemistry-Didactics-Ecology-Metrology

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2019

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R. 24, NR 1-2

45--51

EN

Molecular models derived from results of quantum-chemical calculations present an important category of didactic instruments in chemistry education in upper secondary school and, particularly, at university. These models can be used especially as tools for supporting the students’ understanding by visual learning, which can adequately address complexity of many chemical topics, incorporate appropriate didactic principles, as well as utilize the benefits brought up by the actual information technology. The proposed molecular models are non-trivial examples of didactic application of computational chemistry techniques in illustration of electron interactions in amidic group, namely the interaction of the free electron pair on the nitrogen atom with the carbonyl group and also the interaction of atoms in the amide group with other surrounding atoms in the molecule. By these molecular models it is possible to explain acid-base properties of amides applying knowledge of electron density distribution in the molecules and the resulting electrostatic potential. Presentation of the structure and properties of the amides within education is important also for the reason that amidic functions are involved in many important natural substances (e.g. proteins, peptides, nucleic acids or alkaloids), synthetic macromolecular substances (e.g. Silon) or pharmaceutical preparations (e.g. paracetamol). Molecular models then serve to support better understanding of the structure of these substances and, in relation to it, their properties.

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Didactic capacity of selected Czech and Russian organic chemistry textbooks

Karásková Natálie, Doležal Rafael, Maltsevskaya Nadezhda, Kolář Karel

Chemistry-Didactics-Ecology-Metrology

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2019

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R. 24, NR 1-2

61--76

EN

This article presents the results of analysis of Czech and Russian textbooks intended for organic chemistry teaching at upper secondary schools. In principle, the estimation of textbook didactic capacity is based on decomposition of the textbook content into a set of different objects and their subsequent frequency analysis. In this study, three Czech textbooks and three Russian textbooks were characterized by particular and total didactic capacity coefficients. The indifference of the calculated didactic capacities was tested by chi-square statistics at a level of significance α = 0.05. The results show that the selected Czech and Russian textbooks are not significantly different.